REPORTS - SPECIAL REPORTS

The Regional Impacts of Climate Change


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2.4. Integrated Assessment of Potential Impacts

Work on integrated assessment of climate change in the Africa region is in its infancy. Several different approaches are being applied in country studies and primary research. These approaches include assessments of illustrative case examples related to ecosystems, water supply/basin management, and socioeconomic activities such as agriculture. These case studies begin to integrate, for specific subregions (such as watersheds or agricultural production areas), the impacts of climate change with the potential impacts of other factors such as land-use change, demographic change, land degradation, air and water pollution, and economic and social change (including factors such as changing resource demands resulting from economic development and technological change).

The use of integrated assessment models has not been widespread in the African context, although it is becoming an item on the agenda of several modeling groups and organizations. More widespread use of integrated assessment models is a priority for the IPCC in the Third Assessment Report, although it will require fundamental advances in the research literature. As a basis for integration, primary research on impacts on the potentially most vulnerable sectors and regions must be conducted so that interactions among the many potential costs and benefits can be assessed and, where possible, quantified.

2.5. Major Challenges Ahead for Africa

One of the first and most pressing scientific steps to address the shortage of data on African climate is the maintenance and (if possible) enhancement of the surface climate observing network. The network is important because, for the detection of long-term climate change, stable and continuous observing sites are necessary. The World Meteorological Organization (WMO) has a program to designate and maintain key sites as Reference Climate Stations. This program needs additional recognition and funding. The observing network also will help in the calibration of new satellite-based methods of observing the climate (WMO, 1992).

There is a continual need to evaluate the results of GCM experiments that simulate greenhouse gas- and aerosol-induced climate change to identify the likely subregional response within Africa to projected global-mean warming. This research should be seen as only one part of the much larger effort underway worldwide to narrow the uncertainties surrounding predictions of greenhouse gas-induced climate change. Determining whether recent desiccation in the Sahel is associated in some way with global air pollution also is of great importance (Hastenrath, 1995; Ringius et al., 1996).

In addition to conducting more comprehensive assessments of the sensitivity and vulnerability of key resource sectors and systems, there is an urgent need to begin to apply existing and developing techniques for integration of potential climate change impacts on several dimensions, as suggested in the introduction to this report. These dimensions include:

  • Integrating the chain of effects from changes in atmospheric composition and climate to changes in biophysical systems to the socioeconomic consequences (the "vertical" dimension)
  • Including interactions among systems, sectors, and activities (the "horizontal" dimension)
  • Considering climate change in the context of other trends and changes in society (the "time" or "global change" dimension)
  • Considering the integrated impacts of current levels and episodes of climate variability.

In light of the large number and magnitude of socioeconomic and environmental changes projected for Africa, developing integrated assessments of climate change is an urgent priority for the region.


Box 2-10. The Potential Impact of Long-Term Climate Change on Vector-Borne Diseases: The Case of Malaria

Malaria is a vector-borne environmental disease; as such, it is greatly influenced by macro- and microenvironmental changes. The impact of human-induced environmental change on malaria can be graded on a scale that commences at a global level and terminates at the level of an individual family homestead. In the investigation of environmentally induced changes in malaria transmission, it is impossible to restrict the study to localized environmental changes because they are nested within the changing macroenvironment. To understand the dynamics of these changes, as well as their interactions and their potential for prediction of occurrence, it is essential that we consider the role of macroenvironmental change (e.g., global warming) as well as microenvironmental change (e.g., deforestation or changes in land-use patterns, housing type, migration).


Degree of Change: a) 5-month model with 1C increase, b) 5-month model with 0.5C increase, c) 5-month model with 0.5C increase at elevation >1,300 m, and d) 5-month model with 1C increase at elevation >1,300 m.

