How did the CO2 concentration in Earth’s atmosphere once decrease?

by David Armstrong McKay and Paul Glantz

During the Cenozoic era – i.e. 66 million years ago until today – the Earth’s climate has shifted from a hot ‘Greenhouse’ state with no polar ice sheets to the cool ‘Icehouse’ state with polar ice sheets that we’re in today. This is revealed by palaeorecords from ancient single-celled marine organisms such as ‘benthic foraminifera’ that provide a geochemical record of past temperatures, ice sheets, and CO2 levels [Zachos et al., 2001b, 2008]. During this time atmospheric CO2 has gradually declined from ~1000 ppm in the Eocene to below ~300 ppm during the late Miocene [Pearson and Palmer, 2000; Royer et al., 2001; Beerling and Royer, 2011]. This decline has been hypothesised to be the result of either declining volcanic emissions as the rate at which new ocean crust forms has slowed, increased rates of silicate rock weathering (a chemical reaction which draws down CO2) due to the tectonic uplift of the Himalayas, or increased burial of carbon in seafloor sediment as a result of either greater plankton abundance in the ocean or carbon being better preserved in sediments [Berner, 1991; Larson, 1991; Raymo and Ruddiman, 1992; Raymo, 1994; Derry and France-Lanord, 1996; France-Lanord and Derry, 1997; Kump and Arthur, 1997; Royer et al., 2004a; Kent and Muttoni, 2008, 2013; Lefebvre et al., 2013].

More recently (the last ~1-2.5 million years), ice core and geochemical data show that CO2 levels have varied between ~180 ppm in cold glacials (a.k.a. “ice ages”) and ~280-300 ppm in warmer interglacials [Sigman et al., 2010; Lisiecki & Raymo, 2005]. The drivers of these changes can be explained by the theory by Milutin Milanković, who found that significant changes in solar radiation received by the Earth have occurred during this period as a result of gradual changes in the Earth’s orbit (known as Milankovitch cycles). This in turn affected the uptake and release of CO2 between the atmosphere and oceans (as more CO2 can dissolve in to colder water, so a cooler planet means more CO2 is taken up by the oceans, and vice versa). Thus, natural changes in the temperature during this period probably determined changes in atmospheric CO2 (as well as in CH4) and the greenhouse effect, which acted as an amplifying feedback to those changes. Today though, it is the release of greenhouse gases from humans burning fossil fuels that are warming both the atmosphere and the ocean. Around a quarter of man-made CO2 has been taken up by the ocean so far, acting as a stabilising feedback on warming, but the rate of this uptake will decrease as the oceans get warmer making even more anthropogenic CO2 stay in the atmosphere.


Thank you to Emil V. Nilsson for starting the question and Magnus Carlbring for linking it to Researchers’ Desk.


Armstrong Mckay, David (2015) Investigating the drivers of perturbations to the Cenozoic carbon-climate system. University of Southampton, Ocean & Earth Science, Doctoral Thesis, 185pp.

Wednesday Zoom Lunch lesson

This week we have invited Ina-Maria Shikongo to talk at the Zoom lunch. Nicholas Eliades will be moderating:

”Undisturbed Under Paradise”

What happens in the Kavango Delta won’t stay in Kavango. As the WG III of IPCC just released and stated clearer than ever we must hurry up to phase out all fossil fuel, the Canadian oil-and gas company ReconAfrica will exploit the fragile and magic land of the Kavango Delta. Listen to Ina- Marias struggle to stop this new Ecocide.

Time: Mar 30, 2022 12:00 Stockholm

Hot potato session on “The tragedy of climate change science”

“The science-society contract is broken.” is the opening of the latest article by Bruce C. Glavovic, Timothy F. Smith and Iain White and it invited us at researchers desk this week to pause and think together with the authors: What kind of scientific activity is meaningful to enable human society to learn, adapt and transform human activities as the climate crisis becomes recognizable today, and when looking at the full picture – Earth? It is indeed a fully-fledged, global tragedy we are talking about: Against better knowledge (IPCC reporting), humanity is driving the crisis, meaning that the most powerful actions you could expect (e.g. covid recovery funds) are accelerating on the same old path (bouncing back) rather than turning around (rebuild and regenerate human relations to our shared environment).

So, if the above-mentioned contract works as a metaphor for the science-society interface, this means that researchers are paid by tax money to think freely and develop the best possible science around the questions they are appointed for by the governments in the world. In return, researchers could expect that this knowledge is acted upon. What if, as with climate science, this exploding knowledge on our climate system and scientific support for the society is ending “in the void” for decades?

