It was the most beautiful moment of a most beautiful day.

More than 50 000 people came together from across Sweden for what was definitely the largest climate demonstration since those same children mobilized 7.6 million people around the world for the global climate strikes of September 2019.

Enade för klimatet – United for the Climate – was organized by Rebel Mothers, Rebel Fathers, the Swedish Society for Nature Conservation and Researchers’ Desk.

More than 200 organisations took part.

The children who danced in the street were at the periphery of the demonstration. They no longer needed to be in the centre because – finally – after seven long years, we – the adult community – acted and by doing so, we became our own hope. We became their hope.

We still needed their help. As we marched along Sveavägen, a few of them gave us spontaneous “crash courses” in demonstration slogans.

And then the Rebel Mothers sung “Mothers gonna rise like the water” in English and “Vi har samlats här” in Swedish. It was beautiful.

When the first of us reached Gustaf Adolf Square, the last of us were still at Vasaparken. The demonstration itself was longer than the 3.3-kilometre route from start to finish.

As we filled the square and – because we were so many – spread out towards the North Bridge, beyond which lies the Old City and the Parliament Buildings, the Bishop of Stockholm called on our political parties to unite for the climate.

Climate change is neither left wing nor right wing. It is a creeping crisis caused by humans. And it is a crisis that can be repaired by humans if we act together. Now. If you understand Swedish, please listen to Lisen Schultz, Deputy Director of Stockholm Resilience Centre. In 1 minute and 58 seconds, she explains why we must unite for the climate. Her speech is here.

Enade för klimatet concluded 24 timmar för klimatet (24 Hours for the Climate).

For 24 hours, Rebel Mothers and Rebel Fathers sat together in Sergels torg in the centre of Stockholm. They sat in peaceful rings, knitting, and listening to speeches and music, and – at midnight – they watched Helena Molin’s powerful documentary about the collective who created the climate strikes of 2019 – Strejkarna (As We Burn).

At the beginning of this beautiful demonstration, I was given the honour of speaking after Sara Nilsson, founder of Rebel Mothers.

This is a translation of what I said (the original Swedish version is below):

On 20 and 27 September 2019, 7.6 million people around the world went on strike for the climate.

Here in Stockholm, we walked together from Parliament Square to the King’s Garden.

In that square, we listened to our own children as they urged us to listen to the science, to save the climate, to save their future, to save everything they love.

In that moment, there was hope.

But then we went home. We carried on as usual. We did not listen.

And now seven years have passed.

1.5 degrees is lost.

Global warming is accelerating.

And Europe is burning.

This is happening because we continue to emit greenhouse gases.

This is happening because we are moving carbon that has been locked away in bedrock for millions of years into the atmosphere.

This is happening because we are making the transparent blanket of greenhouse gases around the Earth thicker and thicker.

And with every passing day, we move closer to a sixth mass extinction.

We are the meteorite.

And by we, I also mean we here in Sweden.

In 2022, we elected a government that, for four years, has failed us, failed our children, failed everything that lives.

Emissions are rising when they should be falling. Here. In Sweden.

We are a small country. But our emissions matter.

Because of their inadequate climate policies, our current government shares responsibility for:

• tens of thousands of species going extinct

• millions of people dying from extreme heat

• 1.5 degrees being lost.

* * *

But now we have a chance.

Now we can change direction.

Now we can listen to our children.

Now we can listen to the science:

1.6 degrees is better than 1.7 degrees.

One tenth of a degree of warming that does not happen means that:

• tens of thousands of species that would otherwise have gone extinct will survive

• millions of people who would otherwise have died from extreme heat will live.

1.6 degrees is better than 1.7 degrees.

* * *

Finally: What can I – as an individual – do for the climate?

The most important thing I can do is vote – and when I decide which party to vote for: to put the climate before the economy.

Why?

Because 1.6 degrees is better than 1.7 degrees.

This is the original version in Swedish (please scroll to the end of this post if you do not understand Swedish):

Den 20 och 27 september 2019 strejkade 7,6 miljoner människor världen över för klimatet.

Här i Stockholm gick vi tillsammans från Mynttorget till Kungsträdgården.

Där lyssnade vi på våra egna barn när de uppmanade oss att lyssna på forskningen, att rädda klimatet, att rädda deras framtid, att rädda allt de älskar.

I det ögonblicket fanns hopp.

Men sedan gick vi hem. Vi fortsatte som vanligt. Vi lyssnade inte.

Och nu har sju år gått.

1,5 grader går förlorat.

Den globala uppvärmningen accelererar.

Och Europa brinner.

Detta sker eftersom vi fortsätter att släppa ut växthusgaser.

Detta sker eftersom vi flyttar kol som varit bundet i berggrunden i miljontals år till atmosfären.

Detta sker eftersom vi gör det genomskinliga täcket av växthusgaser runt jorden allt tjockare.

Och för varje dag som går tar vi oss allt närmare ett sjätte massutdöende.

Vi är meteoriten.

Och med vi menar jag också vi här i Sverige.

2022 valde vi en regering som under fyra år har svikit oss, svikit våra barn, svikit allt som lever.

Utsläppen ökar när de borde minska. Här. I Sverige.

Vi är ett litet land. Men våra utsläpp spelar roll.

På grund av sin otillräckliga klimatpolitik delar vår nuvarande regering ansvaret för att:

• tiotusentals arter kommer att dö ut

• miljontals människor kommer att dö av extrem hetta

• 1,5 grader går förlorat.

* * *

Men nu har vi chansen.

Nu kan vi ändra riktning.

Nu kan vi lyssna på våra barn.

Nu kan vi lyssna på forskningen.

1,6 grader är bättre än 1,7 grader.

En tiondels grads uppvärmning som inte sker betyder att:

• tiotusentals arter som annars skulle ha dött ut får finnas kvar

• miljontals människor som annars skulle ha dött av extrem hetta får leva.

1,6 grader är bättre än 1,7 grader.

* * *

Slutligen: Vad kan jag – som individ – göra för klimatet?

Det viktigaste jag kan göra är att rösta – och när jag väljer vilket parti jag ska rösta på: att prioritera klimatet över ekonomin.

Varför?

Eftersom 1,6 grader är bättre än 1,7 grader.

I would like to conclude this post by thanking Sara Nilsson, founder or Rebel Mothers, for inspiring the adult community to respond to the call made by the children in Parliament Square.

And – as usual – before leaving – I would really appreciate it if you click on the ❤️ at the top (or bottom) of the page if you liked this post.

The cruel act of vandalism cast a shadow of sorrow across Northumberland. Sycamore Gap, near Milecastle 39 on Hadrian’s Wall was a symbol of England’s Northeast.

Why cut the tree down? Why destroy something so beautiful?

At the trial, the prosecutors argued about the monetary value of the sycamore tree, as if some sum of money existed that might equate to raping a landscape of its beauty.

The Sycamore Tree was more than a century old. It was planted in the late 1800s by the landowner, John Clayton of Chesters (1792–1890), alongside the wall that had – at that time – stood there for 1800 years.

Hadrian’s Wall is 80 Roman miles long (one Roman mile equates to 1.48 km). It stretches from the Solway Firth in the West to the River Tyne in the East. It marked the northern frontier of the Roman Empire in 112 CE. Its western section was built of turf. The central and eastern sections were built of stones.

Walking alongside Hadrian’s Wall, I found myself reflecting on the hockey stick. This famous graph was first published by Michael Mann and co-authors in 1998. It compared global warming with the stable climate of the past six centuries. Mann was criticised for “alarmism” on account of the hockey stick. However, comparison of his original graph with temperature data from 0 to 2026 CE shows that his hockey stick stood the test of time.

The power of the hockey stick visualisation is that it makes clear for us that ongoing global warming (1.4 degrees) far exceeds climate variations over the past two millenia (which encompasses both the Medieval Warm period and the Little Ice Age).

As an illustration:

• When Hadrian’s Wall was built from 112 CE, the temperature anomaly (compared with 1850–1900) was 0.1 ± 0.4°C.

• When John Clayton planted the sycamore tree in the late 1800s, the temperature anomaly was (within error) unchanged – 0.0 ± 0.3°C.

• When I walked beside Hadrian’s Wall in 2026 – on the current “toe” of the hockey stick – the temperature anomaly had reached 1.4 ± 0.1°C.

In the 1998 article, Mann pointed an accusatory finger at our greenhouse gas emissions as the cause of global warming. His accusation was and is well-founded. When he made it, our annual emissions of greenhouse gases were 27 billion tons. Now, our emissions exceed 42 billion tons.

In an attempt to visualize “42 billion”, I made a back-of-the-envelope estimate of the number of stones in the stone part of Hadrian’s Wall.

I estimated 80 million stones.

Had Hadrian’s Wall been built of 42 billion stones of equivalent sizes, the five-thousand-strong army who built it, could have extended it so that it encircled the Earth (assumng that they maintained the same proportions of turf and stones).

This would have been a meaningless task.

But would it have been more meaningless that cutting down the Sycamore Tree?

I am not sure.

But what I am sure of, because I walked past it, is that the stump of the cut down sycamore is sprouting.

And with that in mind, I will conclude with a dream.

Imagine – one hundred years from now – when that sycamore tree is, once again, full grown, our grandchildren looking back on our time as that defining moment when we bent the hockey stick. Against all odds – a handful of shoots became a mighty sycamore tree and – against all odds – a handful of climate warriors became a global movement.

A dream. But can we make it a reality?

As wildfires rage across Europe, I ask you to seek inspiration in a sprouting sycamore tree. Together, we can bend the hockey stick. But to do so, we must unite and rise again.

What can I do?

I’ve written this before, but it’s really important, so I’ll write it again:

The single most impactful action a person living in a functioning democracy can take for the climate and nature is to vote. And when voting, rank climate and nature ahead of economy, when choosing a party to vote for.

[If you live in Sweden and can vote in the September 13 elections, I hope you find the assessment of the climate ambitions of the eight main parties by Researchers’ Desk helpful. You can access it here.]

And – as usual – before leaving – I would really appreciate it if you click on the ❤️ at the top (or bottom) of the page if you liked this post.

The islanders on the pier raised both hands skyward, cast them down, and raised them again. Three times.

Oh hey! Oh hey! Oh hey!

We returned the farewell wave from the prow of the ferry.

The islanders repeated the wave that is a symbol of their beloved home – Rödlöga.

Then it was our turn.

Them. Us. Them.

The ritual continued until the captain had turned M/S Sjögull so that her prow was headlong with the northerly gale that had raged since dawn. The islanders returned to the collection of red painted cottages on the raised shore above the harbour, Rödlöga was behind us, and my four-day journey from the farthest reaches of the archipelago to Loch Ness had begun.

The name “Rödlöga” comes from the red (röd) colour of the granite that the island is made of, and an old Swedish verb meaning “to wash” (löga). The latter is the same as in the Swedish word for Saturday – lördag – meaning “washing day” (before Sunday).

Rödlöga is one of more than 30 000 islands and islets that form Stockholm Archipelago. Situated more than four hours northeast of Stockholm, Rödlöga is the most remote island that can be reached by ferry from the Swedish capital.

The archipelagian outpost was the final stop of our book tour. Monica (My) and I had presented our book – En Berättelse om Sverige – which translates to “A Story about Sweden” on three other islands – each of which has its own wonderful story to tell – before we reached Rödlöga.

We arrived on Göstadagen and not by chance. The wonderful Maria had made it possible for us to present our book at this unique festival. Göstadagen is held annually in honour of Gösta and Lisbeth Söderman, founders of the Rödlöga community.

Gösta Söderman was among the last of the “archipelago men”. When fish became scarce and most islanders sought work on the mainland, Gösta established the easternmost village shop in the archipelago and negotiated an extension of the ferry route from Stockholm, so that the boat continued all the way to Rödlöga. Gösta and Lisbeth never had children of their own. Perhaps this is why they left everything – their home, the shop and its outbuildings – to the local cooperative that continues to run the business today. The shop itself – Rödlögaboden – now forms the heart of the community. It is both a grocery store and a delicatessen, selling fine cheeses that are matured in the old root cellar. The shop is also a work place for youths from the island, as is the café that now occupies a former boathouse, where Gösta once built boats and stored fishing nets.

Our book presentation was scheduled to start a few minutes after a wreath had been laid down on a glacially polished surface of granite on which was etched – In Memory of Gösta and Lisbeth Söderman 07.07.07.

