Others are even less convinced of the catastrophic predictions put forward by Prof. Hansen. Andrew Weaver, a physicist at the University of Victoria who works on the dynamics of the polar ice caps and also contributes to the IPCC reports, says he thinks the “upper bound for sea-level rise this century is a metre.
“I don’t disagree with the seriousness of the issue or the importance of these positive feedback effects,” he says, “but runaway feedbacks have extraordinarily low probabilities, which is why they are not given much attention by the IPCC.”He adds that the Greenland ice sheet will almost certainly melt away completely, but the IPCC predicts that this will take 1,700 years – not a century. “The complete disintegration of the ice sheets cannot happen in 100 years,” he says.
Moreover, although he calls Prof. Hansen his “hero” for speaking out about global warming in the 1980s “when nobody was listening,” he criticizes the tone of his recent paper and the use of words such as “cataclysm,” which he believes move “dangerously away from scientific discourse to advocacy.”
To some people, this will mean that Prof Weaver, who is worried about the effects of global warming on Tibetan glaciers amongst other things, has joined the ranks of the “Deniers.”