Where and how can we re-politicize science and address not only the failure to act and explanations for why this happen but also demonstrate where the seeds are for an alternative course of action? What kind of moratorium would invite sufficiently powerful groups to rethink and engage with the discourse and transition towards a sustainable pathway?

This is an invitation for everyone to engage with us, with each other, and question the share of responsibilities we all have to learn and transform our lifestyles. This is about renegotiating the contracts we are embedded in with policy, business and culture. Today we leave this discussion (recording is online) with a few threads for the inspired ones:

While more science does not lead necessarily to more action – there are still several scientific avenues which are promising to focus on leverage points for change:

  • The IPCC report on mitigation is based on conventional assumptions and models like social welfare being dependent on a eternally growing market – which are proven to reinforce inequality rather than sustainable well-being. Mitigation based on post-growth economy is possible and rather a question of will and power redistribution (see article by Hickel et al. 2021).
  • The need and opportunities for an incremental but radically different development of how we institutionalize values, which are underlying to all our societal functions, become apparent in the book by Maja Göpel “The great mindshift”.
  • No single person is deliberately destroying our planet’s climate – but humans are bound to act on much smaller spatial and temporal scales than the technology is providing access to few people (through cars, planes, cement, plastics). When seeing Earth as a system where human health is dependent on a healthy environment, we begin to grasp that there is no deliberate, collective, and global governance which is taking care of this human-environmental relationship at the core. Another way looking at this big picture is like watching a flock of starlings who group in amazingly beautiful formations – with no single bird driving it. While there is no single entity able to drive humanities course of action, at the same time everyone has influence to shape actions. This is called self organization in a complex adaptive system. In the discussion about the climate crisis is now the tragedy emerging or flooding over us – how do we collaborate under this ‘flood’, embrace a more humble, systemic view and ’walk the talk’ of sustainable and globally equitable lifestyle?

In conclusion for today: We agree to disagree where we see the next steps. Some of us doubt that there is this one attainable vision but there are tangible tools for sustainability we know how they work. Others see the vision of sustainability future more clearly, just barriers and opportunities on the way. Let’s go, at least the direction is clear (not the highway …).

Not to mention all the Zoom Lectures we’ve given since Corona broke out.

Debunking myths around Net-zero and climate offsets

Conversations in connection with an Researches Desk lecture sparked collective writing by 23 RD affiliated experts and scientists of one of the most impactful op-eds debunking the myths of net-zero targets and offsets. The article was first published in Sweden at DN Debatt (4 Dec 20020) and then internationally through a translated version at Climate Home News (11 Dec 2020) with further endorsements by an additional 18 international scientists. The article was spread widely and for a long time the most read feature at Climate Home News. It has clearly helped shape the discourse around this important topic. Similar views were for example recently voiced by a former IPCC chair in a widely acclaimed article in The Conversation.

Countering the Scopex solar geoengineering project set for Kiruna, Northern Sweden

After unexpected announcement of geo-engineering research plans for Sweden by a Harvard research group in December 2020, Researchers Desk provided a “Hot potato session” for its members to get informed by international and Swedish scientists about this controversial issue. This lay the ground for synchronised actions and numerous media appearances by Swedish and international scientists (see for example SvD,  Aktuellt, and Klotet) and also direct engagement with the Swedish Space Corporation. Members of Researchers Desk also played key roles in interactions with and mobilisation of civil society as well as the Saami indiengeous people. After combined, concerted pressure by these different stakeholder groups, the Swedish Space Corporation announced on 31 March 2021 that it would cancel the flight.  

SOLAR GEOENGINEERING: Warnings from Scientists, Indigenous Peoples, Youth, and Climate Activists

Wednesday, June 9, 2021

11 am – 1:30 EDT /  5 pm – 6:30 pm CET

Facebook Live

Event Overview

Once relegated to the fringe of the climate debate, ideas to use solar geoengineering to mask rising temperatures are receiving increasing attention from some scientists, governments, and the media. Catchy headlines about silver bullet fixes often downplay the real and profound risks that such technologies pose — including potentially devastating harm to ecosystems, increased droughts and extreme weather events, and the disruption of food production for millions of people around the world. These impacts would affect all of us, but would fall most heavily on Indigenous peoples and communities in the Global South. The illusion of a technological quick fix could also delay real climate solutions, putting both present and future generations at risk.

