"Observations since the beginning of the 20th century for the United States
indicate that intense precipitation events have already increased by about
20 percent, and cold season precipitation has increased by nearly 10
percent," said karl. An increase in the intensity of precipitation has led to an
increased flood potential.
Overall, precipitation totals for the October-December 1996 period exceeded
150% of normal throughout the Northwest. During October, totals averaged
125% of normal throughout the Northwest, following an unusually wet
September. Totals averaged approximately 110% of normal during November.
Very heavy precipitation then inundated the Northwest during December, with
totals averaging more than 200% of normal recorded throughout the region.
On January 7, the statewide-average of snowpack water content went up 150% of
normal in California, Idaho, Montana, Nevada, Oregon, Utah and Washington,
according to NOAA measurements. The largest abnormalities were observed in
Washington, where snowpack water totals increased 225% of normal.
What does global warming have to do with the flooding?
Increased concentrations of greenhouse gases in the atmosphere lead to an
increase in mean global temperatures. As the global climate warms, the water
cycle is affected because small amount of heating will evaporate
larger quantities of water from the earth's surface.
As global temperatures increase, the atmosphere can also support greater
amounts of water vapor. This means there will be more flooding with an increased
rainy events, but also more droughts. Droughts arise where and when
the atmosphere is not favorable to rain and snow, and the evaporated
moisture is transported to other regions. The additional evaporation from
the surface leads to a drying of the soil, and more severe and widespread
droughts.
As the global climate warms, the water
cycle is affected because a portion of the heating will evaporate
larger quantities of water
Getting technical, comparisons of climate.
When carbon dioxide concentrations are doubled, the expected frequency and
extent of extreme droughts and strong precipitation in the United States
increase (more than two inches per day) and Canada (more than one inch per
day). Some models show a three to four-fold increase. There is also a
different increase in wintertime.
Recent events, like the flooding in the Northeast last autumn and the
flooding this winter, offer examples of the kind of situations that are
expected to be associated with an increased risk of global warming.
The World Energy Council, an independent research
organization, released a report July 4, 1996 which found that global
use of carbon dioxide (CO2) increased by 12% between 1990 and 1995.
The Council said the trend would continue unless direct action is taken to
reduce the use.
The World Energy Council report said two to three times as many people may
die in heat waves annually by the year 2050 as do today, even if they become used to warmer temperatures. It also forecast a large spread in
the range of malaria and other tropical diseases over the next several years.
The Intergovernmental Panel on Climate Change (IPCC), a large group of
climate experts who have been conducting research and reviewing studies over
the past several years, has concluded that there has been significant global
warming during this century, based on a careful review of all of the
available data, including ground-based temperature records, satellite data,
balloon-borne temperature profiles, bore hole temperature profiles, and
retreat of mountain glaciers.
