Siberia's scorching, 100-degree temperature record made headlines in late June, but it was just the latest spike in a decade of historic heat waves across the Arctic that also set records for wildfires, thawing permafrost and melting sea ice. Such extremes, scientists said, show that Arctic warming is accelerating to outpace all but the most dire climate projections.
Intensifying warming in the Arctic trickles down to the rest of the world, melting Greenland's ice to raise sea levels and flood coastal communities. It also shifts the paths of storms to intensify droughts, heat waves and flooding in more populated lower latitudes.
Siberia's overall temperatures were more than 9 degrees Fahrenheit above average from January to June. The prolonged heat wave would have been impossible in a climate that had not been warmed by human greenhouse gas emissions, according to research released Wednesday by World Weather Attribution, a team of scientists that studies how warming influences the intensity and frequency of meteorological extremes.
At the current level of warming, about 1.5 degrees Fahrenheit above the pre-industrial era, such a heat wave could be expected once every 130 years, but if emissions aren't cut, they could be commonplace by the end of the century, the scientists concluded in their study, which hasn't been peer reviewed yet.
Lead author Andrew Ciavarella, of the United Kingdom's national weather service, said the findings, which showed that the changing climate increased the chances of the prolonged Siberian heat by at least 600 times, are staggering. Global warming not only increased the likelihood of the six-month Siberian heat wave, but also increased its temperatures "by at least 2, and probably 3 degrees Celsius (3.6 to 5.4 degrees Fahrenheit)," he said.
Regional impacts of the heat wave included large swarms of silk moths that, along with the soaring temperatures, made forests more fire-prone, said co-author Olga Zolina, with the Shirshov Institute of Oceanology. The heat wave also melted permafrost, which caused roads to crumble and a storage tank to collapse, spilling 21,000 tons of oil into a river.
"The heat wave is not only important because of people," she said. "The Arctic is important for forming weather and circulation. The high temperatures are really important for the whole globe."
Siberian Temperatures Climbed Off the Charts—Again
Persistent wind patterns contributed to the unusually warm winter and spring over western Siberia and the extreme early summer heat over the Arctic portion of the Russian province. That fits with recent research showing that the jet stream, which carries weather systems from west to east, is looping farther north and south more frequently, and even getting stuck in those areas, said Susan Conard, a climate researcher at George Mason University and the editor of the International Journal of Wildland Fire.
Those atmospheric patterns are changing and intensifying Rossby Waves—slow-moving ripples in oceans and air circling the globe that form as a result of the rotation of the Earth and affect the planet's weather. "Over time, it seems quite apparent that these atmospheric patterns that change and intensify the Rossby waves have changed," she said.
Other studies have shown that changes in the jet stream and Rossby Waves have contributed to extreme ice melt in Greenland, as well as to floods, heat waves and droughts in more temperate regions of the planet.
"When you have an 'upward' loop in the jet stream, the air masses are drawn up inside the loop," said Conard, who spent years studying Siberian forests. "In most of the U.S., that brings moist air from the Gulf of Mexico. In Asia and Eastern Europe, however, the result is warm, dry air coming across desert areas, or further east across tall mountains that dry the air."
In addition to its warmth, the last winter in Siberia was so dry that, by June, soil moisture was at a record low. That's another factor heating the region, because if soil is moist, incoming heat energy dissipates through evaporation. If it's dry, the ground absorbs the heat energy and warms the air above it, said Felix Pithan, a scientist with the Potsdam Institute for Climate Impacts Research.
The warm and dry conditions continued from winter through early summer, priming the forests and tundra for wildfires that, in just two months, emitted about 60 million tons of carbon dioxide into the atmosphere, more than the annual emissions of mid-size countries like Hungary and Portugal. In the last two years, Siberian fires emitted more carbon dioxide than all the fires in the region during the previous 16 years, according to Thomas Smith, a climate researcher and geographer with the London School of Economics.
Along with direct greenhouse gas emissions, the heat and fires are speeding the thaw of permafrost in some areas, and the warmth over Siberia has accelerated the summer melting of sea ice to a record pace in the adjacent Arctic Ocean. Last year, parts of Alaska experienced similar extreme conditions, and the year before that, northern Scandinavia was blistered by extreme heat and fires.
The effects of this year's persistent Siberian warmth are likely to last so long that it may be misleading to call it a heat wave, said Anders Levermann at the Potsdam Institute for Climate Impacts Research.