On June 9th, leading scientists, Indigenous leaders, youth and climate activists discuss the growing risks and unequal impacts of solar geoengineering and explore how climate action is possible without dangerous technological fixes. 

Speakers include: Michael Mann, Raymond Pierrehumbert, and Jennie Stephens. Along with leading voices from movements, Indigenous peoples and the Global South: Tom Goldtooth, Naomi Klein, Åsa Larsson Blind, Bill McKibben, Vandana Shiva, and Greta Thunberg. 

The event is organized by the Center for International Environmental Law (CIEL), The ETC Group, Heinrich Böll Foundation, Indigenous Environmental Network, Saami Council, WhatNext?, in collaboration with the Hands Off Mother Earth! (HOME) Campaign, the Swedish Stop Scopex Network, and Researchers Desk.
The event will be hosted via Facebook Live. To connect your organization’s page to the livestream, please contact Cate Bonacini at the Center for International Environmental Law or Laura Dunn at The ETC Group.

Zoom Lunch with Johan Rockström

A personal talk with Johan Rockström, Friday the 28/5-21. Welcome to join!

Topic: Lunch med Rockström
Time: May 28, 2021 12:00 Stockholm

Join Zoom Meeting

Meeting ID: 663 985 6178

Happy 2 year birthday to @Researchers Desk!

A lot has happened since some of us realised we should get all those bold researchers to talk to people outside university and in a respectful and pedagogic way about the direness of CC and biodiversity loss.

Thank you all researchers for joining, for your courage to say it like it is, stepping out of your comfort zones to talk to people out on the streets, in schools, at Zoom and elsewhere. Let’s hope this year we’ll be let into some new spaces.

What a Treasure Chest of knowledge RD has become since then!

Thank you Fridays For Future Greta Thunberg #Climatestrike #FFFture, for your support and letting us hang with you on your Global Strikes, and learn from each other at Mynttorget. You bring us hope with your guts, intelligence and clever actions!

This is us from 24/5 2019 to 24/5 2021

May 24 2019: A ”Researchers Desk” was set up at the Fridays For Future Greta Thunberg #Climatestrike #FFF Global Climate Strike at Kungsträdgården, Stockholm. Its purpose was for climate researchers to talk to and answer questions from the general public. RD held 8 Street Lectures. Many thanks to the first 10 researchers present.

June 14: A ”Researchers Desk” was set up at outside the Swedish Parliament, Stockholm. Its purpose was for climate researchers to talk to and answer questions from the general public.

June 17 – August 19: A ”Researchers Desk” was set up at Sergels torg, Stockholm every Monday between 11:30 and 13:30. Its purpose was for climate researchers to talk to and answer questions from the general public.

August 31: A ”Researchers Desk” was set up at the Climate Festival at Vinterviken, Stockholm. Its purpose was for climate researchers to talk to and answers questions from the general public. Thank you Cecilia Holm for organising that super event!

September 6 – December 20: Researchers Desk coordinated street lectures by climate scientists outside the Swedish parliament every Friday. The purpose of these lectures was to provide school strikers with more knowledge about climate.

September 12-13: Researchers desk coordinated school lectures was held for 1250 high school students at ABF House in Stockholm, together with Edit Liedberg and Iris Elmér and Karin Ester Jacobson

September 17: Researchers Desk coordinated together with FFF a school lecture was held for 300 high school students at Värmdö High School in Stockholm. Go Edit Liedberg!

September 20: A ”Researchers Desk” was set up at the @FFF Global Climate Strike at Medborgarplatsen, Stockholm. Its purpose was for climate researchers to talk to and answer questions from the general public. RD was present with 18 researchers.

September 23-24: Researchers Desk coordinated school lectures at Täby Enskilda High School in Stockholm.

September 27: A ”Researchers Desk” was set up at the @FFF Global Climate Strike at Kungsträdgården, Stockholm. Its purpose was for climate researchers to talk to and answer questions from the general public. Researchers Desk, present in the demonstration as well with our desk and 32 researchers

October 3: Researchers Desk was represented at the Gordon Goodman Memorial Lecture at the Royal Swedish Academy Agriculture.

October 5-6: Researchers Desk coordinated lectures at the @PUSH conference on Väddö near Stockholm.

October 22: Researchers Desk held a presentation for Stockholm Resilience Centre.

