Guardian: The chancellor today promised to cut greenhouse gases by 34% by 2020, and “aims” to do this without purchasing credits from projects which have reduced emissions abroad, although he took the precaution of reserving these “offsets” as a “fallback option”. Alistair Darling has now committed the government to carbon budgets, which fix binding limits on greenhouse gas emissions over five-year periods. If they can actually do it, the government’s pledge to cut global warming emissions by …