This pretense has worn thin. The frequency of downpours and heat
waves, as well as the power of hurricanes, has increased so
dramatically that "100-year storms" are striking some areas once every
15 years, and other once rare events keep returning like a bad penny.
As a result, some climatologists now say global warming is to blame.
Rising temperatures boost the probability of extreme weather, says Tom
Karl, director of the National Climatic Data Center and lead author of
a new report from the Bush administration's Climate Change Science
Program; that can "lead to the type of events we are seeing in the
Midwest." There, three weeks of downpours have caused rivers to treat
their banks as no more than mild suggestions. Think of it this way: if
once we experienced one Noachian downpour every 20 years, and now we
suffer five, four are likely man-made.