"The idea of a heat wave is that, at some point, it ends and that you're going back to normal," the researcher said. "But if, for example, you thaw the permafrost, you are not going back to normal. You leave a scar, in a sense."
Levermann said the rapid dwindling of sea ice is another strong sign the entire Arctic system is collapsing. When all the sea ice is all gone in 20 years or so, the Arctic will be in a quantitatively different state. That is likely to affect the climate across large swaths of the Northern Hemisphere, including the mid-latitudes where most people in North America and Eurasia live.
Lingering Heat Impacts in Alaska
Exactly a year ago, Alaska was enduring a heat wave as dramatic as this year's in Siberia. University of Alaska, Fairbanks climate scientist Rick Thoman said he was astonished when Anchorage broke it's all-time high temperature by 5 degrees Fahrenheit, reaching 90 degrees on July 4 during a heat wave that re-wrote the record books in many Alaskan communities.
And just like Siberia, the Alaskan summer heatwave followed an exceptionally warm winter and spring. In early February 2019, archaeologist Anne Jensen tweeted about the unusual conditions in the northernmost town in the United States: "It's February, the coldest month of the year. We have open water in front of Utqiagvik. It is 30 F out at 11:20 at night. Strange days indeed." Just two years earlier the average temperature there changed so fast that the weather station's official instruments and computer programs couldn't keep pace.
In spring and early summer of 2019 the intensifying heat over Alaska accelerated the meltdown of bright, reflective sea ice along the Alaska coast, enabling the ocean to soak up heat, which, in turn, magnified warmth over Alaskan coastal areas and spread inland to drive record heat and wildfires across the state.
The year before that, extreme heat and wildfires spread across the Scandinavian Arctic, following two years with repeated heat waves over the Central Arctic. The timeline of extremes includes a 2012 heat wave that triggered unprecedented melting across most of the Greenland Ice Sheet. Overall, Alaska and the Arctic have warmed more since 1990 than in the previous 90 years. This year's Siberian heat is another dramatic spike in that trend.
"The really outstanding thing in Siberia is that they have been exceptionally warm for months," Thoman said. "The fact they've been running 5 to 10 degrees Celsius (9 to 18 degrees Fahrenheit) above normal for most of this year, are anomalies for that kind of time span that are mind-boggling."
But as shocking as they are, the annual heat waves hopscotching through the Arctic shouldn't be surprising, Thoman said.
"This is all exactly what you expect," he said "With the trend of global warming, someplace is going to be really, really extreme nearly every year."
Thoman said that many areas have crossed thresholds leading to abrupt change. Given the amount of heat going into the ocean, it's not physically reasonable to expect the system to go back to how it was, he said.
The 2019 Alaska heat wave contributed to "unprecedented multi-species deaths," reported from western Alaskan coastal communities, he said, but aside from the growing wildfire threat, his biggest concern is its impact on Alaska indigenous cultures.
"Communities are resilient, but changes are happening so fast, on top of the other problems, it's stretching the capacity to adapt to the limit," he said, noting that the lack of relocation plans for imminently threatened communities like Shishmaref or Kivalina was an "Alaska-specific failure".
The effects of Alaska's record-warm summer persisted through subsequent seasons, particularly with regard to sea ice.
"We had a cold winter ... and yet, overall, Bering Sea ice extent was near record low much of the winter," he said. "This year, we saw the greatest March ice loss of record, a direct result of the heat of last summer. The waters were so warm it took a long time to work that warmth off, so the ice that did form was shallow."
At this point, the warming in the Arctic is so strong that "it's swamping all other climate signals" like natural ocean warming and cooling cycles.
A Vicious Circle of Melting Permafrost and Global Warming
For climatologists, one of the biggest concerns about persistent Arctic warming is the threat to permafrost, a deep layer of frozen ground that releases vast amounts of heat-trapping carbon dioxide when it thaws.
The melting has already advanced to the point that, even during colder winters, such as the last one in Alaska, the permafrost won't refreeze, said Vladimir Romanovsky, a permafrost expert at the University of Alaska, Fairbanks. Every year, a little more thaws.
"It's a very tedious process, thawing about 5-10 centimeters (2 to 4 inches) per year, but it's a completely new situation compared to 15 years ago," he said.