After this ceremony, twenty – maybe thirty – islanders crowded inside the meeting room to listen to our story. In our book, we weave together the geological history of Sweden with a celebration of the beauty if its landscape and kindness of its people.

Because Monica and I are climate activists, our book has a second purpose. Our hope is that by placing ourselves within the enormity of geological time, we can better relate to the speed at which the climate crisis is unfolding.

Our story begins with the breadth of a single hair.

Let this represent the Holocene – the warm period after the last glaciation that set the stage for the rise of civilization. If this period of 11 700 years – corresponding to 134 average lifetimes (in Sweden) – fit within the breadth of a single hair, one million years, would fit within one centimetre.

And with this perspective, we unrolled geological time. In the meeting room on Rödlöga, we unrolled a woven band measuring 46 metres – a visual representation of the 4.6-billion-year-long geological history of planet Earth.

At 2.6 centimetres, we reach the beginning of the Ice Age. The Ice Age, which is still ongoing, encompasses between 45 and 50 glaciations (so far). It is a consequence of global cooling that can at least partly be explained by the rise of the Himalaya. As these great mountains rise, fresh rocks are exposed to the air. They weather. And as they do so, carbon dioxide is sucked out of the air. The greenhouse effect weakens and the climate cools.

At 66 centimetres, we reach the fifth mass extinction. A meteorite hit the Earth causing short-lived climate cooling and killing 76% of species on Earth. Among them were the dinosaurs.

At 252 centimetres, after racing past the Age of Pangea – when all the continents were joined together – we arrive at “the great dying”. This is another mass extinction. More than ninety percent of all species disappeared. The cause may have been volcanically induced climate change.

At 541 centimetres, we reach the Explosion of Life. This is the moment when Earth became special – perhaps unique in a universe of 2 trillion galaxies – as complex multicellular life – all the creatures, all that is green, all that we love – emerged from no more than a handful of opportunistic species.

At 716 centimetres, we reach Snowball Earth. A chance placement of a supercontinent, the birth of a new range of mountains and a runaway spiral of global cooling ended in an entirely frozen Earth – covered by snow and ice for 74 million years.

At 2400 centimetres, cyanobacteria – Earth’s sole occupants for around 3 billion years (30 metres) of the planet’s history – switched mode of photosynthesis, from producing sulphur to producing oxygen, and the stage was set for the rise of complex life nearly 2 billion years (20 metres) later on.

At 3500 centimetres, we are certain that life had emerged on Earth. This is because we find stromatolites from that time. Dome-shaped fossils that are built by communities of cyanobacteria.

At 4000 centimetres, perhaps earlier, we find evidence of the first rocks forming out of the magma ocean that covered the Earth in its earliest years.

At 4600 centimetres (please forgive the roundoff error), we reach the moment when Earth was born from one of a series of standing waves of matter that found themselves trapped between Jupiter and the Sun. And our common home emerged in the habitable zone.

And after witnessing that miracle, we rolled time back in. Our first stop – on our return journey – was at 2834 centimetres. This is the moment when Sweden was born.

Then we tell Sweden’s story – one of volcanoes, of mountains rising up from the plains, of oceans opening and closing, of continents drifting and of dinosaurs. This is the story we tell in our book – En Berättelse om Sverige. It is a joyful story. So, we do not end it with the climate crisis.

But if we did, our metaphor would fail.

The climate has warmed by one degree since I was born in 1968 – a span of time represented by one two-hundredth of the width of a single hair on our woven band of time.

The geological machinery that controls the climate would have taken four million years – a span of time represented by four centimetres on our woven band of time.

When a human life equates with four million years, our metaphor fails.

But this does not matter, because we end our story before it happens. Yet it is still there. In the shadows. Everywhere.

The climate crisis hits you when you are least expecting it.

The European heat wave was waning. The northerly wind was cool and fresh.

And then the lady spoke of the Baltic Sea. How she had fished there as a child. The joy of bringing food home from the sea. But now – even if there had been fish – the joy was gone. The fish are safe to eat. But not if you are pregnant. Nor if you are a child.

Then I saw the tree tops. Made bare and lifeless by an infestation of bark beetles.

What if that beautiful island was no longer green?

The climate crisis is only one of a multitude of causes. Overfishing. Pollution. Monocultures. But everything is connected. Human exploitation of nature is at the root of all of these causes.

What can I do?

The single most impactful action a person living in Sweden (and any other country with a functioning democracy) can take for the climate, for nature, for everything, is to vote. And when voting, rank climate and nature (equating to our children’s futures) ahead of economy, when choosing a party to vote for.

I will stop writing now as I have boarded the Highland Chieftain. In eight more hours, we are scheduled to reach Inverness, beyond which lies Loch Ness, my destination.

And – before you go – sorry to keep asking, but if you liked reading this post, please click on the ❤️ at the top (or bottom) of the page. That way more people will get to read it.

Sector 4 was on the other side of the Dâmbovița – a river named after the oak woods through which it once flowed. The “sectors” are administrative units into which the Romanian capital is divided. In the eighteenth century, these units were called plăși and then, after the Russo-Turkish War (1806 – 1812), culori (colours – red, yellow, black, blue and green). After the onset of the Communist regime, the culori were abolished and replaced with eight raions, which became sectors in 1968. There are now six of them.

I am fairly certain that the location of the Hideaway would have been close to the edge of the city and in what was the blue culoare in 1871.

The 20-minute sprint through torrential rain was the final part of a 3-day journey from Stockholm Central Station to Bucharest Nord, with seven different trains and changing between them in Malmö, Copenhagen, Hamburg, Munich, Budapest and Arad.

I found going by train on this route in early summer quite magnificent. This is not just because it cut my carbon dioxide emissions by 69% compared with flying (or 89% compared with driving). It was magnificent because – over 3 days – I had time to appreciate how the landscape gradually changed from the mixed forests and patchwork fields of southern Sweden to the open grasslands on the Wallachian Plain beyond the Carpathian Mountains in southeastern Romania. The 3000-kilometre-long route crossed a succession of climate zones from the cool temperate climate of northern Europe to the warm temperate climate of southern Europe, and from the wetter (oceanic) climate of western Europe to the drier (continental) climate of eastern Europe.

These climate zones – each of which defines the habitats of countless species – are now moving perilously fast, mainly because humans burn fossil fuels. Their speed is such that my children are at risk of experiencing entirely different – hotter and drier – climate zones in each of the places I passed on my 3-day journey. The temperate climate of Romania will become arid and the cool temperate climate of southern Sweden will fade away. The chance that the many species that live in each of these climate zones will keep pace with the speed at which they are moving is diminishingly small. This is why so many of them risk extinction.

The reason for my journey was to meet with two wonderful groups of young people. The first group are my students from TRACEE (a Masters’ program in Transdisciplinary Studies of Climate, Environment and Energy, which I am a co-founder of) and the second group are climate justice activists.

The purpose of the TRACEE program is for us as educators to prepare students – as best as we can – for the challenges we know that each of them will encounter when facing the ever-worsening climate crisis. The program is taught by a consortium of 11 European universities, working together with partner universities in Africa. Our belief is that climate change solutions cross traditional disciplinary boundaries, and our shared vision is to educate students from any disciplinary background to speak the academic languages of other disciplines than their own. The program has attracted a first cohort of 13 passionate young scholars who collectively represent 9 countries and whom – I am certain – will make real a difference in each of their life journeys. In their passion for knowledge and readiness to put that knowledge in action, I found a glimpse of hope for the future.

The highlight of our time together was visiting mud volcanoes in Buzău County. Here, methane and mud seep upwards along faults, erupting at the surface. The amount of methane escaping to the atmosphere is estimated at 1200 tons per year. For comparison, our emissions of methane (a greenhouse gas that is 27–30 times more potent that carbon dioxide) from fossil fuel burning, livestock, landfill and waste, rice cultivation and biomass burning exceeds 300 millon tons per year. In other words – as a source of methane to the atmosphere – we are 250 000 times more powerful than the mud volcanoes of Buzău County.

Not only methane, but also oil seeps out of the ground in Buzău County. Even if the quantities are much less, crude oil spilling out over the vivid green Carpathian landscape makes vividly clear that oil – a fossil fuel – comes from rocks (a fact that we would do well to remember as we turn the chemistry of the Earth inside out).

The climate justice activists who invited me to Sector 4 had been with me on geological field trips to Utö, Nåttarö and Naxos.

[I have written pieces about each of these islands. The piece about Utö – the Outer Isle – concerns staying closer to home. The piece about Nåttarö is on the meaning of love. And the piece about Naxos is about the train accident in Greece on February 28 in 2023.]

When I entered their Hideaway in Sector 4, I felt immediately at home. The youths that welcomed me reminded me of the seven youths who started Fridays for Future and who are so powerfully portrayed by Helena Molin in her film documentary As We Burn. I will only use one of the names from Sector 4 – Sânziana – as the others have asked to remain anonymous.

The visibility of my TRACEE students – who took the stage in front of 17 universities – contrasted starkly with the climate justice activists in their Hideaway in Sector 4.

I am sure there are good reasons.

The story I shared with the climate justice activists was about the Earth. It began 4.6 billion years ago, when Jupiter created a niche for the Earth that was neither too far from nor too close to the Sun. And because of this, complex life emerged 541 million years ago and the story of all we love and cherish began. And this is what is at stake if we, humans, cause a sixth mass extinction by carrying on burning fossil fuels.

They listened attentively and asked questions that were far beyond the academic level of most professors. Some I could answer and some I could not. And then, from near the back of the darkened room, one youth asked a question about grief. This I could answer. I had spoken of anxiety, but I agreed that grief is a better word. Grief is what we feel when we realise – not in our minds, but in our hearts – that we are extinguishing all that we love. All that is beautiful. It is a grief that can spiral out of control, but also a grief that can make us stronger.

When you feel that grief, do not be afraid to shed tears. Tears of grief are tears of wisdom and tears of wisdom are tears of empowerment. By embracing grief, we can find ourselves empowered to act, and in action, we will find glimpses of hope.

[And our actions make a difference. Since 2013, global CO₂ emissions have largely plateaued. If this had not happened, CO₂ levels would now be ~8 ppm higher, causing an additional 0.07–0.11°C of global warming. In other words, our actions have stopped one tenth of a degree of global warming from happening. A small step – yes – but in the right direction.]

As I was about to leave (the rain had stopped), I spontaneously gave Sânziana and her wonderful friends a fossil trilobite. This was because I suddenly realised that it belonged in Sector 4. I had shown it to them because it was one of the first complex living things that evolved after the explosion of life 541 million years ago. It was a symbol of the geological beauty which we must learn to cherish. She took it home and showed it to her cats – Fae and Spiriduș. They seemed to like it. I don’t know why, but in that bridge across 541 million of years, I found a glimpse of hope.

And then, as I embarked on the 3-day journey home to Stockholm, a bird took to the sky ahead of the night train that would carry me to Arad. And once again, I found myself glimpsing hope.

And – before you go – thank you for reading this post! If you liked it, please click on the ❤️ at the top (or bottom) of the page. That way I know that this post meant something to you.

Last week, I had the honour of listening to Crafoord Prize Laureate, Veerabhadran (Ram) Ramanathan speak at the Royal Swedish Academy. Ram is not only an outstanding climate scientist who laid the foundation for our understanding of how aerosols (small particles that gather in the air) contribute to climate change. He is also a very kind person who cares deeply for his fellow human beings – especially the poor – and for nature. Ram has served as advisory to the Pope on matters relating to climate. With his Bending the Curve education initiative, Ram seeks to empower one million climate warriors. For me, Ram is an inspiration.

I have heard other climate scientists say that global warming is accelerating, and I can even see for myself when I try comparing global temperature data with a linear fit to the data.

But when Ram – the climate scientist I respect most of all – says it and explains why it is happening, I find myself convinced.

This is why global warming is happening faster:

The air we breathe is not just air. A single breath can contain a few million very small particles called aerosols. These particles – which are suspended in the air – can – for example – be mineral dust, sea salt, soot particles or sulfate particles (formed from gases erupted by volcanoes or from burning fossil fuels).

