Geoengineering sometimes looks like a good option: international agreements on greenhouse gas emission reductions don’t seem to be going anywhere so having a back-up plan to deal with global temperatures would be useful.
However, there are potentially big problems with tinkering with the climate system more than we already have.
Haywood et al. outline one of these problems in a new Nature Climate Change paper that was published this week.
They look at the response of the climate in models when you add aerosol particles to the stratosphere – this will reduce the amount of energy entering the climate system by reflecting some of it away.
The unintended consequences, however, are not good: global rainfall patterns change as a result of the intervention and could lead to droughts in some areas e.g. the Sahel. (These outcomes are sensitive to where the aerosol is added and, of course, are subject to all the usual model uncertainties.)
So it would seem that geoengineering might only be useful if there are international agreements on who takes responsibility for the outcomes. Best get those negotiations started ASAP then!
There’s some more comment in The Gaurdian.