Gov’t Study Finds Climate Models ‘Severely Overpredict’ Continent-Scale Droughts

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Michael Bastasch DCNF Managing Editor
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A new government study casts doubt on predictions of severe continental-scale droughts plaguing the planet because of global warming.

It turns out, climate models predicting mega-droughts from increased warming may be wrong since “such drying seems inconsistent with observations of dryland greening and decreasing pan evaporation,” according to government scientists.

“Here we show that the PET estimator commonly used (the Penman–Monteith PET for either an open-water surface or a reference crop) severely overpredicts the changes in non-water-stressed evapotranspiration computed in the climate models themselves in [anthropogenic climate change] experiments,” Chris Milly and Krista Dunne, U.S. Geological Survey scientists working with the Geophysical Fluid Dynamics Laboratory, wrote in their latest study.

“This overprediction is partially due to neglect of stomatal conductance reductions commonly induced by increasing atmospheric CO2 concentrations in climate models,” the authors wrote.

Scientists and environmental activists have been arguing for years that man-made warming will cause more frequent and severe droughts. The National Center for Atmospheric Research found in 2010, using climate models, that “climate change will likely create increasingly dry soil conditions across much of the globe in the next 30 years, possibly reaching a scale in some regions by the end of the century that has rarely if ever been observed in modern times.”

President Barack Obama even echoed such worries in numerous speeches, especially after a major drought hit California several years ago. Obama announced $183 million for California to deal with its prolonged drought, and even warned global warming would make droughts worse.

“A changing climate means that weather-related disasters like droughts, wildfires, storms, floods are potentially going to be costlier and they’re going to be harsher,” Obama said in 2014. “Droughts have obviously been a part of life out here in the West since before any of us were around and water politics in California have always been complicated, but scientific evidence shows that a changing climate is going to make them more intense.”

The Intergovernmental Panel on Climate Change (IPCC) warned in its 2007 comprehensive study on the state of climate science that droughts would become more severe as the world warmed, but they walked back their claims in their 2013 study.

“In summary, the current assessment concludes that there is not enough evidence at present to suggest more than low confidence in a global-scale observed trend in drought or dryness (lack of rainfall) since the middle of the 20th century due to lack of direct observations, geographical inconsistencies in the trends, and dependencies of inferred trends on the index choice,” the IPCC noted in its 2013 study.

“Based on updated studies, AR4 conclusions regarding global increasing trends in drought since the 1970s were probably overstated,” the IPCC reported. “However, it is likely that the frequency and intensity of drought has increased in the Mediterranean and West Africa and decreased in central North America and north-west Australia since 1950.”

So, what’s been happening to the world if droughts haven’t become more frequent?

Scientists are increasingly finding the world has actually been greening as a result of increased carbon dioxide in the atmosphere. The National Aeronautics and Space Administration (NASA) has even reported on this global greening phenomenon.

NASA scientists found the “greening represents an increase in leaves on plants and trees equivalent in area to two times the continental United States.”

“Our findings imply that historical and future tendencies towards continental drying, as characterized by offline-computed runoff, as well as other PET-dependent metrics, may be considerably weaker and less extensive than previously thought,” Milly and Dunne wrote in their new study.

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