Aerosols affect our health and the climate. The manner in which aerosols affect climate is complex. Darker aerosols (e.g., soot particles) can warm the climate by trapping heat, whereas brighter aerosols (e.g., sulfate emissions from volcanoes and burning fossil fuels) can cool the climate by reflecting sunlight. The net (combined) effect of aersols on the climate is cooling and the amount of cooling is around half a degree (Celsius) according to the IPCC.

This presents us with an apparent Catch-22:

• We must stop polluting the air with sulfate emissions from burning fossil fuels because the aerosols that these emissions produce are extremely harmful to our own health – aerosols are associated with 7 million permature deaths annually.

• The good news is that we are reducing this kind of pollution by moving away from burning fossil fuels towards clean energy. This will save lives.

• The bad news is that by reducing this kind of pollution – which we must do because we must save lives – we are also removing the cooling effect of aerosols and removing this cooling effect makes global warming happen even faster.

We can think of this as taking of a mask – By polluting the air with aerosols, we have “masked” around half a degree of global warming. This means that the 1.4°C of global warming, we are currently suffering from, might actually be closer to 1.9°C.

But this Catch-22 is an apparent one, because there is a solution.

So what’s the solution?

The answer is a straightforward one.

We must reduce greenhouse gas emissions and we must do so urgently.

And – yes – we might see accelerated global warming. But this will be short-lived. It will be “overtaken” by cooling and climate recovery if we rapidly reduce greenhouse gas emissions. And climate recovery will be long-lived.

The reason is that aerosols are short-lived climate pollutants, whereas greenhouse gases (especially carbon dioxide) are long-lived climate pollutants. This means that climate change caused by aerosols will be brief, whereas climate change caused by greenhouse gases will last for a very long time.

Thus, rapidly reducing greenhouse gas emissions remains the only safe way to reduce global warming.

Accelerated global warming is a warning.

We must respond quickly by reducing greenhouse gas emissions to protect ourselves and to protect the 8.7 million other species with which we share our common home.

And to conclude with a quote from Ram – “We are never going to solve this problem by pointing fingers. We are all one planet. We have to work together.”

How can I be a part of the solution?

For an answer to this question that is tailored to your life situation, I recommend SHIFT by climate scientist Kimberly Nicholas and the team at Project Drawdown. I found that – for my life situation – my most impactful climate action is to elect leaders who’ll make and implement strong climate policies.

And – before you go – thank you for reading this post! If you liked it, please click on the ❤️ at the top (or bottom) of the page. That way I know that this post meant something to you.

There is sea cave on a small island called Nåttarö. The island, which is renowned for its beautiful sandy beaches and lush coniferous forests, is situated in the southern part of the Stockholm Archipelago, between Utö (“the Outer Isle” I once wrote about) and the harbour town of Nynäshamn.

The sea cave is in the middle of the forest. It is set back 400 meters from the shoreline and 30 meters above present-day sea level. It has been raised to that position since the end of the last glaciation. When the vast ice sheets that weighed down on Sweden melted away around 11 000 years ago, many thousands of islands, islets and skerries bounced up out of the Baltic Sea, creating the Stockholm Archipelago. Nåttarö is one of these islands. I estimate that its highest point – Örnklinten (meaning the eagle rocks) – emerged only 6000 years ago.

The sea cave is called Drottninggrottan (meaning the queen’s cave). It is named after Queen Maria Eleonora. Eight years after her husband – King Gustav II Adolf – fell at the battle of Lützen in 1632, Maria Eleonora fled Stockholm “under dramatic circumstances” for Gotland, where a Danish vessel was waiting to take her to Denmark. Maria Eleonora, who is said to have carried the heart of her dead husband in a gold box around her neck, sought shelter in the sea cave on Nåttarö in a storm, while waiting for better conditions to continue her journey.

According to legend, Maria Eleonora buried the heart of her dead husband in the sand outside the entrance to the cave.

One of the reasons I take my students to Nåttarö is for them to walk along vast shingle beaches, set far back from and elevated far above the present-day shore, and for them to wonder over the enormity of the ice sheets that weighed down on and sculpted the landscape that is their home. We sit amidst rounded cobbles, each of which was rolled back and forth millions of times by waves before being lifted out of reach of the sea by the rising of the land. We see how first lichens, then mosses and even the bravest of trees take footage among them as what was once sea becomes land.

Another reason I take my students to Nåttarö is to visit the sea cave, not because of Maria Eleonora and the story of her flight, but because of her daughter and the story of love.

Maria Eleonora’s daughter was called Kristina. She was six years old when she became Queen of Sweden after her father’s death. She is famed for abdicating, becoming catholic and fleeing to Rome. Although this is a story worth telling, I will tell you a different one.

Kristina was among the most learned of individuals. She was an avid reader in multiple languages and by her eighteenth birthday, she had made her way through much of what was available in the Royal Library in Stockholm. In search of more knowledge, Kristina made contact with the French philosopher, René Descartes, and before inviting him to Stockholm – a visit which brought his life to an end – she had corresponded with him for more than two years.

This correspondence was an exchange of letters, each of which was sent or received by the French ambassador, as was no doubt customary for the time. In that correspondence, Kristina and Descartes explored fundamental questions such as the nature of God, the indefinite size of the universe and the meaning of love.

I speak about the third of these questions – the meaning of love –with my students at the sea cave on Nåttarö. I choose this question because it visually illustrates the dualism which I think is the underlying root of the climate crisis we are a part of.

Queen Kristina and Descartes write about two kinds of love: a rational kind, which happens in the mind and defines us as both human and separate from nature; and a passion, which is purely chemical and “mimics rational love”. They write that “nature” – by which they mean animals (and possible plants) – can feel this kind of love, but not the rational kind. This separation of humans from nature, especially when combined with a view which Descartes wrote of – our human minds are “an emanation of God’s supreme intelligence” – underpins the whole idea of seeing nature as a resource, put there to satisfy our desires. I feel that this view (a view that was realised at different times in different places) or mindset marks the start of a spiral of exploitation that brought about the agriculture and industrial revolutions and, with them, the climate crisis.

Once, when I shared this story with a group of students at the sea cave on Nåttarö one student – Effie from Greece – lit up. She explained that love also has two separate meanings in Greek.

She spoke of Έρωτας (erotas) and Αγάπη (agapi) and promised to write to me about them. Now she has, and what she wrote was so beautiful, I wanted to share it with you, so I asked her, and she replied that I could.

These are Effie’s words:

There is a significant difference between Έρωτας (erotas) and Αγάπη (agapi), regarding mostly the intensity, the depth and the duration. So, allow me to break it down for you:

Έρωτας, is the primary feeling a person is filled with during the first stages of connection, interaction and discovery of someone or something (for example a hobby, a concept, a place…). During this stage we expect to see crazy dopamine spikes that can result in an unexplained source of energy, the need for less sleep or food, often the heart is racing, butterflies have occupied the stomach, the person sees the world through rose coloured glasses and nothing seems impossible. This feeling is born from something new, something often uncertain yet extremely strong, like a wildfire, like the shine of a firework, which are the exact reasons that it lasts only for a glimpse of an eye.

Now, Αγάπη usually needs some time to flourish. This feeling may not be as wild as the other, but it has a different kind of strength, more deep, more sacred, it moves mountains. This occurs, because this feeling is built brick by brick, it is a conscience choice you make every day. The said choice is, after you got to deeply know and understand the other, with all of their possible flaws and imperfections, you decide to love them anyway. You want to protect them, to help them grow, to make them truly happy, even if that means putting yourself second sometimes. This love is admiration and respect, it is observation and action, patience and mistakes, pain and healing, a dive into your own self, to be better for the other. At the end of the day, loving them makes you feel completed, you are each other’s safe place in a chaotic society. That is why, I associate this feeling with a warm, familiar, safe spot near the fireplace, in a home, where you finally feel secure to truly let yourself be real, free, let your guard down and be in peace.

My humble conclusion is that loving someone or something can change many things. It can make you unlearn the worst parts of yourself. Endure situations that once seemed impossible. Love can be so powerful, so bright that it gets imprinted on others, it inspires them, it can even reshape both your worldview and theirs. It shows them that such a feeling is possible for them to experience too, that it is not just a fairy tale we tell children at night. It plants the seed of hope.

And hope always dies last.

I think that we can all learn from her wisdom.

And by embracing Αγάπη, we can solve the climate crisis.

[English: I want to strike!]

These were the words of a small boy at the front of the auditorium after the premiere of Helena Molin’s stunning portrayal of the rise of the youth climate justice movement in Sweden.

The film As We Burn [Swedish: Strejkarna] tells the beautiful, powerful and sorrowful stories of seven children – Anton, Ell, Andreas, Greta, Sophia, Isabelle and Simon – who started Fridays for Future. One of them (Greta) sat down alone outside of the Swedish parliament with a sign “Skolstrejk för klimatet” in August 2018. Then the others joined her: Anton, who loves science because of its purity. Andreas, who turns anger into compassion. The twins – Sophia and Isabelle, who make it all happen. Simon, who quietly creates beauty. And Ell, who cares from them all.

In As We Burn, we follow each of their stories, beginning with glimpses from their early childhoods and then, that wonderful moment when it seems as if the movement has really succeeded as 7.6 million people take to the streets. We are with them, when they crowd around a mobile phone screen to watch as Greta gives her “How dare you!” speech in front of the United Nations Climate Action Summit in New York City.

“They must listen to us now!”

The call of joy echoes across the auditorium.

All is then still. Because we know what happens next.

We share in their slow realisation that we have not listened. We are with them as their sorrow grows like a wave as it approaches the shore, as it rises from seemingly still ocean water, as it breaks, and as it crashes down upon them, and engulfs them all.

We watch as grief kills the purity of childhood that made them so strong.

“They did not listen.”

We did not listen.

In Greta’s own words – we “stole [their] dreams and their childhood[s].”

We stole their childhoods from them, when we went out and marched with them, when we took selfies of ourselves with them, and when, afterwards, we did nothing. We just went home and returned to our normal lives.

Our political leaders stole their dreams from them, when “in the beginning of a mass extinction, all they [could] talk about [was] money and fairy tales of eternal economic growth.”

We watch as innocence abandons them and all that is left for them are measures of desperation.

One of them (who I have not named) is carried away by the police from a building inside which her future and the future of all that she loves is being decided on. We watch when one of the police officers does nothing to protect her dignity as he carelessly lets the contents of her water bottle spill out over her clothes.

One by one they are torn apart.

The one who started it all is afraid that she will die in this fight.

And the last sparkle of hope leaves the one who cares from them all.

Why did we abandon them?

Why did we not listen?

How could it be that seven years later, I face five of those seven brave children – now young adults – and as the curtain comes down, after which I am supposed to update them on the state of the climate, all I can tell them, after all they have done, is that we have failed to keep global warming below one-point-five?

[Until that moment, I had found ways of not saying it. I had clung on to an ever-smaller statistical chance that it might not happen. That we might – somehow – make it. But standing in front of them, knowing that that statistical chance now asymptotes with zero, I knew that I owed it to them. I pushed passive denialism aside and spoke a truth that I did not want to speak.]

We have failed one-point-five.

And now, looking back on the premiere of As It Burns, I remember the boy at the front of the auditorium – Jag vill strejka!

Of course, he wants to strike!

And he has good reason to strike because, citing Greta in the film, “1.6 degrees is better than 1.7 degrees.” It is. Avoiding 0.1 degrees of global warming protects 22 000 species from having been committed to extinction, 130 million humans from having been being cast outside of their climate niche and 33 million humans from having died prematurely by 21001.

And if he does strike, let us all stand alongside him. Let us learn from the beauty we brutally destroyed when we walked away and returned to our lives. Let us never abandon our children again.

Because if we abandon them, they will witness as all of nature falls.

But if we stand alongside them, we will be a part of making sure that aspen leaves continue to rustle in the wind, which is how the film ends.

As You Burn/Strejkarna will be screened in cinemas from May 15. If you only watch one film this year, make sure it is this one. It will be screened in Sweden by Folkets Bio.

My favourite ski tour is neither long nor challenging. It takes about one hour and I can carry my skis from my home to where I put them on. This is at the southern end of Haga in the Royal National City Park of Stockholm – the world’s first national city park. Haga is a fine example of an English landscape park with pelouses, semi-open pastures and woodland areas. Haga occupies the western shore of Brunnsviken. This is a brackish lake, 4 kilometres long and 500 metres wide, that is connected to the Baltic Sea by one narrow inlet.

