To: Member of AGU Council
From: S. Fred Singer, Fellow AGU
Date: January 5, 1999
Re: AGU Position Statement on Climate ChangeThis memo is motivated by a concern that the above Statement will be misused to the detriment of the AGU and its membership
Summary:
In an important decision that could impact unfavorably on the AGU, the AGU Council, meeting on December 9, 1998, approved a Position Statement on "Climate Change and Greenhouse Gases" (Att. A). Speaking from the floor, I had urged that approval be delayed until several scientific inaccuracies were removed. I discussed two of these problems in detail. (See below)
Following the December 9 meeting, I have learned of some procedural problems as well -- by comparing the December draft with a draft displayed on the AGU website in March 1998 (Att. B), and with a draft circulated to members of the drafting panel on November 19 (Att. C). It appears that the AGU membership was not aware of the November and December drafts, and it appears that some members of the AGU Climate Change Panel were not aware of the changes made between November and December.
In spite of this, it is likely that the AGU Statement, when released or even earlier, will be misused to imply that 35,000 AGU members agree that global warming poses a significant threat to mankind. The Statement has already been mentioned by the Christian Science Monitor (Dec. 14).
Some Scientific Problems with the December Document:
At the Council meeting on December 9, I pointed out that the Statement contained phrases that were scientifically misleading or inaccurate, and urged that these be rectified before the Council voted its approval. I specifically mentioned the following two:
1. Paragraph 1 (of Att. A) states that greenhouse gases like carbon dioxide "are predicted to persist in the atmosphere for times ranging to thousands of years." Yet leading experts in this field, have concluded that half of the CO2 released to the atmosphere would be absorbed within 30 years, and the remainder mostly in the following 100 years [Sarmiento et al. 1992]. While a small amount may indeed survive for longer periods, the Statement conveys a misleading impression to the non-expert when it fails to mention the 30-year figure.
2. Paragraph 2 (of Att. A) states that the geologic record "provides evidence of larger climate variations associated with changes in atmospheric carbon dioxide" (emphasis added). This statement, while technically correct, gives the impression that increases of the greenhouse gas CO2 are the cause of climate warming in the geologic past. Yet recent results [Wahlen et al. 1998], analyzing the 400,000-year record of the Vostok ice core, conclude that every one of the three deglaciations (the major warming associated with the end of an ice age) was followed by a CO2 increase after about 1,000 years. This important finding establishes, if anything, a reverse causal relationship, namely that warmings can lead to an increase in CO2.
Procedural Issues
The March draft statement (Att. B) was displayed on the AGU website and drew over 50 comments from AGU members. Most suggested specific changes, and many questioned the need for any kind of statement by the AGU. The March statement contained only 244 words in two paragraphs. The next statement I know of, the November draft, was a complete rewrite, containing five paragraphs and 681 words. It was not displayed on the website nor announced in Eos (as required by AGU procedure; cf. Eos Dec. 29, 1998), but was sent to a panel which contained only five of the 13 members of the original panel. (We don't know why eight of the original panel members did not appear on the final panel.)
The final draft, the December 6 statement, was not circulated to panel members whose names appear there, and was not seen by some of them. Yet it contained changes from the November draft, which are not insignificant. I list two of these here.
1. November draft: "are likely to persist in the atmosphere from decades to thousands of years." December draft: "are predicted to persist in the atmosphere for times ranging to thousands of years." (Apparently, the word "decades" was dropped.)
2. November draft: "the present level of scientific uncertainty should not preclude taking action to mitigate climate change and/or adapt to it." December draft: "the present level of scientific uncertainty does not justify inaction in the mitigation of human induced climate change and/or the adaptation to it."
Conclusion
The Position Statement, as approved, contains phrases that are scientifically misleading. In addition, it appears that the final statement was not reviewed by the full panel, and certainly was not presented to the membership of the AGU for review and comment, as required. If problems arise, the Council can withdraw or modify the Statement, or vote to shorten its (4-year) lifespan.
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Attachment A: (as approved by AGU Council, Dec. 9, 1998)
AGU Position Statement: CLIMATE CHANGE AND GREENHOUSE GASES
Atmospheric concentrations of carbon dioxide and other greenhouse gases have substantially increased as a consequence of fossil fuel combustion and other human activities. These elevated concentrations of greenhouse gases are predicted to persist in the atmosphere for times ranging to thousands of years. Increasing concentrations of carbon dioxide and other greenhouse gases affect the Earth-atmosphere energy balance, enhancing the natural greenhouse effect and thereby exerting a warming influence at the Earth's surface.
