Extreme Events
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Expect hotter days, warmer nights, heavier rain and snowfall events, and more floods over the next century, says a new study published September 22 in the journal Science. The study sizes up extreme weather events that have intensified during the past century and are expected to escalate over the next as carbon dioxide and other greenhouse gases shake up the earth's climate. The study was conducted by researches at the National Oceanic and Atmospheric Administration and the National Center for Atmospheric Research.

The earth's average temperature has risen about 1.1 degrees Fahrenheit since the start of the 20th century, mostly due to higher daily minimum temperatures. In other words, low temperatures are higher than they used to be. This shows itself in the dramatic shrinking of winter over the past century. During the same period precipitation has increased, but just over land areas in the mid- to high latitudes. Precipitation has decreased in the tropics.

In the United States, incidents of heavy rainfall over several days increased most noticeably in the Mississippi River Valley, the Southwest, the upper Midwest, and the Great Lakes.

Other changes are expected to appear later in this century as greenhouse gases continue to accumulate, trapping more heat in the atmosphere. In North America, the south central and southeast regions will get the hotter and drier, just like this year, increasing the likliehood their of major droughts.

Growth in both population and wealth, along with demographic shifts to storm and drought-prone areas, has made the United States more vulnerable to weather assaults. Total federal relief payments for weather-caused disasters from 1990 through 1997 hit $12 billion. These costs are expected to soar if extreme weather continues to intensify over the next century, as it is forecasted to do. For the Weather Notebook, I'm Dave Thurlow.