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While the press widely reported the scientific discovery that 1997 was the warmest year of the century, overlooked was news that global precipitation has dramatically increased during this century.
Global land precipitation has increased by almost nine inches during the 20th century. By contrast, global temperatures have increased about one degree Fahrenheit, mostly during the past few years.
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The new report
on global land precipitation, published in the November issue of the Journal of
Climate, was based on new
analysis of data from 1900-1988. Scientists found a
global land increase of a 2.4 mm per decade -- meaning that there is now almost nine inches more rain falling now each year
than there was at the turn of the century.
"Though much speculation remains as to the cause of this increase... [it's] reminiscent of global climate model predictions of the atmosphere's response to an increase in greenhouse gas concentrations," said Dr. Anthony Del Genio, research scientist at NASA's Goddard Institute for Space Studies (GISS). NASA scientists learned of this rise in precipitation when scientists analyzed the data to detect patterns of historical errors. Researchers developed new ways to objectively determine variations and remove ones that are not accurate. Finally, they performed a statistical test to determine the numerical confidence and came up with the revised database, which they believe shows the long term changes more precisely than previous analyses of the data. As a result, the research analysis confirms the pattern of an El Nino and also depicts the well- known Sahelian drought of the past few decades that has been a major influence over parts of Africa. Scientists have long held that precipitation is one of the most important aspects in Earth's climate system because of its impact on the global biosphere. In addition, precipitation limits the amount of water vapor in the atmosphere. Water vapor is the most important greenhouse gas and thus helps to determine Earth's surface temperature. "The latent heat released when water precipitates out of the atmosphere is the primary way in which the tropical ocean 'communicates' with the atmosphere and drives the tropical atmospheric circulation," said Del Genio.
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The discovery
of heavier rain was overshadowed by news that 1997
was the warmest year of this century. According to the National Oceanic and Atmospheric
Administration,
1997 land and ocean temperatures averaged three-quarters of a
degree Fahrenheit above normal.
The record-breaking warm conditions of 1997 continues the pattern of very warm global temperatures. Nine of the past eleven years have been the warmest on record. Including 1997, the top ten warmest years over the land have all occurred since 1981, and the warmest five years all since 1990.
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Albion Monitor January 19, 1998 (http://www.monitor.net/monitor)
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