The Hindu Business Line : Climate changes — Are greenhouse gases responsible?

THE recent UN Framework Convention on Climate Changes (UNFCC) in New Delhi expressed concern over the view held by the developed nations that the developing countries generated more greenhouse gases (GHG) than their economies warranted. Also, India rejected suggestions that the developing countries should increase their commitments to reduce their GHG emissions.

The view that GHGs such as carbon-dioxide are responsible for the climate changes is only shared by the political leaders of the developed world, and not by the scientific community. Further, a sound and valid scientific foundation is necessary before making public policies regarding the apportioning of responsibilities to the participating nations.

Based on temperature measurements in the presence of GHGs such as carbon-dioxide expected from human activities, sophisticated climatic models are prepared. From these studies, computer predictions of hazards are made when uncontrolled GHG are added to the atmosphere from industrial and other human activities.

Such computer predictions of changing climate patterns are called "greenhouse finger prints". The predictions from these fingerprints are, no doubt, alarming. According to the Intergovernmental Panel on Climate Changes (IPCC), the predictions include a wide range of disasters — unprecedented droughts, the disappearance of coral reefs, melting of glaciers, rise in sea level causing flooding, extinction of species and evidences of insect-borne diseases, to name a few.

Understandably, this causes great concern, and many policies are formulated to limit the GHG emissions. One such policy is the trading in the CO{-2} reduction (called carbon trading) that a nation can contribute by adopting improved methods of emission reductions.

It is reported that Essar power officials in India have made a power-project proposal to run its 515 MW combined power plant on natural gas instead of liquid petroleum fuels such as naphtha and diesel oil. This will increase the CO{-2} savings from 2 lakh tonnes to 4 lakh tonnes every year. While this step will certainly help reduce air pollution and the local temperature, there is no scientific basis of its impact on the global warming problem.

Also, drastic reduction of CO{-2} emissions is not a solution to the threat of major climate changes. The George C. Marshall Institute has been addressing the problem of global warming to arrive at scientific consensus. One must understand what the scientists say about the greenhouse effect. The earth's atmosphere behaves like a greenhouse, and the surface of the earth absorbs most of the incident sunlight at high frequencies, re-emitting it as infrared radiations. The polyatomic gases such as CO{-2}, water vapour (H{-2}O) and methane, and the clouds absorb this energy and are radiated it back to the earth. At night, this layer of GHG acts as a blanket as the absorbed energy prevents the temperature from falling rapidly, especially in regions with a high atmospheric H{-2}O content. Therefore, the greenhouse effect is natural and necessary for life on earth. It should be noted that water vapour and the clouds absorb 90 per cent of the infrared energy.

The "much-traded" CO{-2} (with other trace gases) absorbs only about 10 per cent.

The contribution to the warming effect of the GHG goes largely to water vapour and the clouds. The atmospheric modelling based on the warming due to CO{-2} needs a deeper understanding. The Graphs illustrate the wide gap between the model predictions and the actual observations — the only true test of science. The predicted greenhouse warming (temperature) line on the right-hand side of the Graph shows an increasing trend over 15 years, from 1980 to 1995, while the broken line (passing through the middle points of the actual temperature) based on observations shows a decreasing trend. This clearly shows that it is not CO{-2} that warms the earth, and that atmospheric modelling is still at an infant stage.

The average global temperature of the earth has increased roughly by 0.5{+0} C over last 100 years. Over the last two decades, the earth's temperature has changed very little — by 0.05 {+0}C every decade in the lower atmosphere (at about 8 km height). Satellites measure temperatures by microwave sounding units carried on board. These measurements are precise, but not the temperatures taken on earth. Records show that the changes in global temperatures always do not follow changes in the atmospheric CO{-2} levels. The CO{-2} changes are driven by the vegetation changes in response to the natural variations in air and sea temperatures.

Scientists, after careful studies, have come to the conclusion that solar activity is the dominant natural force that causes global warming and climate changes. One natural factor in climate change may be variations in the brightness of the sun, which is in step with changes in sun's magnetism, which has a period of roughly 11 years, and is known as the sunspot cycle. The earth's temperature deviation is coming down, contrary to the CO{-2} greenhouse modelling. There are other features of the solar system activity that affect global temperature and climate — such as the changes in the earth-sun geometry. Other natural causes, such as high volcanic activity, may raise the dust levels very high, and this may be compounded by sunspot activity. These natural causes have an overriding effect on climate changes in comparison with the greenhouse effect.

Mr P. S. Myers, the distinguished professor of the University of Wisconsin, in one of his addresses to the SAE members, lucidly explained the potential for global warming due to the input of CO{-2} and other gases into the atmosphere, and pointed to the complexities in predicting the effect of these gases on global warming. He feels that atmospheric models used in predicting the effect of these gases on global warming are "embryonic and unproven".

In a recent issue of the Geophysical Research Letter, Professor Chester Gardner says that there is a serious error in global circulation models when it comes to predicting the temperatures in the earth's polar regions. It appears that nobody knows for sure the effect of GHG from human activity. The Marshall Institute is of the opinion that at least 25 years of research is needed to evolve a clear policy on climate changes and CO{-2}.

(The author is a former Professor of the IIT, Madras)

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