Independent (UK): World leaders are to meet for an unprecedented second summit on climate change this year to try to get agreement on a tough new treaty by December, and may even get together for a third time before the end of the year. The UN Secretary-General, Ban Ki-Moon, is to call the world’s heads of government to New York in September to “galvanise political will” about what he describes as “the defining issue of our time”. And there are plans for another G20 summit to discuss the issue in the …