The Earth's frozen 'cryosphere' - from the Arctic to the Antarctic - is showing unequivocal signs of climate change as global warming accelerates the melting of the planet's coldest regions.
The rapid loss of ice is clear from underwater measurements by military submarines, from land records and from satellite observations from space.
It can be seen on the ice sheets of Greenland, the glaciers of the Andes and the vast ice shelves of Antarctic.
The effect of the melting cryosphere will be felt by rapidly rising sea levels that threaten to flood coastal cities and low-lying nations.
One of the greatest threats is the melting of the permafrost regions of the northern hemisphere, which could release vast quantities of methane gas from frozen deposits stored underground for thousands of years.
Scientists are already seeing an increase in atmospheric methane concentrations that could be the result of melting permafrost.
One of the clearest signals of climate change is the rapid loss of floating Arctic ice, which has been monitored by satellites since the 1970s.
The ice is retreating faster and further than at any time on record. This year it probably reached an all-time record minimum in terms of volume and a close second in terms of surface area.
On current projections, if the rate of loss continues, there could be virtually no September sea ice as early as 2015.
The loss of sea ice and the warming of the Arctic is also having an impact on the permafrost regions of the north, both on land and sea, where scientists have documented vast methane releases.
One of the greatest threats is a possible rapid rise in sea levels caused by melting mountain glaciers and polar ice sheets.
Scientists believe that about two-thirds of the current rate of average sea level rise - about 3mm a year - is the result of glaciers and polar ice sheets melting.
Chris Rapley, a professor of climate science at University College London and former head of the British Antarctic Survey, said: "In a warmer world, one thing you can guarantee is that ice will melt.
"Sea levels are rising at a third of the rate they were when we had truly massive ice sheets at the end of the last ice age."
Some parts of the Antarctic are melting faster than at any time on record.
Greenland is also seeing an unprecedented melting of its glaciers.