Mar 19, 2018

Early emergence of anthropogenically forced heat waves in the western United States and Great Lakes

Hosmay Lopez, Robert West, Shenfu Dong, Gustavo Goni, Ben Kirtman, Sang-Ki Lee, Robert Atlas
Nature Climate Change
  • Climate projections for the twenty-first century suggest an increase in the occurrence of heat waves
  • States, however, that the time at which externally forced signals of anthropogenic climate change (ACC) emerge against background natural variability (time of emergence (ToE)) has been challenging to quantify, which makes future heat-wave projections uncertain
  • Combines observations and model simulations under present and future forcing to assess how internal variability and ACC modulate US heat waves
  • Shows that ACC dominates heat-wave occurrence over the western United States and Great Lakes regions, with ToE that occurred as early as the 2020s and 2030s, respectively
  • Finds, in contrast, that internal variability governs heat waves in the northern and southern Great Plains, where ToE occurs in the 2050s and 2070s; this later ToE is believed to be a result of a projected increase in circulation variability, namely the Great Plain low-level jet
  • Concludes that greater mitigation and adaptation efforts are needed in the Great Lakes and western United States regions