An analytical model is developed for estimating the heat fluxes in the lower and upper parts of the atmosphere that would result from possible increases in the carbon dioxide (CO2) concentrations and the ensuing temperature changes. For a doubling of the CO2 concentration by volume, the net heat flux to the troposphere is estimated to increase by 22 percent, and for a quadrupling of the concentration, the net heat flux increases by 39 percent, implying an enhanced energy input to the troposphere where weather phenomena are initiated. As a contingency measure in case efforts to reduce emissions are unsuccessful, a geoengineering project is considered to mitigate the effects of a possible runaway global change. The goal is the restoration of the ancient circumglobal equatorial current by digging a trans-isthmian sea level canal through the Isthmus of Panama using conventional and nuclear civil engineering methods. This would restore the temperate climatic conditions that existed 3 million years ago. Other alternatives involving ocean iron seeding, atmospheric injection of sulfates to increase reflectivity to solar radiation and shading the Earth with Mylar disc reflectors, are discussed.