'No economic or scientific barriers to tackling climate change'
Though it is a daunting task, the rapid decarbonisation of the global economy is an eminently achievable one, according to one of the co-authors of the widely-quoted Stern Report.
"The economics of climate change is driven by the science," he said.
The public could be forgiven for thinking that the latest evidence suggests the problem is not as grave as suspected - given the Climategate email scandal and the lack of urgency shown to reaching an international agreement at the Copenhagen Summit, said Mr Zenghelis.
But, in fact, the majority of climate science to be published since the Stern Report shows that the situation is probably worse than previously suspected.
He reiterated the familiar refrain that when it comes to predicting the impact of climate change, we are looking at probabilities and risk rather than certainties, but the body of evidence increasingly suggests that even if we stop emitting today, we'll be looking at a temperature rise of 1.5 to 3 degrees and in a business as usual scenario we'll see eventual temperature rises of 2 to 7 degrees, averaging on around 5.
"It's very difficult to predict how the changes will occur but we know there will be changes."
He acknowledged that five degrees might not sound like a huge variation - that we could see greater changes than that locally on a day-to-day basis, and certainly seasonal changes are greater than that.
But global changes of 5 degrees mean enormous climatic shifts.
"Last time Earth was 5 degrees cooler was the last ice age and the last time it was 5 degrees cooler was 50 million years ago, with swampy forests all over the world and alligators close to the poles," said Mr Zenghelis.
"The planet has seen these kinds of variations before, but they happened over tens of thousands of years. Here we're talking about the change taking place over a couple of hundred years."
He spoke of irreversible systemic risks - such as dying back of the Amazon rainforests or permafrost melt in Siberia and Canada releasing huge volumes of methane - a greenhouse gas much more powerful than carbon dioxide.
And delaying mitigation is dangerous and costly, he said.
"If we'd have started this ten or 20 years earlier it would have been very easy to do," said Mr Zenghelis.
He said industrialised countries would have to take the lead and show that it could be done without crippling growth before developing countries could be expected to embrace the idea of big carbon cuts.
"The barriers are not economic or scientific, they are institutional, cultural and political," he said.
"The smart money, both corporate and political, actually tries to manage this rather than bury its head in the sand."