The international accord on ozone depletion, or the "Montreal Protocol," marks the first time that countries from all parts of the world have responded so quickly and effectively to a worldwide environmental threat. It sets a hopeful precedent for those concerned about global warming, another environmental risk that, while not directly related to ozone depletion, does portend enormous changes.
The battle over how to respond to global warming scored another victory at the UN Conference on Environment and Development (UNCED) in Rio de Janeiro. The nations of the world reached consensus in the form of the Convention On Climate Change.
A major hurdle that remains is reaching agreement on whether it is a threat at all. To date, there is no scientific consensus on the certainty of global warming or of the potential risks posed to humans.
The theory posed is that the Earth's temperature will increase because industrial activity, population pressures and the burning of tropical forests have caused a build-up of gases that trap sunlight. The primary gases that have been pinpointed are carbon dioxide, methane, nitrous oxide and, to a lesser extent, the chlorofluorocarbons responsible for ozone depletion.
Already, the concentration of carbon dioxide in the atmosphere has increased by 25 percent in the last century, while that of methane has doubled. Average global temperatures have risen by 0.28 to 0.6 degrees Celsius (0.5 to 1.1 degrees Fahrenheit) over the same period. While this "greenhouse effect" has been generally beneficial, scientists fear that its intensification could increase average global temperatures by 1 to 5 degrees Celsius (1.8 to 9 degrees Fahrenheit) in the next 50 years. This rise could mean that the earth will be warmer than it has been for 120,000 years.
The increase in temperature could cause the oceans to rise two meters or more as polar ice melts and warmer water expands. Tropical diseases could spread into what are now temperate areas. Altered precipitation patterns, including an increase in the severity and frequency of storms, would have consequences for agriculture in many countries. Changes in natural ecosystems might also lead to the extinction of certain species of plants and animals.
But climate change is a complex and poorly-understood phenomenon. "The scientific evidence is not as well-established for global warming as it is for ozone depletion," says UNDP's Frank Pinto. "For instance, some scientists feel that the process of warming could be partially offset by the beginning of a new glacial age, or the effects of volcanic emissions."
A comprehensive study recently undertaken by the Danish Meteorological Institute has also raised the possibility that climatic change is overwhelmingly determined by cyclical variations in the sun's brightness. A decrease in the sun's luminosity could counteract greenhouse warming.
The global warming battle is complicated by the fact that billions of dollars of investments and resources are at stake. Carbon dioxide, the principal greenhouse gas, is emitted from fossil fuels, such as petroleum, and from coal-burning power plants that have charged industrial development for the last century. Governments and industries fear that economic growth will be stunted by control measures that require costly environmental engineering or a ban on coal consumption.
An inter-agency study published by the US Department of Energy says that steps taken to reduce carbon dioxide emissions would force the gross national product of the US down by 1 percent, an effect comparable to the oil-price shock of the 1970s. And developing countries with large coal resources are concerned that the costs of reducing emissions from coal burning could have devastating effects on their industrialization process.
Issues of global equity have further confounded the debate. The rich industrialized nations have emitted the vast bulk of greenhouse gases over the last century and some emissions, including carbon dioxide, will persist indefinitely in the atmosphere. Officials in developing countries say this important fact is frequently ignored by the industrialized countries.
While the debate over global warming inches forward, differences in scientific viewpoints are being clarified by further research. At the same time, the Global Environment Facility (GEF), a $1 billion fund managed by the World Bank UNDP and UNEP, is helping developing countries address the global consequences of national environmental problems in areas including climate change, biodiversity and international waters. The GEF is also financing development of environmentally benign energy technologies and interventions that promote fuel efficiency.
Equally important, crucial negotiations on global warming are continuing through the UN Intergovernmental Negotiating Committee for a Framework Convention on Climate Change.
