Sep 18, 2017

Heat wave probability in the changing climate of the Southwest US

Kristen Guirguis, Alexander Gershunov, Daniel R. Cayan, David W. Pierce
Climate Dynamics
  • States that analyses of observed non-Gaussian daily minimum and maximum temperature probability distribution functions (PDFs) in the Southwest US highlight the importance of variance and warm tail length in determining future heat wave probability
  • States that even if no PDF shape change occurs with climate change, locations with shorter warm tails and/or smaller variance will see a greater increase in heat wave probability, defined as exceedances above the historical 95th percentile threshold, than will long tailed/larger variance distributions
  • Projections from ten downscaled CMIP5 models show important geospatial differences in the amount of warming expected for a location
  • Finds that changes in heat wave probability do not directly follow changes in background warming
  • Projected changes in heat wave probability are largely explained by a rigid shift of the daily temperature distribution
  • Finds that in some locations where there is more warming, future heat wave probability is buffered somewhat by longer warm tails
  • Finds that in other parts of the Southwest where there is less warming, heat wave probability is relatively enhanced because of shorter tailed PDFs
  • Concludes by saying the effects of PDF shape changes are generally small by comparison to those from a rigid shift, and fall within the range of uncertainty among models in the amount of warming expected by the end of the century