Before the Industrial Revolution, human activities released very few gases into the atmosphere and all climate change occurred naturally. Since the Industrial Revolution, due to the combustion of fossil fuels, changes in agricultural practices and deforestation, the natural composition of gases in the atmosphere is being affected and significant changes have occurred in the climate and environment.
Over the past 100 years, it was found that the Earth has been getting warmer than ever before, while temperatures have remained relatively stable over the past 8000 years. Current temperatures are 0.3 – 0.6 degrees Celsius higher than 100 years ago.
The major greenhouse gas (GHG) causing global warming is carbon dioxide. CFCs, even though they are present in very small quantities, contribute significantly to global warming. Carbon dioxide, one of the most prevalent greenhouse gases in the atmosphere, has two major anthropogenic (human-caused) sources: fossil fuel combustion and land use change. Net emissions of carbon dioxide from both of these sources are believed to be contributing to the rapid increase in atmospheric concentrations since the Industrial Revolution. Because estimates suggest that approximately 80 percent of all anthropogenic carbon dioxide emissions currently come from the combustion of fossil fuels, world energy use has come to the center of the climate change debate.
1. Sources of greenhouse gases
Some types of greenhouse gases in world occur naturally in the atmosphere, while some others result from various human activities. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone . However, some human activities increase the levels of most of these naturally occurring gases. Carbon dioxide is released into the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal) and wood and wood products are burned.
A Methane named gas in world is emitted during the production and transportation of coal, various natural gas, and oil.Decomposition of organic wastes in municipal solid waste landfills and livestock rearing also produce methane emissions. Nitrous oxide is emitted during agricultural and industrial activities as well as the combustion of solid waste and fossil fuels.
Very potent greenhouse gases that do not occur naturally include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6), which are produced in various industrial processes.
Often, estimates of greenhouse gas emissions are presented in units of millions of metric tons of carbon equivalent (MMTCE), which weighs each gas according to its global warming potential or GWP value.
2. Global warming potentials
Although there are many ways to measure the strength of various greenhouse gases in the atmosphere, global warming potential (GWP) is probably the most useful. GWPs measure the impact greenhouse gases have on the natural greenhouse effect, including the ability of greenhouse gas molecules to absorb or trap heat and the length of time the various types of molecules of greenhouse gas remain in the atmosphere before being removed or broken down. In this way, the contribution of each greenhouse gas to global warming can be assessed.
There are various types of greenhouse gases each greenhouse gas varies in its ability to absorb heat in the atmosphere. in world at present time Methane traps 21 times more heat per molecule than carbon dioxide, and nitrous oxide absorbs 270 times more heat per molecule than carbon dioxide. Conventionally, the Global Warming Potential (GWP) of carbon dioxide measured across all time horizons is 1. The GWP of other greenhouse gases is then measured relative to the GWP of carbon dioxide. Thus the GWP of methane is 21 while the GWP of nitrous oxide is 270. The GWP of other greenhouse gases is much higher than that of carbon dioxide, but because their concentrations in the atmosphere are very low, carbon dioxide is still the most important greenhouse gas, contributing about 60% of the greenhouse effect.
3. Global Warming (Climate Change) Implications
(a) Global Temperature Rise
Observations show that global temperatures have increased by about 0.6 degrees Celsius in the 20th century. There is now strong evidence that most of the warming observed over the past 50 years has been caused by human activities. Climate models predict global temperatures to rise by about 6 degrees Celsius by the year 2100.
(b) Sea Level Rise
In general, the faster climate change occurs, the greater the risk of harm. Average sea level is expected to rise by 9 – 88 cm by the year 2100, which could cause flooding and other damage in low-lying areas.
(c) Food shortage and hunger
Water resources will be affected due to changes in rainfall and evaporation patterns around the world. Agricultural production will be affected by this. Food security is likely to be threatened and some areas are likely to experience food shortages and hunger.
India may be at greater risk than many other countries. Models predict an average increase in temperatures over India of 2.3 to 4.8 degrees Celsius for the benchmark doubling of carbon-dioxide scenario. The temperature will increase more in Northern India than in Southern India. It is estimated that 7 million people will be displaced, 5700 square kilometers of land and 4200 kilometers of roads will be destroyed, and wheat yields could be significantly reduced.
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