By Dan Karpenchuk
ABC News Online, Posted Wed Dec 17, 2008 9:39am AEDT
NASA says it has satellite data that shows more than 2 trillion tonnes of land ice in Greenland, the Arctic, Antarctica and Alaska has melted in the past five years.
Scientists say the melting land ice has raised global sea levels by about 5 millmetres.
They say sea levels are also rising as water expands from warming.
Scientists say parts of the Arctic were nine to 10 degrees Celsius warmer this spring.
They also say warming in the far north is accelerating faster than anywhere else on the globe.
Experts say the pace of change is starting to outstrip the human ability to keep up.
Scientists also point to large amounts of frozen methane that is being released.
Methane is another potent greenhouse gas which could dramatically increase global warming.