For years, there have been legitimate doubts about the seriousness of global warming and climate change, and especially about man's role in it. While the science was uncertain, it was right to be sceptical over starry-eyed and costly cures. One benefit of this caution was that a more informed decision would be possible as the science got better. Another was that new technology might make it easier to curb warming. And a third was that, as the world got richer, it could more easily afford to devote resources to the problem.
Now, however, the science has become clearer; and most new evidence confirms that global warming and climate change should be taken seriously. A report published by the UN's Inter-governmental Panel on Climate Change (IPCC), made up of the world's top climate scientists, concludes that man's actions have "contributed substantially to the observed warming over the last 50 years".
Does mankind deserve the blame?
The strongest argument against this conclusion lies in the scientific uncertainty around the causes of climate change. Long before mankind, and even longer before the industrial age led to large-scale burning of fossil fuels, the climate warmed and cooled in cycles. Among the natural factors affecting it, then and now, are volcanic eruptions, fluctuations in solar radiation and changes in the earth's rotation. Sceptics argue that any impact from man's actions will have been dwarfed by such age-old natural forces.
The trouble is that man's actions affect climate in many complex ways. Carbon dioxide is produced when fossil fuels are used, or when forests are burnt. Agriculture releases other power Green House Gases, such as methane and nitrous oxide. Industrial processes release chemicals known as halocarbons and other long-lived gases, some of which trap heat in the atmosphere. The release of particulars, however, promotes cloud formation and so has a cooling effect.
The more that researchers look at the problem, the more convinced they are that Green House Gases are the main culprit for the earth's recent warming. The evidence they cite is largely based on mathematical models of climate change.
Should we worry?
Inferring a direct causal link between climate change and any specific flood or hurricane is unscientific. But it is not unreasonable to expect that, over time, "mega-disasters" and freakish weather in general may become more commonplace. This is because climate change is likely to have a big impact - and the faster it proceeds, the greater the damage. Climatic zones could move towards the poles by as much as 150-550km in mid-latitude regions, shifting entire ecosystems and agricultural zones with them. Ecosystems will transform and possibly decline, and species that can not readily adapt may die out.
This is not to deny the possible benefits of global warming and climate change. For example, a detailed study of climate change in Europe, led by Britain's University of East Anglia, concludes that climate change will probably be a modest boon for northern countries, in which winters could become milder and harvests would improve. But the impact would be negative on much of southern Europe, which would suffer severe water shortages, crop failures and maybe even desertification. A similar analysis by American scientists, looking at North America, reached broadly similar conclusions: the effect on the continent might be modest, but regional impacts could be far greater.
A bigger reason to worry about global warming is an impact that is already evident: a rising sea-level. As the oceans warm, they expand and rise. A hotter earth has also meant that glaciers are melting at unprecedented rates in both hemispheres. The thinning of the ice in the north is less worrying: since more Artic ice already floats in the ocean, its melting will not raise the sea level. However, much of the ice in Antarctica is on land and would raise the sea level if it melts. Even without massive polar meltdowns, the IPCC expects the mean sea-level to rise by 15-95 centimetres by 2100.
That is disturbing for several reasons. One is that a large human population, whether huddled in cities such as New York and Mumbai or in low-lying countries such as the Maldives and Bangladesh, is vulnerable to even a tiny rise in the world's oceans. A second is that even before the sea-level rises, it could do serious damage. Researchers from Germany's University of Bremen that rougher seas are likely to be a consequence of climate change. Bigger waves and more storms would wear down coastal defences and increase flooding.
More broadly, global warming is troubling because it is likely to do the most harm in parts of the world that are poorest and least-prepared, and, it so happens, the least responsible for causing it. Bangladesh has contributed virtually nothing to the atmosphere's stock of Green House Gases, and yet it will be affected for more than, say, the United States.
There is also the risk that even modest levels of man-made warming could trigger dramatic, step-function responses in the climate. One such example is an ocean circulation system in the mid-Atlantic. Scientists worry that rising temperatures may lead to an abrupt breakdown of this 'conveyor belt', which would result in Britain and neighbouring countries experiencing much harsher winters.
What to do?
It was this gloomy group of predictions that led the world's government to agree to the Kyoto treaty in the first place. And, although the science was less certain in 1997 than now, officials from the developed world were concerned enough to agree to mandatory cuts in their Green House Gas emissions. The real significance of Kyoto was that developed countries had accepted that they should act to curb global warming and climate change, and that they should do it before required less developed countries to do the same. They committed themselves to frequent updates and improvements of the treaty, the first substantive one having taken place in The Hague. They also agreed that cutting emissions might be so expensive that the treaty should allow countries innovative, flexible approaches to reduce compliance costs. Because of the difficulty of hitting the Kyoto targets, the treaty includes provisions for the international trading of emissions rights and the use of forests and soil as "carbon sinks". These will help. But how these mechanisms should be used remains a subject of intense disagreement.
Whatever the outcome at The Hague, science has made at least on thing clear. The problem of global warming and climate change is real, and will not be going away any time soon. Nor will the question of how mankind should respond to it.
Article sourced from: The Economist, 2000.