The ski tour begins on a pelouse that slopes gently northwards from the shore of the lake. The pelouse is sheltered by firs, oaks, maples and, finest of all, enormous Scot’s pines. Its soft lawn accompanied by windstill conditions makes for perfect skiing, especially on a morning like this one, when the sun carries the first warmth of spring. Beyond the first pelouse, a winding trail, packed with snow, passes beneath widely spaced beech trees and a second pelouse slopes more steeply upwards to the base of the Stockholm esker. This is a ridge of sand and gravel left behind by a river that flowed in a tunnel beneath or within the icesheet the once covered Scandinavia. It was one of the reasons that Stockholm was built here. Its porous interior contains fresh water all year round. The surface of the snow on which I am skiing is like velvet. With each stride forward, I cast sparkling flakes in the air with my skis. After the second pelouse, I follow the wide snowclad crest of the esker for 600 meters, before descending to the Copper Tents. These iconic buildings are adorned with blue and gold entrance façades in the form of oriental tents. Below them, I ski down a third pelouse – the finest of them all – carving wide telemark turns in the shimmering blanket of snow, southwards to the lake.

What makes this particular ski tour my favourite one is that when I reach the shore of the lake, I can keep going on to the lake itself. I ski out on to its expansive white surface, with full confidence that beneath me are many centimetres of ice. Then, with strides that seem to carry me forever, I pass two headlands, each adorned with frozen reeds that glisten in the sunlight. And then, I reach the pier from where the summer boats will sail, four months from now.

I climb up on to the pier, with my skis still on, and continue for the final fifty metres to the edge of the park. Here I take my skis off, rest them against a hedge, and then I wonder if that was the last time.

The current forecast is that it will be six degrees next weekend, which means that it will most likely be the last time for this winter. But will it be the last time?

For the lake to freeze such that it is safe to ski on requires sustained cold weather, which is exactly what we have had. The temperature has remained below zero since mid-January. And, although there have been occasional flurries of snow, most days have been cold and clear. The reason was a meandering polar jet stream spilling cold air across Europe (and North America). This happened despite that fact that, globally, this January was the fifth warmest since records began. The “extreme cold” in January 2026 was weather.

I would like to take a moment to reflect on “extreme cold”.

Was it extreme?

Not really. The average temperature for January 2026 in Stockholm was -2.1°C. This is 0.7°C warmer than what would have perceived as “normal” between 1961 and 1990 (-2.8 °C).

However, January 2026 was 1.1°C colder than what was perceived as “normal” 30 years later, i.e., between 1991 and 2020 (-1.0 °C).

What this tells us is that our perception of “normal” is shifting.

It is not that January 2026 was extremely cold. It is that not only the climate is warming but also our perception of “normal” is warming. This is dangerous because it can hinder us from perceiving climate change.

We can see that our perception is changing on more than just temperature plots.

Two weeks ago, I joined my daughter for a cross-country ski race – Engelbrektsloppet – which has been run annually since 1968 in the mining village of Norberg. In the correspondence that I received from the organisers before the race, I was proudly informed that we would be skiing on “natursnö” (natural snow).

I had to think for a minute. What was the alternative?

Since 2020, when Engelbrektsloppet was cancelled because there was too little snow, the organisers bought in snow machines which are needed to keep running the race. The race is 30 kilometres long. That’s a lot of artificial snow.

The “Viking run” (Vikingarännet) – an 80 km race on long distance skates from Uppsala to Stockholm is now referred to in past tense on Wikipedia. After first trying to keep the race going in a warming climate with a moveable start date so as to catch an ever more elusive weekend of suitable ice, Vikingarännet was abandoned in 2017.

Next weekend is Vasaloppet. This is the world’s biggest cross-country ski race – 90 kilometres –from Sälen (which is in the mountains) to Mora (which is on the northern shore of Siljan – a lake that occupies part of a crater formed when a meteorite struck the Earth 377 million years ago). It will be fine this year, but how long before this historical race which attracts 100 000 skiers each year will meet the same fate as Vikingarännet? The race has relied on artificial snow since 2007.

As the climate warms, we must continually remind ourselves what is “normal” and not allow ourselves to be beguiled by that fact that “normal” is a moving target.

This to avoid standing by and watching passively as the climate that life depends on slips away.

And each time weather gives us a brief reminder of what we are losing, we must remind ourselves that climate is worth fighting for, and we might also ask ourselves if this is the last time.

It was beautiful.

Snow fell like it had done when I moved here more than a quarter of a century ago. It fell for several days and nights. And then came one of those perfect winter days. It was the fifth of January. The midday temperature was well below freezing and the snow was that perfect kind – the kind that sparkles in the sunlight and forms dancing clouds around the tips of ones skis as one glides effortlessly through its soft, silent, glistening beauty.

It was as if the climate crisis was gone, as if all had been forgiven, and we had been blessed with a second chance.

I was not supposed to be there. On that day, I should have been with my daughter on the 06:22 to Umeå, but the train had been cancelled.

It was the aftermath of a red warning having been issued by the Swedish Meteorological and Hydrological Institute (SMHI) for snow between Stockholm and Sundsvall (the birthplace of the first IPCC report). The reason was a “snow cannon”. This is a weather phenomenon which I first learned about when I moved to Sweden, but which also occurs elsewhere.

According to SMHI, snow cannons are a weather phenomenon in which very cold air flowing over open water creates rapid vertical air movements and intense snowstorms. The reason for calling them snow cannons becomes obvious when one looks at their appearance on radar imagery.

The snow cannon which closed the railway for 3 days was followed, one week later, by another one. This one caused very heavy snow between Sundsvall and Umeå. I narrowly missed it. Having finally reached Umeå with my daughter on a warning-free day, I was returning home. The 08:17 to Stockholm made an on-time departure even although an orange warning had been issued. And as the train crossed the Ångermanälven – one of the mighty rivers that flows down from the Swedish hinterland to the Baltic Sea – the snow cannon hit with full force and what had been an orange warning became a red one. The train carried on. We moved slowly and steadily. Because I was at the very front of the train, I could hear its frontal snowplough scraping close to the rails, as we battled forwards. We made it, but our train was the last one that did before the railway closed again.

What I did not think about as we battled head-on with the snow cannon was that it had been made more likely because of global warming. It was a part of the climate crisis.

This paradox arises because snow cannons form over the Baltic Sea when it is ice-free and the Baltic Sea is ice-free more often and for longer because its surface is warming more than 3 times faster than the global average for sea surface temperatures.

Those wonderful snowy days at the beginning of 2026 did not mean that the climate crisis was gone. To the contrary, those snowy days may have been caused by it. They were yet another reminder that the climate crisis is here and now, changing everything around us. Faster and faster. Spiralling out of control.

So, can we still enjoy it when it snows?

Can we enjoy it even if we suspect that the reason for it snowing is global warming? Can we enjoy skiing in a winter wonderland even if we suspect that it was sculpted by the climate crisis?

I think so. Indeed, I think that it is important that we do so.

When it snows – for whatever reason – we are reminded what we are fighting for.

Snow is one of nature’s most beautiful miracles. Snow can be deadly, but it can also nurture life. Snow creates a protective blanket that shields the smallest of plants from the bitter cold of winter. Snow counteracts global warming by reflecting sunlight back into space. Snow is a central part of the livelihoods of indigenous peoples of northern regions. Snow brings light in the midst of Arctic darkness. Snow creates joy.

Snow matters.

Snow reminds us of the natural beauty we are fighting for.

And if we fight for this beauty as if our lives depend on us doing so, because they do, we might still create a second chance.

This is because the climate crisis is neither “black” nor “white”. The climate crisis is a sliding scale of grey, where every negative action makes that greyness darker and every positive action softens that darkness and brings us closer to creating that second chance for ourselves and for the other 8.7 million species with whom we share a common home.

In the words of Petteri Taalas, Secretary General of the World Meteorological Organization and Joyce Msuya, Acting Executive Director of the United Nations Environment Programme, concluding the Foreward of the Special Report of the IPCC: Global Warming of 1.5 ºC:

Every bit of warming matters, every year matters, every choice matters.

Today (January 8), my first book written in English – Our Time: Finding Hope in a Climate Crisis – was published by Bloomsbury.

Our Time is about a four-billion-year journey to a single moment in time, when one species gets to decide to protect all that it cherishes, or to stand by and watch as the climate crisis engulfs it all. I tell this story as a professor of geology, who did not understand what it all meant, until it was explained to me by the children of the world.

In Our Time, I write about hope – the kind of hope that climate justice activist Andreas Magnusson refers to when he says “hope is a verb”. This is the hope that comes from acknowledging that the climate crisis is really a crisis and from embracing our fear so that it empowers us with the will to act. And by acting we create the hope we long for.

The hope I write about is neither based on fictive technical solutions nor framed within the limits of an out-of-date economic system. It is hope founded in wonder for the vastness of the beautiful world we are a part of.

Our Time can be purchased from Bloomsbury (in the UK), as well as online retailers such as Bokus or Akademibokhandeln (in Sweden) and Amazon (in the rest of the EU, the US and the rest of world).

Reviews

A remarkable account of the Earth’s long history and our very odd and dangerous moment in that story, from someone who has the both the scientific credibility to tell the story, and the human courage to be doing something about it!”

Bill McKibben, author, “Here Comes the Sun”

Professor Alasdair Skelton is a well-established Earth scientist gifted at explaining complex scientific concepts to the general public. In Our Time: Finding Hope in a Climate Crisis, Skelton masterfully explains the scientific basis for humans’ imprint on the climate, the impacts of global warming, and a much-needed view of the hope we can have for the future. The author’s personal experiences of living in a warming world bring his message to a level we can all relate to. The book is well-grounded in scientific literature and clearly referenced, so the curious reader can explore concepts in more detail. It is a must-read for people from all walks of life.

Todd A. Ehlers, professor and head of school, University of Glasgow

For the first time since I began my journey as a climate justice activist in 2018, I find myself completely engulfed in a book about the climate crisis. For so long I have waited and longed for a book with a real story that is filled with the kind of storytelling we really, really need. The kind of storytelling that gives a perspective on time and our age on this Earth that makes me relate to and understand my surroundings in a completely new and so, so refreshing way. I can only say: read it!

Andreas Magnusson, climate justice activist

Thank you for reading this.

Four billion years ago, the stage was set for life on Earth. Rising from a magma ocean that had covered its surface for hundreds of millions of years, came land, sea and air. Between them, a complex set of chemical reactions was set in motion in a manner that created a stable climate, making it possible for complex multicellular life to evolve billions of years later.

Four hundred million years ago, the Earth became green. Millions of years after complex life had emerged in the seas, and as living things ventured on to the land for the first time, came lichens and land plants, and the Earth was no longer barren. And at the same time, fragmented pieces of its once barren surface, converged on one another, creating the mightiest landmass of all time.

Forty million years ago, Earth’s climate was eight degrees hotter than in the epoch of humans. This was because extensive volcanism added enormous amounts of carbon dioxide to the air, as that mighty landmass was ripped apart.

And Four million years ago, Earth’s climate had cooled by six degrees. This was because the rise of the Himalaya had set chemical reactions in motion that removed that carbon dioxide from the air.

Four hundred thousand years ago, a chance harmony between Earth’s orbital dance around the Sun and its angle of planetary rotation created a corridor of climate stability along which Homo Heidelbergensis migrated southwards to a place in Africa that would become our ancestral home.

And forty thousand years ago, as vast ice sheets advanced from the polar regions, our own species spread across Europe and Asia and our sister species – Homo Neanderthalensis – faded from existence.

Four thousand years ago, after those ice sheets had retreated again, the 147 meter tall Great Pyramid – one of the Seven Wonders of the Ancient World – was newly built from 2.3 million stone masses, each weighing from 2.5 to 15 tons, on a rocky plateau, overlooking the River Nile.

Four hundred years ago, with the Little Ice Age approaching, Dutch settlers had established New Amsterdam at the southern end of Manhattan Island at the mouth of the Hudson River, North America.

Forty years ago, global warming caused by humans reached detectable levels. This was the year when Space Shuttle Challenger fell from the sky and Chernobyl 4 reactor exploded.

Four years ago, global warming caused by humans reached 1.2 degrees. This was the year when a fourth wave of the coronavirus swept across the globe and Russia invaded Ukraine.

