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PART TWO / IMPACTS
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All this, it points out, will have to be achieved in a climate of 'significant scientific uncertainty'. It warns that the unambiguous detection of climate-induced changes in ecological systems will prove extremely difficult in the coming decades, because of both their complexity and their sensitivity. And it recalls the Convention's Article 3, which rules that 'where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing [precautionary] measures, taking into account that policies and measures... should be cost-effective.' | |||||||
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A shortcoming of most research on impacts so far is that it looks mostly at the impact of a doubling of CO2 in the atmosphere. It does not look at the consequences of an increase greater than a doubling, which will occur without policy changes to control the emissions of greenhouse gases. Nor has much research examined the sometimes critical consequences of the speed of change, even though Article 2 specifically mentions how important this will be to the ability of ecosystems to adapt to changing climate.
The IPCC looks at both natural and human systems, and highlights what we know about the vulnerabilities of ecosystems and human communities to climate changes, especially in regard to agriculture and food production and other factors such as water availability, health and the impact of sea level rise which are important considerations for sustainable development. In general 'people who live on semi-arid lands, in low-lying coastal areas, in water-limited or flood-prone areas, or on small islands are particularly vulnerable to climate change'. Sustainable economic development in some countries 'will be threatened by loss of habitat, increases in human diseases and loss of life'. Rising sea levels and extreme weather events will cause migrations, placing additional stress on social and political systems. | |||||||
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The risks in awaiting unambiguous signals are real, since neither climate change nor the impacts of changing climate can be reversed quickly, if at all. And as the climate evolves beyond the boundaries of recent experience, there is a greater chance of 'surprises and unanticipated rapid changes.' Delaying action might reduce the overall costs of mitigation, because of potential technological advances, 'but could increase both the rate and eventual magnitude of climate change, and hence the adaptation and damage costs,' says the IPCC.
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