‘Global warming’ is one facet of the broader term ‘climate change’. It is the increase in the average temperature of the Earth’s surface air and oceans from the mid-20th century, and the projected continuation. The Global warming is primarily the consequence of building up greenhouse gases in atmosphere. Emission rates for most important anthropogenic greenhouse gas, CO2, have increased 120-fold in the past 140 years. While in the 19th century, emissions were mostly from deforestation and the other land use changes, now they are predominantly from burning fossil fuels. As CO2 in the atmosphere has the lifetime of more than a century, the historic emissions play most important role as compared to the current concentrations in atmosphere.
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Increase in Global Temperature. Most of the increase in global temperatures since the mid-twentieth century are very likely due to the increase in anthropogenic greenhouse gases via enhanced greenhouse effect. The natural phenomena such as the solar variation combined with the volcanoes had a small warming effect since pre-industrial times to 1950 and small cooling effect from 1950 onwards. The Climate model projections summarized by IPCC indicate that the average global surface temperature would likely rise a further 1.2 to 6.4 °C (2.0 to 11.6 °F) during the twenty-first century.
Role of Industrialisation. In the past 200 years, Europe, North America, and former Soviet Union, currently having only 20 percent of world’s population, have contributed in more than 85 percent of CO2 emissions. Direct product of industrialisation, emissions now is 7 billion tons of the carbon a year, or around one ton of carbon per head of world’s population. Emissions are very uneven. The per-capita North American emissions are 17 times those of Africa, ten times those of Asia and 2.4 times those of Europe. The Low gasoline prices and pervasive automobile culture in United States ensure that CO2 output, already highest in the world, is rising, while levels in Europe are stable or falling.
Disparity in Emissions. Everyone is indeed responsible in some way or another but the largest contributors are developed nations. Today, developed countries like the United States, Germany, Japan and many others with only 26 percent of the Globe’s population, are responsible for more than 70 percent of accumulated green house gas pollution in atmosphere. If we take a global average, then each person on planet is responsible for emission of approx 6000 kg of GHG emissions every year. In the developed countries, it is 14,000 kg per person. USA tops the list with 24,000 kg per person, and at bottom of the list comes Chad with 30 kg per person.
Causes
Climatic Equilibrium. Earth’s climate changes in response, to external forcing, include variations in its orbit around the Sun, changes in the solar luminosity, atmospheric greenhouse gas concentrations and volcanic eruptions. Detailed causes of the warming remain active field of research, although the scientific consensus is that increase in atmospheric greenhouse gases by human activity caused most of warming observed since start of industrial era. None of these effects of forcing are instantaneous. The thermal inertia of the Earth’s oceans and very slow responses of the other indirect effects mean that Earth’s current climate is surely not in equilibrium with forcing imposed. The Climate commitment studies indicate that even if the greenhouse gases were stabilized on 2000 levels, a further warming of approximately 0.5 °C (0.9 °F) will still occur.
Natural. The natural causes that contribute to global warming are as follows:-
Change in sun’s energy output.
Volcanoes.
Water vapour.
Cloud cover.
However these natural causes have been regularly countered by the natural process of degeneration and Earth’s temperature has been varying within a fixed margin for last hundreds of years.
Human Activity. From old times people suspected that the human activity could change climate. For example, in 19th century many Americans did believe that cutting down forests would bring more rainfall to a region. Amongst the mainstream scientific community, there is no doubt that Earth is warming, and increasing evidence shows that the humans have a significant part in it.
Greenhouse Phenomenon
The major reason of global warming is the emission of the green house gases like methane, carbon dioxide, nitrous oxide etc into atmosphere. The gases in atmosphere like carbon dioxide, water vapour, tropospheric ozone, chlorofluorocarbon (CFC), methane and nitrous oxide trap energy from sun. Without these gases, heat will escape back into the space and Earth’s average temperature will be about 60°F colder. So absorbing and reflecting infrared waves being radiated by Earth, the gases conserve heat as glass in a greenhouse works and are thus called as greenhouse gases.
Source of Gases. Methane is a much more effective greenhouse gas than CO2, but the concentration is much smaller, and total radiative forcing is only about one fourth of that from the carbon dioxide. Some other naturally occurring gases contribute small fractions of the greenhouse effect; one of these, nitrous oxide (N2O), is increasing in concentration owing to human activity such as agriculture.