And the clock strikes midnight on New Year’s Day, the past ends and the future begins.

In four years, global warming could exceed 1.5 degrees and humans will have reversed 4 million years of natural climate variability in one century.

And in forty years, global warming could exceed 3 degrees causing our children to suffer relentless heatwaves, droughts, wildfires, skyfalls and floods and witness comitted extinction of one fifth of all living things.

And in four hundred years, global warming could exceed 8 degrees and humans will have reversed 40 million years of natural climate variability in a few centuries, with a sixth mass extinction as a probable outcome.

And even if all of this comes to pass, Earth will recover.

In four thousand years, nearly half of the carbon dioxide humans added to the air will have been consumed by the land and the sea.

And in forty thousand years, most remaining carbon dioxide humans added to the air will have been removed by the weathering of rocks.

And in four hundred thousand years, Earth’s climate will have made a full recovery from the epoch of humans.

And after making this recovery, Earth’s story will continue without us.

In four million years, as the Somalian Peninsula breaks free from Africa and embarks on its journey across the Indian Ocean, new species – ones that we will never know – will emerge on Earth.

And in forty million years, as that peninsula approaches India with which it will collide and build mountains as tall as the Himalaya, millions of species may – once again – live on the Earth.

And in four hundred million years, after all Earth’s landmasses have converged to build Novopangea in the place where the Pacific Ocean was before, other mass extinctions may have come and gone and life will have emerged again and again.

And in four billion years, as what may have been the only planet in the universe that was ever a home for complex life fades from existence, a question remains for humanity.

What was our part in Earth’s story?

Did we cause one of its mass extinctions or did we rise and face the greatest challenge of our time?

If so, it is one of the most wonderful things I have witnessed.

On Tuesday at the Researchers’ Desk Christmas Party, within the safety of a thinking environment, I listened as – one by one – five children shared their future dreams.

Their dreams were normal ones. They were like the dreams of their peers. They were like my own dreams as I had embarked on life’s journey many years ago. They were going to use their talents to build futures along differing pathways. Normal pathways. The ones many of us want to follow. And what touched me most of all was the one who is so often silent. He spoke with genuine warmth of a hope for the future that was rooted in the goodness of humanity.

And this is despite all that happened to them and all that they made happen.

These five children and a small group of their friends created Fridays for Future – the global movement that mobilized millions of people – mostly children – around the world to speak out for climate justice.

Fridays for Future started “when 15-year-old Greta Thunberg began a school strike for climate” on August 20, 2018. She “sat alone outside the Parliament House in Stockholm, in protest and to raise awareness on the climate crisis before the Swedish election that autumn.”

One year later (August 5–9, 2019), 400 individuals from 38 different countries converged on Lausanne in Switzerland, where they united behind the following Declaration of Intent:

We have come together in Lausanne because we care.

We are at a crossroads in history. If we don’t take radical action and make unprecedented changes in all aspects of society right now, the world as we know and love it could be lost forever. The collapse of our society and our ecosystems are on the horizon and time is running out. What happens in the next months and years will determine what the future of humankind will look like. Our collective extinction is a possible outcome. Politicians all over the world are ignoring the emergency, but we have decided that we cannot wait any longer.

We have come together in Lausanne because we are united by our common fears and goals and the time to act is now.

We care about the future.

And the following Declaration of Demands:

1. Keep the global temperature rise below 1.5 ° C compared to pre-industrial levels.

2. Follow the Paris Agreement and ensure climate justice.

3. Listen to the best-unified science currently available.

One month later (on September 20, 2019), Fridays for Future organized the largest climate demonstration in history. This was the global strike at which more than four million people, many of them children, took to the streets across the world on the first Friday of a global week of climate action. At the same time, Greta Thunberg gave her “How Dare You?” speech at the United Nations Climate Action Summit in New York City after sailing across the Atlantic Ocean to get there.

Six years later, our greenhouse gas emissions continue to rise.

We have failed (so far).

But Fridays for Future have not.

Their achievement can be seen in “Google Trends”. Public awareness of the climate crisis rose massively in conjunction with their climate strike on September 20, 2019, and that rise of public awareness was not just a “blip” but a sustained rise.

But our awareness is insufficient.

Our greenhouse gas emissions do not care if we are aware or not. They will carry on making the Earth hotter regardless of our awareness.

It is our actions that matter.

As Christmas approaches, may I suggest a gift we can give to the children of the world.

We can set them free.

We can set them free from the need to fight against us for their futures.

And all we need to do to give this wonderful gift is to devote parts of our lives that are ours to decide over to actions that set them free.

I cannot tell you what your action is. Only you know that. What I can say is that even if it feels infinitesimally small, it is not. It matters.

This Christmas – if your life situation allows for it – please take this action.

Together, we can set the children of the world free.

In southern Sweden, pear trees normally bloom in May. They started blooming – six months early – in November because the unnatural warmth of a manmade autumn has tricked them. Then the frost came. And my guess is that the pear blossoms will have died and that no new blossoms will come in May. There will be no pears. A year will go by without a harvest.

This is what happens when we change the climate. We play tricks on plants and animals.

As the climate warms, plants and animals have only two choices: adapt or migrate.

How far can a pear tree migrate?

Its blossoms are carried by the wind. Animals can eat its fruit and carry its seed elsewhere. Perhaps to a place where the climate is cooler and it is not tricked into blooming in November – or – perhaps to a place where the climate is hotter and our trickery becomes even more brutal.

What happens if that pear tree is growing on a northern shore, beyond which lies nothing but ocean?

How fast can a pear tree adapt?

How fast can all living things adapt?

The climate zones that define the limits of habitability are moving too fast. Plants and animals cannot keep pace. Some adapt faster. Some adapt slower. They are out of phase. Ecosystems are being ripped apart.

This is what is meant by the speed of climate change. And it is the speed of climate change that kills. It is the speed of climate change that is spiralling us towards a sixth mass extinction.

After the frost was long gone and that uncanny warmth had returned, I visited a local school at which school children were making Christmas cards for our politicians. They were all stunning. Each was a call to action.

One of them was a call to “Save Our White Christmases”.

This one spoke to me because, in my hometown of Stockholm, we are witnessing the end of winter.

In Sweden, winter has a meteorological definition – winter begins when average temperatures fall below 0°C on five consecutive days. When I moved to Stockholm, “normal” was that winter began in December. Now, winter begins in January. And, for my children, statistics tell me[1] that winter will begin in February, if winter begins at all.

Two days earlier – on December 10 – five children from that school had been among the guests who gathered in Stockholm Concert Hall for the Nobel Prize Award Ceremony.

The guests inside the hall were told of a discovery that could pave the way forward for viable carbon capture and storage (CCS) – Metal and Covalent Organic Frameworks (MOFs and COFs). These fascinating molecules can absorb carbon dioxide from the air in a couple of hours and, when heated to 60–100 degrees, release them again within one hour.

This fantastic discovery could help us take on the climate crisis, but only if we hold true to the mitigation pathways of the IPCC which remind us that CCS is an addition to (not an alternative to) emissions reductions.

To illustrate this point – I calculated that to capture the 1125 billion tons of CO₂ we have added to the air (so far), so as to achieve net zero by 2050, we would need to synthesise 180 million tons of the most promising of these molecules (COF-999). Even if this was technically feasible, at an estimated $30/kg, the cost would exceed $5.5 trillion.

I was not one of the guests at the Novel Prize Award Ceremony, but I was there. I joined the Rebel Mothers and Rebel Fathers for a peaceful manifestation outside of the concert hall. With gentle music and caring speeches, worried parents were asking why we are celebrating scientific discovery at the same time as we fail to act in response to the most important scientific discovery of our time.

The temperature was 9 degrees (which is 10 degrees warmer than the 1961–90 average for December in Stockholm). I want to reassure the Rebel Mothers and Rebel Fathers that it was “just weather” because it was, but I also know that behind “just weather” is our shifting perception on what is “normal”. This is climate change and it scares me, so I could not reassure them.

Instead – when they asked me to speak for them – I told them about the pear trees blooming in November. I spoke about the speed of climate change that is spiralling us towards a sixth mass extinction. And I called on them to rise again.

My speech (written in Swedish) is below.

Päronträden blommar i november

Min svärmor skickade mig ett tidningsurklipp om ett musteri i Skåne där päronträden hade börjat blomma i november. Det fanns en bild på ett av dessa päronträd i blom. Det var ganska vackert. Och skrämmande.

Päronträd ska blomma i maj. Den onaturliga värmen från en konstgjord höst har lurat dem att blomma i november. Sedan kommer frosten. Päronblommorna kommer att dö. Och – högst sannolikt – kommer inga nya blommor i maj. Det blir inga päron. Ett år kommer att gå utan skörd.

Detta är vad som händer när vi förändrar klimatet. Vi lurar växter och djur.

När klimatet blir varmare har växter och djur bara två val: anpassa sig eller migrera. Hur långt kan ett päronträd migrera?

Dess blommor bärs av vinden. Djur kan äta dess frukt och bära dess frön någon annanstans. Kanske till en plats där klimatet är svalare och det inte luras att blomma i november – eller – kanske till en plats där klimatet är varmare och vårt bedrägeri blir ännu brutalare.

Vad händer om det där päronträdet växer på en nordlig strand, bortom vilken inget annat än havet ligger?

Hur snabbt kan ett päronträd anpassa sig?
Hur snabbt kan allt levande anpassa sig?

Klimatzonerna som definierar gränserna för vad som är möjligt att leva i rör sig för snabbt. Växter och djur hinner inte med. Vissa anpassar sig snabbare, andra långsammare. De hamnar i otakt. Ekosystem slits isär.

Det är detta som menas med klimatförändringens hastighet. Och det är klimatförändringens hastighet som dödar. Det är klimatförändringens hastighet som skenar mot en sjätte massutrotning.

Detta är vetenskapens brutala sanning.

På denna dag – måste vi kasta ljus över denna vetenskapliga sanning.
På denna dag – måste vi stå upp för framtidens päronträd.
På denna dag – måste vi stå upp för framtidens barn.
På denna dag – måste vi stå upp igen.

[1] This statement is based on a linear extrapolation from a change to the normal start of winter for the periods 1961–1990 and 1991–2020 of 15–20 days [Sveriges meteorologiska och hydrologiska institut (SMHI), “Månads-, årstids- och årskartor.”

But I know what you looked like.

Or at least I think I do.

From the fossils we have found in the extinction layer, we are fairly certain that you were between 4 and 6 feet tall. You walked upright. And we think that you were intelligent, not only because of the size of your brain cavity, but also because of all the “technofossils” we find. We link them to your species, because we find them together with fossils of your bones, and some technofossils match the size of your hands. We are not sure what most of them were used for, but we are sure that they were made from various metals and carbonaceous material, which we assume you gathered from different parts of the planet, as few of them occur naturally in the places where we find the technofossils.

The world looks very different now, compared with when you were here. Now, we only have one landmass. It is all of the landmasses of your time merged together. You guessed that it might be like that. And it is. You called it Novopangea. We call it home. It straddles the equator and it is surrounded by a worldwide ocean, which we named Panthalassa – a name we borrowed from a past long before your time.

Novopangea was formed when the Americas drifted westwards and collided with Eurasia. The collision of those once great continents is still ongoing. It is forming mountains as tall as the Himalaya of your time in the place where the Pacific Ocean once was.

My species evolved to live close to the shore in the warmer parts of Novopangea. We create life from sunlight. We are not alone. We are one of a multitude of living things that inhabit the shores. We have evolved to live together. We are entwined with and depend on one another in the same way that you were entwined with and depended on the other species of your time, even if some of my own kind have speculated that you did not know it at that time.

Now our world is getting colder (not warmer, which is what you thought would happen). Snow falls in places where it never fell before. And it will carry on getting colder. We know it and we accept it. It is because of the mountains. As mountains grow taller – and our great mountains are still growing taller – the climate cools. The same thing happened before you emerged. The rise of the Himalaya between India and Eurasia cooled the climate, but the effect was far less drastic than what is happening now, because plants still existed back then.

There are no plants now. They did not emerge again after the sixth mass extinction. We know that they existed before, because we find fossils of them in rocks that are older than the extinction layer. Some plants were really tall. They had enormous canopies of leaves. Other plants grew close to the ground. There were all different kinds. We suspect that they created life from sunlight, just like we do.

