Wednesday, June 29, 2011
8:36 PM | Author: Bey Filed Under: General Information
Global warming is the current rise in the average temperature of Earth's oceans and atmosphere and its projected continuation. The scientific consensus is that global warming is occurring and was initiated by human activities, especially those that increase concentrations of greenhouse gases in the atmosphere, such as deforestation and burning of fossil fuels. This finding is recognized by the national science academies of all the major industrialized countries and is not rejected by any scientific body of national or international standing.[A]
Scientists directly measured the global surface temperature increase during the 20th century at about 0.74°C (1.33°F).[A] Potential future warming is projected using computer models of the climate system and hypothetical amounts of greenhouse gas emissions for possible future worlds, published in 2000. Actual emissions since 2000 have equaled or exceeded the "A2 scenario", except for small dips during two global recessions. According to the 2007 report of the Intergovernmental Panel on Climate Change (IPCC), the "best estimate" of future warming for the A2 scenario is 3.4°C (6.1°F) by 2100, with a likely range from 2.0-5.4°C (3.6-9.7°F).
An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion ofsubtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent occurrence of extreme weather events including heatwaves, droughts and heavy rainfall events,species extinctions due to shifting temperature regimes, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional changes is uncertain. In a 4°C world, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world. Hence, the ecosystem services upon which human livelihoods depend would not be preserved.
The Kyoto Protocol is aimed at stabilizing greenhouse gas concentration to prevent a "dangerous anthropogenic interference". As of May 2010, 192 states had ratified the protocol. The only members of the UNFCCC that were asked to sign the treaty but have not yet ratified it are the USA and Afghanistan. Proposed responses to global warming include mitigation to reduce emissions, adaptation to the effects of global warming, and geoengineering to remove greenhouse gases from the atmosphere or reflect incoming solar radiation back to space. According to a recent Gallup poll, people in most countries are more likely to attribute global warming to human activities than to natural causes. The major exception is the U.S., where just under half the US population (47%) attributes global warming primarily to natural causes despite overwhelming scientific opinion to the contrary.