THEY'VE GONE OUT OF WHACK

Recent reports suggesting that glaciers and icecaps may be melting much faster than previously predicted, rubbishing computer models that predict melting as sluggish and gradual. At Greenland's ice sheet, for example, temperatures predicted at minus 20 had turned to rain in 2007. Why is this happening, and what does this mean?

The first reason is the nature of sheet ice in Greenland and Antarctica. Snow covering the ice prevents it from melting by reflecting the sun's light and heat; however, once global warming melts the snow, the dark ice (or worse, rock) underneath absorbs heat much faster, defying predictions made only a year ago.

The meltwater produced as a result also absorbs more heat due to its' darker colour. But meltwater is dangerous to ice because it plunges into open moulins and crevasses, breaking up the ice and lubricating its' base. The ice then flows much faster to the sea, where warm ocean currents continue to eat away at the already ravaged ice.

Perhaps more devastating is what is released, not exposed, once ice sheets melt: CO2. Recent research shows that icecaps hold in carbon dioxide from millions of years ago, and that this is released back into the atmosphere once the ice melts. This accelerates the melting of ice, perhaps more so because heat is now trapped closer to the poles itself.

There are two main effects of this acceleration of melting, the first being an impact on polar wildlife. Much more than we already know, ice is central to these animals' lives; phytoplankton, producers in the Antarctic food web, grow on the underside of ice; ice depletion could thus drive bowhead whales to extinction. Polar bears and ringed seals need ice to rest and rewarm in between swims, and with ice melting, they are forced to make longer, riskier swims, causing scientists to fear the extinction of polar bears sometime this century.

Moreover, ice-melting predictions being proved wrong will also impact how the formulation of climate-change policy. Many scientists have now revised ideal atmospheric CO2 concentrations to 350 or 300 parts-per-million, down from a previous 450 ppm. The EU has agreed to temperature cuts of 2 degrees Celsius, which will amount to an 85% emissions reduction. More worrying is how the sudden unreliability of ice models has caused renewed bickering over global warming prevention; geoengineering is now being bandied about as a real option, but is heavily criticized ethically (will we still be willing to cut emissions significantly?) and scientifically ( a parasol in space won't solve ocean acidification)

As we approach a point of no return, one model remains unchanged: that we need to drastically cut emissions now. It we don't, then just like the computer models, our climate will go right out of whack too.