Long-term greenhouse gas emission reductions—what's possible,what's necessary?

Climate is changing (WMO, Press release No. 695, 2003) and there is increasing evidence that this is due to human activity (IPCC, Climate Change 2001—The Scientific Basis, Cambridge University Press, Cambridge, 2001). One way to react is to reduce greenhouse gas emissions into the atmosphere. Although this approach generally does not cause much objection, disagreements do occur when concrete emission targets are to be set. Against this background, the following article provides an arithmetic approach for the determination of long-term emission targets where the US and the EU are studied as examples.