## Friday, August 17, 2007 ... /////

### Stephen Schwartz of Brookhaven: climate sensitivity is 1.1 Kelvin

Many of the recent entries included in the weekly dose of peer-reviewed climate denier literature were published in Geophysical Research Letters. For the sake of diversity, today we offer an article that will appear in Journal of Geophysical Research.

Stephen Schwartz: Heat capacity, time constant, and sensitivity of Earth's climate system (full text)
The author is from Brookhaven National Laboratory, the same one that successfully tests string-theoretical holography through the RHIC experiment. His calculated result for the climate sensitivity is 1.1 Celsius degree, plus minus half a degree: three times smaller than the IPCC figure and consistent with the typical calculations of the Reference Frame.

His method

Schwartz first determines the heat capacity of oceans, by observing links between temperature and the heat content of the oceans on the record. His result is equivalent to a layer of water that is between 60 and 160 meters in thickness which is probably a reasonable result regardless of the method that was used. Other sinks add about 20% to this figure.

The time constant relevant for changes is determined from autocorrelation of the last 125 years of temperature records and ends up being between 4 and 6 years: in five years, the deviation from the expected equilibrium drops 2.718 times. The outcome - 5 years - is obtained in various ways, indicating robustness. Recall that e.g. Nir Shaviv recently talked about 2-10 year lags.

The final energetical sensitivity of 0.30 Celsius degrees per one Watt per squared meter, plus minus 50 percent, that translates to 1.1 Celsius degree plus minus 50 percent for CO2 doubling, is obtained simply by taking the ratio of 5 years and the overall heat capacity that is equal to 17 plus minus 7 yr K^{-1} W m^{-2} in ordinary SI units.

This small result is obtained despite the fact that all other forcings except for radiative and greenhouse forcing are inferred to have contributed only -0.3 plus minus 1 Watt per squared meter of (probably) cooling during the 20th century. Note the huge, 300% uncertainty about the other feedbacks, usually assumed to be dominated by unpredictable aerosols.

Predictions for 21st century

Recall that most of the 1.1 degree - about 0.7 degrees - has already occurred since the beginning of the industrial era. This fact itself is an indication that the climate sensitivity is unlikely to be much greater than 1 Celsius degree: the effect of most of the doubling has already been made and it has led to 0.7 K of warming or so. By the end of the doubling i.e. 560 ppm expected slightly before 2100, assuming a business-as-usual continued growth of CO2 that has been linear for some time, Schwartz and others would expect 0.4 C of extra warming only - a typical fluctuation that occurs within 4 months and certainly nothing that the politicians should pay attention to.

As far as I can say, all the people who end up with 2 or even 3 Celsius degrees for the climate sensitivity are just playing the children's game to scare each other, as Richard Lindzen says, by making artificial biased assumptions about positive feedbacks. There is no reasonable, balanced, and self-consistent work that would lead to such a relatively high sensitivity. But frankly speaking, even if the sensitivity were 2 Celsius degrees, it wouldn't imply any tragedy.

Thanks to Benny Peiser.