Global warming is an increase in average temperature of the air near the surface of the Earth and oceans since the mid-20th century and its production schedule. The temperature of the Earth's surface rose 0.74 ± 0.18 ° C (1.33 ± 0.32 ° C) between beginning and end of the 20th century. Intergovernmental Panel on Climate Change (IPCC) concludes that the greatest increase in temperatures observed since the mid-20th century was caused by rising concentrations of greenhouse gas emissions from human activities like burning fossil fuels and deforestation. IPCC also concludes that changes in natural phenomena such as solar radiation and volcanism have produced most of the warming from pre-industrial times to 1950 and had a slight cooling effect of the result. These basic conclusions have been supported by more than 40 scientific societies and academies of science,including all national academies of science of the major industrialized countries .
Climate model projections summarized in the last IPCC report, is the temperature of the planet is likely to raise a 1.1 to 6.4 ° C (2.0 to 11.5 degrees F) during the 21 century.the uncertainty in this estimate comes from the use of models with different sensitivity to the concentration of greenhouse gases and the use of different estimates of future emissions of greenhouse gases. Some other uncertainties include how warming and related changes will vary from region to region throughout the world. Most studies focus on the period up to 2100.
However, should warming continue after 2100 even if emissions stop, because of the large heat capacity of the oceans and the life of carbon dioxide in the atmosphere.
Increasing global temperature will cause sea levels increase and improve the quantity and distribution of precipitation, probably including the expansion of the subtropical deserts. will be greater warming in the Arctic and will be associated with the continued decline in glaciers, permafrost and sea ice.
Other possible effects include increases in the intensity of extreme weather, species extinction, and changes in agriculture provides.
The political and public debate continues about global warming and what actions (if any) to take in response. Options are mitigation to reduce emissions, adaptation to reduce the damage caused by global warming and more speculative, geoengineering to reverse global warming. Most national governments have signed and ratified the Kyoto Protocol to reduce greenhouse gas emissions.
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