hand, the variation in temperature as we move north or south is reduced from the preindustrial. Given that, and bearing in mind the importance of temperature gradients in determining the weather, it is not surprising that the patterns of precipitation change.  Rainfall is reduced on average over the entire planet, with strong effects over the Americas and northern Eurasia. The total global cloud cover is also reduced in all the models. This contributes to the change in albedo (reflectivity) of the planet, which drops by about 2 % in all four models. The models all predict a stronger effect in Europe but disagree on what would happen in large parts of the tropics or subtropics. Note that the reduction in albedo means that less of the sun's radiation is reflected from Earth, so more particles or mirrors would be required to reduce the incoming radiation sufficiently to maintain the preindustrial mean global temperature. There are of course many uncertainties in the calculations. The sudden quadrupling of CO 2 is not realistic, though the rise to four times the preindustrial level is within the bounds of the current climate change models, albeit at the high end of the range of predictions.  On the other hand, holding the mean global temperature constant is very much a best case scenario, and secondary effects such as decreased precipitation may well be underestimated. To conclude An Earth with a high level of greenhouse gases and a geoengineering scheme that compensates by reducing the amount of