Reuters: Nations aiming to agree on a new global climate deal should focus on achievable greenhouse gas emissions targets, to involve as many nations as possible, U.S. Energy Secretary Steven Chu said on Tuesday. The world is meant to thrash out in December in Copenhagen a new international climate change pact beyond 2012, to replace the Kyoto Protocol. Developing nations want rich countries to cut emissions by 25 to 40 percent from 1990 levels by 2020 to avert the worst effects of …