Global warming refers to an increase in the average temperature of the surface air and the oceans. It has been an issue of concern since the middle of the twentieth century. Various causes have been cited in the global warming debate. These include human activities and natural events. These have caused an increase in greenhouse gases creating the greenhouse effect. The climate system is influenced by processes external to it; these are referred to as external forcing. Some of these include radiative forcing which is mainly due to changes in the composition of gases in atmosphere largely greenhouse gases. Changes in the orbit of the Earth, volcanic eruptions and variations in solar luminosity are other processes involved in external forcing (Gabriele et al, 2007).
The greenhouse effect describes a rise in temperature on the surface of the earth due to the presence of particular gases in the air. These gases have an energy trapping effect. When energy coming from the sun heats the earth’s surface, the earth gives out radiation back to space. Greenhouse gases then trap some of this energy that is going out to space. They are referred to as greenhouse because their effect is similar to that of the glass panels in the greenhouse that is that of trapping energy (Shah, 2009). The main greenhouse gases are methane, carbon dioxide and nitrous oxide which are mainly natural. Other greenhouse gases which are more industrial in nature include perflourocarbons, hydroflourocarbons and sulfur hexafluoride (IPCC, 2007). Water vapor is also a greenhouse gas.
The greenhouse effect is considered natural as most of the greenhouse gases actually have an effect of enabling life by preventing heat from escaping the earth’s surface and thus becoming too cold for life. The danger however lies in the greenhouse effect becoming stronger leading to more heat getting trapped. With a stronger greenhouse effect more heat than necessary is trapped causing the earth to have less habitable conditions for animals, plants and humans (Shah, 2009).
The greenhouse gases which occur naturally cause increases in temperature of about 34 degrees Celsius. Of the gases, water vapour is responsible for about 36% to 70% of the greenhouse effect, carbon dioxide causes up to 26% of the greenhouse effect, methane about 4 to 9% and Ozone about 3 to 7% (Trenberth and Kiehl, 1997; Gavin, 2005; Randy, 2007). Carbon dioxide as is evident from the statistics is not the most potent of the greenhouse gases but it has the most significance especially with relation to the activities of humans. This is because the carbon dioxide levels have been on the rise since the Industrial Revolution. Other greenhouse gases have also been on the increase especially the industrial ones. This has led to the conclusion that human activities have contributed to the climate changes related to global warming. Carbon dioxide levels have increased as a result of the changes in land use and burning of fossil fuels. This has increased the natural cycle of carbon as carbon is moved into the atmosphere at a higher rate than it is being removed. Ultimately, this causes an increase in carbon dioxide concentrations.
Though the variations in the climate have always been there, the reason they have aroused much debate is because of the speed with which they are occurring currently. The danger with the rapid increase is that even a small increase in temperature, (as small as 2 degrees) is would cause impacts on the agriculture, oceans and the biodiversity of the world. One of the most immediate effects of global warming is the rise of sea levels and decrease in the snow cover due to temperature increases. Areas of low latitude and low developed countries are at greatest risk for the costs of global warming (IPCC, 2007).
The predicted impact of global warming as far as weather is concerned includes temperature increases causing increases in precipitation. The regional effects however are variable with some being due to local effects for example melting ice and some are as a result of generalized global change. In certain cases a change could be due to changes in a weather system or an ocean current. In cases such as these, the effect on the region may not follow the trends in the rest of the world. Generally, the impact of global warming on climates in different regions will occur through forming or melting ice, changes in precipitation and evaporation (hydrological cycle) and changes in ocean currents and flow of air in the atmosphere. It is believed that the coast will suffer impacts due to changes in the sea level (IPCC, 2007).These conclusions are backed by the fact that there have been reported decreases in mountain glaciers and snow cover (IPCC, 2007).
Oceans have a complex role in global warming. They serve as sinks for carbon dioxide by taking up most of the carbon dioxide that would otherwise stay in the atmosphere. Increased levels of carbon dioxide have led to the acidification of ocean. This has the effect of depleting oxygen in the ocean which will have adverse effects for aquatic life. Scientists report that there is likely to be more drought and hurricanes with longer periods of intense rain or dry heat. It has been pointed out that Northern Europe is at risk of being severely affected by colder weather if the trends in global warming and climate change are to continue. It is predicted that the arctic will begin to melt and cause fresh waters to flow southward. This would in effect cut off the Gulf Stream which brings warmth to countries like Britain (Shah, 2009). Another possible effect is the retreat of the glaciers in the Himalayas which could lead to scarcity of water in the long term.
It is to be noted that the impact of climate changes will probably be distributed unevenly. Developing countries are thought to be the most vulnerable. It is probable that the population groups severely threatened by high levels of warming are coastal-zone communities and high altitude communities who are significantly poor. It is possible that the effect on various human activities will be mixed. For instance, agriculture in certain regions may benefit from moderate increases in temperature while others are negatively affected. Low-latitude areas may likely suffer decreased crop yields but high-latitude and mid latitude areas could see increases in yields due to increases in temperature (IPCC, 2007).
The coasts and low-lying areas face the risk of floods and extreme weather events especially in areas which are densely populated. The coasts of developing countries may be unable to meet the dangers that come with the floods compared to coasts of developed countries. This is because coasts of developing communities are often inhabited by poor communities with little access to credit, savings or insurance that could help in recovering from disasters. Generally, the effects of global warming may be particularly harsh on development making it difficult for countries and people without resources to mitigate the damaging effects of global warming.
Gabriele CH et al, 2007, Understanding and Attributing Climate Change, Climate Change 2007: The Physical Science Basis. Contribution of Working Group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, IPCC
Gavin S, 2005, Water Vapour: feedback or forcing?, Real Climate
IPPC, 2007, Summary for Policymakers in Climate Change 2007: Impacts, adaptations and vulnerability, Contribution of Working Group II to the Fourth Assesssment Report of the Intergovernmental Panel on Climate Change
Shah A, Climate Change and Global Warming Introduction, Global Issues, available at http://www.globalissues.org/article/233/climate-change-and-global-warming-introduction
Trenberth KE and Kiehl JT, 1997, Earth’s Annual Global Mean Energy Budget, Bulletin of the American Metereological Society, vol 78 no 2, pp 197-208
Randy R, 2007, The Greenhouse Effect and Greenhouse Gases, University Corporation for Atmospheric Research, Windows to the Universe
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