Charney Report

Last updated
Carbon Dioxide and Climate: A Scientific Assessment
Charney Report frontpage.jpg
Cover of the report
Created1979;45 years ago (1979)
Commissioned by National Academy of Sciences
Author(s)

The Charney Report, formally titled Carbon Dioxide and Climate: A Scientific Assessment, is an American scientific report published in 1979 that predicts global warming due to greenhouse gas emissions from human use of fossil fuels.

Contents

When early climate models predicted a rise in average surface temperatures, the White House asked the president of the National Academy of Sciences to assess their scientific robustness. Meteorologist Jule Charney was charged with this task and assembled eight renowned climate researchers.

They concluded that the model projections, particularly those of Syukuro Manabe and James E. Hansen, were consistent with scientific knowledge of the physical processes governing the climate system and indicated that humanity was changing the climate through the greenhouse effect. Despite advances in scientific knowledge, their estimated equilibrium climate sensitivity of 3 °C (±1.5 °C) has remained largely unchallenged - with only minor refinements - over the ensuing forty years.

The publication of the Charney Report is considered a milestone in the history of understanding climate change.

Background

The mechanism of the greenhouse effect and the role of carbon dioxide (CO2) as a greenhouse gas, particularly as emitted by humans by burning fossil fuels, have been known since the 19th century. By the mid-20th century, an increasing number of researchers predicted that anthropogenic greenhouse gas emissions would cause an increase in the average surface temperature of the atmosphere. In the 1950s, the work of Roger Revelle and Hans Suess established that the ocean was a smaller carbon sink than previously thought. In the following decade, the first results of Charles Keeling's measurements showed an increase in the atmospheric concentration of CO2 (the Keeling curve). [1] [2] [3]

In 1975, Wallace Broecker popularized the term "global warming" in a Science article predicting unprecedented temperatures in the 21st century, based on the first digital climate models that appeared in the 1960s. [4] [1] [2] Two years later, the National Academy of Sciences issued a widely publicized report, Energy and Climate, warning of warming in the 21st century that could reach an average of 6 °C by the end of the 22nd century due to fossil fuel use, and calling for more scientific research to reduce uncertainties. [5] [6] [7] [8]

In the 1970s, the scientific consensus recognized humanity's ability to affect the climate, and the scientific community increasingly focused on the possibility of global warming. However, there was no clear consensus on the warming, which was then imperceptible. The hypothesis of global cooling due to anthropogenic aerosol emissions was also circulating, including in the media, where Reid Bryson popularized it for the public. [3] [9] [5]

Meanwhile, scientific climate research coincided with the rise of environmentalism - societal concern about human impact on the environment, especially in the United States. [2] [10] The 1970s also saw global droughts that led to famine and skyrocketing food prices, underscoring the importance of climate to agriculture. The decade was marked by the first oil shock, which led U.S. President Jimmy Carter to consider increasing domestic production of fossil fuels and to create the Department of Energy. [2] [5] [11]

Origins

Jule Charney, Chairman of the Ad Hoc Study Group on Carbon Dioxide and Climate. Photograph taken in 1978. Jule Gregory Charney.png
Jule Charney, Chairman of the Ad Hoc Study Group on Carbon Dioxide and Climate. Photograph taken in 1978.

In 1977, the United States Department of Energy prepared a CO2 research program and requested a report from the JASON Committee, a group of scientists advising the Department of Defense. Although the JASON members were not climatologists, they studied the effect of CO2 emissions on climate using a model they had developed to estimate equilibrium climate sensitivity or the amount of warming caused by a doubling of atmospheric CO2 concentrations relative to pre-industrial levels. They concluded that climate sensitivity is 2.4 °C, which could lead to negative economic and social consequences. This result was consistent with earlier estimates from general circulation models, and as science historians Naomi Oreskes and Erik M. Conway note, the political connections of the JASON committee members gave the report considerable authority. [2] [11] [12]

