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CO2 Newsletter CO2 Newsletter commentary

“It could be posts on social media today”: Ana Unruh Cohen on  the August-September 1980 CO2 Newsletter (Vol 1, No 6)

Ana Unruh Cohen, DPhil, is a climate scientist and policy expert who has served in various roles in Congress, the White House, and NGOs during her 25-year career kindly agreed to write a commentary on the CO2 Newsletter, Vol. 1, no. 6. You can read other commentaries – and issues – here.

It is April in Washington, DC as I review the ‘message in a bottle’ from 1980 that has washed up on my screen thanks to the diligence of Marc Hudson of All Our Yesterdays. Fittingly much of the August-September 1980 CO2 Newsletter Vol 1, No 6 is devoted to an April hearing that same year in the Senate Committee on Energy and Resources.

Twenty-five years ago—in the fall of 2001—I arrived in DC as a freshly-minted DPhil in Earth science ready for a new challenge in the halls of Congress. After almost 5 years in the UK in the somewhat cloistered life of a graduate student, I was aware of the climate politics playing out on the international stage around the Kyoto Protocol and what had come up in the 2000 U.S. presidential election campaign between Al Gore and the ultimate winner George W. Bush. I was ready to dive in with my climate knowledge and eager to find a way to advance climate policy. I had no idea that more than 20 years before Senators were hearing similar warnings about the risks of climate change and the need to shift our energy generation from fossil fuels to carbon-free sources like solar and nuclear power. During my time in DC, historians have done more work on the development of climate science and climate policy that has sparked my own curiosity. But it wasn’t until I opened this volume of the CO2 Newsletter that I learned about the April 1980 Senate hearing.

Opponents of policies that would curb fossil fuel use and address climate change try to make the concern about global heating seem like something new—or for those that call it a hoax, something newly made up—but as the CO2 Newsletter documents back in the spring of 1980 Senators were asking “what we politicians and Congress need to do” about the CO2 problem. This wasn’t a hearing to just explore the science though. The senators already understood that climate impacts and energy decisions were two sides of the same coin. They heard from climate science luminaries George Woodwell, Wally Broecker, and William Kellogg, but also about energy policy from Gordon MacDonald of the MITRE Corporation and David Rose of MIT. That day the senators heard predictions that proved accurate like it taking between 10 to 20 years before warming due to carbon dioxide would be detected against natural fluctuations. Fifteen years later, in 1995, the second IPCC Assessment Report concluded that “the balance of evidence suggests there is a discernible human influence on global climate.” Dr. Woodwell suggested the CO2 problem might be “the preeminent international issue in management of resources during the early decades of the next century.” The gathering of world leaders in Paris 2015 to hammer out the UNFCCC Paris Agreement lends weight to that prediction. 

In surveying the world in 2026, I’d argue that it is the most prevalent international resources issue, impacting energy, agricultural, biodiversity, immigration, and economic development around the world. One of the predictions from the 1980 hearing is still open: will the CO2 content of the atmosphere reach 500-600 ppm sometime in the first half of the 21st century? The answer to that depends on the twin focus of the Senate hearing, energy generation.

The energy debate in the Senate hearing, and captured in the rest of the CO2 Newsletter,  feels as if it could be posts on social media today—the promise of nuclear power, the risks of nuclear proliferation, the need for domestic energy security, the elevation of natural gas as a cleaner fossil fuel, and the energy paradigm shift of solar power. In 1980 the U.S. was recovering from the economic consequences of the OPEC oil embargo. Sadly in 2026, the world is suffering from the economic consequences of the U.S. joining Israel in bombing Iran and Iran’s subsequent retaliation to close the Strait of Hormuz to almost all ships. Both events force re-evaluation of energy policy for economic security that have implications for the CO2 problem.

Luckily, we now have lithium-ion batteries, and their competitors, rapidly expanding the scope of possibility for both energy security and curbing carbon dioxide pollution. Batteries are noticeably absent from the Senate hearing; understandably so since the first commercial lithium-ion batteries were not sold until 1991. They are opening up alternatives in transportation the Senators and the expert witnesses did not foresee and answering concerns about solar variability that were raised in the spring of 1980. The world is in a race to avoid the potential catastrophic impacts of the climate crisis that the CO2 Newsletter records. Coupling battery technology with wind and solar gives us some hope of avoiding the worst while enhancing energy security.

