Recent gridded global temperature analyses have shown that temperature distributions are, on average, shifting in mean and variance. They have also shown that the frequency of extreme temperatures is occurring at much greater percentages than in the past and at frequencies greater than their statistical properties would suggest. We follow a similar methodology as Hansen et al. (2012)—one of the recent global temperature analyses—to assess how seasonal minimum, maximum, and average temperature distributions have changed in the instrumental record across Arizona, New Mexico, Utah and Colorado. We focus on quantifying changes in distributions and extreme temperatures in 20-year periods between 1931 and 2010 for each Historical Climate Network stations in the four states, and compare these results to global analyses. This local, station-based analysis provides insights about seasonal changing temperatures at scales more appropriate to local decision makers.
Results have been used in multiple presentations to local decision-makers. Some results include:
Temperature distributions across the Southwest have shifted in recent decades compared to earlier decades. The percentage of stations experiencing seasonal extreme temperature conditions (i.e. 90th, and 95th percentile temperature) has increased in recent decades.