Environmental Engineering Reference
In-Depth Information
Overview of Climate Changes
and Illustrative Impacts
The following section provides an overview of a number of climate
changes and impacts that can now be identified and estimated at different
levels of warming. Highlighted in bold are the key impacts followed by
supporting details.
CHANGES IN RAINFALL AND STREAMFLOW
Increases of precipitation in high latitudes and drying of the already
semi-arid regions at lower latitudes are projected with increasing global
warming, with seasonal changes in several regions expected to be about
5-10% per degree of warming. However, patterns of precipitation change
show much larger variability across models than patterns of temperature.
The basic large-scale pattern and magnitude of precipitation responses
across the tropics, subtropics, and mid-latitude and high-latitude regions
can be understood largely as the result of increasing water vapor in the
atmosphere; these are broadly consistent with observed trends and physical
understanding, and represent a very robust prediction across models. Pre-
cipitation in many of the world's monsoon regions is expected to increase
during the rainy season. Precipitation associated with mid-latitude storms is
also expected to increase. For some areas, particularly those near transitions
between regions that become wetter and those that become drier, model
disagreement is large. The continental U.S. region straddles changes that are
both positive (over the northernmost areas) and negative (over the southwest
areas) changes in both annual and Dec-Jan-Feb average precipitation. A
large portion of the contiguous 48 U.S. states is in a transition zone where
future rainfall changes cannot be projected with confidence at present. Mod-
els agree in projecting increases in precipitation on the order of 5-10% per
degree C of warming in high latitudes in all seasons, including over Alaska,
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