Global Climate Change Initiative

indicators of human influence on the atmosphere

Global warming refers to the effect on the climate of anthropogenic activities, in particular the burning of fossil fuels (coal, oil and gas) and large-scale deforestation activities, which cause large amounts of ‘greenhouse gases’ to be released into the atmosphere, of which the most important is carbon dioxide. The other greenhouse gases are nitrous oxide, chlorofluorocarbons (CFC’s), methane, and sulfur hexafluoride.



Greenhouse gases allow short wavelength light, such as ultraviolet light, to pass but not long wavelength light (e.g. infrared radiation). Accordingly, the infrared (heat) is trapped near the Earth’s surface keeping it warmer than it would otherwise be. Associated with this warming are changes in the climate, both global and regional (Houghton, 2005). The scientific opinion on climate change, as expressed by the United Nations Intergovernmental Panel on Climate Change (IPCC, 2001) and explicitly endorsed by the national science academies of the G8 nations, is that the average global temperature has risen 0.6 ± 0.2 °C since the late 19th century, and that it is likely that most of the warming observed over the last 50 years is attributable to human activities.



Atmospheric carbon dioxide has increased from around 280 parts per million (by volume) in 1800 to around 315 in 1958 and 380 in 2005, a 31% increase over 200 years (IPCC, 2001). Other greenhouse gas emissions have also increased. Future carbon dioxide levels are expected to rise due to ongoing economic development dependent on fossil fuel usage, though the actual trend for the future will depend on economic, sociological, technological, and natural developments. The Intergovernmental Panel on Climate Change has concluded that there will be both global and regional climatic change, altered precipitation patterns, occurrence of extreme events such as droughts and hurricanes and an increase in climate variability (Houghton et al., 2001) during the next 100 years (IPCC, 1995, 2001). According to ice core climate record, today’s rising atmospheric carbon dioxide concentration, at 380 parts per million by volume, is 27 % higher than its highest recorded level during the last 650,000 years (Brook, 2005).


Written By: Meghna Tare
Meghna Tare was born in India and graduated in 1997 with a BS in environmental science from the University of Nagpur, India. Summer internship in an environmental consultancy exposed her to the application of chemical analysis and instrumentation in the detection of toxic metals in waste water. This led her to study towards a MS degree in Analytical and Environmental chemistry from the Department of Chemistry, University of Nagpur, India. In 2002 Meghna graduated from the University of San Francisco with a MS degree in Analytical and Bio-Inorganic Chemistry, during which she studied the synthesis and characterization of artificial enzymes called metalloenzymes. These enzymes have application in the area of bio-chemistry and environmental biotechnology.



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