It is not necessary for the two countries to have exactly the same percentage level of reduction. For example, in the EU there is a common level for what it must achieve, but there are different targets for different countries depending on the structure of their economies. As long as there is a target that is known for each jurisdiction, the business sector will have certainty in terms of the investment they will have to make. So I don't necessarily think that having different objectives will affect uncertainty in investment decisions.
On November 26th, 2009. See this statement in context.