One of the report's authors, Gordon MacDonald, along with environmental activist Rafe Pomerance, met with Jimmy Carter's science advisor and director of the Office of Science and Technology Policy, Frank Press, to present their findings. [13] [14] On May 22, 1979, Press wrote to National Academy of Sciences President Philip Handler requesting a study to determine the scientific reliability of climate models. [13] [11]

Handler asked Jule Charney, a renowned meteorologist and modeler at the Massachusetts Institute of Technology (MIT), to chair a working group on the issue. Charney brought together eight distinguished scientists to form the Ad Hoc Study Group on Carbon Dioxide and Climate: Akio Arakawa, D. James Baker, Bert Bolin, Robert E. Dickinson, Richard M. Goody, Cecil Leith  [ fr ], Henry Stommel, and Carl Wunsch. [2] [11] [15]

Development and conclusions

Crafoord Prize EM1B0732 (42329290061).jpg
Syukuro Manabe (2018)
James Hansen profile (cropped).jpg
James E. Hansen (2005)
The two main climate modellers in 1979, whose work was analysed by the researchers gathered at Woods Hole.

On July 23, 1979, the nine scientists, accompanied by their families, met in Woods Hole on the Massachusetts coast, where the National Academy of Sciences has a conference center. Also present as observers were members of various federal agencies and staff of the National Research Council, who oversaw the report development. [13] After working together in Woods Hole from July 23 to July 27, and continuing to exchange ideas in the following weeks, [16] the group produced a 22-page report entitled Carbon Dioxide and Climate: A Scientific Assessment.

Jule Charney decided to evaluate not only the JASON committee's model but also the more advanced three-dimensional general circulation models of Syukuro Manabe (from NOAA's Geophysical Fluid Dynamics Laboratory) and James E. Hansen (from NASA's Goddard Institute for Space Studies ). The first model estimated equilibrium climate sensitivity between 2 °C and 3 °C, while the second model estimated values close to 4 °C. Both researchers were invited to present how their models worked, and the difference in their estimates was largely due to different approaches to modeling certain physical processes, such as the positive feedback loop triggered by melting ice (decreasing albedo). [5] [11] [13] [17]

All models, by definition, simplify the complex physics of climate, and uncertainties remain, for example, about the dominant feedback effect of clouds (depending on their altitude) or the interactions between the ocean surface layer and the thermocline. The researchers, led by Jule Charney, therefore examined all possible negative feedback loops that could counteract the greenhouse warming predicted by the models in the presence of increased atmospheric CO2 concentrations. As they wrote in the report: "[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." [18] The document thus concludes with an estimated equilibrium climate sensitivity of 3 °C, with a margin of error of ±1.5 °C (i.e., from 1.5 °C to 4.5 °C). [11] [13] [19] The authors also point out - and this prediction later proved accurate - that the ocean's heat absorption capacity could delay noticeable atmospheric warming by several decades for a given level of CO2 emissions: [20] [21] "We may not be given a warning until the CO2 loading is such that an appreciable climate change is inevitable." [18]

Legacy

The conclusions of the Charney Report have since been confirmed by new instrumental data sets, comparisons with past climates, and more sophisticated computer models. [20] [21] [22] In particular, the range of error estimated in the report for equilibrium climate sensitivity (1.5 °C to 4.5 °C) is consistent with that evaluated in the IPCC Fifth Assessment Report, with the central value (3 °C) consistent with the IPCC Sixth Assessment Report (2021), which concluded with a narrower range of error. [22] [23]

The Charney Report did not introduce new scientific knowledge about climate change, but it did reaffirm the scientific robustness of climate models, based on a solid understanding of physical processes, and demonstrated a growing scientific consensus about future warming. [10] [13] [20] [21] [24] However, knowledge about climate change remained theoretical, and not all researchers were convinced by the computer models. The first tangible evidence of warming came a decade later, with Jean Jouzel and Claude Lorius' reconstructions of past climates using Antarctic ice cores. [5] [3] [25]

