Impacts of Global Warming

Temperature Variability

Perhaps best known, is that temperature variability, specifically temperature increase, will be one of the effects of climate change. While the range of projections relating to temperature rise varies, the IPCC scenarios, using a range of climate models, predict overall a rise in globally-averaged surface temperature of 2.5–10 degrees F (1.4 to 5.8 degrees C) 1990–2100. While at local and regional levels this figure will vary, at a global level it is roughly 2–10 times larger than the observed warming of the 20th century, and is unprecedented during at least the last 10,000 years, based on paleoclimatic data.

Changes in temperature and precipitation (rainfall) patterns have increased all around the world. In the United States, average temperatures have increased by roughly 1 degree F (0.6 degrees C) during the past century, and precipitation has increased by five to 10 percent. Alaska has sustained an average temperature increase of 4–7 degrees F (2–4 degrees C) in just the past 50 years. Temperature increase has also had a number of related effects, such as the increased melting of the summer Arctic sea ice. Since 1979, more than 20 percent of the polar ice cap has melted in response to increased surface and ocean temperatures. The oceans are warming. Global ocean temperature has risen by 0.18 degrees F (0.10 degrees C) from the surface to a depth of (2,297 ft.) 700 m. 1961–2003.

Warming of Water Masses

Key oceanic water masses are changing. Southern Ocean mode waters and Upper Circumpolar Deep Waters have warmed from the 1960s to about 2000. A similar, but weaker pattern of warming in the Gulf Stream and Kuroshio mode waters in the North Atlantic and North Pacific has been observed. Long-term cooling is observed in the North Atlantic subpolar gyre and in the central North Pacific.

Sea-Level Rise

Another predicted effect of climate change is an increase in sea level. Sea-level rise is caused by thermal expansion of the oceans, melting of glaciers and ice caps, melting of the Greenland and Antarctic ice sheets, and changes in terrestrial storage. Changes in sea level will be felt through increases in intensity and frequency of storm surges and coastal flooding; increased salinity of rivers, bays, and coastal aquifers resulting from saline intrusion; increased coastal erosion; loss of important mangroves and other wetlands (the exact response will depend on the balance between sedimentation and sea-level change); and impact on marine ecosystems such as coral reefs.

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