Warming of the earth’s climate system is unequivocal.
CO2 atmospheric concentration--280 ppm in 1750 rose to 379 ppm in 2005. And the average global temperature rose by 0.74 degree Celsius.
Direct observations of changes in temperature, sea level, and snow cover in the northern hemisphere during 1961–90 indicate increased temperatures, rise in the mean sea levels, and decreasing snow cover.
Global average sea levels rose by 1.8 mm/year over 1961–2003.
Eleven of the twelve years—1995-2006—rank among the twelve warmest years since 1850.
Both the hemispheres have observed a decline in the mass of mountain glaciers and snow cover. Precipitation has been found to be more variable, with increased frequency of heat waves, droughts, heavy
precipitation events, and floods.
Projected changes in the climate indicate an increase in global temperatures in the range of 1.8°C to 4.0°C over the twenty-first century and sea level rise is projected to be between 0.18 m and 0.59 m by 2100.