If - Greenland were to continue losing ice mass at a rate of 103 billion tonnes per year, how long would it take to melt say half of the ice sheet? Not all of it, mind you, but half of it. (Note that I am NOT saying that extending a current trend is a way to estimate the future evolution of the ice sheet—I’m merely using it as a way to compare large numbers.)
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To answer our question if 103 billion tonnes lost per year is a big number, we have to compare the annual ice mass loss to the amount of ice in the Greenland ice sheet. The Greenland ice sheet contains about 2.6E+15 (2,600,000,000,000,000) tonnes of water in the form of snow and ice.

So IF the Greenland ice sheet were to lose 103 billion tonnes per year into the indefinite future, it would take about twelve thousand five hundred years to lose half of it …