Warming causes disease outbreaks

In many regions, it is already raining less often but harder. According to The Physical Science Basis, trends from 1900 to 2005 show significantly increased precipitation in many regions, including eastern parts of North and South America. More intense and longer droughts have occurred over wider areas worldwide since the 1970s, especially in the tropics and sub- tropics. Sea surfaces have become warmer, and wind patterns have changed. There is also more evaporation from the ocean. These processes alter precipitation patterns on land, bringing more moisture to some areas and diminishing it in others. A long drought followed by an intense downpour is a recipe for multiple disease outbreaks, says Paul R. Epstein, a physician and associate director of the Center for Health and the Global Environment at Harvard Medical School. Epstein is a reviewer for the forthcoming IPCC Working Group II report. During droughts, water availability is diminished, and water quality is often degraded, for example as people share water with livestock. Then heavy down- pours can cause sewers to overflow, and rain runoff washes microbes off farms, lawns, and streets into drinking water supplies. A number of studies have shown a correlation between heavy downpours and outbreaks of waterborne diseases such as cryptosporidiosis, giardiasis, and cyclo- sporidiosis, according to Climate Change Futures: Health, Ecological and Economic Dimensions, a November 2005 report that Epstein co-edited. A drought followed by flooding also encourages rodent and rodent-borne disease outbreaks as rodent populations boom in the wake of replenished water supplies. Rising temperatures and extreme weather could also affect the breeding and spread of ticks that carry Lyme disease, according to Climate Change Futures. Perhaps most widely documented is the association between intense flooding and explosion of mosquito populations, creating outbreaks of mosquito-borne diseases in humans.