Sensitivity adaptive capacity and vulnerability some definitions

Sensitivity is the degree to which a system is affected, either adversely or beneficially, by climate-related stimuli. These encompass all the elements of climate change, including mean climate characteristics, climate variability, and the frequency and magnitude of extremes. This may be direct (e.g. a change in crop yield in response to a change in the mean, range or variability of temperature) or indirect (e.g. damage caused by an increase in the frequency of coastal flooding due to sea level rise).

Adaptive capacity is the ability of a system to adjust to climate change (including climate variability and extremes), to moderate potential damage, to take advantage of opportunities or to cope with the consequences.

Vulnerability is the degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude and rate of climate change and also the extent to which a system is exposed, its sensitivity and its adaptive capacity.

Both the magnitude and the rate of climate change are important in determining the sensitivity, adaptability and vulnerability of a system.

community. An alternative might be for the affected community to migrate to a region where less adaptation would be needed - a solution that has become increasingly difficult or, in some cases, impossible in the modern crowded world.

As we consider the questions posed at the start of this chapter, it will become clear that the answers are far from simple. It is relatively easy to consider the effects of a particular change (in say, sea level or water resources) supposing nothing else changes. But other factors will change. Some adaptation, for both ecosystems and human communities, may be relatively easy to achieve; in other cases, adaptation may be difficult, very costly or even impossible. In assessing the effects of global warming and how serious they are, allowance must be made for response and adaptation. The likely costs of adaptation also need to be put alongside the costs of the losses or impacts connected with global warming.

Sensitivity, adaptive capacity and vulnerability (see box above) vary a great deal from place to place and from country to country. In particular, developing countries, especially the least developed countries, have less capacity to adapt than developed countries, which contributes to the relative high vulnerability to damaging effects of climate change in developing countries.

The assessment of the impacts of global warming is also made more complex because global warming is not the only human-induced environmental problem. For instance, the loss of soil and its impoverishment (through poor agricultural practice), the over-extraction of groundwater and the damage due to acid rain are examples of environmental degradations on local or regional scales that are having a substantial impact now.3 If they are not corrected they will tend to exacerbate the negative impacts likely to arise from global warming. For these reasons, the various effects of climate change so far as they concern human communities and their activities will be put in the context of other factors that might alleviate or exacerbate their impact.

The assessment of climate change impacts, adaptations and vulnerability draws on a wide range of physical, biological and social science disciplines and consequently employs a large variety of methods and tools. It is therefore necessary to integrate information and knowledge from these diverse disciplines; the process is called Integrated Assessment (see box in Chapter 9 on page 280).

Table 7.1 summarises some expected impacts for different increases in global average temperature that might occur during the twenty-first century. The following paragraphs consider detail of the various impacts in turn and then bring them together in a consideration of the overall impact.

Table 7.1 Examples of global impacts projected for changes in climate associated with different increases in global average surface temperature in the twenty-first century. Add 0.6 °C to obtain temperature increases from pre-industrial times. Also shown are the projections of temperature increases associated with SRES scenarios as in Figure 6.4. Adaptation to climate change is not included in these estimates.

• 2050s 2080s 2090s

5.4

SRES: AR4 WG I multiple sources B1 B2 A1B A2

WATER

Increased water availability in moist tropics and high latitudes

Decreasing water availability and increasing drought in mid-latitudes and semi-arid low latitudes

0.4 to 1.7 billion

1.0 to 2.0 billion

1.1 to 3.2 billion

Additional people with incre. ' water stress

Increasing amphibian extinction

About 20 to 30% species at increasingly high risk of extinction

Major extinctions around the globe

ECOSYSTEMS

Increased coral bleaching Most coral bleached Increasing species range shifts and wildfire risk

Wildspread coral mortality

Terrestrial biosphere tends toward a net carbon source, as: -15% -40% of ecosystems affected

FOOD

Crop productivity

Low latitudes

Decreases for some cereals

Increases for some cereals Mid to high latitudes

All cereals decrease Decreases in some regions

Increased damage from

COAST

Additional people coastal flooding eac loods and storms risk of h year

0 to 3 million

About 30% loss of coastal wetlands

2 to 15 million _

HEALTH

Increasing burden from malnutrition, diarrhoeal, cardio-respiratory and infectious diseases Increased morbidity and mortality from heatwaves, floods and droughts

Changed distribution of some disease vectors Substantial burden on health services

SINGULAR EVENTS

Local retreat of ice in Greenland and West Antarctic

Long term commitment to several metres of sea-level rise due to ice sheet loss

Leading to reconfiguration of coastlines world wide and inundation of low-lying areas

Ecosystem changes due to weakening of the meridional overturning circulation

Global mean annual temperature change relative to 1980-99 (°C)

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