Global warming is simply defined as an increase in the average global temperatures. Though, it is an environmental problem, it has serious implications on the global economics, geopolitics, society, humanity and all living beings. “Global warming is one of the most controversial science issues of the 21st century, challenging the very structure of our global society” (Mark). Though, there has been controversies between two schools of scientific thought, one calling it is a myth and the other considering it is a reality, there is sufficient evidence to support the later. Anthropogenic activities, causing increased emissions of green house gases, are behind the global warming. It has been established, that, if not addressed properly and immediately, it would have catastrophic impacts.
Global warming means earth is becoming warmer gradually. There is increase in average global temperatures of air and oceans, accompanied by widespread melting of glaciers and rising of sea level. The United Nations Intergovernmental Panel on Climate Change (IPCC) in its ‘Synthesis Report on Climate Change’, states that there is clear evidence for a 0.6 0C rise in global temperatures and 20cm rise in sea level during the 20th century. It predicts that “global temperatures could rise by 1.4 to 5.8 0C and sea level could rise by 20 to 88cm by the year 2100.” Majority of the scientists and research organisations, including IPCC have reached on consensus that global warming is caused by massive increase of green house gases such as Carbon dioxide (Co2) in atmosphere resulting from burning of fossil fuels and deforestation.
The temperature of earth is maintained by the balance between the heat energy coming from the sun and the heat energy returned back to space. Some atmospheric gases: Carbon dioxide (CO2), Methane (CH4), Nitrous Oxide (N2OX), Chlorofluorocarbons (CFC) and water vapours are important to this temperature balance. They form the green house blanket in the atmosphere. This blanket absorbs some of the long wave radiation and re-radiate it back to surface, which causes the atmosphere to warm up to 350C. Without these gases the earth’s atmospheric temperature would be 15 to 200C. If more such gases are added to the atmosphere, the earth’s temperature would increase accordingly. And these are being added enormously.
This is why the global warming is taking place with greater pace due to the abundant increase in emissions. “The scientists community is largely persuaded that not only is earth’s climate warming, but rate of warming is accelerating due substantially to, human activity.” says Dr. Terrence M. Joyce, Senior Scientist and Director of Ocean & Climate Change Institute.
The main evidences of global warming are three basic indicators- temperature, precipitation and sea level. Firstly, the temperature of land surface, ocean waters and free atmosphere has been measured through fixed thermometers, balloons in the air and satellites. By these sources, scientists have produced record of last 130 years, which shows a global warming of 0.65(+ - 0.05degree C) over this period. We also know that 2010 was globally the warmest years on record.
Secondly, the recorded data of precipitation also reveals that there is upward trend in global precipitation. It shows that precipitation has increased over land at high latitudes in northern hemisphere, especially during cold seasons. As the cyclones, i.e. hurricanes, tornadoes, storms are closely related with the process of precipitation; the world has experienced more frequent and stronger hurricanes and storms during the recent past; Hurricane Katrina in the US in 2005 and 2010 Super Flood in Pakistan.
Thirdly, the global sea level has risen by about 20cm over the past 100 years. Initially, it was believed that the rise in sea level had occurred due to temperature increase as water expands on heating. But it has been revealed by relevant...
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