Increasing atmospheric abundance of radiatively active trace gases: causes and consequences

Abstract

Carbon dioxide is the most important greenhouse gas followed by chlorofluorocarbons(CFSs), methane, nitrous oxide and tropospheric ozone. Atmospheric abundance of these gases is increasing, respectively at 0.5, 4, 0.9, 0.3 and 0.5% per year. CO₂, CH₄, N₂O, CFCs and tropospheric O₃ have contributed 55, 15, 4, 11 and 10%, respectively, to climate change forcing since pre-industrial times. Global circulation models predict 1.5-5.5 degree C increase in global temperature due to greenhouse warming by the year 2030 which will in turn cause widespread changes in precipitation pattern and monsoon circulations and in sea level rise. Most climatic models predict that doubling carbon dioxide would reduce current food production by between 3 and 17 per cent. Global warming will also affect natural biota as species ranges are expected to shift poleward by 700 to 900 km within the next century. Significant changes in the distribution of major biomes is also suggested.