November 12: Researchers Desk coordinated a school lecture at Estetiska High School in Stockholm.

November 26: Researchers Desk coordinated a lecture for Färnebo folkhögskola in Gävle.

November 28: Researchers Desk coordinated a school lecture at Viktor Rydberg Secondary School in Djursholm.

November 29: ”Researchers Desk” was set up at the FFF Global Climate Strikes in Norrtälje, Uppsala and Gothenburg.

November 30: Researchers Desk coordinated a lecture for the network KlimatSverige

December 2: A ”Researchers Desk” was present at Finland Institute. The event was attended by Princess Victoria of Sweden and @Isabella Lövin Environment minister of Sweden.

December 3 : Researchers Desk at Södra Latin with Paul Glantz to discuss climate with students and teachers.

December 6: A ”Researchers Desk” was set up at the FFF Global Climate Strikes in Rinkeby, a suburb of Stockholm. Researchers Desk present with 7 researchers in the demonstration and with our desk


10/1: Aaron Tuckey x2 Street lecture, Mynttorget and Sagerska
17/1: Paul Glantz x2 Street Lecture, Mynttorget and Sagerska
24/1: Niclas Hällström x2 Street Lecture Mynttorget & Sagerska
27/1: Alasdair Skelton at Västbergaskolan. A talk for the teachers and staff. Lecture for parents and pupils cancelled due to Corona.
31/1: Hans Landeström, Street Lecture Mynttorget
7/2: Isak Svensson x2 Street Lecture Mynttorget and Sagerska
14/2: FFF Global March Medborgarplatsen, RD present with 10 researchers
21/2: Kali Andersson, Climate Psychologist, Street Lecture, Mynttorget
28/2: Jamila Haider x 2 Street Lecture Mynttorget and Sagerska on the importance of seeds
6/3: Roxana Cremer x 2 Street Lecture FFF Mynttorget and Sagerska
13/3: Maria Johansson Street Lecture FFF Mynttorget on Climate Compensation

Zoom Lectures Due to Corona. Thank you Iris Elmér and Martin Hedberg for your excellent moderating (miss you Very much!)

18/3: Martin Hedberg on Extreme weather patterns in the tracks of CC, moderated by Iris Elmér
20/3: Alasdair Skelton, on this is CC and what causes it
25/3: Tim Daw, on Fishery impacts
1/4: Somya Joshi on CC policies and governance
3/4: Maria Johansson, why Climate Compensation doesn’t work
8/4: Niclas Hällström, Fair shares 10/4: My Sellberg, Romina Martin and Paul Glantz discuss CC
15/4: Mathias Lindahl, Kan konsumtionen bli klimatneutral?
17/4: Paul Glantz, CC in the Arctic
22/4: Ola Kalén, Can one mix the role of researcher and activist?
24/4: My Sellberg, Small seeds of a positive future
29/4: Hans Landeström, Activism and psychological health
1/ 5: Alexander Crawford and Jennifer Hinton discuss economy and CC
6/5: Neil Powell,
8/5: Martin Hultman, Ecological Masculinities
13/5: Magnus Nilsson, EU politics on CC
15/5: Daniel Lindwall, Going through a chapter of his book “Upphettning”
20/5: Sebastian Kirppu, Damaging Swedish forestry practices
22/5 Garry Peterson, Explaining IPBES
27/5: Nina von Uexkull, Peace and conflict in the tracks of CC
29/5: Isak Stoddard, Carbon budgets
3/6: Martin Hedberg
5/6: Alasdair Skelton
10/6: My Schüldt, Thinking Environments
12/6: Amanda Wood: Future food
17/6: Tina-Marie Qwiberg, Documentary films
24/6: Åsa Kasimir, Carbon Storage in forests and peatland
26/6: Pella Thiel, End Ecocide

1/9: Climate Communication #1 : Johan Rockström, Per Espen Stoknes, Björn Wiman, Tina-Marie Qwiberg & Maria Wolrath Söderberg / Climate communication

11/9 Mynttorget, Street : Freddie Schenk / “A new synthesis of Earth’s Climate Sensitivity and why we are running out of time”
16/9: Dana Skelly, California fires

18/9 Mynttorget Street / Alasdair Skelton, Climate compensation

19/9 Kulturhuset : Isak Stoddard, Alasdair Skelton, Elin Röös, Jennifer Hinton/ Carbon budgets, Future food production, New economics and Climate compensation

