Global Warming

Causes of Global Warming

Earth's atmospheric temperature rise results from increasing concentration of greenhouse gases (GHGs) such as water vapor, carbon dioxide, methane, ozone, nitrous oxides, and chlorofluorocarbons (CFCs). The greenhouse gases are produced mainly by human (anthropogenic) activities such as burning of fossil fuels, deforestation, and transportation. Fossil fuels dominate the global energy regime and account for over 85 percent of the total global energy consumption.

There is scientific consensus that the global warming is the result of human-induced GHGs emissions. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) estimates that carbon dioxides from fossil fuel burning account for about 57 percent, and another 17 percent result from deforestation and biomass decay and together with other sources, carbon dioxides account for about 77 percent of the total GHG emissions. The other major greenhouse gasses are methane (14 percent), nitrous oxides (8 percent), and other gases (1 percent). Rapid industrialization, urbanization, and the increase in number of vehicles on the roads have contributed substantially to carbon dioxide emissions. Methane, the second potential GHG, is released from landfills and rice fields when bacteria break down organic matters. Clathrates—the frozen ice masses—are also sources of methane that lie at the bottom of the Arctic sea beds. Methane is released when ice melts as a result of the rise of temperature of ocean water. Nitrous oxide is released from chemical fertilizers, pesticides, and gases used in various industrial processes. Different greenhouse gases have different heat-trapping potentials. Methane has 20 times more warming effects than carbon dioxide. Nitrous oxide has 300 times more warming potential than carbon dioxide.

Disagreements have arisen, however, regarding the nature, causes, and consequences of global warming. Some scientists disagree that the causes of global warming are based in human factors, and they argue that it is the result of natural fluctuations in the Earth's temperature and changing climate system cycle. Others view global warming as caused by variability in solar radiation and they argue that the temperature increase over the past century is the result of intense solar activity and varying solar radiation. Studies also show that fossil fuels produce air pollutants that make the clouds reflect more of the sun's rays back into space by a phenomenon known as “global dimming.” Addressing global dimming may cause more global warming, as well as other environmental problems.

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