Researchers at Lamont-Doherty Earth Observatory and other centers have warned that the US Southwest will experience severe droughts over the next several decades. According to climate scientists, the United States’ two most vulnerable regions will suffer droughts that are worse than any seen during times past or present. Drying conditions due to global warming are “primarily” responsible for the extreme dryness. Toby Ault from Cornell, associate professor of earth-atmospheric sciences, stated that the results were “astonishing.” We have weighed the odds in favor of mega-drought as a society. As we add more carbon dioxide to our atmosphere, data clearly shows that there is a significant risk to the Great Plains and Southwest. But, it is possible to reduce the risk if we take action to lower greenhouse gasses within the next year. (Image: Science Advances). Their research has been published online in Science Advances. Citation below. This will be worse than the droughts that affected the area in the previous 1 ,000 year. The expected drying will surpass any “mega-droughts”, which have struck the area in the past 1 ,000years. These conditions will prove to be more severe than those scientists link with the collapse of the Ancient Pueblo Peoples in Colorado Plateau 7100 years ago. Although there have been many studies that predicted that the US Southwest would dry due to global warming, this one is the first to forecast worse conditions than those seen in distant history. The researchers warned that the effects could prove to be catastrophic due to the large populations living in these two US areas. Jason E. Smerdon (climate scientist) was co-author. He said that “we are the first people to make this type of quantitative comparison between projections and distant pasts, and it is quite bleak.” Even when selecting for the worst megadrought-dominated period, the 21st century projections make the megadroughts seem like quaint walks through the Garden of Eden.” Lead author Benjamin I. Cook said: “The surprising thing to us was really how consistent the response was over these regions, nearly regardless of what model we used or what soil moisture metric we looked at. All of it showed that there was significant drying. The likelihood of severe droughts for several decades rises after 2050. (Image: Science Advances). Droughts are already impacting the American West. In large parts of the American West including Arizona, New Mexico and Nevada, 11 have experienced drought years in the past 14. Similar droughts have been observed from the Southern Plains to Texas, Oklahoma and Oklahoma. This is according to the US Drought Monitor. It’s a joint effort of several government agencies. According to NASA, more than 64million people are directly affected by drought in the Southwest and Southern Plains. However, many millions of others, mainly farmers, may be indirectly affected. Western states have had to impose water usage restrictions due to dwindling water resources. Aquifers are being dredged to an unsustainable level, and key reservoirs like Lake Powell or Lake Mead are at their lowest levels ever. The Los Angeles Department of Water and Power announced in February that winter snowpack levels in the Sierras — a crucial source of water for Los Angeles and surrounding cities – were less than 25% of “normal”. 2014, Hundreds of thousands of acres were abandoned in Central Valley because officials cut water flow to the southern part of California. According to climate researcher Kevin Anchukaitis, “Changes to precipitation, temperature, drought and their consequences for society–which is critically dependent upon our freshwater resources–are likely to have the greatest immediate climate impacts as a consequence of greenhouse gas emission.” Edward Cook, Lamont-Doherty scientist (Benjamin Cook’s father) created the North American Drought Atlas 2009.. His research has contributed a lot to scientists’ understanding of droughts in the past. The Atlas reconstructs drought history over the last 2 year based upon the chronologies of many tree-ring readings. These were gleaned from thousands of trees samples throughout North America. The scientists used the Atlas data to show past climate and then applied three drought measures: a modified Palmer Drought Severity Index that gauges rainfall, evaporation, transpiration, as well as two soil moisture measurements at different depths. Although some people have questioned the accuracy of the Palmer Drought Index in determining soil moisture, scientists discovered that it was well-correlated with other measurements. It “provides an intermediary between [climate] models, drought in observations” according to Mr. Cook. The scientists used seventeen climate models for analysis of the potential future effects on these areas from rising temperatures. It was also compared to other global warming scenarios. The other with “business as normal”, which forecasts that greenhouse gas emissions will continue to increase and contribute to global warming. 2. An environment where the emissions are controlled. They came to the same conclusion by most of these measures. David Stahle is a professor at the University of Arkansas, and the director of Tree-Ring Laboratory. He said that the results “are extremely unfavorable to the continuation of agricultural/water resource management as it is currently practiced in Great Plains, and Southwest United States.” Professor Stahle also worked on the North American Drought Atlas. Smerdon and his colleagues are optimistic about their findings. The authors wrote that the effects of CO2 in higher temperatures and subsequent drying in the Southwest, Great Plains and Midwest emerges as a strong signal across all models regardless of drought metrics. These results are consistent with other studies.” Anchukaitis said that the paper provides an “elegant and convincing connection” between climate reconstructions and future drought models. Citation: “Unprecedented 21st Century Drought Risk in the American Southwest & Central Plains,” Benjamin I. Cook, Toby R. Ault and Jason E. Smerdon. Science Advances. 01 Feb 2015: Vol. 1 no. 1 e1400082 DOI: 10.1126/sciadv.1400082. NASA Video: Multi-Decade Mega Droughts Predicted
