Times (UK): WORLD carbon emissions must start to decline in only six years if humanity is to stand a chance of preventing dangerous global warming, a group of 20 Nobel prize-winning scientists, economists and writers has declared. The United Nations climate summit in Copenhagen in December must agree to halve greenhouse-gas emissions by 2050 to stop temperatures from increasing by more than 2C, the St James’s Palace Nobel Laureate Symposium concluded. While even a 2C temperature rise will …