collapse of Arctic sea ice calls for urgent consideration of the new ideas to reduce global temperatures

Polar packs significantly change their size during seasonal changes of the year. However, underlying this seasonal variation, there is an underlying trend of melting as part of a more general process of Arctic shrinkage.

In spring and summer, when melting occurs, the margins of the sea ice retreat. The vast bulk of the world's sea ice forms in the Arctic ocean and theSouthern Ocean, around Antarctica. The Antarctic ice cover is highly seasonal, with very little ice in the austral summer, expanding to an area roughly equal to that of Antarctica in winter. 

One of the world's leading ice experts has predicted the final collapse of Arctic sea ice in summer months within four years. In what he calls a "global disaster" now unfolding in northern latitudes as the sea area that freezes and melts each year shrinks to its lowest extentever recorded, Prof Peter Wadhams of Cambridge University calls for "urgent" consideration of new ideas to reduce global temperatures.

"This collapse, I predicted would occur in 2015-16 at which time the summer Arctic (August to September) would become ice-free. The final collapse towards that state is now happening and will probably be complete by those dates".

He says: "Climate change is no longer something we can aim to do something about in a few decades' time, and that we must not only urgently reduce CO2 emissions but must urgently examine other ways of slowing global warming, such as the variousgeoengineering ideas that have been put forward."

These include reflecting the sun's rays back into space, making clouds whiter and seeding the ocean with minerals to absorb more CO2.

The area of sea ice around the poles in winter is about 15,600,000 km2(6,000,000 sq mi) either for the Antarctic or Arctic. However, whereas the northern cap is shrinking at a rate of about 3% per decade, the southern cap is expanding at a rate of 1.8% per decade. The amount melted each summer is affected by the different environments: the cold Antarctic pole is over land, which is bordered by sea ice in the freely circulating Southern Ocean. The summer icer cover is about 12% of the winter coverage in the Antarctic and 50% in the Arctic.

Sources: guardian.co.uk Common Dreams en.wikipedia