International Herald Tribune
As floods rage in Central Europe and China and drought plagues Africa and North America, it is getting harder to dismiss the scientists who claim that weather is becoming not only warmer but more extreme.
Both of those trends, each in its own way, have ominous implications for the spread of infectious disease.
With this year on track to possibly outdo 1998 as the warmest year on record, according to the British Meteorological Office, it is clear that rising temperatures are enabling carriers of disease such as insects and rodents to expand their range and thus their ability to infect people.
The mosquito, still by far humankind's greatest single enemy in the battle against infectious disease, is rapidly taking advantage of warmer temperatures. It proliferates faster and bites more as temperatures rise, and it has extended its range both in latitude and elevation.
"Not only have we underestimated the rate at which climate would change, we have also underestimated the rate at which biological systems would react," said Paul Epstein, associate director of the Center for Health and Global Environment of the Harvard Medical School.
New Orleans had an explosion of mosquitoes as well as termites and cockroaches after a period of five years, 1990 to 1995, in which the area had no killing frosts
Malaria, which is carried by the Anopheles mosquito, can survive in areas where temperatures do not routinely fall below 16 degrees centigrade (60 degrees Fahrenheit), and has recently made inroads in the Korean Peninsula, Southern Europe, and the former Soviet Union.
Every year the disease kills at least one million people, mostly children. This figure is part of the 300 million victims annually that suffer crippling fevers and other health problems from the disease.
Greater Impact Expected
The danger of greater advances by all mosquito-borne infectious diseases is strong, furthermore, because global warming trends are uneven and are raising night and winter temperatures, which, more than day and summer temperatures, set the thresholds for killing insects.
There is much fear that temperatures, which have been rising fairly gradually over the last century, might at some point undergo upward jolts that spur quantum leaps in the spread of disease.
"Our sense is that change will be gradual, but what we learn from ice records is that we can have sudden flips of 2 to 3 degrees centigrade," said Epstein.