Carbon Dioxide. It is the major source of power plants. These power plants emit large quantity of carbon dioxide produced by burning the fossil fuels for generation of electricity. About twenty one percent of carbon dioxide emitted in the atmosphere comes from burning of gasoline in the engines of the vehicles.
Methane. Methane is more than 20 times as effectual as CO2 at entrapping heat in the atmosphere. Methane is obtained from resources such as bovine flatulence ,rice paddies, bacteria in bogs and fossil fuel manufacture. When fields are flooded, anaerobic situation build up and the organic matter in the soil decays, releasing methane to the atmosphere.
Nitrous Oxide. Main sources of nitrous oxide are nylon and nitric acid, the cars with catalytic converters, use of fertilizers in agriculture and burning organic matter.
Effect. The greenhouse effect is important. Without the greenhouse effect, the Earth would not be warm enough for humans to live. But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual. Even a little extra warming may cause problems for humans, plants, and animals. Present atmospheric concentration of CO2 is about 390 parts per million (ppm) in volume. Future levels are expected to increase due to ongoing burning of the fossil fuels and land-use change. The rate of increase will depend on uncertain sociological, economic, natural , and technological developments, but may be ultimately limited by the availability of fossil fuels.
Deforestation. Another cause of global warming is deforestation that is caused by cutting and burning of forests for the purpose of residence and industrialization.
Solar Variation. A varying hypothesis is that the variations in solar output, possibly being amplified by cloud seeding by galactic cosmic rays, would have contributed to recent warming. It is suggested that magnetic activity of the sun is a very crucial factor which deflects the cosmic rays that influencing the generation of cloud condensation nuclei and therefore affect the climate.
Effects Of Global Warming
The effects of global warming are very large in number and still there are so many that are still to be found out. But recently the problems have become visible and evident because of happening of events that were before only talked off. Although it may be difficult to connect weather events to global warming, a rise in global temperatures may therefore cause following major changes:-
Glacial Retreat and Arctic Shrinkage. As an effect of global warming the glaciers are retreating at an alarming rate and changing the entire environment of the mountains. This will bring about the most intense climatic changes and alteration in the habitat. There will be a considerable increase in the water level of oceans and seas as a result of melting of glaciers.
Rise in Sea Level. Worldwide sea level rise of 180 to 590 millimetres (0.59 to 1.9 ft) in 2090-2100 relative to 1980-1999. This increase in level of seas and oceans will engulf land at the coastal areas and some low lying countries may even become submerged.
Extreme Weather Conditions. Changes in the amount and pattern of precipitation may result in flooding and drought. Floods in the areas without the flood history, is not very common. There are droughts in various places, having good rainfall earlier. Atmosphere gets suddenly very rough in the terms of thunderstorms and cyclones. In the future there are rapid temperature changes expected to occur which will affect length of the seasons. Winters will be quite short. This will indeed imbalance the ecosystem and will therefore effect greatly the attitudinal behavior of the the animals and birds.
Vegetation. Another major effect of global warming would be on the vegetation that is present on the earth surface. Tundra type of vegetation would turn to temperate, and evergreen type of forest. Woody plant population may tend to increase, as a result of rise in precipitation. There would be a dramatic change in all the type of vegetations available in the areas, which will in turn impact the inhabitation of area.
Wild Life. Various species are on the verge of extinction due to global warming. Major changes are often seen in the animals as they do react to the warmer environment, which are effected due to global warming. A behavior pattern of these animals when studied shows that animals are beginning to shift their major population towards north, or towards a higher altitudes.
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(f) Marine Life. The marine life is undoutedly very sensitive to the rise in temperatures. The effect of global warming will surely be seen on many species in the water. As a result many species will die off, or go extinct due to the rise in the temperatures of water, whereas many other species, which prefer the warmer waters, will be on increase tremendously. Perhaps the most annoying changes are expected in coral reefs that are expected to now die off as an effect of the global warming. Due to the melting of polar ice the life cycle is getting disturbed and this leads to death of many an animal.
