Transcripts of 21st_Century_Drought_final-H264_Good_1280x720_29

Narrator: A new NASA study predicts that by the end of the 21st Century, the American Southwest and Great Plains are likely to experience longer and more severe droughts than at any other time in the last thousand years. Cook: So recent droughts like the ongoing drought in California or in the Southwest, or even historical droughts like the dustbowl in the 1930s. These are naturally-occurring droughts that typically last several years or sometimes almost a decade. In our projections what we're seeing is that with climate change, many of these types of droughts will likely last for 20, 30, sometimes even 40 years. Even exceeding the duration of the long-term intense mega-droughts that characterized the really arid time period known as the Medieval Climate Anomaly. Narrator: So how can we peer into the planet’s future? Researchers combined natural harnessed the processing capabilities of powerful supercomputers. The scientists looked at a thousand years of tree ring data and compared those records with soil moisture data from 17 different climate models, in order to extend this information into the future. The models all show a drier world thanks to increased temperatures from human induced climate change. Cook: These computer simulations, these climate models, really represent our best understand of the physics and the workings of the climate system. They're tested extensively against observations, and at the end of the day if we want to investigate future climate, they're really the only tool that we have to use. Narrator: How bad these droughts are likely to get has a lot to do with how much greenhouse gas emissions humans generate in coming years. Scientists looked at two different possibilities. First, a “business as usual” scenario where world-wide greenhouse gas emissions continue on their current course. In this case the future risk of lengthy droughts rises to 80%. lternatively, if the world were to take aggressive actions to reduce emissions, the models still show drying, but the trends will be less severe. In either scenario, droughts could potentially have major impacts in a region already facing water management concerns. Cook: These droughts really represent events that no in the history of the United States has ever had to deal with. And so even in the modern era droughts such as the ongoing droughts in California and the Southwest, these normal droughts act as major stresses on resources in the region, so we expect with these much longer droughts, it's going to be even more impactful and cause even more problems for agriculture and ecosystems in the region. 

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