The zonally averaged response of the Global Change Research Center two-dimensional (2-D) statistical dynamical climate model (GCRC 2-D SDCM) to a doubling of atmospheric carbon dioxide (350 parts per million by volume (ppmv) to 700 ppmv) is reported. The model solves the two-dimensional primitive equations in finite difference form (mass continuity, Newton's second law, and the first law of thermodynamics) for the prognostic variables: zonal mean density, zonal mean zonal velocity, zonal mean meridional velocity, and zonal mean temperature on a grid that has 18 nodes in latitude and 9 vertical nodes (plus the surface). The equation of state, p=&rgr;RT, and an assumed hydrostatic atmosphere, Δp=-&rgr;gΔz, are used to diagnostically calculate the zonal mean pressure and vertical velocity for each grid node, and the moisture balance equation is used to estimate the precipitation rate. The model includes seasonal variations in solar intensity, including the effects of eccentricity, and has observed land and ocean fractions set for each zone. Seasonally varying values of cloud amounts, relative humidity profiles, ozone, and sea ice are all prescribed in the model. Equator to pole ocean heat transport is simulated in the model by turbulent diffusion.

The change in global mean annual surface air temperature due to a doubling of atmospheric CO2 in the 2-D model is 1.61 K, which is close to that simulated by the one-dimensional (1-D) radiative convective model (RCM) which is at the heart of the 2-D model radiation code (1.67 K for the moist adiabatic lapse rate assumption in 1-D RCM). We find that the change in temperature structure of the model atmosphere has many of the characteristics common to General Circulation Models, including amplified warming at the poles and the upper tropical troposphere, and stratospheric cooling. Because of the potential importance of atmospheric circulation feedbacks on climate change, we have also investigated the response of the zonal wind field to a doubling of CO2 and have found distinct patterns of change that are related to the change in temperature structure. In addition, we find that both the global mean kinetic energy and simulated Hadley circulation increase when CO2 is doubled. The increase in mean kinetic energy is a result of the increase in upper level meridional temperature gradients simulated by the model. It is stressed that changes in atmospheric dynamics associated with increased carbon dioxide may also be very important to the final steady state distribution of such greenhouse gases as ozone and water vapor. Hence further research in this regard is warranted. ¿ American Geophysical Union 1995