Image caption The original idea called for cloud-whitening ships - but it could be done from land

An eminent UK engineer is suggesting building cloud-whitening towers in the Faroe Islands as a "technical fix" for warming across the Arctic.

Scientists told UK MPs this week that the possibility of a major methane release triggered by melting Arctic ice constitutes a "planetary emergency".

The Arctic could be sea-ice free each September within a few years.

Wave energy pioneer Stephen Salter has shown that pumping seawater sprays into the atmosphere could cool the planet.

The Edinburgh University academic has previously suggested whitening clouds using specially-built ships.

At a meeting in Westminster organised by the Arctic Methane Emergency Group (Ameg), Prof Salter told MPs that the situation in the Arctic was so serious that ships might take too long.

"I don't think there's time to do ships for the Arctic now," he said.

"We'd need a bit of land, in clean air and the right distance north... where you can cool water flowing into the Arctic."

Everybody working in geo-engineering hopes it won't be needed - but we fear it will be Stephen Salter, Edinburgh University

Favoured locations would be the Faroes and islands in the Bering Strait, he said.

Towers would be constructed, simplified versions of what has been planned for ships.

In summer, seawater would be pumped up to the top using some kind of renewable energy, and out through the nozzles that are now being developed at Edinburgh University, which achieve incredibly fine droplet size.

In an idea first proposed by US-based British physicist John Latham, the fine droplets of seawater provide nuclei around which water vapour can condense.

This makes the average droplet size in the clouds smaller, meaning they appear whiter and reflect more of the Sun's incoming energy back into space, cooling the Earth.

On melting ice

The area of Arctic Ocean covered by ice each summer has declined significantly over the last few decades as air and sea temperatures have risen.

For each of the last four years, the September minimum has seen about two-thirds of the average cover for the years 1979-2000, which is used a baseline. The extent covered at other times of the year has also been shrinking.

What more concerns some scientists is the falling volume of ice.

Peter Wadhams, professor of ocean physics at Cambridge University, presented an analysis drawing on data and modelling from the PIOMAS ice volume project at the University of Washington in Seattle.

It suggests, he said, that Septembers could be ice-free within just a few years.

Image caption Projections suggest the Arctic Ocean could be free of sea ice at the September minimum within a few years

"In 2007, the water [off northern Siberia] warmed up to about 5C (41F) in summer, and this extends down to the sea bed, melting the offshore permafrost."

Among the issues this raises is whether the ice-free conditions will quicken release of methane currently trapped in the sea bed, especially in the shallow waters along the northern coast of Siberia, Canada and Alaska.

Methane is a much more potent greenhouse gas than carbon dioxide, though it does not last as long in the atmosphere.

Image caption Dramatic methane release would bring major impacts to Arctic indigenous peoples

Several teams of scientists trying to measure how much methane is actually being released have reported seeing vast bubbles coming up through the water - although analysing how much this matters is complicated by the absence of similar measurements from previous decades.

Nevertheless, Prof Wadhams told MPs, the release could be expected to get stronger over time.

"With 'business-as-usual' greenhouse gas emissions, we might have warming of 9-10C in the Arctic.

"That will cement in place the ice-free nature of the Arctic Ocean - it will release methane from offshore, and a lot of the methane on land as well."

This would - in turn - exacerbate warming, across the Arctic and the rest of the world.

Abrupt methane releases from frozen regions may have played a major role in two events, 55 and 251 million years ago, that extinguished much of the life then on Earth.

Meteorologist Lord (Julian) Hunt, who chaired the meeting of the All Party Parliamentary Group on Climate Change, clarified that an abrupt methane release from the current warming was not inevitable, describing that as "an issue for scientific debate".

But he also said that some in the scientific community had been reluctant to discuss the possibility.

"There is quite a lot of suppression and non-discussion of issues that are difficult, and one of those is in fact methane," he said, recalling a reluctance on the part of at least one senior scientists involved in the Arctic Climate Impact Assessment to discuss the impact that a methane release might have.

Reluctant solutions

The field of implementing technical climate fixes, or geo-engineering, is full of controversy, and even those involved in researching the issue see it as a last-ditch option, a lot less desirable than constraining greenhouse gas emissions.

"Everybody working in geo-engineering hopes it won't be needed - but we fear it will be," said Prof Salter.

Adding to the controversy is that some of the techniques proposed could do more harm than good.

The idea of putting dust particles into the stratosphere to reflect sunlight, mimicking the cooling effect of volcanic eruptions, would in fact be disastrous for the Arctic, said Prof Salter, with models showing it would increase temperatures at the pole by perhaps 10C.

And last year, the cloud-whitening idea was also criticised by scientists who calculated that using the wrong droplet size could lead to warming - though Prof Salter says this can be eliminated through experimentation.

He has not so far embarked on a full costing of the land-based towers, but suggests £200,000 as a ballpark figure.

Depending on the size and location, Prof Salter said that in the order of 100 towers would be needed to counteract Arctic warming.

However, no funding is currently on the table for cloud-whitening. A proposal to build a prototype ship for about £20m found no takers, and currently development work is limited to the lab.

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