The days in Nuuk, Greenland’s capital, are growing longer. Even after setting, the sun lingers below the horizon, casting a glow over the rocky coastal landscape. On sun-drenched days, when the skies are as blue as the ocean, one can admire Greenland’s striking mountains. Their jagged summits contrast with the smoothness of their lower slopes, fjords shaped by the relentless force of ancient ice sheets. Here and there, splashes of fragrant brownish-green tundra punctuate the scene. Everywhere, the snow is melting, making for slushy treks through a wet and heavy snowpack.

Before landing in Greenland at the start of the melt season, I expected to see more snow. But only patches of winter snow remained. One does not need to be a scientist to observe the trends that we researchers can detect via satellites and other long-term measurements. The snowfall has been arriving later in the year, sometimes after Christmas, and has not been as persistent as it once was. After a quarter-century of losing mass, the Greenland Ice Sheet has been undergoing a rapid and radical transformation.

The US National Oceanic and Atmospheric Administration’s Arctic Report Card for Greenland, which I co-authored, paints a grim picture. In 2022, Greenland marked its 25th consecutive year of ice loss, accompanied by “unprecedented late-season melt events.” On September 3, more than a third of the ice sheet’s surface – including Summit Station, a research camp near the ice sheet’s apex – experienced melting conditions. A year before, in August 2021, Summit Station documented its first-ever recorded rainfall, although it was impossible to say exactly how much it received, owing to the absence of rain gauges at such high altitudes.

Greenland’s accelerating rate of ice loss is projected to exceed that of any period during the Holocene, the geological epoch that began roughly 12,000 years ago. There is compelling evidence that the western portion of the Greenland Ice Sheet is growing increasingly unstable, edging toward a tipping point beyond which its dynamics and structure fundamentally and irreversibly shift.

In fact, scientists may have underestimated how sensitive glaciers are to global warming, which means that the tipping point may be reached sooner than we think. My own research shows that ice loss has been reshaping the ice sheet’s margins and the Greenland coast, altering glacier speeds and rerouting the flows of ice, water, and sediment. These changes, in turn, influence the ice sheet’s response to future temperature increases.

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The message from Greenland is clear: ice will not negotiate.

On my recent visit to Nuuk, I continued work on the QGreenland project, building a geospatial data tool for researchers and educators interested in exploring Greenland and learning about the scientific research taking place there. Although one cannot smell the tundra or hear the Arctic birds through interactive maps, such tools promise to familiarise people with the world’s largest island and help them understand how changes in the Arctic could affect their own communities, even if they are thousands of miles away.

To avoid catastrophe, we must act immediately. Much like the light from distant stars enables us to peer into the past, the changes we now see in Greenland – the result of our previous inaction on greenhouse-gas emissions – offer a frightening glimpse into the future. As the Intergovernmental Panel on Climate Change’s recent Synthesis Report notes, “sea-level rise is unavoidable for centuries to millennia,” largely owing to ice-sheet melt.

Rising sea levels may not seem like a pressing issue if one’s own backyard is not flooding. But roughly 40 per cent of the world’s population lives within 100 kilometers (62 miles) of coasts. Beyond coastal erosion and saltwater inundating freshwater resources and ecosystems, sea-level rise will also affect groundwater levels, causing potential flooding and water contamination further inland. And those of us living thousands of miles from the coastline depend on coastal infrastructure for goods and shipping. We must all plan for a future with continued sea-level rise and work together to respond to it.

The extent and pace of sea-level rise, however, still depends on the choices we make now. The latest IPCC report, which shows global temperatures heading toward a 3.5° Celsius increase by 2100, underscores the urgent need to close the gap between current measures to combat climate change and what must be done to meet our agreed global goal of less than 2°C. If temperatures rise by 2-3°C, the Greenland and West Antarctic Ice Sheets could be lost “almost completely and irreversibly over multiple millennia,” causing several meters of sea-level rise. Estimates suggest that the Greenland Ice Sheet alone holds the equivalent of 7.4 meters (24 feet) of potential sea-level increase.

Fortunately, humanity’s future is not fully predetermined. By taking strong climate-focused action now, we could save much of the Greenland Ice Sheet, curb the spread of wildfires, minimise the rise in drought frequency and severity, enhance food security, and ensure a habitable world.

But achieving this requires a concerted and sustained effort to limit global temperature rise; every degree matters. To prevail against climate change, we must adhere to established deadlines and honor existing commitments to shift away from fossil fuels as our primary energy source. The message from Greenland is clear: ice will not negotiate.

Twila Moon is Deputy Lead Scientist at the National Snow and Ice Data Center at the University of Colorado Boulder.

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