Global Warming
Global warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-twentieth century and its projected continuation. The main cause for global warming is variations in its orbit around the Sun (orbital forcing),volcanic eruptions,and atmospheric greenhouse gas concentrations. Green house gases are components of atmosphere. Greenhouse gases include, water vapour, carbon dioxide, methane, nitrous oxide, ozone and CFCs. Greenhouse gases come from natural sources and human activity; present CO2 levels are 380 ppmv, approximately 100 ppmv higher than they were in pre-industrial times. Since water vapor itself acts as a greenhouse gas, the atmosphere warms further; this warming causes more water vapor to evaporate, and so on until other processes stop the loop. The result is a much larger greenhouse effect than that due to CO2 alone.
Global temperatures on both land and sea have increased by 0.75 °C (1.35 °F) relative to the period 1860–1900. This measured temperature increase is not significantly affected by the urban heat island effect. Since 1979, land temperatures have increased about twice as fast as ocean temperatures. Sea temperatures increase more slowly than those on land both because of the larger effective heat capacity of the oceans and because the ocean can lose heat by evaporation more readily than the land. The Northern Hemisphere has more land than the Southern Hemisphere, so it warms faster. The Northern Hemisphere also has extensive areas of seasonal snow and sea-ice cover subject to the ice-albedo feedback. More greenhouse gases are emitted in the Northern than Southern Hemisphere, but this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres. Based on estimates by NASA's Goddard Institute for Space Studies, 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree.
It is important for us to develop a clear understanding of our emission inventory. We also need to document and analyse our efforts in areas such as renewable energy, wasteland development and afforestation – all of which contribute towards either reducing CO2 emissions or increasing CO2 removal from the atmosphere. Considering that these efforts may often be undertaken for a variety of reasons not directly related to global warming, but yet have benefits as far as climate change is concerned. Finally not only global warmin but we need to significantly improve our ability to plan and adapt to extreme events such as floods, droughts, cyclones and other meteorological hazards.