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NASA – ‘megadrought’ will grip U.S. in the coming decades

– Washington Post: ” The long and severe drought in the U.S. Southwest pales in comparison with what’s coming: a “megadrought” that will grip that region and the central Plains later this century and probably stay there for decades, a new study says. Thirty-five years from now, if the current pace of climate change continues unabated, those areas of the country will experience a weather shift that will linger for as long as three decades, according to the study, released Thursday. Researchers from NASA and Cornell and Columbia universities warned of major water shortages and conditions that dry out vegetation, which can lead to monster wildfires in southern Arizona and parts of California. “We really need to start thinking in longer-term horizons about how we’re going to manage it,” said Toby R. Ault, an assistant professor in the department of Earth and atmospheric sciences at Cornell, one of the co-authors. “This is a slow-moving natural hazard that humans are used to dealing with and used to managing.” Megadroughts are sustained periods of sparse precipitation and significant loss of soil moisture that span generations, about 10 times as long as a normal three-year drought.”
  • Reference – Unprecedented 21st century drought risk in the American Southwest and Central Plains, , , Science Advances 12 Feb 2015: Vol. 1 no. 1 e1400082. DOI: 10.1126/sciadv.1400082: “

    In the Southwest and Central Plains of Western North America, climate change is expected to increase drought severity in the coming decades. These regions nevertheless experienced extended Medieval-era droughts that were more persistent than any historical event, providing crucial targets in the paleoclimate record for benchmarking the severity of future drought risks. We use an empirical drought reconstruction and three soil moisture metrics from 17 state-of-the-art general circulation models to show that these models project significantly drier conditions in the later half of the 21st century compared to the 20th century and earlier paleoclimatic intervals. This desiccation is consistent across most of the models and moisture balance variables, indicating a coherent and robust drying response to warming despite the diversity of models and metrics analyzed. Notably, future drought risk will likely exceed even the driest centuries of the Medieval Climate Anomaly (1100–1300 CE) in both moderate (RCP 4.5) and high (RCP 8.5) future emissions scenarios, leading to unprecedented drought conditions during the last millennium.”

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