1. INTRODUCTIONOur earth daily absorbs large quantity of solar energy from the sun. Most of theenergy is radiated back to atmosphere by the earth, and this process maintains thebalance of heat energy on the earth. There are many gases present in the atmosphere,but only carbon dioxide and water vapour absorb this infrared radiation of the earthstrongly and effectively block the radiation of energy back to the atmosphere.However a considerable part of it is re-emitted to the earth’s surface and consequentlythe earth’s surface gets headed up. This increase in temperature of the earth is calledthe green-house effect. Global warming is defined as the release of green house gasesinto the air that trap heat on the earth, causing for warmer temperatures. Globalwarming is affecting the earth a lot, and it is affecting it fast too. The greenhouseeffect is only troublesome when it gets too strong and warms things too much. Thepeople of industrialized nations have extracted Earth’s vast buried stores of fossilfuels and burned them. All those extra greenhouse gases mean more and more solarenergy is being trapped in the atmosphere, exacerbating the greenhouse effect andmaking things warmer. This decade has been the hottest decade in centuries (Stuart,2005). Because of this the polar ice caps are melting, and it could change the flow ofthe North Atlantic Current. The change in flow could cause immeasurable effects tothe Earth, and could change the weather that occurs on the earth dramatically.According to the IPP 2001 report, the Earth’s surface has warmed by about 1 degreeFahrenheit, and that is the biggest it has raised in centuries (Stuart, 2005). The hotteratmosphere on the earth causes the ocean temperature to rise, and coincidentlyhurricanes get more power from warmer waters. Not only does global warmingaffects the earths weather patterns, it also affect its wildlife.
2. 2. Global warming2.1 Contributors to global warmingA majority of scientists have concluded that human activities are responsible for mostglobal warming. Human activities contribute to global warming by enhancing Earth’snatural greenhouse effect. The greenhouse effect warms Earth’s surface through acomplex process involving sunlight, gases, and particles in the atmosphere. Gases thattrap heat in the atmosphere are known as greenhouse gases. Global atmosphericconcentrations of carbon dioxide, methane and nitrous oxide have increased markedlyas a result of human activities since 1750 and now far exceed pre-industrial valuesdetermined from ice cores spanning many thousands of years. The global increases incarbon dioxide concentration are due primarily to fossil fuel use and land-use change.Source: http://www.koshland-science-museum.org/exhibitgcc/images/causes03a.gif
3. 2.1.1 Natural causesThe Sun is the only source of energy for the functioning of the Earth’s climate system,any changes in solar output may lead to climate change and specifically globalwarming. It is predicted that a change in solar output by only 1% per century maychange the average temperature of the planet by 0.5 to 1.0 Celsius. Changes in theshape of the Earth’s orbit around the sun alter the total amount of solar energyreceived by the planet. This would also affect the planet’s temperature. Volcanicactivity is yet another significant contributor to variations of Earth’s meantemperature. The sun, water vapour and volcanism are far more powerful agents ofchange in climate than carbon dioxide emissions. The world’s natural wetlandsproduce more greenhouse gases annually than all human sources combined.Greenhouse gases and solar forcing affect temperatures in different ways. While bothincreased solar activity and increased greenhouse gases are expected to warm thelowest portion of Earth’s atmosphere, an increase in solar activity should warm thesecond major layer of the atmosphere (stratosphere) while an increase in greenhousegases should cool the stratosphere. The oceans play an important role in determiningthe atmospheric concentration of carbon dioxide. Carbon dioxide gas in theatmosphere and dissolved in the ocean surface reach a balance. Changes in oceancirculation, chemistry, and biology have shifted this balance in the past. Such changesmay affect climate by slowly moving carbon dioxide into or out of the atmosphere.
