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.

The UN secretary-general Ban Ki-moon says his top hopes for 2013 are to reach a new agreement on climate change and to urgently end the increasingly deadly and divisive war in Syria.

The UN chief told the Associated Press that he's also hoping for progress in getting the global economy humming again, restarting Israeli-Palestinian peace negotiations, promoting political solutions in Mali, Congo and the Central African Republic, and providing energy, food and water to all people.'

Ban laid out this ambitious wishlist in an interview before heading to the World Economic Forum in Davos this week, saying he plans to take "the uncommon opportunity" of being with 2,500 government, business and civil society leaders in the Swiss ski resort to exchange frank views on these issues.

Sprinkling billions of tonnes of mineral dust across the oceans could quickly remove a vast quantities of climate-warming carbon dioxide from the atmosphere, according to a new study.

The proposed "geoengineering" technique would also offset the acidification of the oceans and could be targeted at endangered coral reefs, but it would require a mining effort on the same scale as the world's coal industry and would alter the biology of the oceans.

"It certainly is not a simple solution against the global warming problem," said Peter Köhler, at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, who led the study. It would require 100 large ships operating all year to distribute 1bn tonnes of the mineral olivine, although it might be possible to use the ballast water in existing shipping instead.