While the reporting on the Senate hearing captured most of my attention, this issue of the CO2 Newsletter reports on other important climate issues that we are still grappling with today including attribution of weather events, the melting of the Greenland ice sheet, and a report from the U.S. National Academy of Sciences on the “Economic and Social Aspects of Carbon Dioxide Increase” led by future Nobel-prize winning economist Thomas Schelling.

Looking back at the history of climate science and policy can trigger wistful thoughts of “what-if?” And relatable feelings of sadness about what we have lost and anger at fossil fuel and other vested interests that have fought to prevent climate action. Although it can be hard, we need to take the long-known climate science coupled with ever improving clean energy technologies and ask “what now?” We can never surrender our fight to curb carbon pollution and for clean energy to provide a future for all the people and amazing inhabitants of this one Earth. 

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CO2 Newsletter

“Can CO2-induced warming be detected yet?” C02 Newsletter Vol 1. no. 6, from 1980…

The sixth edition of the CO2 Newsletter, published bi-monthly by American geologist William N. Barbat between 1979 and 1982 is live. You can download a pdf and see the full text here.

The eight page issue has a front page story asking “Can CO2-induced warming be detected yet?” Barbat does a good job (as ever) in being fair and balanced. At one point he notes

“Madden and Ramanthan theorized that a CO2-induced warming may have been delayed a decade by ocean thermal inertia or has been compensated by a cooling due to other factors. They noted, however, that “uncertainties remain because our current knowledge of climate does not allow us to distinguish between changes due to CO2 and those not to CO2. In order to prove or disprove the existence of the theoretically predicted effects of increasing levels of CO2, it may be necessary to monitor several variables and formulate arguments based on physical as well as statistical grounds to minimize the effect of the many uncertainties involved.”


There’s also an editorial, (highlighting the April 1980 Senate hearings) feedback from readers, excerpts from recent reports and a concluding article “A need for rational answers about energy.”

It remains heart-breaking, of course. Barbat’s editorial begins

“The hearings of April 3, 1980, before the Senate Committee on Energy and Natural Resources on the Effects of Carbon Dioxide Buildup in the Atmosphere represent a step forward in introducing the CO2 problem into U.S. energy policy. Prominent scientists familiar with the CO2 problem were asked “what we politicians and Congress need to do” by Senator Dale Bumpers. Senator Paul E, Tsongas noted that “Current U.S. energy policy has long-term implications, and what we are going to have to figure out is how bad will those impacts be.”

In a day or two, another excellent commentary on the newsletter will be published. Also, I will do a better job of highlighting the individual articles/nuggets in the issue over the coming weeks, before Vol. 2, no. 1 is published.

As ever, if you have comments, suggestions, memories of reading the Newsletter when it was first published, do get in touch.

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CO2 Newsletter CO2 Newsletter articles

Front page news – “Broecker’s 6 meter rise does not appear unreasonable” – C02 Newsletter Vol. 1, no. 5

Here’s the front page story on the CO2 Newsletter for June-July 1980. You can find out more about the newsletter here.

We knew. We knew. Brave diligent people like William Barbat tried to amplify the science, connect the dots, connect the policymakers, the publics and the evidence.

A sense of urgency was introduced to the CO2-greenhouse problem July 30, 1979, when Wallace Broecker (Lamont-Doherty Geological Observatory) explained to the U.S. Senate Committee on Governmental Affairs, “We have good evidence that during the peak of the last interglacial period, the sea level did indeed stand 6 meters (20 feet) higher than it does now, and we don’t think the temperature of the globe was any more than 1 degree Celsius warmer than now.”

A 1 degree C warming is generally expected to be reached shortly after the turn of the century if the CO2 buildup continues as in the past, The energy scenario of F. Niehaus (International Atomic Energy Agency) which might halt a CO2-induced global warming just short of 1 degree C, as shown in the inset, would call for a rapid phase-out of fossil mostly by nuclear, This scenario was presented at the same Senate hearing. 

