Arctic in Permanent Shift to ‘Entirely Different Climate’, but 1.5°C Would Slow the Process

Adding to a wave of dire news about the Earth’s rapidly warming polar regions, a comprehensive new study is warning that the Arctic is beginning to change permanently to a new—and largely thawed—climate. But all is not yet lost: limiting warming to 1.5°C could substantially alter this outcome.

“The fast-warming Arctic has started to transition from a predominantly frozen state into an entirely different climate,” writes Science Daily, reporting on a study from the U.S. National Center for Atmospheric Research (NCAR) in Boulder, Colorado. The researchers found that natural year-to-year variability in the key metrics of sea ice extent, fall and winter temperatures, and length of the rainy season “is moving outside the bounds of any past fluctuations, signalling the transition to a ‘new Arctic’ climate regime.”

Describing the rate of change as “remarkable” and “unnerving,” lead author Laura Landrum noted that the rapidity is such that “observations of past weather patterns no longer show what you can expect next year.”

A starting point for Landrum and co-author Marika Holland was the fact that “the average extent of sea ice in September, when it reaches its annual minimum, has dropped by 31% since the first decade of the satellite era (1979-88).” Their plan was to determine whether this collapse falls outside the range of natural variability. They asked the same question of the fall and winter air temperatures, “which are strongly influenced by the summertime reduction of sea ice and the subsequent timing of the ice regrowth,” and of “the seasonal transition in precipitation from mostly snow to mostly rain.”

The researchers measured observational data against the huge number of simulations provided by an international research initiative called the Coupled Model Intercomparison Project 5, then applied statistical techniques “to determine when climactic changes exceeded the bounds of natural variability.” Their findings show the sea ice has already entered a new climate, with its emergence taking place “in the late 20th and early 21st centuries.”

Seasonal precipitation cycles, meanwhile, “will change dramatically by the middle of the century,” and air temperatures over the ocean “will enter a new climate during the first half or middle of this century” under the Intergovernmental Panel on Climate Change’s high-emissions trajectory RCP 8.5. The scenario also shows air temperatures over land “warming substantially later in the century.”

The climate shift will affect non-Arctic regions, too. “If emissions persist at a high level, most continental regions will experience an increase in the rainy season of 20-60 days by mid-century and 60-90 days by the end of the century,” notes Science Daily.

While Landrum and Holland do not place their focus on the possibility of averting or reversing this shift, they say there is still a chance to stop the freefall of the Arctic as we know it. “Limiting future warming to 1.5°C could have substantial impacts on September SIE [sea ice extent], with notably more summer sea ice present at the end of the 21st century,” they note in their report. Reductions in greenhouse gases may also “postpone or even avoid the emergence of a new Arctic in many climate properties.”

But there is no time to waste. Scientists have already confirmed that rapid climate change is behind the recent and sudden loss of some 110 square kilometres of ice on the far northeast tip of Greenland.

Commenting on that event, National Geological Survey of Denmark and Greenland scientist Jason Box told the Associated Press that “we should be very concerned about what appears to be progressive disintegration at the Arctic’s largest remaining ice shelf.” AP says this latest evidence that the polar ice is decidedly “sickly” comes in the wake of an August study published in the journal Nature Communications Earth & Environment, showing that Greenland “lost a record amount of ice during an extra-warm 2019, with the melt massive enough to cover California in more than 1.25 metres of water.”

Meanwhile, the Washington Post reports that “two major Antarctic glaciers are tearing loose from their restraints.” The Pine Island and Thwaites glaciers, critically important ice masses located in West Antarctica, “already contribute around 5% of global sea level rise,” according to research just published in the Proceedings of the National Academy of Sciences.

The loss of the Thwaites glacier in particular “could trigger the broader collapse of the West Antarctic ice sheet, which contains enough ice to eventually raise seas by about 10 feet.”