Warmer, drier conditions in the Southwest may be bad for gardeners, real estate developers and fish, but this climatic trend promises to depress the risk of bubonic plague, an international team of scientists reports. Their new study correlates changes in long-term climatic patterns with incidence of the deadly bacterial pestilence, one spread by fleas living on and around mice and other rodents. The El Ni±o Southern Oscillation and P acific Decadal Oscillationare two major patterns of Pacific climate variability, which operate on very different scales. El Ni±o events, also known as ENSOs, tend to last for 6 to 18 months and most directly impact water temperatures in the eastern tropical Pacific. Pacific Decadal Oscillations, or PDOs, persist for 20 to 30 years at a time, bringing long-term swings in sea temperatures, mostly to the northeastern Pacific. Both drive North American climate, setting in motion relatively long-lasting patterns of warmer, wetter weather. Nils C. Stenseth of the University of Oslo ’s Centre for Ecological and Evolutionary Synthesis in Norway and a team of colleagues (from institutions including the U.S. Centers for Disease Control and Prevention) have now linked these patterns of climate variability with ebbs and flow in annual plague incidence from 1950 through 2005. “The underlying mechanism could involve changes in precipitation and temperatures that impact both hosts and vectors,” the researchers write in the September American Journal of Tropical Medicine and Hygiene .