Broecker’s 6 meter rise (point ‘a’) does not appear unreasonable on a plot of temperatures vs. sea elevations ranging from ice ages to no-icecap conditions. Global average temperatures of 4 degrees to 5 degrees C cooler than now are shown for the ice ages, as used by Svante Arrhenius in his CO2 greenhouse model of 1896. Corresponding to these periods of maximum glacial advance are vestiges of shorelines 85 to 130 meters lower than now as shown by bar +b’. (Lag in destruction of the Laurentide ice sheet precludes

other equilibrium values for conditions cooler than now.)

An approximation of the pre-glacial global temperature as shown here 5. degrees C greater than now (point ‘c’) is derived from Eocene and early Oligocene subtropical and tropical sea-surface temperatures in the literature. These sea temperatures were based on oxygen isotope measurements made on shells of pelagic foraminifera which grew at that time,

Arrhenius had also judged that the average Arctic temperatures prior to the existence of ice sheets in that hemisphere were about 8 to 9 degrees C warmer than modern temperatures, based on observations of vegetation and animal life. Allowing for 3X to 4X polar amplification, this would correspond to an average global temperature 2 degrees to 3 degrees C warmer than now, which essentially matches the consensus of estimates for global warming which may accompany a CO2 doubling, Such a doubling is expected to be reached about 2025-2050 if growth of CO2 production continues its historical rise.

Because the West Antarctic icecap is believed by John Mercer (Institute of Polar Studies, Ohio State) to have formed at cooler temperatures than the Greenland icecap, the potential sea elevation corresponding to the absence of the Greenland ice is shown here as the sum of the rise if both icecaps were absent, that is, 12 meters higher than present. This 12 meter height – if valid can be considered to be a minimum value, for it is likely that the East Antarctic ice cap was smaller than its present size when global temperature was 2 degrees to 3 degrees C warmer.

No estimates have been published yet for how fast the Greenland ice sheet might disappear with a CO2 -induced warming, and much controversy still surrounds estimates of how fast the West Antarctic ice sheet may disappear due to a lack of precedents. If the CO2 buildup continues unabated, the  expected warming over the next half century may take place in about one-tenth the time that a similar temperature rise occurred about 10,3000 degrees before present, during which time sea level was about 0.2 to 0.3 meters per decade according to the compilations of Rhodes Fairbridge.

To illustrate the seriousness of a potential equilibrium with the warmness of a CO2 doubling, the Jefferson Memorial is depicted on the same elevation scale. For other comparisons, the absence of icecaps would correspond to sea level at the clock face of London’s Big Ben and up to the roadway of San Francisco’s Golden Gate Bridge.

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CO2 Newsletter

“A sense of urgency was introduced to the CO2-greenhouse problem” -CO2 Newsletter Vol. 1 no. 5

The fifth issue of the CO2 Newsletter, published bi-monthly by American geologist William N. Barbat between 1979 and 1982, is live. You can download a pdf and see the full text here.

The eight page issue has a front page story on testimony by Wally Broecker (famous oceanographer) in July 1979.

A sense of urgency was introduced to the CO2-greenhouse problem July 30, 1979, when Wallace Broecker (Lamont-Doherty Geological Observatory) explained to the U.S. Senate Committee on Governmental Affairs, “We have good evidence that during the peak of the last interglacial period, the sea level did indeed stand 6 meters (20 feet) higher than it does now, and we don’t think the temperature of the globe was any more than 1 degree Celsius warmer than now.”

There’s also an editorial, feedback from readers (including people at the UK Climatic Research Unit), excerpts from recent reports and a concluding article “Some Functions and Merits of Energy.

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CO2 Newsletter CO2 Newsletter commentary

“It is not knowledge we lack. What is missing is the courage to understand what we know and to draw conclusions.” Arwa Aburawa on the CO2 Newsletter…

Arwa Aburawa – photo by Edward Sogunro

Arwa Aburawa is a filmmaker whose work focuses on race, the environment, and the enduring legacies of colonialism.  www.arwaaburawa.co.uk

In his book ‘Exterminate All the Brutes’ (1), the writer Sven Lindqvist carefully and meticulously traces the European colonial legacy of extermination and genocide as he treks across North Africa. And yet, he starts the book with a simple quote: 

You already know enough. 

