The target we've chosen is not driven by comparing what others can do. It is driven by what the scientists are telling us. In the UN climate change conference, they are telling us that two degrees is the maximum level that we can allow the world to warm up without very dangerous security implications that would lead to extreme weather events, mass migrations, and crop failures. If we want two degrees, scientists agree that this means we have to have at least a 50% reduction on 1990 by 2050. In the case of the developed countries, that means we must take on between 80% and 95% of the reductions. So our target is not driven by comparing the highest or the lowest in other countries; it is driven by the science.
On November 19th, 2009. See this statement in context.