A study of the climatic effect of doubling or quadrupling of CO2 in the atmosphere has been continued by the use of a simple general circulation model with a limited computational domain, highly idealized geography, no seasonal variation of insolation, and a simplified interaction between cloud and radiative transfer.
The results from the numerical experiments reveal that the response of the model climate to an increase of CO2 content in air is far from uniform geographically. For example, one can identify the high-latitude region of the continent where the runoff rate increases markedly, a zonal belt of decreasing soil moisture around 42° latitude, and a zone of enhanced wetness along the east coast of the subtropical portion of the model continent.
The general warming and the increase of moisture content of air, which results from a CO2 increase, contributes to the large reduction of the meridional temperature gradient in the lower model troposphere because of 1) poleward retreat of highly reflective snow cover and 2) large increase in the poleward transport of latent heat. The reduction of the meridional temperature gradient appears to reduce not only the eddy kinetic energy, but also the variance of temperature in the lower model troposphere. The penetration of moisture into higher latitudes in the CO2-rich warm climate is responsible for the large increase of the rates of precipitation and runoff in high latitudes of the model.