Global warming refers to the increase in average temperatures on Earth since the mid-20th century, mainly caused by human emissions of greenhouse gases like carbon dioxide and methane from industrialization. This enhances the natural greenhouse effect and is accelerating global temperature rise. Impacts include rising sea levels threatening coastal cities, changes in weather patterns and food production, and increased tropical diseases. Efforts to prevent further warming involve reducing greenhouse gas emissions and developing alternative energy sources.

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Global Warming (Draft)
Benjamin L Saitluanga
The term "global warming" refers to the increase in the average of the Earth's
surface since the mid-20th century and its projected continuation, and implies a
human influence.
Causes:
Global warming is caused mainly by anthropogenic (human) enhancement of
greenhouse gases.
The earth’s surface partly absorbs short-wave solar rays while emits long-
wave infra-red radiation. Carbon dioxide and water vapour in the atmosphere strongly
absorb infra-red radiation (terrestrial radiation) and effectively block a large fraction
of the earth’s emitted radiation. The radiation thus absorbed by carbon dioxide and
water vapour is partly returned to the earth’s surface. The net result is that the earth’s
surface gets heated and the phenomenon is known as the Greenhouse Effect.
Greenhouse effect is a natural phenomenon that warms the Earth by about 33 ° C
without which Earth would be uninhabitable. It is caused by greenhouse gases in the
atmosphere. On Earth, the major greenhouse gases are water vapour, carbon dioxide
(CO2), methane (CH4), and ozone.
Greenhouse Effect
However, the natural greenhouse effect is currently being enhanced through
human activity via the release of additional greenhouse gases into the atmosphere
mainly due to industrialisation. This enhancement of the natural greenhouse effect has
caused global warming over the last 150 years and that this warming is very likely to
accelerate in the future.
Sources of Greenhouse gases:
1) Carbon Dioxide: it is the predominant greenhouse gas. It contributes about 60 per
cent of man made greenhouse effect. The major sources of CO2 are all industries and
machines that run on fossil fuels, automobiles, burning of wood, deforestation etc.
The CO2 concentration has been increased by 27 per cent since 1765.

2. 2) Chlorofluorocarbons (CFCs): these ozone depleting compounds are recent man
made and produced from refrigerators, aerosol cans, coolants etc. they contribute to
around25 % of man made greenhouse effect
3) Methane: this compound is produced from swamps, paddy fields, bogs, moist soils,
guts of termites and cows, garbage dumps etc. Methane concentration has increased
by 100 % since 1765. It causes about 12 % of man made greenhouse effect.
4) Other Greenhouse gases like Nitrous oxides, Water vapour, Carbon monoxide etc.
Effects/Impacts of Global Warming:
1. Sea level Rise: A major possible impact is the rise in sea levels by as much as 15
cm in the next 100 years due to partial melting of polar ice caps. This sea level rise
would threaten coastal cities (Calcutta, Mumbai, Chennai, etc.) and some 60-odd
island nations such as Maldives, Bangladesh, etc. which will be drowned under the
sea.
2. Temperature Change: There will be a gradual increa in global mean
se
temperature. It has been recorded that between 1901 and 2000 most of the Earth
shows warming of approximately 0.2 ° C per decade. Warming was more rapid
between 1910 and 1945.
3. Increase in Rainfall: Precipitation is likely to increase regionally because as the
temperature increases, more evaporation takes place, leading to more precipitation.
4. Change in Food Production pattern: It may be noted that a slight rise in
temperature even by 1° C, can have adverse effect on the world food production. It is
predicted that wheat producing zones will be shifted further polewards from fertile land to
unproductive lands. For e.g., In India, wheat producing zones may be shifted from Punjab &
U.P to the Himalayas.
However, global warming might have a positive impact on agriculture. Higher
Carbon dioxide concentration may accelerate crop development and some areas will be more
productive than before.
5. Effect on Ocean: The biological productivity of the ocean will fall due to warming of the
surface layer. This reduces transport of nutrient from deeper layers of the ocean to the surface
by vertical circulation. Moreover, there will be less photosynthesis by marine plants. In other
words, the production of sea food (marine plants and fish) will decline.
Moreover, there will be large-scale destruction of coral reefs due to coral bleaching
due to increased sea surface temperature.
5. Impact on Human Beings: Global warming is expected to increase the potential
geographic range and virulence of tropical diseases. Climate change could cause a
major increase in insect-borne diseases such as malaria throughout Europe, North
America and North Asia.
6. Economic Impact: According to United Nations Environment Programme (UNEP),
economic sectors likely to face difficulties related to climate change include banks,

3. agriculture, transport and others. Developing countries dependent upon agriculture
will be particularly harmed by global warming.
Apart from the above, g lobal warming is expected to c
ause various
environmental problems like intensification of cyclones, El-Nino, desertification,
destruction of natural habitats, decreased water supply etc.
Prevention, Mitigation and Adaptation:
1. In order to slow down global warming, efforts have been given to decrease
the rate of emission of greenhouse gases particularly carbon dioxide and methane.
This involves reduction in use of fossil fuels, increasing use of renewable energies,
reforestation etc.
2. Efforts have also been made to mitigate the source and impacts of global
warming including release of gases into the atmosphere that could off-set the effects
of greenhouse gases, promote cloud formation and steering cyclones away from
populated areas. However, these are far more expensive.
3. Adaptation involves stopping new settlements and agriculture in coastal
areas, alteration of land use, using different plants and crops etc.
Recognizing the problem of global warming, the World Meteorological
Organization (WMO) and United Nations Environmental Programme (UNEP)
established the Intergovernmental Panel on Climate Change (IPCC) in 1988. Under
the aegis of the IPCC, Conference of Parties-III (COP-III) was held on Kyoto in Japan
in 1997. The Kyoto Protocol provided that developed countries should cut t eir h
carbon dioxide emission by 5 per cent from1991 levels by 2012. Numbers of
countries have already ratified the protocol while countries like U.S.A. failed to ratify
it as it would severely cause their progress in development.
Therefore, apart from causing global environmental problems, Global
Warming has also caused an unending political and economic debate. Poor regions,
particularly Africa, appear at greatest risk from the projected effects of global
warming, while their emissions have been small compared to the developed world. At
the same time, exemption of developing country from provisions of the Kyoto
Protocol have been criticized by the United States and Australia, and used as part of a
rationale for continued non-ratification by the U.S.