Model Projections of the Climatic Changes Induced by Increased Atmospheric CO2

Abstract

The simulations of CO2-induced equilibrium climatic change by energy-balance models, radiative-convective models and general circulation models are reviewed and characterized in terms of the direct radiative forcing of the increased CO2, the response of the climate system in the absence of feedback processes, and the feedbacks of the climate system. Five recent simulations of CO2-induced climatic change by atmospheric GCM/mixed-layer ocean models are contrasted in terms of their surface air temperature and soil moisture changes. The simulations of CO2-induced transient climatic change by planetary energy-balance models, radiative-convective models and general circulation models are reviewed in terms of the e-folding time τe of the response of the climate system. Theoretical studies for a time-dependent CO2 increase between 1850 and 1980 indicate that the sequestering of heat into the ocean’s interior is responsible for the concomitant warming being only about half that which would have occurred in the absence of the ocean. These studies also indicate that the climate system will continue to warm towards its as-yet unrealized equilibrium temperature change, even if there is no further increase in the CO2 concentration.