So do I. 

It is not knowledge we lack. 

What is missing is the courage to understand what we know and to draw conclusions. 

As I look over the previous editions of the CO2 newsletter that Marc wants to explore and examine, I know his work is guided by one quest: to carefully and meticulously trace how long we’ve known about the carbon dioxide and global warming problem. 

And yet, we all know that the answer, sadly, is much too long. 

Kevin Anderson states that since the newsletter’s publication, “humanity has become extraordinarily adept at observing and quantifying the world it is reshaping. With increasing accuracy, we can measure, model, and project the climate system, supported by ever more sensitive instruments, richer datasets, and stronger scientific confidence. Yet this growing clarity has not led to restraint or correction.” Michiel van den Broeke, reflecting on an article on glacial melts in the third edition states that it was “remarkably accurate.” So all the newsletters reveal, in great detail, is how even back in the 1980s we knew enough. 

You did. And so did I. So it is not knowledge we lack. 

But courage to understand what we know and to draw conclusions. 

What does it mean to understand what we know and draw conclusions in this context? 

It means to take action. To transform ourselves and our societies.

It’s to ask the same question the writers of this newsletter asked, to ask the same question Dr Abi Perrin asked, the same question that Marc’s work is ultimately shaped by: When should the studying stop and political action begin?(2)

The newsletter once again gives us another answer; long ago. 

And yet here we are. So once again we are forced to look for the courage to ask why we have failed to take action and draw conclusions about that too.

When Lindqvist asks himself to draw conclusions and confront a reality he already knew – the roots of European colonialism, white supremacy, and genocide – he asks himself to really know and understand his society. To understand what is at the heart of his world and what drives it.

We must find a way to do the same thing. To confront the murderous, genocidal, white supremacist society which continues to accept the horrendous consequences of the climate crisis. A society where billionaire elites fight information, fact and science not with countering information but with a steady stream of confusion and distraction to destabilize us and rob us of any real clarity of what we might do next.

Ruth Wilson Gilmore defined racism as a premature exposure to death(2). I think that its also a fitting definition for the climate crisis and global warming. Colonialism never went away. It is here with us right now. It’s mutated, evolved into the same world which has failed to act on the climate crisis, 

And so it’s time, once again, to look for that courage Lindqvist talked about, and draw conclusions. 

References

Golden Gulag: Prisons, Surplus, Crisis, and Opposition in Globalizing California by Ruth Wilson Gilmore

Footnote

(1) A book Marc introduced me to many, many years ago now

(2) I think it’s rather telling that the first option mentioned in the newsletter as a course of action  for  Energy and environmental planners in the U.S. was to “Postpone the decision to halt the CO, buildup (inaction itself may be a form or action)”

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CO2 Newsletter Energy Germany

March 3, 1980 – Amory Lovins at a workshop in Germany

On this day, 46 years ago, energy guru Amory Lovins was at a workshop in Germany.


As per the wonderful CO2 Newsletter of William Barbat –

From ‘ Efficient Energy presented Futures’, by Amory B, Lovins, at the Workshop on Energy/Climate Interactions, Munster, FRG, March 3, 1980, and pending publication with the Proceedings (Energy/Climate Interactions, W. Bach, et al., editors) by Reidel (Dordrecht, Netherlands)

“The integrated burn of fossil fuel, and the associated risk of global climatic change, can be minimized by economically efficient energy policies based on very efficient energy use and rapid deployment of appropriate renewable energy sources. Such policies can stabilize the rate of burning fossil fuel and gradually, over a half-century or so, reduce it to approximately zero. Economically and technically sophisticated recent studies in many industrialized countries have shown that it is cheaper, faster, and easier to increase national energy productivity by severalfold than to increase energy supply. If such studies are taken as an existence proof, a worldwide Western European material standard of living for 8 X 10 people could be maintained with today’s rate of world energy use ( 8 TW) or less, even with un-changed life-styles in the developed countries and complete industrialization of the developing countries. At these cost-effective levels of energy productivity, virtually all long-term energy needs can be met by appropriate renewable sources that are already available and that are significantly cheaper, faster, and otherwise more attractive than competing power stations and synthetic-fuel plants. Only major efficiency improvements and, secondarily, appropriate renewable sources can substantially change the timing of, or reduce the risk of CO2 problems.”