We suspect that plants were green, because we are green. We think that it was their green colour that counteracted the cooling effect of the Himalaya rising. Canopies of green would have absorbed sunlight, warming the climate. The barren hinterland of Novopangea is like a giant mirror. It reflects sunlight back into space. It absorbs none of it. This is why the climate is cooling so quickly now. And it will cool even faster as snow continues to fall, because snow reflects sunlight even more than it is reflected by the barren hinterland. This is why we fear a seventh mass extinction.

We hope that it will be gentler than the one before. We are fairly certain that the sixth mass extinction was devastating. It was not as severe as the great dying (which happened more than 200 million years earlier), but it was almost as severe. Our best estimate is that more than 90 precent of species died out in a handful of centuries.

We are almost certain that the cause was warming (not cooling). This is because we find compelling evidence in the extinction layer of sea level rise, and we suspect that it rose because glaciers and ice sheets melted. We think that there was a landmass at the south pole and that, before the sixth mass extinction, that landmass was glaciated, but we are not sure.

We are less sure about the cause of warming. We know it happened quickly. The rapid loss of species tells us that. We have searched for evidence of excessive volcanism at that time, but found nothing out of the ordinary. Indeed, we find that the geological stage – with a continent at the south pole and the Himalaya still rising – was set for cooling, not warming. We have searched for evidence of a meteorite, but found none. Also, a meteorite impact would also have caused cooling, and cooling cannot explain sea level rise.

We are beginning to wonder if you were the cause.

The reason we wonder this is the technofossils.

Many of them are small, but some are really big. And some of the bigger ones are hollow, with a cavity so large that it could house several of your species. The hollow technofossils are made of the same metals and carbonaceous material that we think you gathered from different parts of the planet. Also, where we find them, we find fossils of circular parts, from which we suspect motion. We wonder if some larger technofossils could move with you inside them. But how? How can metal move?

And one of our kind found an even larger one. It had wings. It is just like the flying things we find fossils of in rocks that are older than the extinction layer, only far bigger. And unlike the flying things we find fossils of, the wings of that giant technofossil are made of metal, not bones. Finding it, makes us wonder if your species could fly. Not by yourselves. We can see that. We can see that you had no wings. But did you make something of metal that could fly?

We think that the carbonaceous material we keep on finding wherever we find technofossils is a part of the story. Was it some kind of fuel? Did you burn it? Was this how you made metal move? Was this how you made metal fly? Did you make movement by burning carbonaceous material, like we make life from sunlight?

This would explain the warming. When carbonaceous material is burnt a gas is made. And that gas warms the climate. But to warm the climate so much and so fast, you must have burned vast amounts, extremely quickly.

This could explain the sixth mass extinction.

But then I think about your brain cavity, and none of it makes sense. You were intelligent. And an intelligent species would not have caused its own extinction.

So, I must be missing something.

What are climate tipping points?

Climate tipping points are “points of no return” beyond which “changes in a part of the climate system become self-perpetuating”. Climate tipping points can be abrupt, irreversible and dangerous.

Have you ever whipped cream so hard that it turned into butter? This is a “tipping point”. It happens abruptly. Once you notice it happening, you’re too late. It is irreversible. You cannot turn butter back into cream. But, at least it’s not dangerous …

In contrast to accidently turning cream into butter, climate tipping points can be extremely dangerous.

For example, 716 million years ago, a “perfect storm” of geological processes caused the climate to become dangerously cold. The climate became so cold that ice sheets began to form at tropical latitudes. These ice sheets enhanced Earth’s “albedo” – reflecting away sunlight that would otherwise have warmed the Earth’s surface. This made the climate even colder. The ice sheets expanded, further enhancing Earth’s albedo. The climate became even colder. The ice sheets continued to expand … and so on until, because of this self-perpetuating “ice-albedo feedback”, Earth was entirely encased in ice. This was Snowball Earth. Its onset may have been the most extreme climate tipping point in Earth’s geological history.

A less dramatic, but nevertheless worrying example of an ice-albedo feedback is currently happening in the Arctic Ocean. Since 1990, sea ice coverage in the summer months has halved. This has weakened Earth’s albedo – because there is less sea ice, less sunlight is reflected away and the climate has become warmer. As the climate warms, sea ice coverage will continue to diminish until the Arctic Ocean is ice-free in the summer months. This self-perpetuating ice-albedo feedback is fully underway, meaning that we have most likely passed this climate tipping point. Indeed, loss of Arctic sea ice may be a cause of one tenth of a degree of climate warming.

However, one might speculate that additional climate warming due to Arctic sea ice loss is necessarily limited, because once all summer ice is gone, no more can be lost.

Can passing one climate tipping point “trigger” other ones?

Possibly.

A potentially dangerous aspect of passing a climate tipping point is that if that tipping point causes climate warming, other climate tipping points might be “triggered”. This “chain of falling dominoes” is sometimes referred to as “cascading tipping points”.

Here’s an example:

• Climate warming causing permafrost to thaw and risks adding methane to the atmosphere.

• Adding methane to the atmosphere will cause additional climate warming because methane is a potent greenhouse gas.

• This additional climate warming could trigger further climate tipping points, e.g., collapse of ice sheets in Greenland and/or Wester Antarctica.

• Collapse of either of these ice sheets will cause catastrophic sea level rise.

Which climate tipping points are we at most risk of passing?

In a study published in Science (2022), Armstrong McKay and co-authors argue that at 1.5–2°C of warming, we are at risk of:

• Arctic sea ice loss (weakening Earth’s albedo and causing additional warming),

• permafrost thaw (releasing methane and causing additional climate warming),

• weakening of ocean-circulation in the North Atlantic (potentially causing cooling in western Europe),

• collapse of ice sheets in Greenland and/or West Antarctica (causing sea level rise), and

• coral die-off (causing a “chain reaction” of biodiversity loss in the ocean).

The IPCC refer to some of these risks (sea ice loss, coral die-off) as “likely” and others (weakening of ocean circulation, collapse of ice sheets) as “low-likelihood, high-impact outcomes” – meaning that their “probability of occurrence is low or not well known” but their “potential impacts on society and ecosystems could be high”.

What are likely outcomes of our climate (in)action?

Current pledges and targets point at 2.7 (2.2–3.4) degrees of warming by 2100.

At 2.7 degrees of warming, likely outcomes (by 2100) are:

• extreme heatwaves that are 3–4 degrees hotter, occurring (on average) every 1–3 years,

• extreme droughts that are 25–30% drier, occurring (on average) every 3–4 years,

• extreme rainfall events that are 20% wetter, occurring (on average) every 5 years, and

• sea level rise of 0.44–0.76 meters.

• committing 5% of all plants and animals to extinction.

• leaving 1 in 3 humans outside of the “human climate niche”.

And outcomes could be worse if we pass any climate tipping points.

Then, I was asked a really important question:

With a room full of investors in front of you, each of whom needs to make decisions about the future and each of whom has some small capacity to influence the future, what would you like to say to us?

That we can turn all of those numbers around.

Because every tenth of a degree of warming matters – every tenth of a degree of warming that does not happen is a success.

Imagine if, by investing in replacing fossil fuels, we could reduce future warming by one tenth of a degree. We would then have:

• protected more than 100 million human from being cast outside of their “climate niche”, and

• saved more than 20 thousand plants and animals from extinction.

Then one of the investors said something that stayed with me.

That person spoke humbly and honestly about how difficult it was.

Investors are chained to expectations from their clients of maximising their profits. Investors are not always at liberty to choose investments that make less money for their clients. If one does, one loses clients. If one loses clients, one can no longer invest … so, what should one do?

What should I do? What should we all do?

I do not know the answer to these questions, but I feel that it might be wise to focus on changing what we can change, while trying not to feel guilty about what we cannot change … but (and the “but” matters) – share the frustration – speak about it.

When we speak about the challenges we face when we try to do the “right thing” but we can’t, we are communicating humbly about the climate crisis, and by doing so, we are opening a door for others who are also trying, but cannot always succeed. And then we become more. And as we become more, we become part of a different kind of tipping point – a societal one.

And, beyond that societal tipping point, lies a future worth rising for.

I am sharing something beautiful, fully aware of the outcome of COP30: a perilous step backwards – removing any mention of fossil fuels from the final agreement. This is perilous because burning fossil fuels accounts for 87% of our greenhouse gas emissions and a one-year delay in reducing our emissions from burning fossil fuels equates to a 0.026°C (0.021–0.034°C1) rise of global temperature.

I am sharing something beautiful now, because in a moment of planetary despair, when political leaders have scarificed the children of the future for short-term gain, I hope that by reflecting on the beauty we are fighting for, we can find empowerment and rise again.

I will begin four and a half billion years ago.

In one of 2 trillion galaxies, a cloud of gas and dust (a nebula) collapsed inward on itself, flattening into a spinning disk and giving birth to the Sun and its planets. This “nebular hypothesis” explains the formation of our solar system and was first suggested by the German philosopher Immanuel Kant in 1755.

In the earliest stages of our solar system being formed, something wonderful happened. A fast-growing Jupiter cut off the flow of gas and dust towards the searing hot interior of the solar system and created “planet traps” one of which was at just the right distance from the young Sun for liquid water – a prerequisite for complex life – to exist.

And so, an unlikely chance of nature placed the Earth – our home – in the habitable zone that is not too far from and not too close to the Sun.

From the chemistry of one of the oldest mineral grains ever found, we can infer that no more than 200 million years after the Earth had formed, there were continents and oceans on its surface, and with their emergence, an elegant set of chemical reactions had been set in motion that would create a stable climate from that point forwards until the present day.

The beating heart of that set of chemical reactions is a rock called granite, a rock which continents are made of.

Granite is a made of four minerals. These are quartz, feldspar and a pair of darker minerals that give granite its speckled appearance. The name feldspar refers to a family of minerals which are closely related to one another. One of them gives granite its pink, orange or beige colour.

This seemingly ordinary mineral made it possible for complex life to emerge on Earth.

This is how:

• Complex life requires a stable climate.

• Earth has a stable climate because its greenhouse effect has an “off switch” that stops the climate overheating.

• Feldspar is that “off switch”.

We think of rocks and minerals as lasting “forever”. But they don’t. Rocks and minerals are broken down ever so slowly by a process which geologists call chemical weathering and which an American songwriter (perhaps unknowingly) hinted at when he asked how long it would take before a mountain would be washed to the sea.

Chemical weathering happens when rocks and minerals are “attacked” by an acidic mixture of rainwater and carbon dioxide from the air.

When feldspar is “attacked” it breaks down to clay and at the same time something wonderful happens – carbon dioxide gets permanently removed from the air2.

The is the “off switch” of the greenhouse effect. It works as follows:

If the climate starts overheating:

• chemical weathering speeds up (chemistry happens faster when it is hot),

• more carbon dioxide is permanently removed from the air,

• the greenhouse effect weakens, and

• the climate cools.

That this works at all is a second and quite miraculous chance of nature. It is why the climate has been stable – a vital condition for complex life – for millions of years.

And even when the climate spirals out of control as has happened in the past and is happening now, it recovers, as has also happened in the past, and as will also happen in the future (albeit a far and distance one that we might not be a part of).

Can you imagine something so beautiful as a planet that a first chance of nature – a planet called Jupiter – placed it in the habitable zone and a second chance of nature – a seemingly ordinary mineral called feldspar – gave it the power to heal its own climate time and time again.

And it need not have been that beautiful.

There are other planets out there that might be habitable at least for life in the sea. But will any of these planets have something so elegant as a feldspar that carries with it the gift of climate stability, or will those faraway planets be ravaged by climate catastrophes that repeatedly eradicate any attempts at crossing the miraculous divide from simple to complex life?

I don’t know.

So, I ask:

What if we are living on the only planet that is home to complex life in a universe so vast?

What if we were entrusted with something so beautiful?

Take a look at the living world with its 8.7 million species – a biodiversity so vast, made possible by chances of nature.

This is what is at stake.

Contrast this with the watered-down Mutirao from COP30 – a “collective effort” that risks casting many millions of humans outside of our “climate niche” and risks committing many thousands of plants and animals to extinction.

It is time for us all – climate scientists, climate justice activists and every local hero, who is working to make a difference – to unite and to rise again.

If there is one climate action you are thinking about taking – but you are undecided – please do take this action for our beautiful living planet and all that it means.

