Charney Report

• 1. Introduction

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  The Charney Report, published in 1979, warned that humanity might not notice global warming in time to prevent it. By the time warming became detectable, the atmospheric loading of carbon dioxide might already have made significant climate change unavoidable. Nine scientists produced this 22-page document after five days of work at a National Academy of Sciences conference center in Woods Hole, Massachusetts. Their leader was Jule Charney, a meteorologist and modeler at MIT. The Academy had chosen him at the direct request of a White House science advisor. The report circulated in scientific and business circles but prompted no political action to reduce greenhouse gas emissions. Why a White House science advisor felt compelled to write that request to the National Academy is a story that begins two years earlier. It starts with a group of scientists advising the Department of Defense.

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• 2. A Century of Signals

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  Roger Revelle and Hans Suess upended a key assumption in the 1950s. They showed that the ocean absorbed far less carbon dioxide than scientists had previously believed. This mattered because it meant greenhouse gases from fossil fuels would accumulate in the atmosphere faster than expected. The basic physics of the greenhouse effect and carbon dioxide's role in it had been understood since the 19th century. What Revelle and Suess changed was the scale of urgency. If the ocean buffer was smaller, the gap between burning fossil fuels and atmospheric warming was narrower.

  Charles Keeling's atmospheric measurements, begun in the following decade, turned theoretical concern into observational data. His records showed a steady rise in atmospheric carbon dioxide concentrations, a dataset that became known as the Keeling curve. This was direct evidence from instruments, not inferences from models.

  Wallace Broecker's 1975 article in Science brought the phrase "global warming" into common use. Broecker drew on early digital climate models from the 1960s. Using those tools, he predicted that temperatures in the 21st century would be unlike anything in recent human experience. Two years later, the National Academy of Sciences issued a widely publicized report called Energy and Climate. It warned that fossil fuel use could drive significant warming that might build through the 22nd century. The report called for more research to narrow the uncertainties.

  Reid Bryson had given broad circulation to a competing hypothesis: that human aerosol emissions would cool the climate, not warm it. This idea appeared in the media alongside the warming predictions, leaving genuine uncertainty in public understanding. Global droughts in the 1970s caused famine and drove food prices higher, connecting climate to agriculture in the most direct terms. The first oil shock pushed U.S. President Jimmy Carter to create the Department of Energy. Carter also considered increasing domestic fossil fuel production.

  Philip Handler would soon receive a formal request that would set the summer of 1979 apart from all that came before.

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• 3. The Washington Chain

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  In 1977, the United States Department of Energy commissioned a study on climate and emissions. It turned to the JASON Committee, a group of scientists that advised the Department of Defense. Its members were not climatologists. But the group developed its own model to estimate equilibrium climate sensitivity, reaching conclusions consistent with earlier climate research. Science historians Naomi Oreskes and Erik M. Conway later examined the JASON report. They noted that the committee's political connections lent its conclusions an authority that purely academic work often lacked.

  Gordon MacDonald, one of the JASON report's authors, took the findings beyond the academic world. He and environmental activist Rafe Pomerance met with Frank Press. Press served as science advisor to President Jimmy Carter and directed the Office of Science and Technology Policy. On the 22nd of May, 1979, Press wrote to Philip Handler, president of the National Academy of Sciences. Press asked Handler to assess the scientific reliability of climate models.

  Handler asked Jule Charney, a renowned meteorologist and modeler at MIT, to chair a working group on carbon dioxide and climate. Charney formed what he called the Ad Hoc Study Group on Carbon Dioxide and Climate, assembling eight distinguished scientists to fill it. Among them were Akio Arakawa, D. James Baker, Bert Bolin, Robert E. Dickinson, Richard M. Goody, Henry Stommel, and Carl Wunsch.

  Syukuro Manabe and James E. Hansen had each been invited to present their work in person. Their three-dimensional models represented the most advanced climate simulations then available.

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• 4. Five Days at Woods Hole

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  On the 23rd of July, 1979, Charney's assembled group gathered at the Academy's conference center in Woods Hole. Federal agency observers and National Research Council staff were on hand alongside the scientists. The group worked together through the 27th, then continued exchanging ideas in the weeks that followed.

  Jule Charney defined the scope of the evaluation. The group would assess the JASON model and the more advanced work of Syukuro Manabe and James E. Hansen. Both had built three-dimensional general circulation models. Manabe worked at NOAA's Geophysical Fluid Dynamics Laboratory; Hansen came from NASA's Goddard Institute for Space Studies. The estimates the two models gave for equilibrium climate sensitivity differed, largely because of different approaches to modeling physical processes. One example was the feedback loop triggered by melting ice. When white ice gives way to darker land or ocean, the planet absorbs more heat.

  The feedback from clouds posed the greatest acknowledged uncertainty in the study; its direction and magnitude depended on the altitude at which clouds formed. Ocean-thermocline interactions added complexity of their own. The researchers examined every plausible negative feedback that might counteract the warming the models predicted.

  'We have concluded that the oversimplifications and inaccuracies in the models are not likely to have vitiated the principal conclusion that there will be appreciable warming,' the group wrote in the report. Their estimate of equilibrium climate sensitivity was set with a specific margin of error. The ocean's capacity to absorb heat could delay atmospheric warming by several decades behind any given level of emissions. As the authors stated: 'We may not be given a warning until the CO2 loading is such that an appreciable climate change is inevitable.'

  The complete document bore the formal title Carbon Dioxide and Climate: A Scientific Assessment.

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• 5. The Long Confirmation

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  Science magazine covered the Charney Report with a headline that declared the doomsday predictions had no faults. Climate change remained, for many researchers at the time, a largely theoretical matter. Not all were persuaded by what computer models could show.

  Jean Jouzel and Claude Lorius provided the first concrete confirmation of warming, roughly a decade after the report. Their reconstructions of past climates, drawn from Antarctic ice cores, produced physical records that matched what the models had projected. That evidence came from the planet itself.

  The IPCC Fifth Assessment Report examined the Charney panel's range of equilibrium climate sensitivity. That range proved consistent with the latest science. The IPCC Sixth Assessment Report, published in 2021, produced a narrower range of uncertainty. Its central estimate aligned with what the Charney panel had concluded at Woods Hole.

  Nine years after the Charney Report, the Intergovernmental Panel on Climate Change was created. Bert Bolin, one of the scientists Charney had assembled for the study, led the effort that brought the panel into being.

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