Projected changes in drought occurrence under future global warming from multi-model,multi-scenario,IPCC AR4 simulations |
| |
Authors: | Justin Sheffield Eric F Wood |
| |
Institution: | (1) Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA |
| |
Abstract: | Recent and potential future increases in global temperatures are likely to be associated with impacts on the hydrologic cycle,
including changes to precipitation and increases in extreme events such as droughts. We analyze changes in drought occurrence
using soil moisture data for the SRES B1, A1B and A2 future climate scenarios relative to the PICNTRL pre-industrial control
and 20C3M twentieth century simulations from eight AOGCMs that participated in the IPCC AR4. Comparison with observation forced
land surface model estimates indicates that the models do reasonably well at replicating our best estimates of twentieth century,
large scale drought occurrence, although the frequency of long-term (more than 12-month duration) droughts are over-estimated.
Under the future projections, the models show decreases in soil moisture globally for all scenarios with a corresponding doubling
of the spatial extent of severe soil moisture deficits and frequency of short-term (4–6-month duration) droughts from the
mid-twentieth century to the end of the twenty-first. Long-term droughts become three times more common. Regionally, the Mediterranean,
west African, central Asian and central American regions show large increases most notably for long-term frequencies as do
mid-latitude North American regions but with larger variation between scenarios. In general, changes under the higher emission
scenarios, A1B and A2 are the greatest, and despite following a reduced emissions pathway relative to the present day, the
B1 scenario shows smaller but still substantial increases in drought, globally and for most regions. Increases in drought
are driven primarily by reductions in precipitation with increased evaporation from higher temperatures modulating the changes.
In some regions, increases in precipitation are offset by increased evaporation. Although the predicted future changes in
drought occurrence are essentially monotonic increasing globally and in many regions, they are generally not statistically
different from contemporary climate (as estimated from the 1961–1990 period of the 20C3M simulations) or natural variability
(as estimated from the PICNTRL simulations) for multiple decades, in contrast to primary climate variables, such as global
mean surface air temperature and precipitation. On the other hand, changes in annual and seasonal means of terrestrial hydrologic
variables, such as evaporation and soil moisture, are essentially undetectable within the twenty-first century. Changes in
the extremes of climate and their hydrological impacts may therefore be more detectable than changes in their means. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|