Atmospheric CO 2 : Principal Control Knob Governing Earth’s Temperature

Abstract

Turning Up the Heat: The physical effect of atmospheric carbon dioxide on Earth's energy budget—that is, its “greenhouse effect”—has been understood for more than 100 years, but its role in climate warming is still not universally accepted. Lacis et al. (p. 356 ) conducted a set of idealized climate model experiments in which various greenhouse gases were added to or subtracted from the atmosphere in order to illustrate their roles in controlling the temperature of the air. The findings clearly show that carbon dioxide exerts the most control on Earth's climate, and that its abundance determines how much water vapor the atmosphere contains, even though the radiative effect of the water vapor is greater than that of carbon dioxide itself.