Impacts of climate change observed in global precipitation patterns

Climate change is already affecting precipitation patterns, probably playing a role in the 2012 summer drought.

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More evidence turned up this week indicating that climate change impacts are already underway—this time in rainfall patterns. It's pretty hard to clearly link climate change to individual droughts, like the summer of 2012 in the United States, or specific storms, like Hurricane Haiyan that devastated the Philippines last week. These events are driven by a complex set of factors, including natural variations. But new research that tracked a broad look at precipitation patterns found that they have already shifted beyond the bounds of natural variations.

Typically, precipitation change is the afterthought in climate predictions—temperatures increases are carefully projected by models, but precipitation patterns are more complex and subject to more natural variation. We know things will change, but we're not sure exactly how—that seems to be the general answer to important questions about storm frequency and droughts.

To study these complex patterns on a global scale, scientists first needed to smooth the noise of natural variation from the data while holding on to the key patterns. This required some rather involved statistics.