Ramayana

Global warming
Is the rise in the average temperature of Earth's atmosphere and oceans since the late 19th century and its projected continuation? Since the early 20th century, Earth'smean surface temperature has increased by about 0.8 °C, with about two-thirds of the increase occurring since 1980. Warming of the climate system is unequivocal, and scientists are morethan 90% certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation. Thesefindings are recognized by the national science academies of all major industrialized nations.
Climate model projections were summarized in the 2007 Fourth Assessment Report (AR4) by theIntergovernmental Panel on Climate Change (IPCC). They indicated that during the 21st century the global surface temperature is likely to rise a further 1.1 to 2.9 °C for their lowest emissionsscenario and 2.4 to 6.4 °C for their highest. The ranges of these estimates arise from the use of models with differing sensitivity to greenhouse gas concentrations.
Warming and relatedchanges will vary from region to region around the globe. The effects of an increase in global temperature include a rise in sea levels and a change in the amount and pattern ofprecipitation, as well a probable expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with the continuing retreat of glaciers, permafrost andsea ice. Other likely effects of the warming include a more frequent occurrence of extreme-weather events including heat waves, droughts and heavy rainfall, ocean acidification and speciesextinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the loss of habitat from inundation.