Climate

Climate change is warming the Arctic tundra about four times faster than the rest of the planet. Now, a study suggests that rising temperatures will spur underground microbes there to produce more carbon dioxide — potentially creating a feedback loop that worsens climate change.The tundra is “a sleepy biome,” says Sybryn Maes, an environmental scientist at Umeå University in Sweden. This ecosystem is populated by small shrubs, grasses and lichen growing in cold soils rich with stored organic carbon. Scientists have long suspected that warming will wake this sleeping giant, prompting soil microbes to release more of the greenhouse gas CO2 (SN: 8/11/22). But it’s been difficult to demonstrate in field studies.

Maes’ team included about 70 scientists performing measurements in 28 tundra regions across the planet’s Arctic and alpine zones. During the summer growing season, the researchers placed clear, open-topped plastic chambers, each about a meter in diameter, over patches of tundra. These chambers let in light and precipitation but blocked the wind, warming the air inside by an average of 1.4 degrees Celsius. The researchers monitored how much CO2 microbes in the soil released into the air, a process called respiration, and compared that data with measurements from nearby exposed patches. More

A torrent of giant hailstones in northeast Spain may have been fueled by climate change.

On August 31, 2022, a brutal hailstorm struck the small Spanish city of La Bisbal d’Empordà. The storm unleashed balls of ice up to 12 centimeters wide, causing widespread damage to property and crops, injuring dozens of people and killing a 20-month-old toddler. Computer simulations now suggest that in a preindustrial climate, the storm could not have generated hailstones this big, researchers report in the March 28 Geophysical Research Letters.   More

Earth’s largest ecosystem is broiling. Every day for the last 12 months, the average temperature of most of the sea’s surface has been the highest ever recorded on that calendar date, preliminary data from the National Oceanic and Atmospheric Administration show.

“And we’re currently outpacing last year,” says Robert West, a NOAA meteorologist in Miami. “We’re continuing to set records, even now over last year’s records.”

One of the primary reasons that global sea surface temperatures are so high is El Niño, a natural climate phenomenon that involves warm surface waters spreading across the tropical Pacific Ocean. El Niño is a recurring event, and this one emerged late last spring (SN: 7/13/23). More

On the MoveAbrahm LustgartenFarrar, Straus and Giroux, $30

Ellen Herdell’s nerves were nearing a breaking point. The fortysomething, lifelong Californian had noticed her home was increasingly threatened by wildfires. After relatives lost their house to a blaze and the constant threat traumatized her 9-year-old daughter, Herdell found herself up at 3 a.m. one night in 2020 searching Zillow for homes in Vermont.

She’s not alone. Across the United States, people facing extreme fires, storms, floods and heat are looking for the escape hatch. In On the Move, Abrahm Lustgarten examines who these people are, where they live, where climate change may cause them to move and how this reshuffling will impact the country (SN: 5/12/20). More

For those who enjoy pondering the Roman Empire’s rise and fall — you know who you are — consider the close link between ancient climate change and infectious disease outbreaks. 

Periods of increasingly cooler temperatures and rainfall declines coincided with three pandemics that struck the Roman Empire, historian Kyle Harper and colleagues report January 26 in Science Advances. Reasons for strong associations between cold, dry phases and those disease outbreaks are poorly understood. But the findings, based on climate reconstructions from around 200 B.C. to A.D. 600, help “us see that climate stress probably contributed to the spread and severity of [disease] mortality,” says Harper, of the University of Oklahoma in Norman.   More

Numbats are curious creatures. The only marsupials that are active solely during the day, when they scratch at soil and rotting logs for termites, these squirrel-sized animals are built to hoard body heat. But that same energy-saving trait may put the already endangered animals at risk as the climate warms, a new study suggests.

Already, even brief sun exposure on days over 23° Celsius (73° Fahrenheit) can severely limit the time the Australian marsupials can spend foraging, researchers report January 11 in the Journal of Experimental Biology. Numbats might rapidly overheat in the sun, even at relatively reasonable temperatures, the team finds. More

SAN FRANCISCO — Several Antarctic glaciers are undergoing dramatic acceleration and ice loss. Hektoria Glacier, the worst affected, has quadrupled its sliding speed and lost 25 kilometers of ice off its front in just 16 months, scientists say.

