USGS Expert Explains How Global Warming Likely Contributes to East Africa's Brutal Drought | ThinkProgress

A key point I and others have made over and over again is that the most extreme weather occurs when climate change compounds the natural variability of the climate. In this case, global warming appears to be intensifying the impact of the La Niña.

How do we know that CO2 doesn't slightly dampen, rather than compound, the natural variability of the climate?