Is global warming already happening? Yes. The IPCC concluded in its Fourth Assessment Report, that nearly 90 percent of the 29,000 observational data series examined revealed changes consistent with the expected response to global warming, and the observed physical and biological responses have been greatest in the regions that warmed the most. The kinds of changes already observed that create this consistent picture include the following: Examples of observed climatic changes • Increase in global average surface temperature of about 1°F in the 20th century • Decrease of snow cover and sea ice extent and the retreat of mountain glaciers in the latter half of the 20th century • Rise in global average sea level and the increase in ocean water temperatures • Likely increase in average precipitation over the middle and high latitudes of the Northern Hemisphere, and over tropical land areas • Increase in the frequency of extreme precipitation events in some regions of the world Examples of observed physical and ecological changes • Thawing of permafrost • Lengthening of the growing season in middle and high latitudes • Poleward and upward shift of plant and animal ranges • Decline of some plant and animal species • Earlier flowering of trees • Earlier emergence of insects • Earlier egg-laying in birds ucsusa.org/global_warming/science_and_impacts/science/global-warming-faq.html
Posted on: Thu, 15 Jan 2015 02:33:14 +0000
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