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  • Kharin, V.V., F. W. Zwiers, X. Zhang, and G. C. Hegerl, 2007: Changes in temperature and precipitation extremes in the IPCC ensemble of global coupled model simulations. J. Climate, 20, 1419-1444.

Temperature and precipitation extremes and their potential future
changes are evaluated in an ensemble of global coupled climate models
participating in the Intergovernmental Panel on Climate Change (IPCC)
diagnostic exercise for the Fourth Assessment Report (AR4). Climate
extremes are expressed in terms of 20-yr return values of annual
extremes of near-surface temperature and 24-h precipitation
amounts. The simulated changes in extremes are documented for years
2046-65 and 2081-2100 relative to 1981-2000 in experiments with the
Special Report on Emissions Scenarios (SRES) B1, A1B, and A2 emission
scenarios. Overall, the climate models simulate present-day warm
extremes reasonably well on the global scale, as compared to estimates
from reanalyses. The model discrepancies in simulating cold extremes
are generally larger than those for warm extremes, especially in sea
ice-covered areas. Simulated present-day precipitation extremes are
plausible in the extratropics, but uncertainties in extreme
precipitation in the Tropics are very large, both in the models and
the available observationally based datasets. Changes in warm extremes
generally follow changes in the mean summertime temperature. Cold
extremes warm faster than warm extremes by about 30%-40%, globally
averaged. The excessive warming of cold extremes is generally confined
to regions where snow and sea ice retreat with global warming. With
the exception of northern polar latitudes, relative changes in the
intensity of precipitation extremes generally exceed relative changes
in annual mean precipitation, particularly in tropical and subtropical
regions. Consistent with the increased intensity of precipitation
extremes, waiting times for late-twentieth-century extreme
precipitation events are reduced almost everywhere, with the exception
of a few subtropical regions. The multimodel multiscenario consensus
on the projected change in the globally averaged 20-yr return values
of annual extremes of 24-h precipitation amounts is that there will be
an increase of about 6% with each kelvin of global warming, with the
bulk of models simulating values in the range of 4%-10% K 1. The very
large intermodel disagreements in the Tropics suggest that some
physical processes associated with extreme precipitation are not well
represented in models. This reduces confidence in the projected
changes in extreme precipitation.


Last Updated: 2007-07-30

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