Scientists have significantly less confidence in regional or national climate forecasts. Other uncertainties include future population and economic growth rates and how these rates will impact future GHG emissions levels. As a result, there is a great deal of uncertainty about how great the risks of climate change truly are.
Economists recognise that people dislike uncertainty and tend to be risk averse . . .
People are often willing to exchange a risky asset with a high expected return for an asset with a lower, yet more certain rate of return. One of the most useful services economists could render to policy-makers would be to calculate the optimal level of GHG emissions, given the costs and benefits of making emissions reductions. To make the necessary calculations for such a cost-benefit analysis, economists usually assign definite values to uncertain parameters such as climate sensitivity. They use the expected, or most likely, values. This allows economists to offer some insights, but it does lead to treating the problem as if it were one of perfect certainty.