ABSTRACT
For the fourth time in 17 years, the world’s leading scientists who study the Earth’s climate system have pronounced. In 1990, the First Assessment Report of the IPCC concluded that ‘the unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more.’ In 1996 the ‘balance of evidence’ suggested a discernible human influence on climate, while in 2001 most of the warming of the last 50 years was ‘likely’ due to greenhouse gas increases. And now, seventeen years after the first IPCC report, we now have the statement from the IPCC scientists that ‘it is very likely’ that most of the warming of the last 50 years has been caused by humans.
