Global warming

Global warming is the increase in the average tempreture of the Earth’s near surface air and oceans since the mid-20th century and its projected continuation. Global tempreture increased 0.74 plus or minus 0.18o celsius during the last century.
Created On: Dec 13, 2010 11:02 IST
Modified On: Mar 31, 2011 12:29 IST

Global warming is the increase in the average tempreture of the Earth’s near surface air and oceans since the mid-20th century and its projected continuation. Global tempreture increased 0.74 plus or minus 0.18o celsius during the last century. The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the observed tempreture increase since the middle of the 20th century was aused by increasing concentrations of greenhouse gases resulting from human activity such as fossil fuel  burning and deforestation. Climate model projections summarized in the latest IPCC report indicate that the global surface tempreture will probably rise a further 1.1 to 6.4o celsius during the 20th century. Warming is expected to continue beyond 2100 even if emissions stop, because of the large heat capacity of oceans and the long lifetime of carbon dioxide in the atmosphere.

An increase in global tempreture will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts. The continuing retreat of glaciers, permafrost and sea ice is expected, with warming being strongest in the Arctic. Other likely effects include increases in the intensity of extreme weather events, species extinctions, and changes in agricultural yields.

Green house effect
The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet’s lower atmosphere and surface. It was discovered by Joseph Fourier in 1824. Naturally occuring greenhouse gases have a mean warming effect of about 33o C. The major greenhouse gases are water vapor, which causes about 36-70 percent of the greenhouse effect, carbon dioxide which causes 9-26 percent, methane causes 4-9 percent and ozone which causes 3-7 percent.Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, lead in to increased radiative forcing from carbon dioxide, methane, tropospheric ozone, chlorofloro carbons and nitrous oxide. The concentrations of carbon dioxide and methane have increased by 36% and 148% respectively since the mid- 1700s. Fossil fuel burning has produced about three-quarters of the increase in carbon dioxide from human activity over the past 20 years. Most of the rest is due to land-use change, particularly deforestation. The future rate of carbon dioxide concentrations will depend on uncertain economic, sociological, technological and natural developments. Accordingly, the IPCC Special Report on Emissions Scenerios gives a wide range of future carbon dioxide scenerios, ranging from 541 to 970 ppm by the year 2100.

 

 

 

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