One of our Huntsville, local climate deniers had once testified about his concern for the poor people of Africa. His position was reducing carbon emissions would condemn poor Africans to a life of inefficient, non-powered agriculture and starvation. Then this article came out: Source: Coal-Burning in the U.S. and Europe Caused a Massive African Drought - Olga Khazan - The Atlantic No climate model need apply but it would be interesting if the models showed this pattern. Bob Wilson
Interesting things are revealed by digging a bit deeper here. First, even if I can't drag y'all to the library to read things, you can download the ms (the as submitted version) here http://www.atmos.washington.edu/~yting/papers/hfk_submitted.pdf The study is global. It supports earlier studies along the lines that wet areas get wetter and dry areas get drier. We have talked about this here before. A variety of rainfall data history are compared and found coherent. Climate models don't match the pattern, however, leading to speculation that changes in ocean circulation are also involved. So, this can be compared to the most recent claim posted in the global warming thread. Here, there is a big look at all the data. Not so in the other case. here mechanisms are proposed , and they are testable. That is good. However, I think it can be appreciated that the regional patterns of combustion-aerosol emission through time (presented in this study) represent correlation not demonstrated causation. As usual, the fundamental issue is the accuracy with which we can anticipate climate in the future. If you 'get the ocean right' in the models, and if they then do a superb job of hindcasting, then I (at least) would like the models much better. There is another aerosol-emission reduction in progress now, from China. Mechanisms proposed in Hwang et al would lead to testable predictions about regional rainfall. Perhaps you can see where I'm going with that? The difficulty is that we are talking about precipitation changes over parts of the Pacific, we need TRMM data for that, and that satellite will not have a long future service like. We need a new microwave look-down bird.
A temperature trend analysis from the same research group may actually be more interesting to readers here http://www.atmos.washington.edu/~yting/papers/fhcf_submitted.pdf We could actually understand this thing; a happy prospect. I suggest that it will require extensive analysis of existing data and careful work on the hypotheses.
There was a study a few years ago that concluded that precip increases to a point with increasing aerosol concentration before maxing out and falling off at very high aerosol concentrations due to the competition between individual aerosols and the amount of water vapor available. Dirty Air Brings Rain – Then Again, Maybe Not: Scientists Reconcile Contradictory Effects
Just reading the abstracts, it looks like the European study is more about the mechanics of aerosols. The University of Washington used the climate models to identify aerosol migrations paths. It would be helpful to see if the U of Washington paper cites the EU study and provides aerosol metrics and non-rain associated humidity data to support their claim. BTW, I signed up for "Science Journal" which may provide free access to articles over a year old. Rosenfeld has been quite prolific with an earlier article: Source: Flood or Drought: How Do Aerosols Affect Precipitation? (requires free subscription) Bob Wilson
It would be great if we get this down to a science, but then again, maybe our local conspiracy theorist, Alex Jones, seemed to think some people in the US government caused Sandy. Both ghg and aerosols change rainfall patterns for good or ill. If the US government or the Chinese government got good enough understanding, perhaps they could get focus the pollution to cause the "right" rain. Or maybe they would dry out other countries to provide good crops for their own.