The Charney Report, published in 1979, was covered by Science under the headline CO2 in Climate: Doomsday Predictions Have No Faults. [14] [26] The report circulated in scientific and business circles but did not lead to political action to reduce greenhouse gas emissions. [9] [13] [20]

The year 1979 is considered a landmark in the history of knowledge about human-caused climate change because of the publication of the report and the simultaneous organization of the first World Climate Conference by the World Meteorological Organization (WMO). It preceded by nine years the creation of the Intergovernmental Panel on Climate Change (IPCC), an initiative led by Bert Bolin, one of the authors of the Charney Report. [9] [27] [28] [29] [30]

See also

Related Research Articles

<span class="mw-page-title-main">Causes of climate change</span> Effort to scientifically ascertain mechanisms responsible for recent global warming

The scientific community has been investigating the causes of climate change for decades. After thousands of studies, it came to a consensus, where it is "unequivocal that human influence has warmed the atmosphere, ocean and land since pre-industrial times." This consensus is supported by around 200 scientific organizations worldwide, The dominant role in this climate change has been played by the direct emissions of carbon dioxide from the burning of fossil fuels. Indirect CO2 emissions from land use change, and the emissions of methane, nitrous oxide and other greenhouse gases play major supporting roles.

<span class="mw-page-title-main">Global warming potential</span> Potential heat absorbed by a greenhouse gas

Global warming potential (GWP) is an index to measure how much infrared thermal radiation a greenhouse gas would absorb over a given time frame after it has been added to the atmosphere. The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide, which is taken as a reference gas. Therefore, the GWP has a value of 1 for CO2. For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered.

<span class="mw-page-title-main">Global cooling</span> Discredited 1970s hypothesis of imminent cooling of the Earth

Global cooling was a conjecture, especially during the 1970s, of imminent cooling of the Earth culminating in a period of extensive glaciation, due to the cooling effects of aerosols or orbital forcing. Some press reports in the 1970s speculated about continued cooling; these did not accurately reflect the scientific literature of the time, which was generally more concerned with warming from an enhanced greenhouse effect.

<span class="mw-page-title-main">Scientific consensus on climate change</span> Evaluation of climate change by the scientific community

There is a nearly unanimous scientific consensus that the Earth has been consistently warming since the start of the Industrial Revolution, that the rate of recent warming is largely unprecedented, and that this warming is mainly the result of a rapid increase in atmospheric carbon dioxide (CO2) caused by human activities. The human activities causing this warming include fossil fuel combustion, cement production, and land use changes such as deforestation, with a significant supporting role from the other greenhouse gases such as methane and nitrous oxide. This human role in climate change is considered "unequivocal" and "incontrovertible".

<span class="mw-page-title-main">Radiative forcing</span> Concept for changes to the energy flows through a planetary atmosphere

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<span class="mw-page-title-main">Climate sensitivity</span> Concept in climate science

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<span class="mw-page-title-main">Greenhouse gas emissions</span> Greenhouse gases emitted from human activities

Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide, from burning fossil fuels such as coal, oil, and natural gas, is one of the most important factors in causing climate change. The largest emitters are China followed by the United States. The United States has higher emissions per capita. The main producers fueling the emissions globally are large oil and gas companies. Emissions from human activities have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 GtC, of which 484±20 GtC from fossil fuels and industry, and 219±60 GtC from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2022, coal 32%, oil 24%, and gas 10%.

<span class="mw-page-title-main">Greenhouse gas</span> Gas in an atmosphere with certain absorption characteristics

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<span class="mw-page-title-main">History of climate change science</span> Aspect of the history of science

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<span class="mw-page-title-main">Climate change feedbacks</span> Feedback related to climate change

Climate change feedbacks are natural processes that impact how much global temperatures will increase for a given amount of greenhouse gas emissions. Positive feedbacks amplify global warming while negative feedbacks diminish it. Feedbacks influence both the amount of greenhouse gases in the atmosphere and the amount of temperature change that happens in response. While emissions are the forcing that causes climate change, feedbacks combine to control climate sensitivity to that forcing.

