United Nations Environment Programme (UNEP)
Global  Environment Outlook-1 - The Web version

Chapter 4: Looking to the Future

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Climate Change and Acidification

Trend Implications

The time-frame required to adjust the climate system to a different level of emissions ranges from decades to centuries. Even if emissions were immediately and sharply reduced, some climate change would still occur because of inherent inertia in the system. This underlines the importance of system inertia when evaluating impacts and response options.

The Framework Convention on Climate Change stipulates the goal of stabilizing greenhouse gas concentrations. For the short term, as a first step, Annex I countries (industrialized countries, including those in transition to a market economy) are required to bring their greenhouse gas emissions in 2000 back to the 1990 level. An even more stringent protocol is set to be adopted in 1997. In contrast with the emissions of some other pollutants (such as sulphur dioxide and particulate matter), emissions of greenhouse gases have not been demonstrated to decrease as national income levels rise. Even if best efforts are made to reduce greenhouse gas emissions, some degree of climate change will inevitably occur. This is due to lags in the climate system and to the difficulty in reducing global greenhouse gas emissions because of inertia in socio-economic systems.

Experiments with the model illustrate that the longer responses to climate change are delayed, the more drastic will emission reductions need to be to achieve the same results that could have been realized if measures had been adopted early (Alcamo and Kreileman, 1996). There are significant interim impacts caused by emissions during any period of delay in initiating action. Early action has additional advantages of keeping options open, increasing flexibility, and avoiding a shift of the responsibility to future generations to act on a problem caused by past and present generations. Delaying responses may make the costs of reclaiming lost resources, including agricultural areas, prohibitive for future generations. On the other hand, delaying further emission reductions can have advantages, according to some economic analyses: technological developments and the discounting, in economic terms, of response measures both make any responses in the future cheaper, and avoid premature retirement of current capital goods (see, for example, Wigley et al.,1996).

Contingency plans are required to adapt to impacts of climate change such as coastal and river flooding, alterations in water availability, changes in the occurrence of extreme meteorological events, shifts in natural vegetation zones and crop zones, and other developments that will have a major effect on people and the natural environment. Important examples of such useful adaptations are the development of drought-resistant crop varieties, increases in the efficiency of water use, and avoidance of the fragmentation of ecosystems.

The issues discussed in this section all stem from a high level of economic activity that produces enormous amounts of emissions of polluting substances to the atmosphere. The most important source of these is the burning of fossil fuels. Hence, modifying the amount or type of fossil fuels burned is an effective strategy for mitigating all these problems at the same time. This could be considered as the next great transition in the world's energy system.

The so-called LESS scenario (Low CO2-Emitting Energy Supply System) developed by IPCC (1996) indicates that a global energy system with emissions of carbon dioxide below current levels by 2050, which is compatible with stabilization of carbon dioxide concentrations well below twice pre-industrial levels, is feasible with current technology. The importance of paying serious attention to energy issues at the global scale is echoed in an International Institute for Applied Systems Analysis/World Energy Council study, which states that "the single most important conclusion is that, given the expected divergence of development paths post-2020, and the foreclosure of potentially desirable options unless relevant policies are initiated and decisions taken long before then, action needs to start now" (Nakicenovic and Jefferson, 1995). Posch et al., 1996).

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