The thawing also enables water to drain from the surface of the permafrost, leaving it drier and more easy to ignite with wildfires, he said. And global warming also increases the source of ignitions as the moisture and heat it adds to the atmosphere brings more thunderstorms, he added.
Emissions from the burning forests and melting permafrost are feeding an increasingly vicious circle of warming.
"We are going to see more fires and more severe fires," he said. "They will cover more areas and burn more deeply into the organic layer, and this will trigger more thawing of permafrost."
"The thawing will accelerate significantly," he said. In a few decades, permafrost "could be thawing at the rate of 1.6 feet per year, spreading across much of the Alaskan interior. That will be a massive change in the environment."
Romanovsky also monitors permafrost on remote Nunavut Territory islands in the Canadian Arctic. The changes there, he said, are even more unexpected than in Alaska and Siberia, and show how warming is intensifying and spreading across the entire Arctic.
There, on some of the most northward land of the planet, maximum summer temperatures since 2006 have increased from just a few degrees above freezing to 50 degrees Fahrenheit. As a result, the summer permafrost thaw has increased from about six-inches deep to between 15 and 23 inches—"enough to thaw massive ice layers and physically change the landscape," said Romanovsky, who in that time has seen flat, unvegetated land fill with troughs and plants.
Arctic Warming Scars Scandinavia With Sinkholes, Landslides
In Scandinavia, the extreme heat of recent summers has penetrated even deeper into the frozen ground. At a research site at Janssonhaugen, at 78 degrees north in the Svalbard archipelago north of Norway, permafrost 130 feet deep has warmed by nearly a full degree Fahrenheit since 1998.
Such abrupt thaws "can be triggered by a single weather extreme, like this year's warm spring and summer in Siberia," he said.
The combined effects of warm air temperatures, fires and water spreading through the ground can "thaw through meters of permafrost within a short time—much more rapidly than would be caused by increasing air temperature alone," Isaksen said.
In the Nordic Arctic, rapid thaw brings huge landslides and sinkholes, he added. About 20 percent of the northern permafrost region appears to be vulnerable to such abrupt thaw, according to the latest report from the Intergovernmental Panel on Climate Change.
Isaksen said the 2018 heat wave in Scandinavia was most noteworthy not for its impacts on permafrost, but because it fueled widespread, intense and persistent drought.
"The drought started early, in May," he said. "When the rainfall came in August, it was too late to save the crops. In Norway, almost 200 million euros were paid in compensation for the crop failure in 2018."
The extreme heat and drought also increased electricity prices, closed power plants for lack of cooling water, emptied reservoirs and led to water restrictions in many communities, he said. They also spurred "the most extreme forest fire period in Sweden and Norway in modern history."
Arctic warming kicked into high gear in Scandinavia about 15 to 20 years ago, said Lars Holger Pilö, an archaeologist who scours melting snow fields and ice patches for remnants of ancient civilizations.
In addition to bringing floods, landslides and wildfires, the heat is also affecting wildlife, he said. Reindeer, for example, seek out snow and ice patches to avoid biting bugs during the summer. As those refuges melt away, they move around more and eat less, which reduces the weight of calves, leaving them less likely to survive the following winter. The reindeer are also affected by winter melts, which, when they refreeze, form ice caps over the animals' forage, making it harder for them to find any food at all, he said.
The current pace of warming in the Arctic has generally been underestimated by climate models, said Xavier Fettweis, a University of Liége climate researcher who focuses on polar regions. Only the models showing the highest levels of warming of the climate by greenhouse gases match the current rate of warming, he said.
As if to underscore that point, Fettweis recently posted on Twitter that new record high temperatures may have been recorded near the North Pole on July 5 and July 6. If the current trend in greenhouse gas emissions continues, the Arctic could heat up by as much as 29 degrees Fahrenheit by 2100, according to new climate models, he said.
Penn State climate scientist Michael Mann said the heat wave in Siberia is "consistent overall with a slower, wavier jet stream, leading to more persistent weather extremes." Several recent studies have shown how global warming can cause those jet stream changes, he said.
He also noted that weather extremes in the High North have exceeded most climate models' projections because those computer simulations are based on broad climate averages over wide areas. They also can't account very well for the impacts of vicious cycles of warming like those involving permafrost and wildfires.
"This is indeed part of a larger pattern of record weather extremes in recent years that undoubtedly are exacerbated by human-caused climate change," he said.