Britain's leading climate change economist, Nicholas Stern, has warned Australian politicians that they are mistaken if they think tackling climate change is too costly. New Liberal leader Tony Abbott has put his party on a collision course with the Government over its emissions trading laws, which are expected to be voted down in the Senate this morning. In London overnight Lord Stern released two new reports which he will take to this month's United Nations conference in Copenhagen. They detail 11 points which he has worked on with the United Nations to help shape a final political agreement. He says...