Drought Potential in the 21st Century

The United States and many other heavily populated countries face a growing threat of severe and prolonged drought in coming decades, according to a new study by National Center for Atmospheric Research (NCAR) scientist Aiguo Dai. The detailed analysis concludes that warming temperatures associated with climate change will likely create increasingly dry 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. The movie shows the evolution of the annual mean self-calibrated Palmer Drought Severity Index (PDSI), a measure of meteorological drought, calculated using surface meteorological data from multiple models of the CMIP3 project under a moderate emissions scenario (A1B) and the Penman-Monteith equation for potential evapotranspiration. Negative values are for dry conditions and values below -3 are considered severe to extreme drought by today’s standard.



Palmer Drought Severity Index

Further Information

  • Palmer Drought Severity Index (PDSI)
  • Dai, A., 2011: Drought under global warming: A review. Wiley Interdisciplinary Reviews: Climate Change, 2, 45-65. DOI: 10.1002/wcc.81.
  • Dai, A., 2013: Increasing drought under global warming in observations and models. Nature Climate Change. 3: 52-58. doi:10.1038/nclimate1633


Multiple models from the CMIP3 project

Data Source



Tim Scheitlin