Persistent Drought Of 2000-04 Worst Drought In 800 Years
July 30, 2012

Persistent Drought Of 2000-04 Worst Drought In 800 Years

Lawrence LeBlond for - Your Universe Online

Western North America was plagued by a seemingly unending drought from 2000 to 2004 that left forests parched, riverbeds dry and, according to scientists, was the strongest such drought in 800 years, and could be a sign of a new “normal” standard for decades to come.

The climatic extremes, which are linked to global warming, as bad as they have been, may be seen as the good old days, say a team of researchers, who believe the times are going to be much worse in the near future.

Analyzing climate models and precipitation projections, the team of 10 scientists said the 2000-04 drought may be closer to the “wet end” of a drier hydro-climate predicted for the last half of the 21st century.

And as a result of the impact the drought had on crops, forests and rivers, carbon sequestration faltered by as much as 51 percent in a large region of the western US, Canada and Mexico. As vegetation withered away, more carbon dioxide was able to release into the atmosphere, which amplifies global warming even further.

“Climatic extremes such as this will cause more large-scale droughts and forest mortality, and the ability of vegetation to sequester carbon is going to decline,” study coauthor Beverly Law, professor of global change biology and terrestrial systems science at Oregon State University, said in a statement.

“During this drought, carbon sequestration from this region was reduced by half,” she said. “That's a huge drop. And if global carbon emissions don't come down, the future will be even worse.”

Law said it is not yet clear whether the recent Midwestern drought, being labeled as the worst since the Dust Bowl, is related to the same forces, as the study did not address that association. However, the multi-year drought was unlike anything seen in many centuries, scientists estimated based on tree ring data.

In calculating that data, the researchers found the last two periods with chronic droughts occurred in the Middle Ages, from 977-981 and 1146-1151.

Law said the North American land sink is usually able to sequester about 30 percent of the carbon emitted into the atmosphere by the use of fossil fuels. However, based on projected changes in precipitation and drought severity, she and colleagues believe this land sink could be gone in western North America by the end of this century.

“We expect more extremes,” noted Law. “And it's these extreme periods that can really cause ecosystem damage, lead to climate-induced mortality of forests, and may cause some areas to convert from forest into shrublands or grassland.”

Colorado river runoff was cut in half during the 2000-04 drought and crop productivity fell by 5 percent in much of the west. Forest and grassland productivity also declined.

Although regional precipitation patterns are hard to forecast, the researchers said the climate models are underestimating the severity of the drought, compared to actual observations. They believe the situation will continue to worsen, and that the next 80 to 90 years will produce precipitation levels as low as, or even lower than, the levels seen during the 2000-04 drought.

The National Science Foundation, The US Department of Energy, and a number of other organizations supported this research. The study researchers hailed from Northern Arizona University, University of Colorado, University of California at Berkeley, University of British Columbia, San Diego State University, and other institutions.