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Saturday, December 10, 2016

A new study published in the Journal of Climate warns that decade-long droughts are likely to occur in the U.S. Southwest within the coming century if no action is taken against climate change.

Megadroughts (or droughts that last for two decades or longer) are cyclical, and long periods of drought have plagued the Southwest in the past (such as the Dust Bowl). However, National Drought Mitigation Center climatologist Mark Svoboda points out, “We are simply much more vulnerable today than at any time in the past. People can’t just pick up and leave to the degree they did in the past.”

According to the study, “the risk of a decade-scale megadrought in the coming century [in the SW] is at least 80 percent, and may be higher than 90 percent in certain areas.”

As this map from USA Today shows, some of the most densely populated regions of the country are at very high risk of extended, civilization-threatening droughts.

Drought Map

Prolonged drought is no longer a far-off, abstract concept. The state of California is facing one of the most severe droughts on record. Governor Jerry Brown declared a drought State of Emergency in January, and as of August 28, 100 percent of the state of California was considered to be in a drought, according to the U.S. Drought Monitor. More than 58 percent is in “exceptional” drought, the highest level of intensity listed. Californians are in the midst of the worst three years for precipitation in 119 years of records. Reservoir storage levels have continued to drop, prompting comedian Conan O’Brien to launch a series of PSA videos urging Californians to conserve water.

O’Brien is right to be concerned about his state’s drought, but the recent study shows that California’s current situation is far from the worst of what we can expect to see if action against climate change is not taken.

Drought Map 2

This graphic from ThinkProgress reveals that for most parts of the Southwest, there is an over 40 percent chance of a megadrought lasting 35 years or longer during this century, if we do nothing (Figure i). As the scale shows, the percentages drop significantly in the other two scenarios (Figures g and h), where aggressive action is taken against carbon emissions. In Figure g, the nation and the world keep carbon pollution levels to 450 parts per million of total greenhouse gasses in the atmosphere, and in Figure h the levels are limited to 500 parts per million.

The study goes on to note that our action or inaction is more than just a national concern. After extending their analysis of megadrought risk, scientists found that “risks throughout the subtropics appear as high or higher than estimates for the U.S. Southwest.”

The prolonged drought that California has faced these past months would be a mere drop in the bucket, compared to a megadrought that lasts multiple decades. The most alarming aspect of the study is that scientists based their evaluations on conservative precipitation projections and did not take any possible increases in temperatures into account. These increases in temperature would make the risk of megadrought within the next century 100 percent, as ThinkProgress notes.

Photo via Wikimedia Commons

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