Sept. 20, 2007.
Submitted by S. Fred Singer (Fellow and Life Member, AGU)
www.sepp.org
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Dear AGU Panel Members,
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.
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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, etc., what 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, to critique it where necessary, but at least to mention explicitly that the causes of warming (and cooling) are not yet settled but that a substantial fraction of the climate science community believes that Global Warming is produced largely by natural causes.
Fig. 1: Model-calculated zonal mean atmospheric temperature change from 1890 to 1999 [degC per century] as simulated by the PCM model from [a] solar forcing, [b] volcanoes, [c] well-mixed greenhouse gases, [d] tropospheric and stratospheric ozone changes, [e] direct sulfate aerosol forcing, and [f] the sum of all forcings [IPCC 2007, p.675]. Note the pronounced increase in warming trend with altitude as a ‘fingerprint’ of greenhouse forcing.
Fig. 2: Cover page of CCSP report SAP-1.1, April 2006: “Temperature Trends in the Lower Atmosphere”
Fig. 3: GH-model-predicted temperature trends versus latitude and altitude; this is figure 1.3F from CCSP 2006, p.25. Note increased trends in tropical mid-troposphere.
Fig. 4: Observed temperature trends versus latitude and altitude; this is figure 5.7E from CCSP 2006, p.116. Note absence of increased trends in tropical mid-troposphere.
Fig. 5: Negative feedback from water vapor (WV). The cartoon shows that drying of the upper troposphere (UT) would lead to increased emission to space by WV bands from the warmer boundary layer. To keep total outgoing long-wave radiation (OLR) the same, less radiation is now emitted from the surface, escaping to space through the atmospheric ‘window’ of 8 – 12 microns; i.e., requiring a cooler surface.
Fig. 6: Values of Carbon-14 [a solar proxy] correlates extremely well with Oxygen-18 [temperature proxy], from a stalagmite in Oman [Neff et al 2001 Nature 411, 290-93]. The lower graph shows a particular well-resolved time interval.
