There are strong indications that the climate is changing, partly under the influence of human activity. A substantial reduction in emissions of greenhouse gases is required in order to slow down the rate of climate change sufficiently. However, while the total global volume of CO2 emissions needs to fall sharply, they are expected to increase steeply as a result of rising prosperity and population growth. There are considerable uncertainties and all manner of complicating factors which make it difficult to formulate an effective climate strategy. The magnitude of the climate effects (and sometimes the direction in which they operate) is difficult to predict. There are large gaps in our knowledge about the climate system, partly due to the extreme slowness of that system. This raises the danger of setting in motion irreversible changes. The problem of policy formulation is also exacerbated by the global setting in which it has to be achieved. Different countries have widely diverging interests and consistently place the emphasis on economic growth, leading to an increase rather than a decrease in greenhouse gas emissions. Moreover, international coordination of emission reduction efforts is problematic, which could well lead to inadequate policy. These uncertainties and complicating factors could engender high costs. Given these uncertainties, climate policy ought to strive not only for optimisation, but also robustness. A robust strategy is aimed at effectiveness in a wide variety of potential scenarios.

Difficult judgments

There are wide differences in the way individual countries view the climate issue. The global divergence in perceptions, interests and preferences can make it difficult to formulate an effective climate strategy. The effectiveness of that strategy depends on the goals that countries pursue, and reaching agreement on them (in the sense of hard commitment) will not be easy. Differences in perceptions and preferences can lead to unbridgeable differences in the degree of willingness to bear the costs. One of the problems when deciding on the cost distribution is that both the costs of adaptation and of reducing the rate of climate change are unclear. Moreover, policymakers have to weigh those costs against completely different objectives which also require government intervention (economic growth, education, health care, infrastructure, pensions, military spending, and soon); the emphasis given to these objectives also varies considerably from one country to another.