Fire, Drought, and Flood

This last connection is explored in the next Ste ti OD, in which a group investigation-ton associated with the Scrips Institution of Oceanography, the Laboratory of Tree :Ring Research at the University of Arizona. the University of California, and the U.S. Geological Survey have sought to analyze the history of wildfires in the western United States. In an analysis of fire history, their Research Article published in &tut in 2°06 shows an abrupt (fourfold) increase in wildfire frequency during the outpost. Associated with glossolalia warming, higher springtime temperatures in the Rocky Mountains begin earlier than (omit*, and of cone snowmen is accelerated. The result is drier forests and a fire season that begins much earlier and lasts longer. The increase in early snowmen has been associated not only with an increased fire frequency, but also with increases in the area burned. The focus on snow and snowmen naturally calls to mind the question of how much effect global warming may have on the amount of precipitation and on its timing--and the importance of these changes for human residents. Higher average temperatures not only influence the melting times of mountain snowfall. They also strongly influence the water content of the snow pack that accumulates during the winter. This is a critically important issue, since melting snow packs supply water for irrigation, industrial use, and human consumption on dependent flat lands. Thus, for example, residents of causal California and the Central Valley can anxious glances toward die High Sierra hoping for a good snow pack and listen eagerly to the regular forecasts of its water content. Of course, precipitation is not all in the form of snow. Rainfall and its distribution is critical to human life: an excess produces floods and landslides, whereas an insufficiency may result in droughts. Went, Tricia dully, Hill burn, and Mars analyzed the question "How Much More Rain Will Global Warming Bring?" in a Zukor Selma Report. It is known that evaporation of water from the ocean surface increases as the avenge temperature increases, which in turn should make precipitation events more frequent and severe, at lean in certain regions. But various models predict that rainfall would increase far more slowly than the data on evaporation rates would suggest. So Went Te at compared results from different models and looked at historical data on the increase in global rainfall to sec whether the models used to "Lind cast" the observed changes in precipitation did so accurately. The empirical observations actually showed that the increase in rainfall—over a time period that included two Fl Inflow events—matched the increase in evaporation much more closely than the models had predicted. The result clearly suggests that as global warming continues, we can expect the kinds of rainfall events that have already been experienced as hazardous landslides and local flooding in some pans of the world—and droughts in other places.