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Unformatted text preview: century (Chapter 9) suggest that there was little change prior to about 1915, and that a substantial fraction of the early 20th-century change was contributed by naturally occurring inﬂuences including solar radiation changes, volcanism and natural variability. From about 1940 to 1970 the increasing industrialisation following World War II increased
pollution in the Northern Hemisphere, contributing to cooling, and increases in carbon dioxide and other greenhouse gases dominate the observed warming after the mid-1970s.
(Bottom) Patterns of linear global temperature trends from 1979 to 2005 estimated at the surface (left), and for the troposphere (right) from the surface to about 10 km altitude,
from satellite records. Grey areas indicate incomplete data. Note the more spatially uniform warming in the satellite tropospheric record while the surface temperature changes
more clearly relate to land and ocean.
1 From the HadCRUT3 data set. 253 Figure 18.x Difference in instrumentally determined surface temperatures in the period
January 1999 through December 2008 and “normal” temperatures at the same locations, as
defined to be the average over the interval January 1940 to December 1980. The average
increase on this graph is 0.48ºC. Widespread temperature increase is observed primarily at
high latitudes in the Northern Hemisphere. (source: Wikipedia/NASA)
Figure 18.x Graph of CO2 (middle), temperature (top) and dust concentration (bottom)
measured from the Vostok, Antarctica ice core. Higher dust levels are believed to be caused
by cold, dry periods. Unlike with current warming, the rise in temperature led the rise in CO2.
Under current warming, CO2 rises faster and has an earlier onset. Temperature and CO2
follow a saw-tooth pattern, with sharp rises and slow decreases. (source: modified from
Wikimedia/NOAA) Figure 18.x Of all natural processes, only solar warming may contribute to the current
warming. But the amount predicted is only 0.2ºC. Warming from other causes is
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- Fall '08