California’s epic drought got even worse last week. The U.S. Drought Monitor reports that the area of California under moderate drought (or worse) rose from 94.6 percent of the state to a stunning 99.8 percent. The area under extreme or exceptional drought rose from 65.9 to 71.8 percent, encompassing the entire agriculture-rich Central Valley
Back in January, we interviewed 8 of the leading climate and drought experts in the country, who explained in great detail how climate change is worsening California’s epic drought in multiple ways. As I discussed in my 2011 literature review in the journal Nature — even in regions where climate change does not alter the amount of precipitation, it will have these effects:
What precipitation there is will probably come in extreme deluges, resulting in runoff rather than drought alleviation. Warming causes greater evaporation and, once the ground is dry, the Sun’s energy goes into baking the soil, leading to a further increase in air temperature…. Finally, many regions are expected to see earlier snowmelt, so less water will be stored on mountain tops for the summer dry season.
The president’s science advisor John Holdren made precisely the same points in a recent paper.
These points are disputed by very few. So why is there any confusion? A relatively small subset of experts are focused very narrowly on the issue of whether global warming caused a reduction in precipitation — but they generally fail to make clear how narrow their perspective is. NOAA’s Martin Hoerling did this in a recent New York Times piece, asserting “At present, the scientific evidence does not support an argument that the drought there is appreciably linked to human-induced climate change.”