[This is a sorrowful post. Please don’t feel obliged to read it.]

On Monday, I was at the cinema.

It was the premier of an outstanding movie directed by Nathan Grossmann called Climate in Therapy. Nathan Grossmann also directed I am Greta – a movie that received what I perceive of as the best possible rating from Google – almost exactly as many ones as fives (and almost no twos, threes or fours). You either liked it or you hated it. I am Greta provokes thought (which is the point of the film). It’s not a “feel good” movie. It’s a wake-up call. It forces us to face the question that we – as adults – must ask ourselves: Why have we walked away and abandoned our children in the face of the worst crisis of our time?

Climate in Therapy is very different. It is a film about a group of climate scientists from around the world who participate in a therapy session which is held in a hotel on the outskirts of New York City by therapist Richard Beck. He is excellent. He worked with survivors of 9-11. That cannot have been easy. He provokes, but with respect and kindness. One by one, each of the climate scientists started to share what it feels like to know what they know (what we know) about the future of life on this planet.

The moment I want to share with you is the empty chair, because it is a visualization that will stay with me forever.

The climate scientists are sitting in a ring facing inwards and Richard places an empty chair in the middle of the ring. He then asks them to close their eyes and imagine that there is a child from the future sitting in that chair. What would each of them say to that child?

Richard was with us in Stockholm. So was Nathan. They placed an empty chair at the front of the cinema and Richard asked us that same question.

He asked us to close our eyes and imagine that there was child from the future sitting in that chair.

What would we say?

Please stop reading for a moment. What would you say?

I said nothing.

Staring at that empty chair, I was lost in my own thoughts.

My thoughts were not about the future. They were about the past.

I thought about lichen.

Lichen evolved over four hundred million years ago and their expansion on Earth changed the chemistry of the air. Lichens made rocks weather faster and weathering of rocks removes carbon dioxide from the air. This happened too fast. Too much carbon dioxide was removed from the air. The greenhouse effect was weakened and the Earth became colder. Too cold. By changing the climate, expansion of lichens might have caused the first mass extinction.

Then I thought about soil.

The expansion of land plants, over three hundred million years ago, created the first soils. Making soil from rock released large amounts of phosphorus that was carried by rivers to the ocean, where it caused explosions of algal blooms, which, as they died, created vast ocean dead zones. By changing the chemistry of the oceans, creation of the first soils might have caused part of the second mass extinction.

Then I thought about volcanoes.

Massive volcanic eruptions, over two hundred million years ago, first in Siberia and then in the place that would become the Central Atlantic Ocean, filled the air with dangerous amounts of carbon dioxide. The climate warmed. The ocean acidified. Twice. By changing the climate, volcanoes may have caused the third and fourth mass extinctions.

Then I thought about the meteorite that hit the Earth, sixty-six million years ago. The darkened sky blocked out incoming sunlight. It was only for a few decades, but the climate was perilously cold, causing the fifth mass extinction.

And then I did think about the future, but I thought about it from the future.

I thought about one species that had evolved quickly at what became the end of an Ice Age. That species dug up and burned most of the coal, oil and gas that had been accumulating beneath the ground for hundreds of millions years. This added vast amounts of carbon dioxide to the air, causing climate warming. By changing the climate, that species had caused the sixth mass extinction.

Once more, I was staring at that empty chair.

What would I say to a child in the future?

That I was sorry? That I had tried? That I had done what I could? That I hoped that it wasn’t too bad? That I hoped that there would still be snow?

I would say none of these things.

Because the chair would still be empty.

There would be no child in the future.

This is what mass extinction means.

In her pioneering work “Limits to Growth” which was published in 1972, Donella Meadows concluded:

If the present growth trends in world population, industrialization, pollution, food production, and resource depletion continue unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years.

This makes sense to me as a geologist because the “resources” we are depleting (e.g., fossil fuels, rare earth elements and uranium) for various forms of industrialization occur in concentrations that make mining of them economically viable mostly because of geological processes (e.g., making mountains) that operate on timescales of millions of years. Yet, we seem to be using them very quickly …

Nevertheless, I just spent a weekend “doing the maths” just to see if anything has changed in the 53 years since Donella Meadows publisher he seminal report for the Club of Rome’s project on “the predicament of mankind”.

First a status report:

Since 1972, global population and global energy consumption have more than doubled. Because most (76% in 2025) of the energy we consume still comes from burning fossil fuels, our carbon dioxide emissions have also more than doubled. This is the main reason for a 100 parts-per-million increase of the amount of carbon dioxide in the air and a 1°C rise in global temperature (also since 1972).

The first calculation:

If we continue to burn fossil fuels at current (2025) levels (and switch from oil to gas and then coal as each resource gets used up), I calculate that we will have burnt all known fossil fuel reserves by 2130. I further estimate that this alone will further increase the amount of carbon dioxide in the air by 230 parts-per-million [1], which will (in turn) cause an additional 2.1–3.3°C of global warming [2].

The second calculation:

If we successfully switch to renewable energy, our dependence switches from fossil fuels to other resources. Of particular importance are four rare earth elements (REEs). These are called neodymium, praseodymium, dysprosium and terbium. They are the “magnet-REEs” which are needed to make the permanent magnets that are needed to make wind turbines and electric cars work properly. These REEs are found in minable quantities in rocks formed by geological processes that operate on timescales of millions of years.

Based on forecast rates of growth in demand for these magnet-REEs and assuming no further growth after reaching net zero, I calculate that we will have consumed all known magnet-REE reserves by 2115 at current levels of recycling (1%) or 2165 at forecast levels of recycling (27–39%).

The third calculation:

If we rely instead on nuclear energy, our dependence switches to uranium. As with the REEs, uranium occurs in minable quantities in rocks formed by geological processes that operate on timescales of millions of years.

Based on forecast rates of growth for low and high demand scenarios for uranium, and assuming no further growth after 2050, I calculate that we will have consumed all known uranium reserves by 2115 (low demand) or 2085 (high demand).

Based on this analysis, I conclude that the forecast made by Donella Meadows that growth is limited by resources depletion, pollution or a combination of the two, still holds true. This is why we need to reduce consumption.

[1] Calculated assuming no change to carbon uptake apportioning between the ocean, land and atmosphere.

[2] Calculated for an assumed climate sensitivity of 2.5–4°C (IPCC, 2021).

Maybe this is why Swedes often tell me that it makes no difference what we do for the climate when, for example, climate action at a political level seems to be falling apart in the United States – a country with a population that is more than 30 times larger than our own.

Sometimes, I try to rationalise with them that if all small countries acted is if their actions made no difference, we would be in an even worse place than we find ourselves in today. But this kind of rationalisation does not work. For a start, if one does the maths, one finds that the population of all countries as small as, or smaller than Sweden, added together is not much larger than the population of the United States. More importantly, rationalisation (in my experience) might “win” arguments, but seldom reaches people’s hearts and seldom inspires action.

What I have found to inspire action are success stories. Instead of seeking to instil a sense of shame over our failures, I have found that instilling a sense of pride over our successes, inspires action.

What are our successes? Where should Swedes seek a sense of pride in a time when, according to our own Climate Policy Council, “[our] current climate policies are insufficient to meet [our] climate targets and EU commitments for 2030”?

I will share two success stories, and as you read them, I ask you to think broadly about your own country and its successes, and how you might use them to instil a sense of pride and inspire climate action.

The first story begins with a speech made by Mr. Ingvar Carlsson, Prime Minister of Sweden, in August 1990.

The speech was held in Sundsvall. This is a small industrial town on the east coast of Sweden. It is where two of the great rivers that drain the Swedish hinterland – Indalsälven and Lungan – reach the Baltic Sea. Its main industries are paper and pulp and aluminium. On calmer days, the former casts a faint sulphurous smell (which I found a little reminiscent of the hot spring fields of Iceland) across the town.

The occasion was the fourth meeting of the – at that time – recently formed Intergovernmental Panel on Climate Change (the IPCC). These are Mr. Carlsson’s words:

I would like to share with you my understanding of the issues you have presented to us.

• First, the estimates. Your best estimates are that the rate of climate change is now some 0.3 °C per decade. The Earth’s ecosystem has never before been exposed to such a high rate of change.

• Second, the equally clearly presented uncertainties. Decades could in fact pass before scientists can claim to fully understand whether a change due to human activities actually occurred or not.

• Third, the inertia of the climate. Once knowledge is at hand, further change is already unavoidable.

• Fourth, the uncertain, perhaps even unpredictable but extremely worrisome consequences of a possible climate change – in particular for developing countries.

These four impressions alone are sufficient to state the unique challenge you have presented to us. No generation of political leaders has ever been presented with a similar task.

The chairperson of the meeting was professor Bert Bolin – a Swedish scientist who was famous, not only for his role as a founder of the IPCC, but also for participating in the first numerical weather forecast and for successfully forecasting the rise of carbon dioxide in the atmosphere as a result of fossil fuel burning.

Here is Bolin’s own statement at the same meeting:

We are, however, confronted with a dilemma which is not easily resolved. The uncertainty of the predictions about future changes of climate and associated impacts are considerable and it does not seem likely that much more accurate predictions will be available for quite some time. The question then being asked by some is: Is it really justified to prepare for actions already now with the aim to slow down the build-up of greenhouse gases in the atmosphere – why not wait until our knowledge is more accurate?

My answer is: We need to reach agreements on some action programmes soon [because]:

• We know for sure that the greenhouse gases are increasing.

• There will be a change of climate, even though we do not know its magnitude very well, nor how rapidly it will come about.

• The inertia of the climate system delays and conceal the climate change that well may be on the way, but does not prevent them from occurring.

• Increased concentrations of greenhouse gases that may occur in the future will return to preindustrial levels slowly.

The crucial question becomes: How much of a climate change is going to be acceptable, whatever we may mean by the word acceptable?

The result of this dialogue between scientists and politicians is best exemplified by the crystal-clear wording in the outcome of the Sundsvall meeting – the first assessment report of the IPCC:

We are certain [that] emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases carbon dioxide, methane, chlorofluorocarbons and nitrous oxide [and that] these increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth’s surface.

The elegance of this statement is that it was made by scientists and politicians together. This was, and is, the purpose of the IPCC. It is a bridge between science and policy – a bridge that guided the contents of the Paris Agreement – a globally accepted benchmark against which we can measure our successes and failures.

I would like to share two “take home” messages from this story:

For politicians: Please seek comfort in the words of Mr. Carlsson. Especially in his acknowledgement of the enormity of the challenge politicians are facing. He did not claim to have all of the answers. Nor did he seek an easy way out by denying the science. He engaged in constructive and respectful dialogue with the scientific community and in doing so, he contributed towards finding a way forward. The climate crisis is a call for political greatness. Please rise to that call.

For Swedes: With the IPCC – a bridge between science and policy – as a part of our legacy: How can we claim that our small country can make no difference?

The second story begins outside of the Swedish parliament – 28 years later on – on August 20, 2018.

This was when the “youth-led and -organised global climate strike movement” – Fridays for Future started – “when 15-year-old Greta Thunberg began a school strike for climate” …

In the three weeks leading up to the Swedish election, [Greta Thunberg] sat outside Swedish Parliament every school day, demanding urgent action on the climate crisis. She was tired of society’s unwillingness to see the climate crisis for what it is: a crisis.

Thirteen months later – on September 20, 2019 – more than 4 million people took to the streets for one of the manifestations of all time.

Sometimes, people ask me what happened to the youth climate movement. My answer is straightforward – what happened is still happening.

A simple search using “Google trends” makes clear that the success of the youth climate movement is still ongoing.

This plot shows clearly that public awareness of the climate crisis rose massively (the vertical scale is relative) in conjunction with the climate strike on September 20, 2019, and that this rise of public awareness was not just a “blip” but a sustained increase of public awareness that has continued at similar levels since then.

This plot elegantly qualifies the statement made by Fridays for Future on their strike statistics page.

In just over a year, from one solitary school striking girl, Greta Thunberg, to one of the biggest manifestations of all time.

History is written here.

Once again, I would like to share two “take home” messages from this story:

For the youth who created Fridays for Future: Please feel proud of what you have done. However hard this must be when we, the adult world, continue to fail you (and ourselves). The climate strikes of 2019 and beyond are among the most successful public awareness campaigns of all time. You wrote history.