Although greenhouse gas concentrations and their climatic influences are projected to increase, the detailed response of the system is uncertain. Principal sources of this uncertainty are the climate system's inherent complexity and natural variability. The increase in global mean surface temperatures over the past 150 years appears to be unusual in the context of the last few centuries, but it is not clearly outside the range of climate variability of the last few thousand years. The geologic record of the more distant past provides evidence of larger climate variations associated with changes in atmospheric carbon dioxide. These changes appear to be consistent with present understanding of the radiative properties of carbon dioxide and of the influence of climate on the carbon cycle. There is no known geologic precedent for the transfer of carbon from the Earth's crust to atmospheric
carbon dioxide, in quantities comparable to the burning of fossil fuels, without simultaneous changes in other parts of the carbon cycle and climate system. This close coupling between atmospheric carbon dioxide and climate suggests that a change in one would in all likelihood be accompanied by a change in the other.
Present understanding of the Earth climate system provides a compelling basis for legitimate public concern over future global- and regional-scale changes resulting from increased concentrations of greenhouse gases. These changes are predicted to include increases in global mean surface temperatures, increases in global mean rates of precipitation and evaporation, rising sea levels, and changes in the biosphere. Understanding of the fundamental processes responsible for global climate change has greatly improved over the past decade, and predictive capabilities are advancing. However, there are significant scientific uncertainties, for example, in predictions of local effects of climate change, occurrence of extreme weather events, effects of aerosols, changes in clouds, shifts in the intensity and distribution of precipitation, and changes in oceanic circulation. In view of the complexity of the Earth climate system, uncertainty in its description and in the prediction of changes will never be completely eliminated.
Because of these uncertainties, there is much public debate over the extent to which increased concentrations of greenhouse gases have caused or will cause climate change, and over potential actions to limit and/or respond to climate change. It is important that public debate take into account the extent of scientific knowledge and the uncertainties. Science cannot be the sole source of guidance on how society should respond to climate issues. Nonetheless, scientific understanding based on peer-reviewed research must be central to informed decision-making. AGU calls for an enhancement of research to improve the quantification of anthropogenic influences on climate. To this end, international programs of research are essential. AGU encourages scientists worldwide to participate in such programs and in scientific assessments and policy discussions.
The world may already be committed to some degree of human-caused climate change, and further buildup of greenhouse gas concentrations may be expected to cause further change. Some of these changes may be beneficial and others damaging for different parts of the world. However, the rapidity and uneven geographic distribution of these changes could be very disruptive. AGU recommends the development and evaluation of strategies such as emissions reduction, carbon sequestration, and adaptation to the impacts of climate change. AGU believes that the present level of scientific uncertainty does not justify inaction in the mitigation of human induced climate change and/or the adaptation to it.
AGU Climate Change Panel
Tamara Ledley, Chair TERC
Jack Fellows UCAR (representing COPA)
Dorothy Hall Goddard Space Flight Center
Tim Killeen University of Michigan (representing AGU Council)
Stephen Schwartz Brookhaven National Laboratory
Eric Sundquist US Geological Survey, Woods Hole
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Attachment B: (posted at http://www.agu.org/sci_soc/draftdoc.html during March
1998)
Comments Invited: Working Draft Statement on Global Climate Change
A panel has been authorized and is working on a position statement on global
climate change. The working draft statement is as follows. The panel welcomes
comments on this working draft from the membership. Comments should be
addressed to the Committee on Global Environmental Change
(ebierly@kosmos.agu.org) . Members of the panel are: Tamara S. Ledley, Subir K.
Banerjee, James B. Garvin, Peter H. Gleick, Dorothy K. Hall, Timothy L.
Killeen, Debra Knopman, W. Richard Peltier, Henry N. Pollack, Stephen E.
Schwartz, Eric T. Sundquist, Paul Switzer, and Starley L. Thompson.
Atmospheric concentrations of carbon dioxide and other greenhouse gases are
rising substantially as a consequence of human activities, primarily
combustion of fossil fuels. The AGU considers anthropogenic emissions of
carbon dioxide and other greenhouse gases to be affecting the earth-atmosphere
energy balance and global climate at present. Continued emissions are likely to
cause increases in global mean temperatures, rising sea levels, and other
substantial climate changes. Uncertainties are inherent in such climate
predictions, particularly relating to local effects of climate change,
occurrence of extreme weather events, effects of clouds and aerosols, and
unanticipated changes in oceanic circulation. Such uncertainties will persist
into the foreseeable future.
