Scientists have their own way of putting things. This is how Dr Oerjan Gustafsson of Stockholm University announced the approach of a climate apocalypse in an e-mail sent last week from the Russian research ship Jakob Smirnitskyi in the Arctic Ocean.

"We had a hectic finishing of the sampling programme yesterday and this past night. An extensive area of intense methane release was found. At earlier sites we had found elevated levels of dissolved methane. Yesterday, for the first time, we documented a field where the release was so intense that the methane did not have time to dissolve into the seawater but was rising as methane bubbles to the sea surface."

Gustafsson's preliminary report, published in The Independent on September 23, is a development far more frightening than the current financial crisis, although it will get only one-thousandth of the coverage. The worst that the financial crisis can bring is some years of recession. The worst that massive methane releases in the Arctic can bring us is runaway, irreversible global warming.

Molecule for molecule, methane gas is 20 times more potent than carbon dioxide as a warming agent. However, since methane doesn't stay in the atmosphere as long––around 12 years, on average, compared with 100 years for CO2––and human activities do not produce all that much of it, concerns about climate change have mostly been focused on carbon dioxide. The one big worry was that warmer temperatures might cause massive releases of methane from natural sources.

There are thousands of megatonnes of methane stored underground in the Arctic region, trapped there by the permafrost (permanently frozen ground) that covers much of northern Russia, Alaska, and Canada and extends far out under the seabed of the Arctic Ocean. If the permafrost melts and methane escapes into the atmosphere on a large scale, it would cause a rapid rise in temperature, which would melt more permafrost, releasing more methane, which would cause more warming, and so on.

Climate scientists call this a feedback mechanism. So long as it is our emissions that are causing the warming, we can stop it if we reduce the emissions fast enough. Once feedbacks like methane release start to drive the warming, it's out of our hands: we might even cut our emissions to zero, only to find that the temperature is still rising.

Fear of this runaway feedback is why most climate scientists (and the European Union) have set a rise of two degrees Celsius (3.5 degrees Fahrenheit) in the average global temperature as the limit which we must never exceed. Somewhere between two and three degrees Celsius (3.5 and 5.2 degrees Fahrenheit), they fear, massive feedbacks like methane release would kick in and take the situation out of our hands.

Unfortunately, the heating is much more intense in the Arctic region. The average global temperate has only risen 0.6 degrees Celsius (1.1 degrees Fahrenheit) so far, but the average temperature in the Arctic is up by 4 degrees Celsius (7 degrees Fahrenheit). So the permafrost is starting to melt, and the trapped methane is escaping.

That is what the research ship "Jakob Smirnitskyi" has just found: areas of the Arctic Ocean off the Russian coast where "chimneys" of methane gas are bubbling to the surface. What this may mean is that we have no time left if we hope to avoid runaway global warming––and yet it will obviously take many years to get our own greenhouse gas emissions down. So what can we do?

There is a way to cheat, for a while. Several techniques have been proposed for holding the global temperature down temporarily in order to avoid running into the feedbacks. They do not release us from the duty of getting our emissions down, but they could win us some time to work on that task without running into disaster.

The leading candidate, suggested by Nobel Prize-winning atmospheric chemist Paul Crutzen in 2006, is to inject sulphur dioxide into the stratosphere in order to reflect some incoming sunlight. (This mimics the action of large volcanic eruptions, which also lower the global temperature temporarily by putting huge amounts of sulphur dioxide into the upper atmosphere.)

Another, less intrusive approach, proposed by John Latham of the National Center for Atmospheric Research in Boulder, Colorado and Prof. Stephen Salter of Edinburgh University, is to launch fleets of unmanned, wind-powered vessels, controlled by satellite, that would spray seawater up into low-lying marine clouds in order to increase the amount of sunlight that they reflect. The great attraction of this technique is that if there are unwelcome side-effects, you can turn it off right away.

These techniques are known as "geo-engineering," and discussing them has been taboo in most scientific circles because of the "moral hazard": the fear that if the public knows you can hold the global temperature down by direct intervention, people will not do the harder job of cutting their emissions. But if large-scale methane releases are getting underway, the time for such subtle calculations is past.

Starting now, we need a crash programme to investigate the feasibility of these and other techniques for geo-engineering the climate. Once the thawing starts, it is hard to stop, and we may need them very soon.