摘要：The effect of climate change on the frequency and intensity of droughts across the
contiguous United States over the next century is assessed by applying Standardized
Precipitation Indices and the Palmer Drought Severity Index to the full suite of 22
Intergovernmental Panel on Climate Change General Circulation Models for three
IPCC-SRES emissions scenarios (B1, A1B, and A2 from the Special Report on Emissions
Scenarios (SRES) listed in order of their emissions through 2100 from high to
low). The frequency of meteorological drought based on precipitation alone is
projected to increase in some parts of the US, for example the southwestern states,
and decrease in others. Hydrological drought frequencies based on precipitation
and temperature are projected to increase across most of the country, however,
with very substantial and almost universally experienced increases in drought
risk by 2050. For both measures, the southwestern US and the Rocky Mountain
states are projected to experience the largest increases in drought frequency,
but these areas may be able to exploit existing excess storage capacity. Drought
frequencies and uncertainties in their projection tend to increase considerably over
time and show a strong worsening trend along higher greenhouse gas emissions
scenarios, suggesting substantial benefits for greenhouse gas emissions reductions.