The rapid retreat “is really unheard of,” says Mathieu Morlighem, a glaciologist at Dartmouth College who was not part of the team reporting these findings.

The collapse was triggered by unusually warm ocean temperatures, which caused sea ice to retreat. This allowed a series of large waves to hit a section of coastline that is normally shielded from them. “What we’re seeing here is an indication of what could happen elsewhere” in Antarctica, says Naomi Ochwat, a glaciologist at the University of Colorado Boulder who presented the findings December 11 at the American Geophysical Union meeting.

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Hektoria Glacier, Green Glacier, and Crane Glacier sit near the tip of the Antarctic Peninsula, which reaches up toward South America. The crescent moon–shaped bay, called the Larsen B Embayment, once seemed stable. As these glaciers oozed off the coastline, their ice used to merge into a floating slab around 200 meters thick. This slab, called the Larsen B Ice Shelf, was about the size of Rhode Island and filled the entire bay.

Having existed for over 10,000 years, this ice shelf buttressed and stabilized the glaciers flowing into it. But during a warm summer in 2002, it suddenly fragmented into thousands of skinny icebergs (SN: 3/27/02).

Hektoria, Green, and Crane glaciers — no longer contained by the ice shelf —  began to flow into the ocean several times faster than they had before, shedding billions of tons of ice over the next decade.

Then starting in 2011, the hemorrhaging slowed down. The thin veneer of sea ice that forms over the bay each winter began to persist year round, preserved by a series of cold summers. This “landfast ice,” attached firmly to the coastline, grew five to 10 meters thick, stabilizing the glaciers. Their floating tongues gradually advanced back into the bay. But things changed abruptly in early 2022. On January 19 and 20, the landfast ice disintegrated into fragments, which drifted away.

Satellite images taken just 10 days apart reveal the dramatic breakup of sea ice in Antarctica’s Larsen B Embayment. On January 16, 2022, sea ice filled the bay (left). By January 26 (right), the ice had fractured and was drifting away following a series of powerful waves that struck the bay several days earlier. Left: Joshua Stevens, MODIS/LANCE/EOSDIS/NASA, WORLDVIEW/GIBS/NASARight: Joshua Stevens, MODIS/LANCE/EOSDIS/NASA, WORLDVIEW/GIBS/NASA

Using data from ocean buoys farther north, Ochwat and colleagues determined that a series of powerful waves, higher than 1.5 meters, had swept in from the northeast — cracking apart the landfast ice. Those waves were highly unusual for this area.

The Southern Ocean, which encircles Antarctica, holds some of the world’s roughest waters. The Antarctic Peninsula extends up into this turbulent region, but its east side, where the Larsen B Embayment sits, rarely feels the waves. It is normally protected by several hundred kilometers of pack ice — floes of sea ice, pressed together by ocean currents — that dampen the waves, leaving the waters near Larsen as flat as a mirror.

In 2022, water temperatures near the surface of the Southern Ocean rose several tenths of a degree Celsius higher than normal, causing pack ice to shrink and peel away from the peninsula. This exposed the area to waves, which then broke up the landfast sea ice.

The glaciers accelerated as their floating tongues, no longer held in place, fragmented into bergs. Crane Glacier lost 11 kilometers of ice, nearly erasing its floating tongue; Green Glacier lost 18 kilometers, encompassing all of its floating ice.

Hektoria lost all 15 kilometers of its floating ice — followed by another 10 kilometers of ice that is normally more stable, because it rests on the seafloor. That “is faster than any tidewater glacier retreat that we know of,” Ochwat says.

The previous standout, Alaska’s Columbia Glacier, had lost 20 kilometers of ice in 30 years, records show. But Hektoria lost its 10 kilometers of nonfloating ice in just five months — including 2.5 kilometers that crumbled in a 3-day period.

All of this suggests that people trying to predict sea level rise need to consider sea ice, Morlighem says. Up until now, “its role in [glacier] dynamics has been completely ignored.”

Ochwat is waiting to see what will happen as the current Antarctic summer heats up between December and March. Hektoria and the other glaciers have been retreating only during summer months, when sea ice is absent; they pause during winter, when the surface of the bay freezes for a few months.