25/9 FFF Global Street/ City hall : Miriam Huitric / Paul, Magnuz, Martin, Caroline, Maria & David 7/10 : Maria Johansson / Klimatkompensation – Fungerar det?
9/10 Mynttorget Street : Jojo Mehta / End Ecocide
14/10: Dr Lan Wang / “What is the role of the water cycle for rainforest resilience?”
16/10 Mynttorget Street : Amanda Wood / Why food is such a big part of the environmental crisis and what we can do to fix our food systems.
21/10: Amanda Wood / Can we feed a future population of 10 billion a healthy diet within the planetary boundaries?
23/10 Mynttorget Street : Jakob Trollbäck / Hur tänker jag kring symboler och kommunikation
28/10: Vala Ragnarsdottir / “Crafting the regenerative economy for wellbeing of people and planet”
30/10 Mynttorget Street : Henrik Lagerlund / Matens filosofi
4/11 : Hans Landeström
6/11 Mynttorget Street : Tim Daw & Beatrice Crona

10/11 : Hot Potato – Biofuel vs. Fossil fuel with Stig-Olof Holm. A talk within the network to learn from each other

11/11 : Stig-Olof Holm / Vårt svenska skogsbruk

17/11: Climate Communication #2, Jytte Guteland, Jakob Trollbäck, Kimberly Nicholas and Björne Larsson

18/11: Niclas Hällström on “Net 0” 20/11: Ola Kalén, FFF
20/11: Alasdair Skelton, Cinema Zita, premiere of Greta the movie
20/11 Zita Cinema : Alasdair /Greta the movie première
22/11 Bio Roy Cinema : Martin Hultman och Ola Kalén / cancelled due to corona restrictions
25/11: Cinema Kapsylen: Erik Huss / Cancelled due to Corona
25/11: Caroline Greiser, interactive talk on forest microclimate
27/11: Alasdair Skelton, FFF
2/12: Pascoe Sabido, Fossil Lobbyism in the EU
4/12: Isak Stoddard, FFF

Networking, discussions and lectures within RD led to the writing of a very appreciated article by 23 RD researchers on myths about Net Zero targets and Climate Compensation. The article later got translated and signed by another 18 researchers.

9/12: Niclas Hällström, Fossil Non Treaty
16/12: Duncan Mc Laren
6/1: Per Ribbing, Electrify everything with solar
13/1: Ramanathan Veerabhadran, moderated by Sophia Axelsson FFF
20/1: Flora Hajdu, Carbon Forestry
27/1: Ola Kalén, Sea level rise
3/2: Peter Stenvinkel, Biomimetic

3/2: Hot Potato: Raymond Pierrehumbert, Albedo hacking, A talk within the network to learn from each other
This resulted in articles, meetings with politicians and finally the halting of the very controversial experiment “Albedo hacking”

10/2: Bo Becker, Can our investments influence a green new deal?
17/2: Erik Pihl, Future Earths 10 points
24/2: Tina Nyfors, Ecological Sufficiency
3/3: A talk about the forest, David Thurfjell and Björne Larsson
10/3: Alasdair Skelton on Immediacy
17/3: Frederik Schenk, Gulf stream slow down
19/3: Charlie Gardener, what role for researchers in CC

19/3: FFF Global Digital Action day. RD sent postcards with your quotes to politicians

31/3: Erik Huss, why we must take care of the glaciers
14/4: Thomas Dahlgren, Why we must understand life in the deep ocean
17/4: Alasdair giving a lecture to PUSH
21/4: We Hope to get: Andreas FFF, how does it feel being young and aware of CC
28/4: Maria Niemi Ki, What did we really need, lessons from a year of Corona
⅗ : RD at Lund Hållbarhetsvecka med Alasdair, Stig Olof, Maria Johansson och Karin
5/5: Katherine Trebeck, moderated by Jennifer Hinton, WellBeing Economy
12/5: Kimberly Nicholas talks with Alasdair about her book “Under the sky we make”
19/5: Paul Glantz, the warming in northern Europe

Today Researchers desk consists of 76 researchers and experts ready to spread awareness on the Climate change and biodiversity loss. We believe everyone can contribute and take an important part of the solution – and that everyone is needed! Join us this Friday for a personal talk with Johan Rockström and with time for interactive Q&As. The more we know and understand, the better the solutions will be.

28/5: Johan Rockström, 2021 and COP26.

2/6: Paula Richter

9/6: Magnuz Engardt