-Abstract.

The amount of carbon dioxide in the air was roughly 338ppm. As of 2026 it is 428ppm, but check here for daily measures. 

The broader context was that scientists had been thinking about the likely consequences of the build-up of carbon dioxide from the early 1950s, and measuring its rise accurately from 1958.

The specific context was that by the mid-1970s,that measuring was turning to awareness/alarm and the desire to do something before the shituation got completely out of hand. This workshop happened in the aftermath of the First World Climate Conference, which had failed to be a rallying point.

What I think we can learn from this is that we knew.

What happened next  We failed to do anything before the shituation got completely out of hand.

What do you think? Does this pass the ‘so what?’ threshold? Have I got facts wrong? Interpretation wrong? Please do comment on this post, unless you are a denialist, obvs.

References

Xxx

Also on this day: 

March 3, 1980 – International Workshop on the energy climate Interactions in Germany

March 3, 1990 –  “A greenhouse energy strategy : sustainable energy development for Australia” launched … ignored #auspol

March 3, 1990 – Energy efficiency could save billions a year, Australian government told (says ‘whatevs’).

March 3, 1990 – The Science Show on the “backlash to Greenhouse warnings”

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CO2 Newsletter

“The only feasible method for halting the CO2 buildup soon… is nuclear power.” CO2 Newsletter Vol. 1, no.4

The fourth issue of the CO2 Newsletter, published bi-monthly by American geologist William N. Barbat between 1979 and 1982 is live. You can download a pdf and see the full text here.

The eight page issue has a front page story on potential temperature increases we could expect, taken from Wally Broecker’s pivotal August 1975 article in Science “Climatic Change: Are We on the Brink of a Pronounced Global Warming?

There’s also an editorial, feedback from readers (including Congressman George Brown), excerpts from recent reports and a concluding article “What would be needed to bring the C02 buildup to a halt”

Barbat was convinced that only a very rapid and widescale roll-out of nuclear energy could help us avoid the worst. Barbat’s editorial begins

The only feasible method for halting the CO2 buildup soon – while still permitting large scale mechanization – would place nuclear energy in the dominant role. Whether civilization will be allowed to use nuclear energy on a sufficiently large scale depends on nuclear energy overcoming its military legacy and on an informed public being allowed to make energy decisions rather than socioeconomic lobbying groups.

The impetus for the scientific pursuit of nuclear energy early in this century was clearly the desire to find a substitute for the chemical energy of fossil fuels. Unfortunately, nuclear weapons were developed first because a succession of scientific breakthroughs happened to culminate in the discovery of the fission chain reaction on the eve of World War II.

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CO2 Newsletter CO2 Newsletter editorial

CO2 Newsletter Editorial: “The new decade begins on an optimistic note”

Every issue of the CO2 Newsletter had an editorial. They are William Barbat’s attempt to share (and shape) situational awareness.

Here, in March 1980, he is breathing a sigh of relief because it seems the various elements of the state (the Department of Energy, the Council on Environmental Quality) is finally beginning to get its act together. Sadly, all that would be wrecked from November 1980, with the coming of the Reagan gang. (And yet, Barbat persisted. The man had brains and guts).

The new decade begins on an optimistic note as the CO2-greenhouse problem is beginning to receive deserved attention in scientific, political, and economic institutions. Also this particular environmental issue may unite former adversaries in a common effort. David Burns, head of the AAAS Climate Program, has noted a great increase in the number of major papers which are being prepared for publication on the CO2 problem. Also our growing readership indicates to us that the Newsletter is fulfilling its role of enlightenment. Soon a European distributorship for the Newsletter may be established. Most heartening though is the apparent absence of polarization toward the CO2 problem.

Still much skepticism remains concerning the seriousness and urgency of the CO2 problem. Although a rapidly growing number of scientists feel that we now have sufficient knowledge of impending CO2– induced impacts on which to base energy policies, others feel that much more concrete evidence must first be gained throughout the world to substantiate theories and models. Some non-technical people grossly misinterpret this skepticism as representing negative proof.