Increase in Diseases. Lately, as an effect of the global warming various new diseases have emerged. These diseases are occurring frequently due to the increase in earth’s average temperature since the bacteria can survive easily in elevated temperatures and multiply faster when the conditions become favorable. Due to global warming, the distribution of mosquitoes is being extended owing to the increase in humidity levels and so their frequent growth in the warmer atmosphere. Various diseases are expected due to Ebola, Hanta and Machupo virus owing to warmer climates. The global warming is sure to cause irreversible changes in ecosystem and the behaviour of animals.
Other Effects. These include changes in the agricultural yields, reduced summer stream flows and, addition of new trade routes, possible slowing of thermohaline circulation, resultant reductions in the ozone layer and the lowering of ocean pH.
(j) Extinction of Plants and Animals. According to an international study a quarter of land animals and plants may become extinct if global warming continues unchecked. The study reveals that as the earth hots up, all species may not be able to physically migrate to new locations. This will lead to smaller habitats for far fewer species. Rare and endangered species will generally move closer to extinction.
(k) Damage to the Natural Environment. Glaciers, coral reefs and atolls, mangrove swamp, tropical forests, polar and alpine grasslands are likely to undergo significant damage.
(l) Shortage of Water. Water shortage, which affects approximately 1.7 billion people today, will affect 5.4 billion people in 25 years, according to a study.
(m) Effect on Food Supplies. Food supplies are likely to be affected with grain yields falling across Africa and deserts spreading. Yields are likely to fall in Asia too and subsistence farming in Latin America will be damaged.
(n) Loss of Human Life. According to the study more than 160,000 people die globally ever year due to the side effects of climate change. Heat waves are likely to kill more people, particularly among the elderly and urban population.
(o) Floods and Droughts. As global warming increases the frequency of rapid precipitation, protracted droughts and floods will increase. There will be heavier rainfall across northern Europe- increasing the risk of floods- and lower rainfall over northern Africa and Australia.
(p) Disrupted Energy Demand Patterns. Global warming would result in hotter and drier summers, decrease in the soil moisture, coastal erosion, lower the snowfall, ,increased flooding, and disrupted energy demand patterns .
13. Effects on India. The assessed India specific effects are as under :-
(a) Decreased snow cover, affecting snow-fed and glacial systems such as the Ganges and Bramhaputra. 70% of the summer flow of the Ganges comes from meltwater
Erratic monsoon with serious effects on rain-fed agriculture, peninsular rivers, water and power supply.
Drop in wheat production by 4-5 million tones, with even a 1°C rise in temperature,
(d) Increased frequency and intensity of floods. Increased vulnerability of people in coastal, arid and semi-arid zones of the country
(e) Studies indicate that over 50% of India’s forests are likely to experience shift in forest types, adversely impacting associated biodiversity, regional climate dynamics as well as livelihoods based on forest products.
(f) According to Head of the IPCC, Dr. R.K. Pachauri, the climate change could adversely affect India. By 2100, higher sea-level on the eastern coast could lead to the disappearance of Sunderbans.
(g) In India, the region most vulnerable to accelerated sea level rise is the low-lying coral atolls of the Lakshadweep archipelago.
(h) Experts feel that the Indian coast is more vulnerable to storm surge than the West coast. Nearly one-third of the human population living within 60 kilometers of the coast could be lost due to the rise in sea level.
(j) Glaciers are receding at a faster rate in India. Researchers have found that the Gangotri glacier – which feeds the Ganges – is retreating at a faster rate than before. The melting of Himalayan glaciers would adversely impact 500 million people residing on the Indus, Ganges and Brahmaputra river basins. As glaciers are frozen reservoirs of water, their melting would lead to a decrease in water, affecting drinking water supply, irrigation and hydropower.
(k) There would be precipitation changes all over India, weather would be more erratic and post monsoon rainfall would become uncertain, according to Dr. Pachauri.
(l) According to Prof. M.S. Swaminathan, the ecological and economic damage arising out of global warming would have an adverse impact on agriculture, which was the mainstay of the country. The erratic weather could cause damage to crop patterns leading to an adverse impact on food security.
(m) The IPCC report has estimated that India could bear a huge loss of bio-diversity because of greater greenhouse emissions.
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