Over two trillion tons of land ice in Antarctica, Greenland and Alaska have melted since 2003, according to satellite data that show the latest signs of global warming. Between Greenland, Antarctica and Alaska, melting land ice has raised global sea levels about a fifth of an inch in the past five years.

More than half of the loss of landlocked ice in the past five years has occurred in Greenland, based on measurements of ice weight by NASA. The water melting from Greenland seems to be accelerating.

“The pace of change is starting to outstrip our ability to keep up with it, in terms of our understanding of it,” said Mark Serreze, senior scientist at the National Snow and Ice Data Center.

As sea ice melts, the Arctic waters absorb more heat in the summer, having lost the reflective powers of the huge packs of white ice. That absorbed heat is released into the air in the fall which has led to fall temperatures in the last few years that are six to ten degrees warmer than they were twenty years ago.