For the next few decades, the rate of sea-level rise is partly locked in by past emissions,
and will not be strongly dependent on early 21st century greenhouse gas emission.
However, sea level projections closer to and beyond 2100 are critically dependent on future
greenhouse gas emissions, with both ocean thermal expansion and the ice sheets potentially
contributing metres of sea-level rise over centuries for higher greenhouse gas emissions.
Present day contributions from the Greenland come from both surface melting and iceberg
calving and for the Antarctic ice sheet from iceberg calving only. The contribution from the
ice sheets is poorly understood at the moment and is an active area of research.
In the case of the Greenland Ice Sheet, if global average temperatures cross