Abstract This study uses 25 CMIP6 global climate model simulations, bias‐corrected and dynamically downscaled to 9 km, to examine regional changes in extreme precipitation, and predictive uncertainty, in the western United States under global warming levels (GWL) of 2°C and 3°C. This resolution is needed to capture orographic precipitation enhancement. Most models agree on significant increases in both the Rx1day and R99p indices. The largest increases in extreme precipitation are anticipated in California, both in an absolute sense, with Rx1day increases up to ∼10 mm/day, and in a relative sense, with up to a doubling of R99p in the more arid parts of the state for GWL 3°C. The most significant reductions in return intervals of extreme precipitation events are anticipated in the Rocky Mountain region. For instance, 50‐year Rx1day events become 3 to 4 times more frequent under GWL 2°C and 6 to 8 times more frequent under GWL 3°C.
Observations from the Little Bunker
Last updated: October 16, 2025 02:57 AM
Atmospheric CO₂
424.4 ppm
+18.2
ppm/year
Atmospheric CH₄
1933.54 ppb
+12.29
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year