From the very beginning, much work on the CO2 problem has been performed under adverse conditions or severe financial restraints. Tyndall had to trouble-shoot his galvanometers and have them reconstructed in order to measure the absorption and radiation of heat by CO2. He found that the green dye used in the silk covering of the copper coils of the most delicate instruments of his day contained some iron compound which caused the needle to deviate. Arrhenius lacked laboratory determinations of the absorption coefficients for CO2 and water vapor at plus 15 degrees C, and he also lacked the laboratory equipment needed to make the determinations. “Such experiments . . . would require very expensive apparatus beyond that at my disposal.” Ingeniously, Arrhenius used the earth’s atmosphere instead as his laboratory. Ernest Rutherford described the challenges of those days clearly’ “We haven’t the money, so we’ve got to think.”

Modern workers on the CO2 problem seem to be little better off. The federal funding of Keeling‘s invaluable monitoring of atmospheric CO2 concentrations fell victim to the race to put a man on the moon for several months in 1963. The General Circulation Model of Manabe and Wetherald reportedly contained a programming error, which apparently could only be eliminated by a computer rerun which exceeded their resources. Glaciologists are asked to make predictions of future ice sheet behavior from very sparse data. As far as we can tell, the only available forecast of the warming threshold for West Antarctica Ice Sheet destruction relies solely on a temperature datum provided by a map made from Russian observations taken during the International Geophysical Year. Polar research has been funded meagerly by the U.S. in recent years.

Meetings which bring together atmospheric scientists, climate modelers, terrestrial and marine biologists, ocean geochemists, and other workers to analyze the CO2 problem collectively are greatly limited as to frequency and numbers of invited participants. Publications concerning such meetings are usually incomplete and much delayed. Some important results of the scientific analyses are not even available for purchase through normal channels because some agencies seem to act more as a sink than a source of information. Thus, we owe a great debt of gratitude to the relatively small number of scientists who have brought us so much understanding with so little.

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Antarctica CO2 Newsletter CO2 Newsletter Barbat articles CO2 Newsletter commentary Science Scientists

“remarkably accurate statements” – Professor van den Broeke assesses “CO2 Newsletter” article on glacial melt

Michiel van den Broeke, Professor of Polar Meteorology at Utrecht University (longer bio at end of post) very kindly agreed to read William Barbat’s article “Glacier melt: How soon? How fast?” and explain what Barbat got right (and wrong) and where the science has gone in the almost 50 years since then. It’s a brilliant (imo) piece, and I hope you learn as much as I did. Please do share it, comment on it.

Professor van den Broeke

In the March 1980 edition of the CO2 NEWSLETTER, William Barbat reported about the threat of melting ice sheets and the rapid, multi-metre sea level rise that could ensue. Undoubtedly, Barbat had been triggered by the 1978 scientific publication of British glaciologist John Mercer (1922-1987), then employed at (what would later become) the Byrd Polar Research Centre of Ohio State University (Mercer, 1978). In his Nature article: West Antarctic ice sheet and CO2greenhouse effect: a threat of disaster, Mercer pointed out that the increase in CO2 concentration in the Earth’s atmosphere caused by the burning of fossil fuels would result in strong Antarctic warming, potentially leading to the disintegration of the large Ross and Filchner-Ronne ice shelves. In the absence of their buttressing effect, the West Antarctic ice sheet would collapse, raising global sea levels by several metres.

Today’s cryospheric research relies heavily on three complementary techniques: in situ observations, satellite observations and numerical models. In situ observations are often scattered in space, but to their credit have relatively long time series (typically decades in the Polar Regions), indispensable for trend detection. They moreover provide ground truth for satellites and serve to evaluate/calibrate climate and ice sheet models. Satellites, on the other hand, with their limited mission lifetime of typically 5-10 years, produce short time series, but they have the advantage of near-complete spatial coverage, filling in the spatial gaps left by the in situ observations. Numerical models, once evaluated and/or calibrated with the in situ and remotely sensed observations, can help us isolating the physical processes at work and, when they perform satisfactorily, make credible future projections.

