John Kerry's confirmation as secretary of state on Tuesday installs a veteran climate champion in a pole position for Barack Obama's second term.

Kerry, who describes himself as a "passionate advocate", sailed through his confirmation on Tuesday afternoon, a legacy of his nearly three decades in the Senate.

Now campaigners hope Kerry will help deliver a win on their signature issue: blocking the Keystone XL pipeline from the Alberta tar sands.

Lord Stern, author of the government-commissioned review on climate change that became the reference work for politicians and green campaigners, now says he underestimated the risks, and should have been more "blunt" about the threat posed to the economy by rising temperatures.

In an interview at the World Economic Forum in Davos, Stern, who is now a crossbench peer, said: "Looking back, I underestimated the risks. The planet and the atmosphere seem to be absorbing less carbon than we expected, and emissions are rising pretty strongly. Some of the effects are coming through more quickly than we thought then."

Lord Stern, author of the government-commissioned review on climate change that became the reference work for politicians and green campaigners, now says he underestimated the risks, and should have been more "blunt" about the threat posed to the economy by rising temperatures.

In an interview at the World Economic Forum in Davos, Stern, who is now a crossbench peer, said: "Looking back, I underestimated the risks. The planet and the atmosphere seem to be absorbing less carbon than we expected, and emissions are rising pretty strongly. Some of the effects are coming through more quickly than we thought then."

The European Union's flagship climate policy, its emissions trading scheme (ETS), saw the price of carbon crash to a record low on Thursday after a vote in Brussels against a proposal to support the struggling market.

The price of a permit to emit a tonne of carbon dioxide fell 40% at one point to €2.81 today, far below its record high of €32, before recovering to more than €4 later in the day.

The ETS, aimed at reducing emissions from Europe's entire energy and industrial sectors, has been plagued by an oversupply of permits due in part to over-generous initial allocations following lobbying by industry.