A climate change scenario is a hypothetical future based on a "set of key driving forces". Scenarios explore the long-term effectiveness of mitigation and adaptation. Scenarios help to understand what the future may hold. They can show which decisions will have the most meaningful effects on mitigation and adaptation.

<span class="mw-page-title-main">Representative Concentration Pathway</span> Projections used in climate change modeling

Representative Concentration Pathways (RCP) are climate change scenarios to project future greenhouse gas concentrations. These pathways describe future greenhouse gas concentrations and have been formally adopted by the IPCC. The pathways describe different climate change scenarios, all of which were considered possible depending on the amount of greenhouse gases (GHG) emitted in the years to come. The four RCPs – originally RCP2.6, RCP4.5, RCP6, and RCP8.5 – are labelled after the expected changes in radiative forcing from the year 1750 to the year 2100. The IPCC Fifth Assessment Report (AR5) began to use these four pathways for climate modeling and research in 2014. The higher values mean higher greenhouse gas emissions and therefore higher global surface temperatures and more pronounced effects of climate change. The lower RCP values, on the other hand, are more desirable for humans but would require more stringent climate change mitigation efforts to achieve them.

<span class="mw-page-title-main">Climate inertia</span> Slow response of complex feedback systems

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<span class="mw-page-title-main">Special Report on Global Warming of 1.5 °C</span> Special climate change report published by the Intergovernmental Panel on Climate Change

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<span class="mw-page-title-main">IPCC Sixth Assessment Report</span> Intergovernmental report on climate change

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References

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  6. ↑ Sullivan, Walter (July 25, 1977). "Scientists Fear Heavy Use of Coal May Bring Adverse Shift in Climate". The New York Times . Archived from the original on May 18, 2024.
  7. ↑ "Hotting up the debate". Physics Bulletin. 28 (9): 402. 1977. doi:10.1088/0031-9112/28/9/016.
  8. ↑ Energy and Climate. National Academy of Sciences. 1977. doi:10.17226/12024. ISBN   978-0-309-11234-5.
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  12. ↑ MacDonald, Gordon (1979). Long term impact of atmospheric carbon dioxide on climate. JASON. Archived from the original on September 2, 2023.
  13. 1 2 3 4 5 6 7 Rich, Nathaniel (August 1, 2018). "Losing Earth: The Decade We Almost Stopped Climate Change". The New York Times . Archived from the original on September 29, 2024.
  14. 1 2 Bell, Alice (July 5, 2021). "Sixty years of climate change warnings: the signs that were missed (and ignored)". The Guardian . Archived from the original on September 28, 2024.
  15. ↑ Charney et al. 1979 , p. V
  16. ↑ Charney et al. 1979 , p. iv (preface by J. Charney)
  17. ↑ Charney et al. 1979 , pp. 21–22
  18. 1 2 Charney et al. 1979 , p. 2
  19. ↑ Charney et al. 1979 , pp. 1–3
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  21. 1 2 3 Santer, Benjamin D (2019). "Celebrating the anniversary of three key events in climate change science". Nature Climate Change . 9 (3): 180–182. Bibcode:2019NatCC...9..180S. doi:10.1038/s41558-019-0424-x.
  22. 1 2 McNutt, Marcia (2019). "Time's up, CO2". Science . 365 (6452): 411. doi: 10.1126/science.aay8827 . PMID   31371582.
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  26. ↑ Wade, Nicholas (1979). "CO2 in Climate: Gloomsday Predictions Have No Fault". Science . 206 (4421): 912–913. doi:10.1126/science.206.4421.912.b.
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Bibliography

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