On Sunday, The New York Times ran an opinion piece stating that the terrible drought in California is not due to global warming.
Martin P. Hoerling, a research meteorologist at the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration, wrote, “At present, the scientific evidence does not support an argument that the drought there is appreciably linked to human-induced climate change.” Hoerling observed that the severe nature of the drought has been observed before, in 1976 and 1977, and that there hasn’t been a notable change in California’s average precipitation since 1895.
Hoerling argued that the reason the drought is making so much news is that the demand for water has greatly increased. He added that other factors, such as the gap between rainy days and the intensity of the rains when they come, could affect the drought-like conditions. Hoerling suggested that examining soil moisture can give a clearer picture of how severe the drought is.
In order to get a reasonably accurate picture, Hoerling turned to a 2012 report by the Intergovernmental Panel on Climate Change, which examined regional changes in soil moisture since 1950. The study said that for western North America, there was “no overall or slight decrease in dryness since 1950; large variability, large drought of the 1930’s dominates.” That conclusion was reiterated by a 2013 report from the same organization, which stated:
Recent long-term droughts in western North America cannot definitively be shown to lie outside the very large envelope of natural precipitation variability in this region, particularly given new evidence of the history of high-magnitude natural drought and pluvial episodes suggested by paleoclimatic reconstructions.