The following submission statement was provided by /u/Vucea:

Once we emit about 1000 gigatons of carbon, much of the massive ice sheet will melt irreversibly. We’ve emitted 500 gigatons so far.

The Greenland Ice Sheet covers 1.7 million square kilometers (660,200 square miles) in the Arctic. If it melts entirely, global sea level would rise about 7 meters (23 feet), but scientists aren’t sure how quickly the ice sheet could melt. Modeling tipping points, which are critical thresholds where a system behavior irreversibly changes, helps researchers find out when that melt might occur.

Based in part on carbon emissions, a new study using simulations identified two tipping points for the Greenland Ice Sheet: releasing 1000 gigatons of carbon into the atmosphere will cause the southern portion of the ice sheet to melt; about 2500 gigatons of carbon means permanent loss of nearly the entire ice sheet.

Having emitted about 500 gigatons of carbon, we’re about halfway to the first tipping point.

Please reply to OP's comment here: https://old.reddit.com/r/Futurology/comments/123zxg2/the_greenland_ice_sheet_is_close_to_a_melting/jdx4blf/