GLOBAL WARMING POTENTIALS (GWP)

World Environment Day is commemorated each year on June 5 to enhance the awareness regarding our environment. As on today, greenhouse gas emissions and the resulting climate change, i.e., global warming is the global issue of great concern.

Climate change is generally understood as change of the climate on a large scale of space and time as a result of anthropogenic activities which are not of natural origin. Greenhouse gas effect is the increase of the heat content of the environment due to absorption or trapping of the infrared heat by the greenhouse gases. The concentration levels of the greenhouse gases are increasing by the industrial activities, mainly from fossil fuel fired power plants. Global warming is only a part of the greenhouse effect. Some of the typical greenhouse gases are CO2, CH4, N2O and CF4.

Assuming CO2 as the reference GHG, the effect of other greenhouse gases is expressed in the CO2 equivalents. This conversion factor is called Global Warming Potential (GWP). This is the ratio of the time integrated radiative forcing of the atmosphere due to an instantaneous release of 1 kg of a greenhouse gas relative to that of 1 kg of CO2. It is reported that for a time horizon of 20 years, the GWP for methane (CH4) is 35 times higher and for nitrous dioxide (N2O), it is 260 times higher than carbon dioxide (CO2).

The implication of this finding is that even though the release of CH4 and N2O may be in small quantities as compared to CO2 in some industries, the greenhouse effect can be more severe than CO2 and hence needs proper understanding and assessment of its overall contribution to global warming. For example, in ultimate analysis, the contribution from global warming due to the release of methane (from the decay of submerged forestry and vegetation) in hydroelectric power generation may be comparable to the CO2 release from fossil fuel powered plants! Any comments?