AGU’s Position on Human Impacts on Climate: Comments Invited
AGU’s current position statement on understanding climate was adopted in 2003. The charge to the panel that is considering an update to this position reiterates the need for consideration of the growing body of scientific evidence and asks that the panel include information that reflects the scientific progress that has occurred in the past 4 years on this subject. AGU members may provide comments for consideration by the panel via this online discussion.
As published in Eos | Position Statement | Procedures for Developing Union Positions
September 2nd, 2007 at 1:25 pm
Comments on AGU position paper on “Human Impacts on Climate,” Adopted by Council December, 2003
Comments by Alan Robock
September 2, 2007
I think the current position paper is a good starting point for the revised statement, and would like to suggest the committee consider the following changes:
1. In light of the 2007 IPCC reports, some of the statements about natural causes not explaining the recent warming and anthropogenic impacts very likely to have caused the warming need to be made stronger in the AGU statement.
2. I think the statement “AGU believes that no single threshold level of greenhouse gas concentrations in the atmosphere exists at which the beginning of dangerous anthropogenic interference with the climate system can be defined. Some impacts have already occurred, and for increasing concentrations there will be increasing impacts.” needs to be substantially revised, especially in light of the recent work of Jim Hansen and others. The current AGU statement can be interpreted as a call for no action on the problem and no hope of determining what is dangerous.
Clearly “dangerous” is a subjective judgment, but AGU has to much more strongly say, based on the latest scientific evidence, that business as usual will produce dangerous climate change soon. I think the definition of dangerous should be the one Hansen and many Europeans have already adopted, 1°C above current global mean temperature, or 2°C above pre-industrial global mean temperature. This level will be exceeded if CO2 concentration goes much above 450 ppm (depending a little on what the other anthropogenic greenhouse gases do).
My definition of “dangerous anthropogenic interference with the climate system” is because of the following impacts projected with more than 1°C of global warming (partly from Jim Hansen):
A. Massive Extermination of Animal & Plant Species
1. Extinction of Polar and Alpine Species
2. Unsustainable Migration Rates
B. Ice Sheet Disintegration: Increasingly Rapid Global Sea Level Rise
C. Regional Climate Change
1. More Strong Hurricanes
2. Increased Frequency of Droughts and Floods
3. Threats to Human Water and Food Supply
Global warming is the second most serious threat to the planet (after nuclear weapons), and society needs excellent scientific advice (as the current statement says) to deal with this threat. AGU has the responsibility to convey to the public our best judgment of what this threat is so that society can promptly address the problem, without further delay.
September 11th, 2007 at 4:40 pm
Comments from Sarah Wise, U. of Colorado at Boulder, CIRES Outreach. I am recently trained in climate change education, but I am not a climate scientist.
1) My first reaction is that the statement is too long, and goes into too much detail about research findings. This is in contrast to the evolution position statement, which may benefit from the inclusion of a short summary of major research findings. Can paragraphs 1-5 be made more concise? I also think that the IPCC 2007 report should be cited here.
2) I agree with Alan Robock about potential misunderstandings around paragraph 6.
3) In paragraph 7 there is a call for additional research and training of climate scientists. While this is laudable it stands in contrast to recent statements suggesting that the need for additional research should not delay taking action.
4) I would like to see paragraph 8 completely rewritten for clarity, and with a greater emphasis on the responsibility for scientists to inform the public about climate change. Methods by which scientists can meet this responsibility could be discussed. The comparisons to natural hazards information is not necessary.
5) The position statement does not include a statement on the inclusion of climate change education in public schools. What is AGU’s position on this?
September 14th, 2007 at 5:11 pm
It is known and can be verified scientifically, that increased CO2 concentration in the atmosphere is not causing global warming.
From 1980 to 2000, the stratosphere cooled off 1.3 degrees C and the troposphere increased 0.4 degrees C. The cooling of the stratosphere was caused by Chlorofluorocarbon (CFC) destruction of stratospheric ozone. This allowed more radiation to hit the troposphere and the earth. The ozone loss caused the earth to warm some 0.3 degrees C during the same time the stratosphere cooled. The other 0.1 degree rise was caused by the natural 11-year change in solar irradiance (more or less sunspots).
Loss of ozone is greatest at the poles and the poles have warmed twice as much as the average temperature of the earth has warmed. Therefore, glaciers and permafrost are starting to melt. Researchers have found that this melting permafrost is releasing carbon to the atmosphere at a rate some 100 times the rate of fossil fuel emissions. Methane slowly converts to CO2 in the atmosphere and is the logical cause for recent increased CO2 in the atmosphere that started its spike upward also in 1980.
