claim: Just 1.25 per cent of the carbon dioxide in the atmosphere-ocean system has been released by ­humans in the past 250 years.
evidence: In 2000 Hansen authored a paper called "Global warming in the twenty-first century: an alternative scenario" in which he presented a more optimistic way of dealing with global warming, focusing on non-CO2 gases and black carbon in the short run, giving more time to make reductions in fossil fuel emissions.