Dramatic slowdown in melting of Arctic sea ice surprises scientists. Natural climate variation is most likely reason as global heating due to fossil fuel burning has continued

Melting is likely to start again at about double the long-term rate in the next five to 10 years, the scientists said. Photograph: Keren Su/China Span/Alamy

 

The melting of sea ice in the Arctic has slowed dramatically in the past 20 years, scientists have reported, with no statistically significant decline in its extent since 2005.

The finding is surprising, the researchers say, given that carbon emissions from fossil fuel burning have continued to rise and trap ever more heat over that time.

They said natural variations in ocean currents that limit ice melting had probably balanced out the continuing rise in global temperatures. However, they said this was only a temporary reprieve and melting was highly likely to start again at about double the long-term rate at some point in the next five to 10 years.

The findings do not mean Arctic sea ice is rebounding. Sea ice area in September, when it reaches its annual minimum, has halved since 1979, when satellite measurements began. The climate crisis remains “unequivocally real”, the scientists said, and the need for urgent action to avoid the worst impacts remains unchanged.

 The natural variation causing the slowdown is probably the multi-decadal fluctuations in currents in the Atlantic and Pacific oceans, which change the amount of warmed water flowing into the Arctic. The Arctic is still expected to see ice-free conditions later in the century, harming people and wildlife in the region and boosting global heating by exposing the dark, heat-absorbing ocean.

 

Dr Mark England, who led the study while at the University of Exeter, said: “It is surprising, when there is a current debate about whether global warming is accelerating, that we’re talking about a slowdown.

“The good news is that 10 to 15 years ago when sea ice loss was accelerating, some people were talking about an ice-free Arctic before 2020. But now the [natural] variability has switched to largely cancelling out sea ice loss. It has bought us a bit more time but it is a temporary reprieve – when it ends, it isn’t good news.”

The research, published in the journal Geophysical Research Letters, used two different datasets of Arctic sea ice levels from 1979 to the present day. The scientists analysed the sea ice area for every month of the year and the slowdown was seen in all cases.

To see if such a slowdown could be a result of natural variation, they examined the results of thousands of climate model runs. “This is not an extremely rare event – over a century, it should happen a couple of times,” said England, now at the University of California, Irvine. Furthermore, all the simulations showed sea ice loss accelerating again after the slowdown.

Prof Julienne Stroeve, of University College London, said: “We know climate records, be it in global temperatures or sea ice, can remain the same for several years in a row as a result of internal climate variability.”

Stroeve’s analysis of the long-term trend from 1979 to 2024 shows that about 2.5 sq metres of September ice is lost for every tonne of CO₂ emitted.

 

Prof Andrew Shepherd, of Northumbria University, said: “We know that the Arctic sea ice pack is also thinning, and so even if the area was not reducing, the volume still is. Our data show that since 2010 the average October thickness has fallen by 0.6cm per year.”

The rate of the rise in global surface temperature has also slowed down in the past, before resuming a rapid rise. A major El Niño event in 1998 was followed by a decade or so of similar global temperatures, which was nicknamed “the pause”. However, the planet continued to accumulate heat throughout and global temperatures have since risen rapidly.

England rejected any suggestion the sea ice slowdown suggested climate change was not real. “Climate change is unequivocally real, human-driven, and continues to pose serious threats. The fundamental science and urgency for climate action remain unchanged,” he said.

“It is good to explain to people that [the slowdown] is happening, else they are going to hear it from someone who is trying to use it in bad faith as a way to undermine our very solid understanding of what’s happening with climate change.”

Environmental row over ‘last chance tourism’ in Canada’s melting Arctic

 

Link to https://www.theguardian.com/world/2024/mar/08/environmental-row-last-chance-tourism-canada-melting-arctic-pond-inlet

Martianization - Arctic Warming Is Happening Faster Than Described, Analysis Shows

The warming at the top of the globe, a sign of climate change, is happening much faster than previously described compared with the global average, scientists said Thursday.

By Henry Fountain

Aug. 11, 2022

The rapid warming of the Arctic, a definitive sign of climate change, is occurring even faster than previously described, researchers in Finland said Thursday.

Over the past four decades the region has been heating up four times faster than the global average, not the two to three times that has commonly been reported. And some parts of the region, notably the Barents Sea north of Norway and Russia, are warming up to seven times faster, they said.

One result of rapid Arctic warming is faster melting of the Greenland ice sheet, which adds to sea-level rise. But the impacts extend far beyond the Arctic, reaching down to influence weather like extreme rainfall and heat waves in North America and elsewhere. By altering the temperature difference between the North Pole and the Equator, the warming Arctic appears to have affected storm tracks and wind speed in North America.

Manvendra K. Dubey, an atmospheric scientist at Los Alamos National Laboratory and an author of an earlier study with similar findings, said the faster rate of warming of the Arctic was worrisome, and points to the need to closely monitor the region.