September 20th, 2007 at 12:01 pm
Sept. 20, 2007. Submitted by S. Fred Singer (Fellow and Life Member, AGU) www.sepp.org
<To view the six figures cited, go to http://science-sepp.blogspot.com/>
Dear Members of AGU Panel on “Human Impacts on Climate”
You have the awesome responsibility to develop a draft statement for the Council that fully reflects the views of the AGU membership. It is not likely that the Council will make significant changes in your draft, which increases the level of your responsibility.
You have basically two choices: To accept the IPCC position, or to examine the scientific evidence independently.
1. The easy choice is to accept the IPCC [2007] position and adopt its major conclusion – specifically, that the current warming is ‘very likely’ human-caused. The IPCC mandate was to examine human causes of global warming. The IPCC does not follow the procedures of the scientific method and does not adequately examine natural causes as alternatives. Similarly, the name of your panel — “Human Impacts on Climate” — suggests a one-sided approach that ignores the contribution of natural causes.
2. Or you can show your scientific independence by confirming or denying the IPCC conclusions, but based on your own examination of the evidence. While this might look like a forbidding task, it is really not very difficult. Do not abdicate your responsibility to examine this critique of the IPCC conclusions, and then use your own best judgment.
We propose to look at three major questions:
1. Is current global warming (GW) mostly natural or anthropogenic?
2. If the former, why do greenhouse (GH) models give so much higher rates of warming than are observed?
3. If models are inadequate to explain observations, what then are the major causes of current climate variability?
NB: Those who do not accept the IPCC conclusion about the importance of anthropogenic GW are obligated to provide answers to the second and third question.
1. To examine the cause of warming, we first ask what is the evidence that leads the IPCC to conclude that the cause is anthropogenic. While the IPCC report discusses melting of glaciers, shrinking of sea ice, etc., they surely realize that this cannot establish the cause of warming. Any warming, whether natural or anthropogenic will cause ice to melt.
Neither can correlation with greenhouse gases, like CO2, be used to prove that current warming is anthropogenic. In principle, correlation cannot establish causation. Furthermore, the correlation is quite poor; for example, during much of the 20th century climate cooled while CO2 levels rose.
One cannot simply argue that climate models based on the greenhouse effect show a warming trend. Of course, they do; but model results are not evidence. Published warming trends from different models differ by an order of magnitude, depending mainly on subtle assumptions about cloud microphysics and cloud optics. How can one tell which model is correct? However, the IPCC does offer a method for establishing the cause of warming, as seen in Fig. 1 [IPCC 2007, fig. 9.1]. It shows the warming patterns (‘fingerprints ‘) arising from different forcing mechanisms. Greenhouse forcing is quite distinctive and shows a characteristic increase of warming rate with altitude, reaching a maximum at about 10 km in the tropics, about 200-300% that of the surface rate. The next step is taken by the CCSP Report 1.1, based on the federal government’s Climate Change Science Program [Fig. 2]. One can examine the calculated pattern [Fig. 3] [CCSP-1.1 fig. 1.3F], which agrees with the IPCC’s in showing the two- to three-fold increase in warming rate. This result can then be compared to the observed pattern [Fig. 4] from balloon radiosonde data [CCSP-1.1 fig. 5.7E]. It is quite clear that the ‘fingerprints’ don’t match – no matter what is claimed by the IPCC [2007, p.5], which distorts this main result of CCSP. The observed pattern shows no increase at all with altitude; perhaps even a slight decrease.
This discrepancy between calculated and observed patterns leads us to the conclusion that the (human) greenhouse contribution to current warming is not significant when compared to natural causes.
2. Why don’t the models show a warming pattern that agrees with the observations? Or putting it differently, why is the climate sensitivity calculated by current greenhouse models so much greater than any empirical value? The answer may be that there is negative feedback in the atmosphere, which has not been incorporated into the models. This feedback could either be an increase in cloudiness [and in cloud albedo] or a misjudgment about the amount of water vapor in the upper troposphere. It can readily be shown that the humidity levels of the upper troposphere (i.e., levels of UTWV) have a powerful effect on the emission of IR radiation from the atmosphere into space, and consequently on the surface temperature. See the cartoon of Fig.5.
