Green house fingerprint
A UNIQUE pattern of changing climate is `green house finger print', suggesting that recent warming is caused by emission of excessive amounts of greenhouse gases (GHG) — particularly Carbon dioxide consequent to burning of fossil fuels in industrial activities as opposed to natural causes.
There are divergent views on this issue. Since the environmental policies are conditioned by many political imponderables, besides physical, chemical and biological laws of nature, additional information based on recent reports are given in this companion article.
Specialists' suggestions
It is generally believed that carbon dioxide from combustion of fossil fuels is the main greenhouse gas — and the automobile, in particular, has become synonymous with this emission. Suggestions are made, even by specialists, that zero-carbon fuels like hydrogen should be encouraged for combustion processes.
Water vapour, which is the exhaust product, is undoubtedly not an atmospheric pollutant, but it is the most powerful greenhouse gas.
Actually it traps nearly 90 per cent of the heat as compared to carbon dioxide. A group of Brussels based European oil companies recently reported that using hydrogen as a road transport fuel would increase Europe's GHG emissions (International Oil Company's journal, March 2004).
Excepting single-element molecules like oxygen and nitrogen, which are transparent to heat, all other polyatomic gases like water vapour, methane, carbon dioxide and other gases in atmospheric air, block heat at their selective frequencies in the infrared spectrum. It should be remembered that nearly 70 per cent of the globe is covered by ocean.
Reaching the limit
Greenhouse effect of water vapour is natural and without it, life will not be sustained on the globe. It is only when human activity exceeds the limit, the GHG may increase the global temperature. The question is, have we reached this limit?
The George Marshall institute has answers to this question. These are itemised briefly: (a) The National Academy of Sciences has clearly stated that our understanding of the climate system is still in an embryonic stage as climate is believed to be "a complex, dynamical and nonlinear system with positive and negative feed backs."
The interactions and responses are too difficult to predict. (b) Average temperature over the last 100 years has increased by about 0.5 degrees C. Much of the warming on account of this increase occurred in the early parts of the century, much before the industrial activity of the later part when addition of GHG was significant.
This is clear evidence that the temperature of the earth has not increased in step with the increasing carbon dioxide. (c) The influence of the solar activity on climate is significant and has an overriding influence on global temperature as compared to the minor effect of increase in carbon dioxide due to human activity. This has to be taken into effect in the model.
The warming due to solar activity reportedly shows greater swings in temperature according to the solar magnetic cycle length (period of 11years.)
In fact, the trend of measured temperature is decreasing over years ( Source: Marshall Institute), whereas climate modelling shows an increasing trend. (d) This casts serious doubts on the status of climate modelling.
It is not just Carbon dioxide that causes warming. The impact of water vapour, clouds, sulphate aerosols or particulates are to be assessed — whether they amplify or diminish the human made impacts. (e) Most of the surface temperature measurements are made over land, primarily over inhabited regions.
Measurement over the oceans, which occupy 3/4 of the surface of the globe is sparse. Models are as good as the accuracy of the assumptions and observations.
Based on the inaccurate mathematical modelling, forecasts of the impact on the biosphere may be premature and misleading. It is reported that no evidences for the catastrophic global warming have been indicated as a result of increase in carbon dioxide resulting from human activities.
Automobile emission
Just taking the case of automobile-related carbon dioxide emission, Professor P.S.Myers of the University of Wisconsin, in a key-note address, says that the annual carbon dioxide produced by residential water heaters in Wisconsin is approximately equal to the carbon dioxide produced by all the personal cars in the U.S. (SAE Paper,1998).
In one of the issues 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 activities. It is unfortunate that the automobile, our workhorse, has become the target for excessive emissions of GHG.
B. S. Murthy
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