If Antarctic sea ice continues to shrink, as it has since 2022, it could spell trouble, says study coauthor Ted Scambos, a glaciologist also at UC Boulder. “You’re going to have a longer section of coastline where wave action can act on the front of ice shelves and glaciers,” potentially accelerating glacial retreat. More

Days of contentious wrangling in Dubai at the United Nations’ 28th annual climate summit ended December 13 with a historic agreement to “transition away” from fossil fuels and accelerate climate action over the next decade. The organization touted the agreement as a moment of global solidarity, marking “the beginning of the end” of the fossil fuel era.

But the final agreement reached at COP28, signed by nearly 200 nations, did not include language that explicitly mandated phasing out fossil fuel energy, deeply frustrating many nations as well as climate scientists and activists.

The agreement is considered the world’s first “global stocktake,” an inventory of climate actions and progress made since the 2015 Paris Agreement to limit global warming to “well below” 2 degrees Celsius above the preindustrial average (SN: 12/12/15).

It acknowledges the conclusions of scientific research that greenhouse gas emissions will need to be cut by 43 percent by 2030 compared with 2019 levels, in order to limit global warming to 1.5 degrees Celsius by the end of the century. It then calls on nations to speed up climate actions before 2030 so as to reach global net zero by 2050 — in which greenhouse gases entering the atmosphere are balanced by their removal from the atmosphere. Among the actions called for are increasing global renewable energy generation, phasing down coal power and phasing out fossil fuel subsidies.

But among many scientists gathered in San Francisco at the American Geophysical Union’s annual meeting to discuss climate change’s impacts to Earth’s atmosphere, polar regions, oceans and biosphere, the reaction to the language in the agreement was more frustrated than celebratory.

“The beginning of the end? I wish it was the middle of the end,” says climate scientist Luke Parsons of the Nature Conservancy, who is based in Durham, N.C. “But you have to start somewhere, I guess.”

It is a step forward, says Ted Scambos, a glaciologist at the University of Colorado Boulder. “Saying it out loud, that we are aiming to phase out fossil fuels, is huge.”

It’s not a moment too soon: The globe is already experiencing many climate change–linked extreme weather events, including the hottest 12 months ever recorded (SN: 11/9/23). Still, Scambos says, “it’s a tribute to the science and the negotiators that we can take this step now, before the disastrous global impacts truly get underway.” But, he added, “I fear that the pace [of future climate action] will … still be driven by impacts arriving at our collective doors.”

Other researchers had a grimmer take.

“It was weak sauce,” says climate scientist Michael Mann of the University of Pennsylvania. “What we really need is a commitment to phase out fossil fuels, on a very specific timeline: We’re going to reduce carbon emissions by 50 percent this decade, bring them down to zero mid-century. Instead, they agreed to transition away from fossil fuels — the analogy that I use is, you’re diagnosed with diabetes, and you tell your doctor you’re going to transition away from doughnuts. That’s not going to cut it. It didn’t meet the moment.”

Eric Rignot, a glaciologist at the University of California, Irvine, called the agreement “deeply disappointing and misleading,” noting that it didn’t include any language specifically calling for phasing out fossil fuels. Furthermore, he says, “COP28 keeps entertaining the idea that 1.5 degrees Celsius may be achievable, but everyone is offtrack to meet that goal. [And] for ice sheets and glaciers, even 1.5 degrees is not sustainable.”  There already are fears, for instance, that the melting of Greenland’s ice sheet can’t be stopped (SN: 8/9/21).

Even if the world stays close to that average temperature, “the ice sheets are going to be retreating,” says Rob DeConto, a glaciologist at the University of Massachusetts at Amherst. “But you start getting out toward the end of the century, and all hell is going to break loose if we go much above 1.5. You’re talking about actually exceeding the limits of adaptation around so much of our coastlines.”  

On December 12, the eighth anniversary of the signing of the Paris Agreement, the European Union’s Copernicus Climate Change Service noted that the world has, in effect, “lost” 19 years by delaying action to reduce fossil fuel emissions. Back in 2015, climate projections suggested that Earth’s average temperature would reach the 1.5 degrees C threshold by the year 2045 — then 30 years away. Now, projections show that the planet may reach that benchmark by 2034, just 11 years in the future.

“We’ve got a shrinking window of opportunity,” Mann says. “And that window of opportunity will close if we don’t make dramatic and immediate reductions to our carbon emissions.” More