Guest Essay by Willis Eschenbach
Abstract
The Thermostat Hypothesis is that tropical clouds and thunderstorms actively regulate the temperature of the earth. This keeps the earth at a equilibrium temperature.
Several kinds of evidence are presented to establish and elucidate the Thermostat Hypothesis – historical temperature stability of the Earth, theoretical considerations, satellite photos, and a description of the equilibrium mechanism.
Historical Stability
The stability of the earth’s temperature over time has been a long-standing climatological puzzle. The globe has maintained a temperature of ± ~ 3% (including ice ages) for at least the last half a billion years during which we can estimate the temperature. During the Holocene, temperatures have not varied by ±1%. And during the ice ages, the temperature was generally similarly stable as well.
In contrast to Earth’s temperature stability, solar physics has long indicated (Gough, 1981; Bahcall et al., 2001) that 4 billion years ago the total solar irradiance was about three quarters of the current value. In early geological times, however, the earth was not correspondingly cooler. Temperature proxies such as deuterium/hydrogen ratios and 16O/18O ratios show no sign of a 30% warming of the earth over this time. Why didn’t the earth warm as the sun warmed?
This is called the “Faint Early Sun Paradox” (Sagan and Mullen, 1972), and is usually explained by positing an early atmosphere much richer in greenhouse gases than the current atmosphere.
However, this would imply a gradual decrease in GHG forcing which exactly matched the incremental billion-year increase in solar forcing to the present value. This seems highly unlikely.
A much more likely candidate is some natural mechanism which has regulated the earth’s temperature over geological time. Read the rest of this entry »
RSS - Posts
Recent Comments