Guardian: The government last night moved to tighten its commitment to the 80% reduction of carbon emissions by the year 2050, introducing a safeguard that a limit be placed on reductions achieved by buying international offsetting credits. During what will probably be the last few days of scrutiny before the climate change bill becomes law, the government made concessions in the House of Commons and the Lords, surprising green campaigners by tabling a further amendment to the energy bill – …