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close this bookEco-restructuring: Implications for sustainable development (UNU, 1998, 417 pages)
close this folderPart I: Restructuring resource use
close this folder2. The biophysical basis of eco-restructuring: An overview of current relations between human economic activities and the global system
View the document(introductory text...)
View the documentIntroduction
View the documentThe earth system
View the documentThe climate system and climatic change
View the documentClimatic change and vulnerability
View the documentBiological diversity
View the documentFresh water
View the documentSoils
View the documentThe solid earth (lithosphere)
View the documentLand-cover and land-use changes
View the documentHuman impacts and industrial metabolism
View the documentThe case of West Africa
View the documentOutlook

The climate system and climatic change

The basic objective of the Framework Convention on Climate Change (1992; further discussed by the Berlin Conference in 1995) was to further a political process leading to "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent anthropogenic interference with the climate system" (Article 2) and to do so in such a manner as to allow ecosystems to adapt naturally, and so as not to interfere with food production and economic development. Needless to say, it is also important to understand better the processes that are influenced by the earth's atmosphere on a global, regional, and local level. These include biophysical, geochemical, hydrological-oceanic, and socio-economic processes. This calls for an improved understanding of the socioeconomic consequences of climatic change and for further investigations of the response mechanisms to mitigate such changes.

The climate system is mainly driven by solar radiation. The major engine of global atmospheric circulation is the so-called hydrological cycle. Solar heating of the ocean surface causes evaporation of water. The moist air rises until it cools to condensation point. The water vapour condenses and returns to the earth, partly over land. The condensation process releases heat in the atmosphere. Water from precipitation then flows from the land back to the sea, carrying nutrient elements (and causing salinity gradients). Thermal imbalances between high and low latitudes drive both winds and ocean currents, redistributing energy and matter within the atmosphere and the hydrosphere.

As a result of the interactions between solar radiation and the geo/ biosphere, the climate system changes continually. This has occurred throughout the history of our planet. However, in the recent past a new factor has appeared: increased emission of "greenhouse gases" or GHGs (e.g. carbon dioxide, methane, nitrous oxide, chlorofluorocarbons). These emissions are strongly linked to human activities, especially the combustion of fossil fuels and high-intensity agriculture. The build-up of these gases in the atmosphere has made it act somewhat like a mirror for heat radiation. This has led to a marked global warming process, whose magnitude and rate are still under discussion.

The task of determining likely "winners" and "losers" resulting from this ongoing climatic change is extremely difficult. It will affect mainly agriculture. Among the industrialized countries, agriculture accounts for only a very small part of the economy. This has led some economists (mainly in the United States) to conclude that climate warming is not a great concern and that major efforts to counteract it would not be economically justified. Yet it is undeniable that agriculture is essential for human survival and that it counts for a much larger part of the economies of poorer developing countries. The Intergovernmental Panel on Climate Change (IPCC 1990) projects that the results of global warming, such as increased precipitation and longer frost-free periods, could bring about rather limited immediate benefits to some regions, located mainly in the northern hemisphere. In the South, however, where food supplies are regionally more limited, difficulties related to food security problems may increase. Since climate warming would also be accompanied by sealevel rise, it is of even more immediate concern to small low-lying island nations and countries such as Bangladesh with large populations heavily concentrated in estuarine zones.

One of the most significant results of climate change is likely to be the shifting of agro-climatic zones, although the spatial distribution of such shifts is still difficult to predict. Also sealevel rise affecting low-lying coastal areas by flooding will influence industrial planning and development. The establishment of international funds to counter the adverse consequences of climatic change and the creation of an International Insurance Pool (IIP) to provide insurance against the consequences of sealevel rise are under discussion.

An important implication of the IPCC's work is that uncertainty is itself costly. In other words, it is important to find out (and quantify) the real costs of action (or inaction) in the area of climatic change and to establish economic incentives or disincentives for achieving the stabilization and eventual reduction of greenhouse gas emissions. In this respect, a narrow application of the "polluter-pays" principle would adversely affect economic development in some countries (notably China and India) that are heavily committed to the use of coal. Hence, there is increasing interest in "joint implementation" and such devices as tradable permits (see chap. 12 in this volume).

Other important aspects of human activities on the global level include stratospheric ozone depletion and its potential biospheric effects, as well as the processes involved with acid deposition. Both can be directly linked to industrial emissions of gaseous pollutants. Stratospheric ozone is important for the biosphere because of its absorption of ultraviolet (UV) radiation, which is harmful to humans, animals, and plants. But long-lived chlorinated fluorocarbons (CFCs), which gradually diffuse from the lower atmosphere into the stratosphere, are broken up by UV radiation, releasing atomic chlorine (Cl) atoms. These, in turn, react with ozone (O3) molecules, which are converted back into ordinary molecular oxygen and atomic oxygen, leaving the chlorine atoms free to attack more ozone. Each chlorine atom can destroy hundreds of thousands of ozone molecules. Hence, CFCs are literally capable of destroying the ozone layer. Thanks to the Montreal Protocol (1987) and the subsequent London revision (1990), CFCs are being phased out of production, at least in the industrial world. But, because so many CFCs are already in the atmosphere, their environmental impacts are likely still increasing and will not disappear for many decades.

Acid deposition is caused by the emission of chemicals such as nitrogen oxides (NOx) and sulphur dioxide (SO2) to the atmosphere, mainly from combustion processes. Nitrogen oxides are produced in high-temperature flames when there is excess air. This happens mainly in coal-burning electric power generating plants and internal combustion engines. The nitrogen in the air itself is oxidized. Sulphur dioxides are produced when coal, containing a small percentage of sulphur, is burned or from the smelting of sulphide ores of copper, nickel, lead, or zinc. These gaseous oxides are further oxidized in the air or on the surfaces of small particles, which act as catalysts. These oxides, reacting with and dissolved in water, become nitric and sulphuric acids, respectively. They may travel hundreds of miles through the atmosphere and descend in the form of rain, fog, and snow or even in dry form. These acids are eventually deposited by rain on the surface of the earth or on the surfaces of trees and other vegetation.

This acid deposition has had great effects on aquatic ecosystems by increasing the acidity of rivers and lakes. This has negatively affected both the flora and fauna. It also has a marked direct impact on terrestrial vegetation, mainly because of its effects on soils. The acidification of forest soils releases and mobilizes metal ions (especially aluminium) that were formerly bound to clay particles. Some of these metals are toxic to trees. The ongoing discussion of the complex causes of "Waldsterben" (forest die-back) is largely related to acidification.

An interesting integrated approach to climatic impact assessment that takes into account the primary, secondary, and tertiary sectors of the economy has been proposed by Parry et al. (1988). This interaction concept not only focuses on climatic parameters but also includes social factors such as poverty, war, or hunger as necessary for a useful evaluation of the effects of climatic change. In addition to policy implications, this allows for feedback regulating and enhancing possible change effects. For instance, a change in climate may lead to a change in natural vegetation belts, which itself will influence the climate through changes in fluxes of gases or through changes in surface reflectivity. This integrated approach will allow a more comprehensive treatment of interactions between climate and society.