For Swedes: With not only IPCC but also the youth climate movement as parts of our legacy: How can we claim that our small country can make no difference?

If you have read this far, I ask you once more to think about your own country (or place) and its successes, and how you might use them to instil a sense of pride and inspire climate action.

The year before 9/11, I had visited the twin towers with my beloved aunt. I remember the beautiful skyscape of New York City. I remember pondering on the fact that the tower I was standing atop was taller than the first mountain I climbed – Meall Gorm (a Gaelic name that speaks of a hill that turns blue as the shadows of evening fall upon it, and that has been rounded by the last glaciation).

I was on a commuter train between my university town, Uppsala, and my home town, Stockholm, when I learned that one of the towers had been hit by a plane. And then the other one. And then they fell. Both of them. And one day later, came the photograph of the falling man. He was one of the 2753 people who died there.

The World Trade Center may have been a symbol of the economic system that is crushing nature, but every person who died there was somebody’s loved one and each of those somebodies was left broken hearted. Therefore, on September 11, every year, I say a silent prayer for them all. It is my feeble attempt to share their sorrow.

Today — September 11 — 24 years later, a peaceful manifestation was organised by climate and church organisations of Stockholm. It was a march of sorrow for the climate (sorgmarsch över klimatet).

It can be hard to see parallels between the immediate sorrow of 2753 people losing their lives in the twin towers, and the seemingly far away and abstract sorrow of the climate crisis. But there are parallels, brutally real ones — even if it is our children, not ourselves, who will become the firefighters of the climate crisis. They have no choice. By acknowledging such parallels and allowing them to touch our hearts, we can be empowered to act, so that we create the hope that we so long for in these darkening times.

These were my thoughts when I tried to join the march of sorrow for the climate on September 11, 2025.

I had spent the afternoon with my students exploring a chapter of the history of science that played out in my hometown nearly four hundred years ago. I had shared what I knew about Queen Kristina of Sweden and about how her pursuit of knowledge had shaped the thinking of one of the greatest philosophers of all time, René Descartes. As the rain began to fall, I had taken them to the French philosopher’s last residence — von der Lindeska huset — at the Corn Market in the Old Town, where he died of infleunza on February 12, 1650. And as the wind gained speed, I went with them to the churchyard where he was buried alongside the city’s orphans on the outskirts of the city. And there, I took them indoors, out of the rain, to see the Cartesian Monument which depicts an angel revealing a globe from a veil of darkness — a symbol of Descartes’ pursuit of truth that is certain — and to the enlightenment that sculpted the pathway along which we now walk.

Some students went home after we visited the church, but a group of them joined me for the march.

But we didn’t find it.

The march had been rerouted because of the storm that was now raging across the city. Instead of winding its way through the city streets to Haymarket, the march went directly along Harbour Road to the Church of Saint Clara.

This was where we finally found the marchers of sorrow. There was 620 of them. The church was at full capacity. The doorman allowed us to enter. Myself, because I had the privilege of speaking for these beautiful people. My students, because he is kind person, for which I am truly thankful.

Because I was a speaker, I was ushered to the front, separating me from my students, which did not feel right. But at the front, I sat next to a priest who has cared for me in the past. I felt safe.

My speech was the last one. Before it was my turn, my good friend Petter Kallioinen played a beautiful tune together with Åsa Larsson, who had earlier filled the four-hundred-year-old church with the powerful melody of “kulning” – an ancient Swedish herding call.

The Bishop of Stockholm spoke before me. He reflected on how long that ancient church had been there, and on what the Earth would be like that far again in the future. Sadly, I know the answer to that question: If we carry on as we are doing, four hundred years from now, what remains of our species risks witnessing a sixth mass extinction of our own making. This brutal reality was vocalized by a choir who sung “No Birds in the Air, No Fish in the Sea” and by the priest who cared for me, when she spoke about the small creatures and how they are suffering as climate zones race around the globe at speeds not witnessed before.

And then it was my turn to speak. I did not speak about the twin towers. I thought about it, but it is not my story to tell. Instead, I sought other ways of conveying immediacy. Ways that I can relate to, so that I can convey them with feeling.

I spoke in Swedish, but I have translated my speech so that I can share it with you. It is similar to, but not the same as, the speech I gave for the Rebel Mothers on August 22, 2025.

(Det finns på svenska längs ner).

“The new coronavirus has put our country, our society, and us as human beings to the test. Each of us must prepare ourselves mentally for what lies ahead. The virus is spreading widely in Sweden. More people will fall ill. More families will be forced to say a final farewell to someone they love. The only way we can get through this is by facing the crisis together — as a society where everyone takes responsibility.”

Do you remember Prime Minister Stefan Löfven’s address to the nation on March 22, 2020?

At that moment, we had crisis awareness. Before there was a vaccine, we did the best we could. We stayed at home. We kept our distance. We washed our hands. And we saved lives.

We must approach the climate crisis in the same way — with crisis awareness.
Cut our carbon dioxide emissions. Care for nature. Capture carbon dioxide in the ground. And once again, we will save lives.

Why?

Because when we emit carbon dioxide, we strengthen the greenhouse effect.

The greenhouse effect has a built-in safety mechanism that keeps Earth from overheating.

Scientists call it weathering — When rocks break down into clay, carbon dioxide is sucked out of the air. That simple and beautiful process has regulated the climate for 3.5 billion years.

But by burning fossil fuels, we release carbon dioxide faster than weathering can remove it. And the excess carbon dioxide stays in the atmosphere until weather catches up – in 200,000 years.

That is why Earth’s temperature is rising.

• At 1.5 degrees of warming, one in fifty species goes extinct.

• At 2.7 degrees, one in twenty species disappears.

That is why we must face the climate crisis with crisis awareness.

---

Let me share two metaphors with you. One about sorrow and one about hope.

On sorrow

A young man is standing on a beach, gazing out at the sea. Beside him are his wife and their three daughters. The youngest is playing in the sand.

In front of him are granite skerries, partly swathed by sand. Beyond them, the ocean. Far on the horizon, a thin white line.

To the man’s right, a boy runs to a pool between the skerries, where fish are trapped.

The fish are trapped because something is terribly wrong. The skerries should be under water. The white line on the horizon is the tsunami.

Why did the man let his child play in the sand with a tsunami approaching?

The answer is simple: he didn’t know it was a tsunami. How could he?

From the shoreline, the horizon is about five kilometres away. A tsunami grows taller as it nears land. He would not have known how big it was. How close it was.

But the signs were there. The save had receded from the beach. A wave was visible on the horizon.

And the signs are here:

• Heatwaves. Drought. Floods. Wildfires.

• Melting ice. Rising seas.

• Plants and animals are dying.

All the signs are here. Yet we stand and watch while our children play in the sand in front of the tsunami wave of the climate crisis.

We must face the climate crisis with crisis awareness.

On hope

Now, may I take you to Vättern — Sweden’s second largest lake. Its southern end is occupied by a single island — Visingsö. On that island, at its southern end, one finds an oak forest. It is magnificent. The oaks were planted in 1831 to ensure that there would be sufficient timber for building future ships.

When harvest time came in 1975, the oaks were left standing — because ships were built of steel.

Imagine being the person who planted the acorns that would become those might oaks. Would you ever have believed that ships of the future would be made of metal? Probably not. You would have expected the expected — ships would always be made of wood.

And that is what we do today: we expect the economic system, the legal system, the political system to stay the same.

But history shows us that it is the unexpected that comes to pass.

Imagine once more that you planted those acorns, knowing they would one day become mighty oaks. You would not have planted them for yourself. You would have known you would not live to see them harvested.

And yet, you would have planted them anyway — not for yourself, but for future generations.

And that is exactly how we must face the climate crisis.

We act not for ourselves, but for our children, for the children who have not yet been born, and for all the living things that will one day share creation with them

And when I finished speaking, I thanked my audience for being among the cherished ones who listen to the science. Then, I stepped down from the stage with tears in my eyes, for the climate, for my audience, and for the love that was lost as the twin towers fell to the ground 24 years ago.

”Det nya coronaviruset prövar vårt land, vårt samhälle och oss som medmänniskor. Nu behöver varje person förbereda sig mentalt på vad som väntar. Vi har en allmän smittspridning i Sverige. Fler kommer att bli sjuka. Fler kommer tvingas säga ett sista farväl till en älskad. Enda sättet att klara av detta är att vi möter krisen som ett samhälle där alla tar ansvar …”

Minns du Stefan Löfvens tal till nationen den 22 mars 2020?

Då hade vi krisinsikt. Innan vaccinen gjorde vi så gott vi kunde. Vi stannade hemma. Vi höll avstånd. Vi tvättade händerna. Och vi räddade liv.

Vi måste möta klimatkrisen på samma sätt. Med krisinsikt.

Dra ner på koldioxidutsläppen. Ta hand om naturen. Fånga koldioxid i berggrunden. Och då kommer vi att rädda liv.

Varför?

Genom att släppa ut koldioxid förstärker vi växthuseffekten.

Växthuseffekten har en inbyggd säkerhetsmekanism. Den gör att klimatet inte blir för varmt.

Forskare kallar denna säkerhetsmekanism för vittring.

När vanliga stenar vittrar till lera sugs koldioxid upp ur luften, och på så vis har klimatet reglerats i 3,5 miljarder år.

Men genom att förbränna fossila bränslen släpper vi ut koldioxid snabbare än vittringen hinner suga upp den.

Och koldioxiden stannar i luften tills vittringen hinner i kapp om 200 000 år.

Därför stiger jordens temperatur.

• Vid 1,5 grader dör 1 av 50 arter ut.

• Vid 2,7 grader dör 1 av 20 arter ut.

Därför måste vi möta klimatkrisen med krisinsikt.

---

Låt mig dela två metaforer med dig. En om sorg och en om hopp.

Om sorg

En ung man står på en strand och tittar ut mot havet. Vid hans sida står hans fru och deras tre döttrar. Den yngsta leker i sanden.

Framför honom syns granithällar omgivna av sand. Bortom dem syns havet. Långt ute anar man en tunn vit rand på horisonten.

Till höger om mannen springer en ung pojke fram till en pöl mellan hällarna där fiskar har fastnat.

De har fastnat därför att allt är fel. Hällarna borde ligga under vattenytan. Den vita randen på horisonten är tsunamin.

Varför lät mannen barnet leka i sanden framför en tsunami?

Svaret är enkelt: Han visste inte att det var en tsunami.

Hur skulle han veta?

När man står vid vattnet ligger horisonten ungefär fem kilometer bort. En tsunami växer när den närmar sig land. Man har ingen uppfattning om hur stor den är, eller hur nära den är.

Men alla tecken fanns. Vattnet hade dragit sig tillbaka från stranden. Det fanns en våg på horisonten.

Och alla tecken finns.

• Värmeböljor. Torka. Översvämningar. Skogsbränder.

• Isen smälter. Havet stiger.

• Djur och växter dör ut.

Alla tecken finns men vi tittar på medan våra barn leker i sanden framför klimatkrisens tsunamivåg.

Vi måste möta klimatkrisen med krisinsikt.

Om hopp

Du befinner dig i ekskogen på Visingsö. Ekarna planterades 1831 för att det i framtiden skulle finnas virke till att bygga skepp.

När ekarna skulle skördas, 1975, lät man dem stå kvar. Numera byggs skepp i metall.

Tänk att du hade varit den som planterade frön som en dag skulle bli dessa ekar. Skulle du ha trott att framtidens skepp skulle byggas i metall?

Antagligen inte. Du skulle ha förväntat dig det förväntade — Att skepp fortfarande skulle byggas i virke.

Och det är precis det vi gör nu. Vi förväntar oss att det ekonomiska systemet, det juridiska systemet, det politiska systemet — ska förbli detsamma.

Men historien berättar för oss att det är det oförväntade som faktiskt sker.

Tänk en gång till att du hade planterade frön som en dag skulle bli dessa mäktiga ekar.

Du hade inte planterat dem för dig själv. Du hade vetat att du inte skulle finnas kvar när ekarna skulle skördas.

Men du hade planterat det ändå. Inte för dig själv. Utan för framtida generationer.

Och så är det när vi löser klimatkrisen.

Vi löser klimatkrisen för våra barn, för barnen som ännu inte är födda, och för allt levande som en dag ska dela skapelsen med dem.