Present observations are not refined enough to establish either effect with any degree of certainty, and models do not as yet incorporate such negative feedbacks — hence their inability to account for current observations.
3. If not greenhouse forcing from increased CO2, what then could be the natural causes of current warming? They can either be external or internal, produced by oscillations of the atmosphere-ocean system. Best known is the El Nino-Southern Oscillation [ENSO], but there is also a North Atlantic Oscillation, an Atlantic Multi-Decadal Oscillation, a Pacific Decadal Oscillation, and probably others. But many believe that the Sun is the basic cause of climate change on a decadal and century time scale. The IPCC report considers only the rather small variability of Total Solar Irradiance [TSI]. But it is likely that changes in solar activity exert a much greater influence than TSI on terrestrial climate, through variations of the solar wind. The mechanism consists of two parts: first, a modulation of galactic cosmic rays by magnetic scattering centers carried within the solar wind. And then, a change in atmospheric cloudiness as the variable level of the incident cosmic rays produces varying levels of cloud condensation nuclei.
The ‘solar wind, cosmic rays, cloudiness’ mechanism has not been fully accepted as yet. However, there is much empirical evidence that supports it. One such example is shown in Fig. 6; it is a very detailed correlation, extending well over 3000 years, between Carbon-14 [a proxy for cosmic-ray flux into the atmosphere] and Oxygen-18 [a proxy for temperature] from stalagmites in a cave in Oman. Together with similar examples from around the world, this strongly suggests that solar activity has a dominant influence on climate change.
We would urge the AGU Panel to consider carefully the evidence presented here and to critique it where necessary. But the Panel should at least mention explicitly that the causes of warming (and cooling) are not yet settled and that a substantial fraction of the climate science community believes that Global Warming is produced largely by natural causes.
November 27th, 2007 at 11:24 am
The American Geophysical Union invites comments on the existing position statement, “Human Impacts on Climate”, adopted by the Council in December 2003. There are nine brief paragraphs in that position statement. My comment concerns only the fifth of these nine paragraphs, and then only the first two sentences (of four) in that paragraph. Those two sentences are:
“Scientists’ understanding of the fundamental processes
responsible for global change has greatly improved during
the last decade, including better representation of carbon,
water, and other biogeochemical cycles in climate models.
Yet model projections of future global warming vary,
because of differing estimates of population growth, economic
activity, greenhouse gas emission rates, changes in atmospheric
particulate concentrations and their effects, and also because
of uncertainties in climate models.”
My comment supposes that the position statement is addressed to an informed public who have only a small percentage of scientists in their number. Does the Council agree that this is their intended audience?
Given this audience, there are three points to my comments.
(1) The first of the two sentences says “…understanding has greatly improved in the last decade”. The ‘last decade’ means the calendar years 1994 - 2003. Since then, four years have passed, so there is not now a new decade to compare with the earlier. It requires care to avoid the bias of the present toward the most recent activity, absent a detailed historical evaluation of progress in the last four years, compared to the benchmark decade referenced in the existing position statement. How will these added four years be mentioned?
(2) Both sentences under discussion contain lists of variables. In the first sentence, there are three: “representation[s] of carbon,
water, and other biogeochemical cycles in climate models.” A typical member of the intended audience would believe that the variables are ranked in order of decreasing importance, lacking any statement to the contrary. Is that true? There should be a reason for the order, and it should be stated.
In the second sentence, there is a list of five variables causing differences in model projections. They are, in the order given:
“population growth, economic activity, greenhouse emission rates, changes in atmospheric particulate concentrations and their effects, and also because of uncertainties in climate models.” The same typical member of the audience will assume a ranking, and the most reasonable assumption would be the same as in the last sentence:
most important cause of differences first, least important last. But the actual ranking in this second sentence seems to be in reverse order of that in the first sentence. That is, the variables appear in order of increasing importance in causing model projections to vary. The given order in the second sentence starts with the best determined (population estimates for the end of the present century) and ends with the most problematic (uncertainties in climate models). The apparent reversal in order, and the use of the phrase “and also because of uncertainties”, in context makes it appear as though the model uncertainties are a trivial afterthought.
(3) Finally, the typical member of the intended audience would assume that the variables listed are, in scientific terms, independent variables (the typical member of the intended audience would think of it as ‘no double-counting’). In the first of the two sentences, are carbon, water, and biogeochemical cycles independent variables? In the second of the two sentences, to what extent are population growth, economic activity, greenhouse gas emission rates, particulate concentrations, and model uncertainty independent variables?