The Heat Is On.....

The Intergovernmental Panel on Climate Change(IPCC) makes its strongest statement yet on global warming and its dangerous consequences.

"Relying on comprehensive data, the IPCC report states that hot extremes, heat waves & heavy precipitation events will become more frequent. Tropical cyclones will be more intense, with larger wind speeds. Rising sea level will threaten vast populations."

There can be no room any more for scepticism on Global Warming."The warming of the climate system is unequivocal, as is now evident from increase in global average air and ocean temperatures, widespread melting of snow and ice & rising global mean sea level." as per IPCC report. The report summarises the progress made in understanding human & natural drivers of climate change, observed climate change, climate processes & causes and projections on climate change.

The report notes that the rates of warming accelerated in the 20th century."Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gases (GHG) concentrations." The report adds that the impact of human activities now extends to other aspects of climate, including ocean warming & sea level rise, continental average temperatures, temperature extremes & wind patterns. An important new finding is that sea level rise accelerated in the 20th century. The report describes other important changes that have become pronounced in recent years, such as more intense precipitation, an increase in precipitation in higher latitudes & its decrease in lower latitudes, the increased frequency of droughts across the world and probably tropical cyclones too, more warm nights and fewer cold nights, thye increased retreat of glaciers since the 1990s & its contribution to sea level rise and greater warming of Arctic than the rest of the world.

ANALYSES OF ICE CORES



On the basis of analyses of ice cores spanning thousands of years, the report concludes that anthropogenic emissions have resulted in a marked increase in atmospheric concentrations of Carbon Dioxide, Methane & Nitrous Oxide since 1750 and now far exceed 'preindustrialization' values. The global increase in CO2 concentration is primarily due to fossil fuel use and land use change, while the increases in CH4 and N2O concentrations are because of agriculture. In particular, the increase in CO2 concentration from 280ppm to 379ppm in 2005 is far greater than the natural increase over the last 650,000 years of 180ppm to 300ppm. While the preindustrial concentration of CH4 was 715ppb, its value in the 1990s was 1732ppb & in 2005 it was 1774ppb. This, again is above the natural range over the last 650,000 years of 320ppb to 790ppb. However the growth rate of methane, the report points out, has declined since the 1990s. Similarly, N2O concentration increased from 270ppb in 1750 to 319 ppb in 2005 with the growth rate more or less constant since 1980.

The report notes that numerous long term changes in climate have been observed at continental, regional & ocean basin scales. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts and wind patterns and extreme weather conditions such as droughts, heavy precipitation, heat waves and greater intensity of tropical cyclones. Eleven of the last 12 years (1995-2006) rank among the 12 warmest years since the global surface temperature began to be recorded in 1895. Observation since 1961 show that ocean has warmed to a depth of atleast 3000 metres and has been absorbing more than 80 percent of the heat added to the climate system. Such warming causes water to expand, resulting in a rise in sea level. Mountain glaciers and snow covers have declined in both hemispheres, which also contribute to the rise in sea level.

PRECIPITATION TREND

While there is increased precipitation in the upper latitudes, there is decrease in the lower latitudes, including parts of south Asia, an aspect of concern to India. This is also consistent with the finding that while mid and high latitude ocean waters have freshened, low latitude waters have become more saline, leading to changes in evaporation and precipitation. Further, consistent with the observed warming and increased atmospheric water vapour, the frequency of intense precipitation events has increased over most land areas. Cold days, cold nights and frost have become less frequent. While there is observational evidence of intense tropical cyclone activity, including the North American hurricanes, there is no clear long term trend in the annual number of tropical cyclones, the report points out. Some aspects of climate have, however, not been seen to change. As against the Arctic, the Antarctic sea ice extent, while inter annual variability, does not seem to indicate any long term trend.

On the basis of model studies, the report projects a warming of 0.2*C a decade for the range of emission scenario considered. Significantly, it says that even if the concentrations of all GHGs and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1*C a decade would be expected.

Clearly, no nation can afford to be complacent on the issue any more. There is pressure mounting on all countries to act decisively, including developing countries that have no targets to meet up to 2012 under phase-I of the Kyoto Protocol.