Increasing planetary temperatures resulting from our greenhouse gas emissions have led people to be concerned about the fate of our future food supply. In response to this threat posed by climate change, people have proposed these radical ideas of reflecting additional sunlight away from the earth in order to counteract the effect of these greenhouse gases.
But it had been proposed or suggested that, if this were done, it would threatened the food supply for billions of people. So Julia Pongratz, working in my group, led a very nice study where we ran two different climate models and then used the same kinds of crop models that are used for projecting the effects of climate change on crop productivity to see how would these geoengineering schemes affect crop productivity.
In two different climate models, the result was that--in the models at least--the crop productivity increased. This is largely because under a high CO2 warm world, the crops are increasingly stressed by high temperatures. In the model with the geoengineering, there’s cooling, and this releases the thermal stresses on the plants, but you still get the CO2 fertilization effect.
This result might not hold regionally. You can imagine that there would be certain regions that would have reduced crop yields. And these are climate models which are simplifications of the real world, so real world results might differ from these model results. So it would be premature to act on these, but at least the initial evidence seems to be that geoengineering proposals would seem more likely to increase rather than decrease crop yields on a global basis.