When Mercer published his study almost 50 years ago, he had to make do with very limited observations and crude models. Although the density of in situ observations in the polar regions increased sharply after the 1957/58 International Geophysical Year (IGY, also referred to as the Third International Polar Year), observations remained very scarce notably in the ice sheet interiors. While some satellites for earth observation, notably Landsat, were available at that time, time series were less than a decade long. For Earth’s cryosphere, the satellite era started in earnest more than a decade later, with the launch of European Space Agency‘s radar-equipped ERS-1 in 1991. Finally, in the late 1970’s, climate and ice sheet models were still in their infancy; the model projections of future Antarctic warming used in Mercer’s study were from Syukuro Manabe, who in 2021 was co-awarded the Nobel prize in Physics for his pioneering contributions to climate modelling.

In spite of this, both Mercer’s 1978 Nature paper and William Barbat’s 1980 report in the CO2NEWSLETTER highlight the remarkable body of knowledge on the world’s ice sheets that had been gathered. Their reported total volume expressed in sea level rise equivalent of 66 m only deviates by 1% from today’s numbers1. Estimates of sea level stands of 6 m above present during the last interglacial (~125.000 years ago) fall well within the range of current estimates (6 to 9 m) (Dutton et al., 2015). Other remarkably accurate statements concern the approximately 50/50 partitioning of meltwater runoff and iceberg calving as sink terms in the mass balance of the Greenland ice sheet and the importance of ice shelf buttressing for grounded ice flow in Antarctica, which decades later was observationally confirmed after the sudden disintegration of Larsen B ice shelf in 2002 (Scambos et al., 2004). Mercer also correctly identified the apparent temperature threshold for the viability of Antarctic ice shelves, later corroborated by the demise of Antarctic Peninsula ice shelves after several decades of strong warming (Morris & Vaughan, 2013; Scambos et al., 2004). Also recently been confirmed is Mercer’s statement that a 5 K atmospheric warming could destabilize parts of the large Ross and Filchner-Ronne ice shelves (Van Wessem et al., 2023).

Inevitably, these early reports also have flaws and large uncertainties, which the authors frankly admit. Lacking direct observations, and realising that around 1980 mass changes of both ice sheets were significantly smaller than they are today (IMBIE, 2018, 2020), not much could be said about the magnitude of mass loss of the ice sheets, let alone the processes that caused them. It would take the launch in 2002 of the satellite pair of the Gravity Anomaly and Climate Experiment (GRACE) before mass loss from both ice sheets was convincingly demonstrated (Velicogna & Wahr, 2005; Velicogna, 2006). GRACE also showed that the recent mass loss in Antarctica is concentrated in the Amundsen and Bellingshausen Seas sectors, and is associated with ice shelf thinning owing to increased ocean melting at their base, rather than weakened buttressing of the Ross and Filchner-Ronne ice shelves. Making projections based on scanty information proved even harder. Mercer’s assumption that CO2 concentration in the atmosphere would double in 50 years was too pessimistic: atmospheric CO2 levels increased by 26%, from 337 to 426 parts per million, between 1979 and 2025. As a result, Antarctic warming remains far from the values reported in his paper.

This begs the question: if we were in Mercer’s shoes today, would we do much better in projecting the future of the Earth’s big ice sheets? Based on the latest IPCC report (IPCC, 2021), my take is that the uncertainties are still surprisingly large and not so dissimilar to what they were in 1978. Since then, our knowledge and technical (observational, modelling) capabilities have of course expanded tremendously, but we have also identified numerous new unknowns. The net result is that future ice sheet mass change and associated sea level rise remain highly uncertain, and that we still may be in for unpleasant surprises from nonlinear processes leading to tipping points that are currently not or poorly understood. Given the complex interactions between atmosphere, ocean and ice sheets that straddle several orders of magnitude in temporal and spatial scales, it is clear that this deep uncertainty will not be resolved anytime soon. It thus seems fitting to conclude with the statement made by Mercer in his 1978 paper, which still firmly stands: “…despite the crudities and inadequacies of present techniques for modelling the climatic effects of increasing atmospheric CO2content and the resultant doubts […], we cannot afford to let the atmosphere carry out the experiment before taking action because if the results confirm the prognosis, and we should know one way or the other by the end of the century, it will be too late to remedy the situation…”.

