Changes have also occurred in other
important aspects of climate (see Table 2-1).
|2.17||Over the 20th century there has been
a consistent, large-scale warming of both the land and ocean surface, with
largest increases in temperature over the mid- and high latitudes of northern
continents. The warming of land surface faster than ocean surface
from the years 1976 to 2000 (see Figure 2-6b) is
consistent both with the observed changes in natural climate variations,
such as the North Atlantic and Arctic Oscillations, and with the modeled
pattern of greenhouse gas warming. As described below, statistically significant
associations between regional warming and observed changes in biological
systems have been documented in freshwater, terrestrial, and marine environments
on all continents.
||WGI TAR Sections 2.2.2, 2.6.3, & 2.6.5, & WGII TAR Section 6.3|
|2.18||Warm episodes of the El Niño Southern
Oscillation (ENSO) phenomenon have been more frequent, persistent, and intense
since the mid-1970s, compared with the previous 100 years. ENSO consistently
affects regional variations of precipitation and temperature over much of
the tropics, subtropics, and some mid-latitude areas. It is not obvious
from models, however, that a warmer world would have a greater frequency
of occurrence of El Niño events.
||WGI TAR Section 2.6.2|
|2.19||Some important aspects of climate appear
not to have changed. A few areas of the globe have not warmed
in recent decades, mainly over some parts of the Southern Hemisphere oceans
and parts of Antarctica (see Figure 2-6b).
Antarctic sea-ice extent has stayed almost stable or even increased since
1978, the period of reliable satellite measurements. Current analyses are
unable to draw conclusions about the likelihood of changes in the frequency
of tornadoes, thunder days, or hail events for the limited regions that
have been studied. In addition, insufficient data and conflicting analyses
prevent an assessment of changes in intensities of tropical and extra-tropical
cyclones and severe local storm activity in the mid-latitudes.
||WGI TAR Sections 2.2.2, 2.2.5, & 2.7.3|
|WGI TAR Figure 11-7|
|WGI TAR Figure 2-25|
|WGI TAR Figure 2-9d|
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