4. The above graph shows the departure from the long-term average, of average globaltemperatures, in degrees Fahrenheit, since 1880. (Source: EPA)2.1.2 Human activitiesThe main human activities that contribute to global warming are the burning of fossilfuels (coal, oil, and natural gas) and the clearing of land. The focal point of this causeis the generation of energy for use both in industry and commercial/ private sector.Fossil fuel combustion is especially heavily used as a source of energy for industry.However, we have burned these fuels faster than the rate at which it was removed bythe early tropical forests, in other words very large amounts of carbon dioxide isreleased at a very high rate and the nature is unable to remove it in good time. Thisleads to the accumulation of extra carbon in the atmosphere and consequently toglobal warming. For example, burning occurs in automobiles, in factories, and inelectronic power plants that provide energy for houses and office buildings as well asdeforestation and various agricultural and industrial practices are altering thecomposition of the atmosphere and contributing to climate change. These human
5. activities have led to increased atmospheric concentrations of a number ofgreenhouse gases, including carbon dioxide, methane, nitrous oxide,chlorofluorocarbons, and ozone in the lower part of the atmosphere. Carbon dioxide isproduced when coal, oil, and natural gases (fossil fuels) are burned to produce energyused for transportation, manufacturing, heating, cooling, electricity generation, andother application. There are some other industry-related activities usually calledindustrial processes which are also significant sources of greenhouse gases. Theproducts whose manufacturing causes emission of these gases include cement,minerals, chemicals, metals. Many activities related to industrial processes use largeamounts of energy and thus produce significant amounts of greenhouse gas emissionsthrough fossil fuel combustion.2.1.3 Land useLand use changes for example clearing land for logging, ranching, and agriculturelead to carbon dioxide emissions. Vegetable contains carbon that is released as carbondioxide when the vegetation decays or burns. Normally, lost vegetation would bereplaced by re-growth with little or no net emission of carbon dioxide. However, overthe past several hundred years, deforestation and other land use changes in manycountries have contributed substantially to atmospheric carbon dioxide increases.Methane (natural gas) is the second most important of the greenhouse gases resultingfrom human activities. It is produced by rice cultivation, cattle and sheep ranching,and by decaying material in landfills. Methane is also emitted during coal mining andoil drilling, and by leaky gas pipelines. Nitrous oxide is produced by variousagricultural and industrial practices. When land is cleared for expansion of humansettlements or for timber sales, a cocktail of pollution is released as part of this
6. process and the main greenhouse gas emitted is carbon dioxide. Most importantly istropical deforestation especially by forest fires and alongside other pollutants causesthe release of carbon dioxide. The main greenhouse emitted as a result of wastemanagement is methane, with some small amounts of nitrous oxide. Tropicalrainforests play a very important role in regulating global and regional climatepatterns. An extremely important service provided by the rainforests is the removal ofcarbon dioxide from the atmosphere by photosynthesis. It acts as a pollution or carbondioxide sink and storage. Deforestation leads to release of carbon dioxide from thetrees back to the atmosphere, release of carbon stores held in soil into the atmosphereand destruction of forests as carbon sinks for future carbon dioxide removal and all ofthese will further contribute to the global warming effect.
7. 2.2 Impact of global warming2.2.1 WorldThe impact of global warming is far greater than just increasing temperatures.Warming modifies rainfall patterns, amplifies coastal erosion, lengthens the growingseason on some regions, melts ice caps and glaciers, and alters the ranges of someinfectious diseases. The IPCC has concluded that global temperatures will likely risefrom 1.2 to 6.5 degrees Celsius by the end of the century depending on differentscenarios regarding greenhouse gas emission. Rainfall patterns will continue tochange around the world. In general, global warming should accelerate thehydrological cycle. Warmer air cause more water to evaporate. A warmer atmospherecan hold more water vapour, so more water is available to fall back to Earth when itrains or snows. As a result, extreme precipitation events should become more frequentand intense leading to worse flooding. In addition, increased evaporation in someregions will lead to drier conditions, with a higher probability of drought. Ice ismelting worldwide especially at the Earth’s poles. This includes mountain glaciers,ice sheets covering West Antarctica and Greenland, and Arctic sea ice. For moreplaces, global warming will result in more frequent hot days and fewer cool days withthe greatest warming occurring over land. Most importantly, global warming willaffect on ecosystems, the plants and animals that co-exists in particular climate zone,both on land and in the ocean. Warmer temperatures have already shifted the growingseason in many parts of the world. This change in the growing season affects thebroader ecosystem. Migrating animals have to start seeking food sources earlier. Theshift in seasons may cause the lifecycles of pollinators to be out of synch withflowering plants and trees. This mismatch can limit the ability of both pollinators and
8. plants to survive and reproduce which would reduce food availability throughout thefood chain.