“One has to measure it much better, and all the time, because we are at the precipice of many tipping points,” like the complete loss of Arctic sea ice in summers, he said.

The two studies serve as a sharp reminder that humans continue to burn fossil fuels and pump greenhouse gases into the atmosphere at rates that are dangerously heating the planet and unleashing extreme weather.

Just weeks after a deadly heat wave clamped down on European capitals, shattering records in Britain, extreme temperatures are again engulfing western Europe this week. The heaviest rainfall in decades inundated Seoul, South Korea, killing at least nine and damaging nearly 3,000 structures. And the McKinney wildfire continues to rage in Northern California, destroying 60,000 acres, killing four people and triggering a mass fish kill.

If the rate of warming in the Arctic continues to speed up, the influence on weather could worsen, one of the researchers said. And projections of future climate impacts might need to be adjusted, said Mika Rantanen, a researcher at the Finnish Meteorological Institute in Helsinki.

Even as Congress is on the cusp of passing historic climate legislation, the United States is still far from its goal to stop adding carbon dioxide to the atmosphere by 2050. That’s the target all major economies must meet, scientists say, for the planet to constrain average global temperature rise to 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial levels. Beyond that threshold, the likelihood increases significantly of catastrophic droughts, floods, wildfires and heat waves. The planet has already warmed an average of about 1.1 degrees Celsius.

While scientists have long known that average temperatures in the Arctic are increasing faster than the rest of the planet, the rate has been a source of confusion. Studies and news accounts have estimated it is two to three times faster than the global average.

Dr. Rantanen said he and his colleagues decided to look at the issue in the summer of 2020, when intense heat waves in the Siberian Arctic drew a lot of attention.

“We were frustrated by the fact that there’s this saying that the Arctic is warming twice as fast as the globe,” he said. “But when you look at the data, you can easily see that it is close to four.”

Their study was published Thursday in the journal Communications Earth and Environment.

The findings are bolstered by the earlier study, by Dr. Dubey and others at Los Alamos and elsewhere, which found similar rates of warming, although over a different time span.

The Arctic is heating more rapidly in large part because of a feedback loop in which warming melts sea ice in the region, which exposes more of the Arctic Ocean to sunlight and leads to more warming, which in turn leads to even more melting and warming. The result of this and other oceanic and atmospheric processes is called Arctic amplification.

How the rate of warming in the Arctic is described compared with the global average is related in part to the time period that is analyzed and how the region is defined.

The new analysis begins with data from 1979, when accurate temperature estimates from satellite sensors first became available. The researchers also defined the Arctic as the area north of the Arctic Circle, above about 66 degrees latitude.

Thomas Ballinger, a researcher at the University of Alaska Fairbanks, said how the region is defined “is a very, very relevant conversation for understanding Arctic change.” A bigger Arctic would include more land, reducing the impact of the ice-ocean feedback on average temperatures.

Dr. Ballinger, who was not involved in either study, is an author of the annual Arctic Report Card prepared for the National Oceanic and Atmospheric Administration.

The latest report card, for 2021, details a region undergoing vast change, overwhelmed by rising temperatures. Indeed, some scientists now say that the Arctic’s fundamental climate has changed, to one characterized more by liquid water than ice, with profound effects on the plants, animals and people living there.

Loss of sea ice is putting polar bears in jeopardy, which in turn affects the well-being of the people who have hunted them for centuries. Sailing routes that were once perpetually choked with ice are opening up, bringing the environmental risks of ocean shipping to pristine waters. Shorelines are eroding more quickly, and more permafrost is thawing, leading to increased greenhouse gas emissions and damaging Arctic infrastructure.

Dr. Ballinger said some of the findings in the Finnish study were especially interesting, including those showing very high rates of warming in the late 1980s and 1990s. “That really was when Arctic amplification rates were the strongest,” he said

 

The earlier study, published last month in Geophysical Research Letters, looked at data from 1960 onward and defined a larger Arctic, north of 65 degrees latitude, which includes more land. It found that the rate of warming reached four times the global average starting about 20 years ago. And unlike the Finnish study, it found that there were two decade-long periods, from the mid-1980s to the mid-1990s, and in the 2000s, with large jumps in warming in the region.

“It doesn’t change continuously, it changes in steps,” Dr. Dubey said. And because the data spanned decade-long periods, they suggest a connection to natural climate variability, as well as warming resulting from increased emissions of greenhouse gases from human activity.

Dr. Rantanen said his group’s results also point to a role played by natural variability in the rate of warming, perhaps some long-term changes in ocean or atmospheric circulation.

But clearly the interaction between water temperature and ice is most important, he said, especially in areas like the Barents Sea where the warming rate is even higher.

“The warming trends are quite strongly coupled with the decline of sea ice,” he said. “They’re most highest over those areas where the sea ice has been declining the most. That’s the primary reason.”