The AGU emphasizes the importance of informed public debate that takes into
account the extent of scientific knowledge and the implications of persistent
uncertainties in considering potential actions to limit and/or to respond to
climate change. To reduce uncertainties in climate predictions and thereby
permit better-informed decision making on emissions limitations and other
societal actions, the AGU endorses international programs of research to
quantify anthropogenic influences on climate and the nature of climate system
response to such influences. Despite present uncertainties, it can be stated
with confidence that continued unabated emissions of carbon dioxide and other
anthropogenic greenhouse gases will lead to enduring influences on climate
that exceed recent historical experience. Therefore, AGU joins with other
scientific organizations and internationally constituted bodies in urging all
nations to promptly develop and implement strategies for substantially
limiting emissions of greenhouse gases.
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Attachment C: (distributed to AGU Panel on Climate Change)
Draft Position Statement on Climate Change AGU Climate Change Panel November 19, 1998
Atmospheric concentrations of carbon dioxide and other greenhouse gases have
increased substantially as a consequence of human activity, primarily the
combustion of fossil fuels. These elevated concentrations of greenhouse gases
are likely to persist in the atmosphere for decades to thousands of years. AGU
considers that increased concentrations of carbon dioxide and other greenhouse
gases are affecting the earth-atmosphere energy balance, enhancing the natural
greenhouse effect, and thereby exerting a warming influence at the Earth's
surface. This perturbation can be expected to increase as greenhouse gas
concentrations increase.
The projected response of the climate system to increased concentrations of
greenhouse gases is uncertain. A principal source of this uncertainty is the
climate system's inherent natural variability, which occurs over interannual to
geologic time scales. The increase in global mean surface temperatures over the
past 150 years appears to be unusual in the context of the last few centuries,
albeit not clearly outside the range of climate variability of the last few
thousand years. The geologic record of the more distant past provides evidence
of larger climate variations associated with changes in atmospheric carbon
dioxide. These changes appear to be consistent with present understanding of
the radiative properties of carbon dioxide and of the influence of climate on
the carbon cycle. There is no known geologic precedent for the transfer of
carbon from the Earth's crust to atmospheric carbon dioxide, in quantities
comparable to the burning of fossil fuels, without simultaneous changes in
other parts of the carbon cycle and climate system. This close coupling
between atmospheric carbon dioxide and climate suggests that a change in one
would in all likelihood be accompanied by a change in the other.
Present understanding of the Earth climate system provides a compelling basis
for legitimate public concern over future global and regional scale changes
resulting from increased concentrations of greenhouse gases. These changes are
thought to include increases in global mean surface temperatures, increases in
global mean rates of precipitation and evaporation, rising sea levels, and
changes in the biosphere. Understanding of the fundamental processes
responsible for global climate change has greatly improved over the past
decade. Predictive capabilities are emerging; for example many of the effects
of the 1997-98 El Niņo were predicted. However significant scientific
uncertainties remain, particularly in predictions of local effects of climate
change, occurrence of extreme weather events, effects of aerosols, changes in
clouds, shifts in the intensity and distribution of precipitation, and possible
changes in oceanic circulation. In view of the complexity of the Earth climate
system, uncertainty in its description and in the prediction of changes will
never be eliminated.
Because of these uncertainties there is much public debate over the extent to
which increased concentrations of greenhouse gases have caused or will cause
climate change, and over potential actions to limit and/or respond to climate
change. AGU emphasizes the importance of informed public debate that takes
into account the extent of scientific knowledge and the uncertainties. Science
cannot be the sole source of guidance on how society should respond to climate
issues. Nonetheless, scientific understanding based on peer reviewed research
must be central to informed decision-making. AGU calls for an enhancement of
research to improve the quantification of anthropogenic influences on climate.
To this end international programs of research are essential. AGU encourages
scientists worldwide to participate in such programs and in scientific
assessments and policy discussions.
The world may already be committed to some degree of human-caused climate
change, and further buildup of greenhouse gas concentrations may be expected to
cause further change. Some of these changes are likely to be neutral, some
beneficial, and others damaging for different parts of the world. The rapidity
and uneven geographic distribution of these changes could be very disruptive.
AGU recommends the development and evaluation of strategies such as emissions
reduction, carbon sequestration, and adaptation to the negative impacts of
climate change. Given the current understanding of the climate system and
potential responses to increased greenhouse gases, AGU believes that the
present level of scientific uncertainty should not preclude taking action to
mitigate climate change and/or adapt to it.