RAPID CLIMATE CHANGE

‘GRIM SCENARIO FOR EARTH’

THE world is now faced with some very serious environmental problems due to the rapid increase in the consumption of fossil fuels and hydrocarbons, which have drastically altered, the atmospheric concentrations of trace gases, warns a leading British scientist.

“On regional scales, rain is being acidified, indicated by the rising concentrations of oxide of nitrogen and sulphur, of hydrocarbons such as chlorofluorocarbons [CFCs]. And in sprint and summer, ozone is being severely degraded,” observed Dr J. C. Farman of the British Antarctic Survey and the discoverer of the “ozone hole” over Antarctica.

He was participating in three day indo-British symposium on Climate change which was inaugurated by the British high commissioner Sir Nicholas Fenn, here today.

GROWING CONCERN: on a global scale the stratospheric ozone layer is being depleted, and there is growing concern over the speed at which climate change is being forced” Dr  Farman said.

The scientific assessment of climate change prepared for the UN’s Inter-governmental Panel on Climate Change (IPCC), and presented at the, symposium by Dr Goeff Jenkins, of British meteorological office, also predict scenario for the earth.

The report said the natural greenhouse effect (GHE) already keeps the earth warm enough for habitation, but emissions from human activities have substantially increased concentrations of carbon dioxide, nitrous oxide and CFCs. The longer emissions continue to increase at present rates, the greater reductions would have to be made to stabilise at a given level.

The report was prepared in 1990 by some, 200 scientists from 26 countries, through 15 international meetings and workshops, and was pre-reviewed by a further 150 or so. It is the most comprehensive, authoritative and internationally accepted assessment of the current understanding of climate and climate change. It is being updated for the “Earth Summit to be held in Rio de Janeiro next June.

RFDUCTION NEEDED: According to the report, stabilising atmospheric concentrations of carbon-dioxide at present day levels would require emission reduction. of over 60 per cent; and methane reductions would have to be 1 5 to 20 per cent.

In a greenhouse, glass allows sunlight in but keeps some infrared radiation from   escaping. The presence of greenhouse gases in the atmosphere creates a similar condition and keeps the earth warm. But for this effect, the earth’s average temperature would be at least 30 degrees Celsius less than at present, making it uninhabitable.

Although carbon dioxide is the least potent greenhouse gas on an equal mass basis, its high emission rate ensures that it is singly the most important. Since the industrial revolution, its total contribution to the man-made GHE has been about 60 per cent.

Carbon dioxide is exchanged naturally between huge reservoirs of carbon in the atmosphere, oceans and the living world. Biological processes on land contribute110,000 million tones of carbon as carbon dioxide to the atmosphere each year. This is largely balanced by an annual uptake of carbon during photosynthesis (plants absorbing sunlight to get energy for growth).

MAN’S CONTRIBUT[ON: The oceans are reckoned to send out and absorb similar amounts. Man’s activities emit 5,700 million tons to the atmosphere through burning fossil fuels (coal and oil), and possibly more than 2,000 million tons through land use changes, mainly through loss of tropical forests.

Man’s actions mean that, allowing for losses in the oceans, an excess of 3,800 million tons of carbon remains in the atmosphere as carbon dioxide each year. Its level began to increase in the 19th century with the industrial revolution and increasing deforestation.

Currently, about 45 per cent of total manmade emission of the gas come equally from electricity generation and transport deforestation accounts for upto 25 per cent. For carbon in trees and other vegetation, removed from the atmosphere during photosynthesis, represents a bank of carbon, but this carbon returns to the atmosphere during forest clearance.

Based on current mathematical models, the report predicts that under a “business as usual” emission scenario, global mean temperature would increase by about one-third of a degree Co per decade.

MOST DRAMATIC: The other most dramatic effect is the severe depletion of the ozone layer over Antarctica each spring. Dr Farrnan said the total ozone column is reduced by more than 50 per cent; and in a layer about 12 kilometre thick, centred at about 17 km altitude, the destruction exceeds 95 per cent. In the northern hemisphere, the decrease in ozone is less dramatic but is more widespread. It is about 12 per cent in spring and early summer, in mid-latitudes.

Earlier, in a keynote address, Prof. M.G.K. Menon, President of the International Council of Scientific Unions (ICSU), stressed the need for more research in this area.

The Times of India, January 16, 1992