As a field glaciologist, I've worked on ice sheets for more than 30 years. In that time, I have witnessed some gobsmacking changes. The past few years in particular have been unnerving for the sheer rate and magnitude of change underway. My revered textbooks taught me that ice sheets respond over millennial time scales, but that's not what we're seeing today.

A study published Aug. 29, 2022, demonstrates – for the first time – that Greenland's ice sheet is now so out of balance with prevailing Arctic climate that it no longer can sustain its current size. It is irreversibly committed to retreat by at least 59,000 square kilometers (22,780 square miles), an area considerably larger than Denmark, Greenland's protectorate state.

Even if all the greenhouse gas emissions driving global warming ceased today, we find that Greenland's ice loss under current temperatures will raise global sea level by at least 10.8 inches (27.4 centimeters). That's more than current models forecast, and it's a highly conservative estimate. If every year were like 2012, when Greenland experienced a heat wave, that irreversible commitment to sea level rise would triple. That's an ominous portent given that these are climate conditions we have already seen, not a hypothetical future scenario.