| |
The possibility of significant warming of the Earth\'s atmosphere over the next century is arguably the most important environmental problem facing humanity. If it does occur, it will disrupt human settlements and agriculture throughout the world, as well as destabilizing natural processes which have taken billions of years to reach their present state. To prevent it would require radical changes in human activities, including a redefinition of the idea of ‘progress’. At present, atmospheric scientists expect a rise of some 4°C over the next 50 years, but they are uncertain what this will mean for certain areas. Such a rise would be a temperature change of the same order as the change from glacial to interglacial, so any additional warming would be an unprecedented interference with the atmosphere.
Global warming is sometimes blamed on the greenhouse effect, but it is important to realize that the natural greenhouse effect is a vital contributor to life on Earth. Without the warming effect of the absorbtion of heat in the atmosphere, the Earth\'s surface temperature would be similar to that of the Moon (-18°C). What is at issue is an enhanced greenhouse effect as a result of changes in the composition of the atmosphere, notably increases in carbon dioxide, CFCs (chlorofluorocarbons), methane, nitrous oxide and water vapour. These greenhouse gases are particularly effective in absorbing radiation from the Earth\'s surface and so warming the atmosphere. Even a small overall warming could change climatic patterns and melt snow, ice and permafrost, with unpredictable effects on ecosystems and sea levels. However, though these gases have been increasing in concentration for a century or more, it is by no means certain that they have caused any warming yet. The Earth\'s average temperature has risen by .5°C since 1860, but that is within the normal range of variability. So all current worries are based on predictions of the response of the atmosphere to expected increases in emissions of greenhouse gases. The Second World Climatic Conference brought a high level of consensus among scientists that warming was probable and would be best avoided, but responses from politicians were muted.
There are two major problems for politicians seeking to respond to the threat of global warming—leaving aside that it is a problem involving timescales far greater than political terms of office. First, the causes of increased emissions include the key activities which sustain life and promise affluence. Second, an effective response must be global and is prevented by sharp differences in the interests of different countries. The main sources of carbon dioxide emissions are fossil fuel burning (in power stations, smelters and vehicles) and deforestation. Methane is produced by rice paddies and cattle, as well as leaks from gas pipelines. Nitrous oxide comes from vehicles, deforestation and agriculture. Only CFCs are relatively easy to control, but they are extremely persistent once emitted. Apart from CFCs, controlling emissions of greenhouse gases would require huge increases in energy efficiency and the transformation of agriculture as well as reversal of deforestation. Agreement to implement such huge changes would have to overcome differences between countries. The more developed countries use much more energy than the less-developed, so they are arguably responsible for the problem. But they are reluctant to reduce coal or oil burning appreciably. The less-developed countries have plans to increase power generation and therefore emissions. Most east European countries use energy very inefficiently, but lack capital to invest in more modern plant. Agriculture and deforestation will probably be even harder to change, because it will involve changes to the diet of whole populations, including a sharp reduction in consumption of intensively-reared cattle. An international agreement was reached at the 1992 Earth Summit, but the policies agreed will only reduce the rate of increase of greenhouse gases.
In the US, one factor that has reduced the willingness of politicians to take action is that industrial lobbies have been arguing that global warming is a left-wing plot intended to block economic growth. This, coupled with a fear that American voters regard their right to drive large cars as on a par with the constitutional right to bear arms, made the administration of President Bush very obstructive in international negotiations. Given the economic and political power of the US, and their consumption of energy, this stance has reduced other countries\' readiness to respond. This seems particularly unfortunate when the risks are so high, and most of the preventative measures make sense for other environmental reasons, and some, especially, energy efficiency, are also economically advantageous. It is true that tackling global warming has major implications, but if it requires a change toward sustainable development rather than exploitative and unequal methods this would appear to most people to be a gain rather than a loss.
Finally, it is worth noting that any suggestion that global warming threatens life on Earth is highly exaggerated. The changes in atmospheric composition are significant in relation to changes in the last few million years, but are very small compared with the changes brought about by life (see atmosphere and life). PS |
|
