XX December 2013
Global warming is the gradual rise of the average temperature of the earth’s atmosphere due to presence of certain gases in the atmosphere that traps heat. Under normal circumstances there are always gases that trap heat in the atmosphere. This is done by gases like water vapor and carbon dioxide present in the atmosphere. Others include methane, nitrous oxide and chlorofluorocarbons. They trap outgoing terrestrial long wave radiation and keep the earth’s atmosphere warm. Otherwise during night time when the solar radiation absorbed by the earth’s surface and the atmosphere escape, temperatures would have fallen drastically. That would have made life on earth, as we know it, impossible to survive. This effect is called the greenhouse effect and these gases are called the greenhouse gases (see figure 1). The greenhouse effect is named thus as it replicates the same effects as induced in a glass house built specifically to grow certain types of plants. However, due to current human activities the addition of greenhouse gases to the atmosphere has been accelerated manifold. The increased emission is from a variety of sources. The contribution is mainly from the combustion of fossil fuels in vehicles in the form of nitrous oxide and carbon monoxide, smoke from factories and in the production of thermo electric power by the combustion of coal. Methane is released from landfills by the decomposition of buried vegetative matter and digestive systems of cattle. Methane is further released when there is melting of permafrost in the tundra region. Nitrous oxide also comes from chemically manufactured fertilizers which are used in modern agricultural practices and chlorofluorocarbons from refrigeration systems, various cosmetic products in the form of sprays and industrial emissions.
Heat trapping capabilities of different greenhouse gases are different. A molecule of methane has the ability to trap heat 20 times more than that of a molecule of carbon dioxide while a single molecule of nitrous oxide can trap upto 300 times more heat than carbon dioxide. Chlorofluorocarbons can trap heat thousand times greater than carbon dioxide in addition to having a dangerous effect in the ozone layer, which protects the earth from harmful ultra-violet rays.
In 1988 The Intergovernmental Panel on Climate Change (IPCC) was set up by the United Nations to access scientific information which deals with climate change due to anthropogenic pressure, impacts of such climate change and various options for mitigating such adverse effects.
Effects of Global Warming
As a result of global warming the average temperature of the globe has already risen by over one degree Fahrenheit. The most prominent effect we hear about every day is the melting of polar ice caps. Due to increase in temperature the ice caps are melting adding to the sea water and causing rise in sea levels. Studies suggest that, at the current rate of warming, by the end of the century we can expect a rise of 7 to 23 inches in the sea water level. This poses grave danger to coastal human settlements as they may get inundated due to rise in sea levels. Glacier up in the mountains are also melting resulting in devastating floods in rivers downstream and dwindling supply of freshwater in rivers. As a result we have seen range shifts of different animals that live at the poles or in the high altitudes. There has been a change in pattern of precipitation which may cause expansion of subtropical deserts. Because of global warming and range shifts of animals there has been new and unexpected pest infestation in forest, like the Spruce bark beetles in Alaska (National Geographic; Global Warming; Web).
Alternative explanation of Global Warming
According to studies done on trapped air in ice cores drilled out in the poles, scientists have seen that global temperatures and atmospheric carbon dioxide levels have fluctuated in a cyclic manner over the past thousands of years (see figure 2). As a result there has been multiple ice ages, times when the atmosphere become very cold due to decrease in heat trapping carbon diode in the atmosphere. Like Roman Warming, the cooling in Dark Ages , Climate Optimum of the medieval times, the Little Ice Age, and the current warming of atmospheric temperatures. The only difference this time is that in this cycle is that the rise in temperature is accelerated by extensive use of fossil fuels and other greenhouse gas emissions.
There is another possibility that people have mentioned about warming of the atmosphere by cosmic ray from the sun that bombard the earth’s atmosphere. Cosmic rays are charged subatomic particles from space. These cosmic rays are correlated with the solar spot cycle. Sun spots are related to the magnetic field of the sun and along with solar flares regulates the input of cosmic rays into our atmosphere. The atmospheric levels of cosmic rays rise and fall with the strength of solar winds. These fluctuations may significantly affect the quantity and type of clouds in the atmosphere. This theory was pondered over by scientists and thinkers at least since the 1970s. But this theory did not become mainstream until Henrik Svensmark, a Danish physicist, in 1991 saw a publication by Eigil Friis-Christensen and Knud Lassen. Following this various scientific experiments, especially ones carried out at CERN (European Organization for Nuclear Research) starting 1997, helped crystallize the validity of this theory (Wall Street Journal; Web).
