issue 206 - April 1990
Kurbandurdy Muradov / CAMERA PRESS
Seen from space, our planet is a green and blue orb floating in an
apparently lifeless cosmos. A fragile balance, a fine ecological interdependence,
exists in the natural world which keeps the earth pulsing with life. Here the NI
details how that balance is now being upset by the depredations of humans.
The difference between climate and weather is like the difference between the forest and the trees.
Weather is what we experience (and complain about) on a daily basis. We understand it in the familiar terms of the weather report: cloudy, windy, rainy, humid, sunny or snowy.
Climate is a description of average weather conditions over time, a period of at least 30 years or more.
Climate results from interaction between the atmosphere, the oceans, the land surface, the polar ice caps and biological life (plants, animals and humans). Our climate is constantly changing, but most of the change takes place over generations and goes unnoticed. However, a sudden extraordinary event in one place can bring about rapid change all over the globe. For example:
Dust in the atmosphere from volcanic explosions can result in cooling due to increased reflection of solar energy. A huge volcanic eruption in Indonesia in 1815 has been linked to the 1816 'year without summer' in the eastern US and Canada.2
In 1983 El Niño, a warm ocean current off the Peruvian coast, was 70°C warmer than usual. Weather across the world was altered - including floods along the west coast of North and South America and droughts in southern Asia, Africa and Australia.
Carbon dioxide is the single most important greenhouse gas and is linked directly to industrial development and deforestation.
When all greenhouse-gas sources are added together the responsibility for global warming is as follows10:
The West (15% of world pop.) - 46%
A layer of gases in the atmosphere acts like an insulating blanket trapping solar energy that would otherwise escape into space. Without these 'greenhouse gases' the earth would be frozen, barren and lifeless.
HOW IT WORKS
By analyzing gas trapped in glacial ice scientists have found CO2 levels have risen steadily since the Industrial Revolution. CO2 concentrations are presently rising by 3-4% a decade and have increased by 25% over the last 300 years.
Over the past 300 years, as a result of human activity, concentrations of the main greenhouse gases have increased significantly. There are strong indications that global warming has already begun as a result.
In the last 90 years the earth has warmed by about half a degree centigrade. That may not sound like much - but a small change can make a big difference. Our average global temperature is only 5°C warmer today than during the last ice age 13,000 years ago.5
The present global surface temperature is about 0.4°C higher than the mean value from 1950 to 1980.
The 1980s were the warmest decade on record; the warmest years this century were (in order) 1988,1987,1983,1981,1980 and 1986.6
Estimated contribution to global warming of main greenhouse gases in the 1980s.
THE MAIN GREENHOUSE GASES
Carbon dioxide (CO2)
Nitrous oxide (N2O)
Surface Ozone (03)
Sophisticated computer models predict the earth's surface temperature will rise between 3 and 5°C by the middle of the next century - change unprecedented in human history. The exact impact of such a change is unclear. But scientists predict12:
greater extremes of weather; more storms and hurricanes in humid tropical countries and drier, hotter weather in semi-arid tropical regions with consequent disruption of food production and water availability.
higher temperatures will melt polar icesheets and glaciers, increasing sea levels by between 1 and 3 metres in 60 years, and causing widespread flooding. The great river deltas of the world would be inundated - it is estimated that a mere 50 cm rise in sea level would permanently flood 12% of Bangladesh. Egypt could lose 20% of its arable land, affecting some 10 million people.
plants and animals will be unable to adapt to rapid temperature increases and new climatic conditions. Vast forests in Canada, Scandinavia and the USSR could die resulting in massive forest fires and the release of a huge volume of additional CO2, thus accelerating global warming.
1 The Gaia Atlas of Planetary Management, ed. Norman Myers (Doubleday, 1984).
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