Aug 26, 2015

The more extreme nature of U.S. warm season climate in the recent observational record and two “well-performing” dynamically downscaled CMIP3 models

Chang, Hsin‐I, Castro, Christopher L., Carrillo, Carlos M., Dominguez, Francina
Journal of Geophysical Research: Atmospheres
  • Aims to answer the following questions: (1) How is the mean character of warm season precipitation in the U.S. changing? and (2) Does natural climate variability synergistically interact with anthropogenic climate change to intensify extremes?
  • States that during the warm season, observations and Intergovernmental Panel on Climate Change global climate models generally support a “wet gets wetter, dry gets drier” hypothesis in arid and semiarid regions located in subtropical zones
  • Considers changes in U.S. early warm season precipitation in the observational record and regional climate model simulations
  • Finds that, for the observational period (1950–2010), it is fair to say that anthropogenic global warming has already had a profound impact on the U.S. warm season climate over the past 30 years (1981–2010)
  • Finds that temperatures increases are largest strongly in the western U.S., with a “warming hole” in the central U.S. that is likely related to enhanced precipitation and evapotranspiration
  • Finds that both observations and model results show amplification in historical seasonal transitions of temperature and precipitation associated with North American Monsoon System (NAMS) development
  • Finds that similar extreme trends are also projected by Weather Research and Forecasting (WRF)-MPI for the next 30 years (assuming the influence of remote Pacific sea surface temperature (SST) forcing associated with the El Niño–Southern Oscillation and Pacific Decadal Variability (ENSO-PDV) on U.S. regional climate remains the same in the 21st century)
  • Develops a methodology to objectively analyze how climate change may be synergistically interacting with ENSO-PDV variability during the early warm season
  • Analysis suggests that interannual variability of warm season temperature and precipitation associated with Pacific SST forcing is becoming more extreme, and the signal is stronger in the observed record