There is little doubt that global warming is now a reality (IPCC 1990, Chapters 5, 7, 8). Over the past three decades there has been a marked increase in mean temperatures, especially at higher latitudes; in the tropics, the increase is estimated to be about 0.2C (IPCC 1990, Chapter 5). Some attention has focused on global climate change and its implications for epidemic malaria transmission (Bouma et al., 1994; Martens et al., 1995a; Martin and Lefebvre, 1995). The impact of these climatic changes on malaria is likely to be greatest in regions where malaria transmission previously was limited physiologically by low temperatures, which limit the development of the vector and the parasite. In these areas, transmission is likely to be limited to specific seasons (when temperatures are favorable) or may not occur at all. Increased temperatures will lengthen the transmission season, resulting in a marked increase in incidence. Increased temperatures also can expand transmission into regions that previously defined the limits of malaria transmission because of the effects of latitude or elevation (or both).

Studies in Rwanda (Loevinsohn, 1994) and Kenya (Knight and Neville, 1991; Some, 1994) have investigated the extent to which small-scale land-use changes can be responsible for dramatic increases in highland malaria. The effects of short-term environmental changes, as well as changes in human behavioral patterns (e.g., migration, changes in control activities in adjacent regions), are superimposed on more general effects of macroenvironmental change and are likely to play an important role in the onset of epidemics. Thus, although climate change may mean certain regions become more susceptible to malaria transmission, the actual risk of epidemics may remain low because of the absence of local contributory risk factors.

The accompanying figures a, b, c, and d provide a delineation of regions that would be environmentally affected by 0.5C and 1.0C increases in temperature. Figures a and b limit the modeling process to the highland areas of Africa, whereas Figures c and d include regions in which malaria distribution previously was restricted by elevation and latitude. These "new" zones of malaria transmission would be intermediate between areas of known annual transmission and those where malaria has never occurred. With respect to the latter (the upper limit), the simulation errs on the side of caution: Malaria always is limited (cannot occur at present) and is not subject to interannual variation. It uses existing long-term, retrospective, climatological (temperature and rainfall) and topographic surfaces that already exist for Africa (Hutchinson et al., 1995). Inherent in the prerequisite for such epidemic fringe malaria (elevation or latitude) is that in certain years a window of suitable environmental conditions will exist. This window consists of a number of consecutive months with suitable environmental conditions. The graphic provides a conservative estimate; it assumes a prerequisite of five consecutive months, whereas in some regions (such as the Sahel) this may be as short as three (Bagayako, pers. comm.). Despite the occurrence of such a window, transmission may not occur. Transmission then will be contingent on human activities that result in the introduction of the parasite into this suitable (short-term) climatological environment.

The premise that climate variables, on their own, may not always reliably predict epidemic risk has important implications for the forecasting of epidemics and changes in distribution. This model is not definitive but provides an illustration of how climate may impact upon disease distribution and how regions of impact may be delineated. Similarly, the change or shift in severity in existing malarial regions could be modeled. The figures illustrate that increased temperatures would significantly increase susceptible regions in areas of the Southern Hemisphere where distribution previously was constrained by latitude. In contrast, northern Africa is not affected because the distribution concurs with the Sahelian region, where the absence of rainfall and high temperatures limits the disease (similarly with Botswana). Conversely, in certain areas of southern Africa, especially South Africa, low temperatures previously were limiting-thus, a significant increase in distribution is likely.

As this information on sectoral vulnerabilities and integrated assessment of potential climate change impacts is developed, it must penetrate more fully into national government organizations and international donor agencies. This penetration is necessary to ensure that what is known about past and present climate variability is properly taken into account in developing national economic and environmental plans (Sadowski et al., 1996). Such sensitization of the policymaking process to climate variability also ensures that as knowledge about future climate change improves, it too can be sensibly used to guide drought/climate-related economic policy (OECD, 1996).

Within Africa, priority areas for environmental policy include securing sustainable water supply and quality; preventing and reversing desertification; combating coastal erosion and pollution; ensuring sustainable industrial development; making efficient use of energy resources; maintaining forests and wildlife resources; managing demographic change; and ensuring adequate food security. These priority areas highlight environmental and developmental concerns in the region that require immediate attention from the research and policy communities (Hulme, 1996a).


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