Bibliography

Dutton, A., Carlson, A. E., Long, A. J., Milne, G. A., Clark, P. U., DeConto, R., Horton, B. P., Rahmstorf, S., & Raymo, M. E. (2015). SEA-LEVEL RISE. Sea-level rise due to polar ice-sheet mass loss during past warm periods. Science, 349(6244), aaa4019. https://doi.org/10.1126/science.aaa4019

IMBIE. (2018). Mass balance of the Antarctic Ice Sheet from 1992 to 2017. Nature, 558(7709), 219-222. https://doi.org/10.1038/s41586-018-0179-y

IMBIE. (2020). Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature, 579(7798), 233-239. https://doi.org/10.1038/s41586-019-1855-2

IPCC. (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.), Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://doi.org/10.1017/9781009157896.

Mercer, J. H. (1978). West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster. Nature, 271(5643), 321–325. https://doi.org/https://doi.org/10.1038/271321a0

Morris, E. M., & Vaughan, D. G. (2013). Spatial and Temporal Variation of Surface Temperature on the Antarctic Peninsula And The Limit of Viability of Ice Shelves. In Antarctic Peninsula Climate Variability: Historical and Paleoenvironmental Perspectives (pp. 61-68). https://doi.org/10.1029/AR079p0061

Scambos, T. A., Bohlander, J. A., Shuman, C. A., & Skvarca, P. (2004). Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophysical Research Letters, 31(18). https://doi.org/10.1029/2004gl020670

Van Wessem, J. M., Van den Broeke, M. R., Wouters, B., & Lhermitte, S. (2023). Variable temperature thresholds of melt pond formation on Antarctic ice shelves. Nature Climate Change. https://doi.org/10.1038/s41558-022-01577-1

Velicogna, I., & Wahr, J. (2005). Greenland mass balance from GRACE. Geophysical Research Letters, 32(18). https://doi.org/10.1029/2005gl023955

Velicogna, I. a. J. W. (2006). Measurements of Time-Variable Gravity Show Mass Loss in Antarctica. Science, 311(5768), 1754-1756. https://doi.org/DOI: 10.1126/science.1123785

Footnotes

1 Combining radar flight lines of ice thickness with mass conservation provide us with accurate estimates of the sea level equivalent volumes of the ice sheets of Greenland (7.4 m) and Antarctica (57.8 m), (Morlighem et al., 2017; Morlighem et al., 2019).

Michiel van den Broeke (Rotterdam, 1968) has been Professor of Polar Meteorology at Utrecht University since 2008, where he studies the interaction between the climate and the large ice sheets of Antarctica and Greenland. Between 2016 and 2022, Michiel served as Scientific Director of the Institute for Marine and Atmospheric Research Utrecht (IMAU), where around 90 people work on developing a fundamental understanding of all components of the climate system.

Categories
CO2 Newsletter

C02 Newsletter Vol. 1, no. 3 (Feb 1980) – “the problem is beginning to receive deserved attention in scientific, political, and economic institutions.”

The third edition of the CO2 Newsletter, published bi-monthly by American geologist William N. Barbat between 1979 and 1982 is live. You can download a pdf and see the full text here.

The eight page issue has a front page story on the Greenland ice sheet and sea level rise (and a full page analysis on page 3 “Glacial icemelt? How soon? How Fast?”

There’s also an editorial, feedback from readers, excerpts from recent reports and a concluding article “the cost of halting the CO2 buildup.”

It remains heart-breaking, of course. Barbat’s editorial begins

“The new decade begins on an optimistic note as the CO2 greenhouse problem is beginning to receive deserved attention in scientific, political, and economic institutions. Also this particular environmental issue may unite former adversaries in a common effort. “

Barbat had switched on to environmental problems over a decade earlier, including carbon dioxide build-up. In 1979 he started the Newsletter. It was intended to fill a

“communications gap by capsulizing both the published and unpublished reports on the CO2 problem which are deemed important. This newsletter will also publish original material. invited articles. and letters of inquiry, fact and opinion.”

Each 8 page Newsletter had a lead story, an editorial, excerpts of recent documents (reports, newspaper articles, scientific abstracts, testimony by scientists to Congressional hearings) and deeply researched and argued articles by Barbat about a range of issues. Most issues had feedback from readers.