CO2 Does Not Pollute: But Kyoto's Demise Won't End Debate
"tuned" to yield responses similar to several complex models. The range narrows considerably, to somewhere between 2.0°C and 4.6°C, when one calculates the average of these various models over all of the scenarios. Also, the media reports fail to note that the larger range stated in the third report includes climate sensitivities to doubling of CO 2 concentrations of anywhere from 1.5°C to 4.5°C. The "Policymakers Summary" for the Third Assessment Report does not acknowledge that the most likely climate sensitivity for a CO 2 doubling, as per the Second Assessment Report, is only 2.5°C. Reliance on that figure reduced the range of forecasted temperature increases for all scenarios to 1.3°C to 2.5°C, for the period 1990 to 2100 1.
In a similar fashion, the scenarios in the third report appear to encourage alarm by again using a range from between 770 to 2190 GtC of cumulative carbon emissions between 1991 and 2100. As was pointed out in the 1995 report, the most probable scenario is that CO 2 concentrations will stabilize between 450 and 650 ppmv between 2100 and 2200. At the midpoint of 550 ppmv, this would correspond to less than 1000 GtC of cumulative emissions between 1991 and 2100. That scenario assumed a gradual phase-out of fossil fuels during the second half of the 21st Century and their replacement with renewable or essentially inexhaustible energy sources. In fact, it is the most carbon-intensive of these fuels - coal - that is expected to continue to lose energy market share most rapidly. Next to lose share would be oil, and then eventually natural gas, the least carbon-intensive and polluting of all the fossil fuels. (However, global gas use and market share are expected to continue to grow well into the 21st Century.) Therefore, at the most likely climate sensitivity of 2.5°C (to a doubling of CO 2), the further temperature increase between 1990 and 2100 will probably be nearer to 1.5°C than 5.8°C - even on the basis of the flawed surface temperature measurements used by IPCC ().
Consider also the question of recent temporary anomalies in weather patterns.
One reason for criticism of the "Summary for Policymakers" for the new IPCC Third Assessment Report is that it again fails to give greater weight to the large disparity between its surface temperature measurements and NASA satellite measurements. For example, it doesn't discount the "fly-up" in mean temperatures seen recently by these satellites in the lower troposphere (from the surface up to about 15,000 ft.) in both the Northern (1°C) and Southern Hemispheres (0.6°C). This fly-up was due to the large El Niño anomaly in 1998. It quickly abated during 1999. By 2000, NASA satellite measurements had dropped below the 1979-98 average in both hemispheres 5. NASA satellites uniformly and accurately measure lower tropospheric temperatures for the entire globe, unlike the statistically much less uniform and highly unreliable surface temperature measurements which, among other uncertainties, are greatly affected by the "urban heat island" phenomenon (i.e., the ever-growing and spreading heat release from human activities in urban and suburban