An international team of top boffins say that current climate models are based on faulty assumptions which lead them to predict more drought than will actually be the case.
At the moment, climate modelling assumes that areas of land that are wet give off more evaporated water, which means that air above such areas will tend to give up any water it is carrying in the form of rain. By contrast air will tend to pass over dry regions without giving up any raindrops, and thus dry places will get drier.
Source: The Register. Read full article. (link)