"Although all the simulations showed that blocking the Sun's rays – or solar radiation management, as it is called – did reduce the global temperature, the models revealed profound changes to precipitation including disrupting the Indian Monsoon.
Prof Piers Forster of Leeds University said: "We have found that between 1.2 and 4.1 billion people could be adversely affected by changes in rainfall patterns.
"The most striking example of a downside would be the complete drying-out of the Sahel region of Africa – that would be very difficult to adapt to for those substantial populations – and that happens across all the scenarios."
Despite the risk of catastrophic side-effects from geo-engineering, the study authors believe that research should continue just in case…."
http://www.bbc.com/news/science-environment-30197085