Transcript Regional Patterns of Climate Change

Regional Patterns
of Climate Change
Kenneth Hunu & Bali White
EESC W4400 Dynamics of
Climate Variability and Climate Change
December 5, 2006
Evidence and trend
• Regional patterns in climate change are evident. Recent
warming has been greatest over the midlatitude continents
in winter and spring, with a few areas of cooling, such as the
North Atlantic ocean. Precipitation has also increased over
land in high latitudes of the Northern Hemisphere,
especially during the cold season (IPCC)
• There has been an increase of temperature across the US
amounting to nearly 0.5 C since the turn of the certury
(Karl et al. 1996).
• Precipitation changes over the US during the 20th C have
increased significantly over most of the contiguous US in all
seasons except winter The trends range from 7% to 15% per
century during the summer and transition seasons
• Natural forcings are unlikely to cause the global average
temperature to vary by more than about 0.5 K around its
multidecadal average which indicates that these changes are
due to man’s activities. (Mann et al. 1999).
Main Point #1(what are models
saying about temperature changes)
• There is a notable warming in the northern regions of North
America, and northern and central Asia, which exceeds
global mean warming in each model by more than 40%. In
contrast, the warming is less than the global mean change in
south and southeast Asia in summer and in southern South
America in winter (IPCC, TAR)
• Most models show weakening of the ocean thermohaline
circulation which leads to a reduction of the heat
transport into high latitudes of the Northern Hemisphere.
The northern hemisphere is however projected to warm up
due to greenhouse gases.
Main Point #2(what are the
models saying about
precipitation changes)
• There has been about 5 to 10% increase in Northern hemisphere,
mid-to-high latitude precipitation since 1900 with much of it due to
heavy/extreme events. Widespread significant increases in water
vapor in the Northern hemisphere has also been observed from
1925 to 1995.
• By the second half of the 21st century, it is likely
that precipitation will have increased over northern mid- to
high latitudes and Antarctica in winter. At low latitudes
there are both regional increases and decreases over land
areas. Larger year to year variations in precipitation are
very likely over most areas where an increase in mean
precipitation is projected.
Main Point #3(Uncertainties)
• Significant uncertainties remain in the science underlying regional
climate changes and their impacts. Large uncertainties still remain
in the prediction of local details of climate change especially in the
water vapor feedback, cloud and precipitation efficiency.
References
• Patz J.A, Campbell-Lendrum D, Holloway T, Folay J.A (2005).
“Impact of regional climate change on human health” nature pages
310-318.
• Groisman, PY and co-authors, 2004. Contemporary changes of the
hydrological cycle over the contiguous United States: Trends
derived from in situ observations. Journal of Hydrometeorology, 5
(1): 64-85.
• Groisman, PY, WE Knight and TR Karl, 2001. Heavy precipitation
and high streamflow in the contiguous United States: Trends in
the twentieth century. Journal of Climate, 82 (2): 219-246.
• MacCracken, MC and co-authors, 2003. Climate change scenarios
for the US National Assessment. Bulletin of the American
Meteorological Society, 84 (12): 1711-+.
• The IPCC third report.