New research from Stephen Schwartz of Brookhaven National Lab concludes that the Earth's climate is only about one-third as sensitive to carbon dioxide as the IPCC assumes. Schwartz's study is “in press” at the Journal of Geophysical Research and you can download a preprint of the study here.
According to Schwartz's results, which are based on the empirical relationship between trends in surface temperature and ocean heat content, doubling the CO2 concentration in the atmosphere would result in a 1.1oC increase in average temperature (0.1–2.1oC, two standard deviation uncer-tainty range). Schwartz's result is 63% lower than the IPCC's estimate of 3oC for a doubling of CO2 (2.0–4.5oC, 2SD range).
Right now we're about 41% above the estimated pre-industrial CO2 level of 270 ppm. At the cur-rent rate of increase of about 0.55% per year, CO2 will double around 2070. Based on Schwartz's results, we should expect about a 0.6oC additional increase in temperature between now and 2070 due to this additional CO2. That doesn't seem particularly alarming.
A couple of other interesting implications of Schwartz's results:
Aerosols have a relatively small effect on temperature. A doubling of CO2 has an estimated climate “forcing” of 2.7 watts per square centimeter (W/cm2). In contrast, actual aerosol concentrations during the 20th Century had a forcing of -0.3 W/cm2 with a large uncertainty range that could mean either net cooling or net warming from aerosols.
The response time, or “time constant”, of the climate to greenhouse gas forcing is relatively small—only five years. In other words, there's hardly any additional warming “in the pipeline” from previous greenhouse gas emissions. This is in contrast to the IPCC, which predicts that the Earth's average temperature will rise an additional 0.6oC during the 21st Century even if greenhouse gas concentrations stopped increasing.
Schwartz is careful to include the appropriate caveats to his results. But he also shows that his estimates are consistent with much of the previous literature on the subject. His study also has the virtue of relying largely on empirical measurements of actual climate behavior during the 20th Century, rather than on climate models.
Stephen Schwartz is a pretty mainstream climate scientist. Yet along with dozens of other studies in the scientific literature, his new study belies Al Gore's claim that there is no legitimate scholarly alternative to climate catastrophism.
Indeed, if Schwartz's results are correct, that alone would be enough to overturn in one fell swoop the IPCC's scientific “consensus”, the environmentalists' climate hysteria, and the political pretext for the energy-restriction policies that have become so popular with the world's environmental regulators, elected officials, and corporations. The question is, will anyone in the mainstream media notice?