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When it comes to global warming and sea level rise, scientists have made some dire predictions. One of the most calamitous involves the widespread collapse of ice cliffs along the edges of Greenland and Antarctica, which could raise sea level as much as 4 meters by 2200 (SN: 2/6/19). Now, new simulations suggest that massive glaciers flowing into the sea may not be as vulnerable to such collapses as once believed.

One hypothesis that projected calamitous sea level rise is called the marine ice cliff instability. It suggests that sea-facing bluffs of ice more than 100 meters tall will fail and then slough off to expose fresh ice. Those new cliffs will in turn disintegrate, fall into the sea and float away, setting off a relatively rapid retreat of the glacier that boosts sea level rise.

Although discussed for years, the phenomenon hasn’t yet been seen in today’s glaciers, says Jeremy Bassis, a glaciologist at the University of Michigan in Ann Arbor. “But that may not be surprising, due to the relatively short record of observations in the field and by satellites,” he says.

Because of the dearth of field data, Bassis and colleagues decided to use computer simulations to explore ice-cliff behavior. Unlike previous models, the researchers’ simulations considered how ice flows under pressure as well as how it fractures when highly stressed. This blended model is “a pioneering composite,” says Nicholas Golledge, a glaciologist at the Victoria University of Wellington in New Zealand, who wasn’t involved in the study.

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First, the researchers simulated the collapse of a 135-meter-tall ice cliff on dry land. Over a virtual period of weeks, the face of the cliff shattered and then slumped down to the base, where the icy rubble helped buttress the cliff against further collapse. Researchers have often seen this result in the field, Bassis says.

Then, the team simulated a 400-meter-tall glacier flowing into water that was 290 meters deep. These dimensions are typical of some of the massive glaciers in Greenland flowing into deep fjords, Bassis says. When the cybercliff collapsed, ice that fell into the water at the cliff’s base floated away, leading to repeated failures and rapid, runaway collapse of the glacier. But adding even a small amount of back pressure at the base of the cliff — as would happen if icebergs got stuck and couldn’t waft away, or if they froze in place — prevented a runaway collapse, Bassis and his team reports in the June 18 Science. “We didn’t expect this to be the case,” Bassis says. “But if small bergs got stuck in the shallows ahead of the ice cliff, it was enough to buttress the [cliff] face,” he says.

Simulations of an 800-meter-tall glacier flowing into 690 meters of water, comparable to the dimensions of the Thwaites and Pine Island glaciers in Antarctica, yielded similar results. The researchers also found that in relatively warm ambient temperatures, ice flow upstream of the cliff thins the glacier and reduces the height of the cliff, thus reducing the likelihood of runaway collapses.

The team’s simulations “capture what I think of as realistic behavior,” says Golledge, who coauthored a commentary on the study in the same issue of Science. Future fieldwork may help validate the group’s results. If the simulations hold, Golledge says, the less dire results may mean slower sea level rise in the short term than otherwise predicted.

Bassis and his colleagues’ analysis “is an important piece of work,” says Ted Scambos, a glaciologist at the University of Colorado Boulder, who was not involved in the study. The results, he says, “provide a balance between the possibilities for extreme runaway collapse and some that are more realistic.” More

There’s a new normal for U.S. weather. On May 4, the National Oceanic and Atmospheric Administration announced an official change to its reference values for temperature and precipitation. Instead of using the average values from 1981 to 2010, NOAA’s new “climate normals” will be the averages from 1991 to 2020.

This new period is the warmest on record for the country. Compared with the previous 30-year-span, for example, the average temperature across the contiguous United States rose from 11.6° Celsius (52.8° Fahrenheit) to 11.8° C (53.3° F). Some of the largest increases were in the South and Southwest — and that same region also showed a dramatic decrease in precipitation (SN: 8/17/20).  

The United States and other members of the World Meteorological Organization are required to update their climate normals every 10 years. These data put daily weather events in historical context and also help track changes in drought conditions, energy use and freeze risks for farmers.

That moving window of averages for the United States also tells a stark story about the accelerating pace of climate change. When each 30-year period is compared with the average temperatures from 1901 to 2000, no part of the country is cooler now than it was during the 20th century. And temperatures in large swaths of the country, from the American West to the Northeast, are 1 to 2 degrees Fahrenheit higher. More

If a tree farts in the forest, does it make a sound? No, but it does add a smidge of greenhouse gas to the atmosphere.

Gases released by dead trees — dubbed “tree farts” — account for roughly one-fifth of the greenhouse gases emitted by skeletal, marshy forests along the coast of North Carolina, researchers report online May 10 in Biogeochemistry. While these emissions pale in comparison with other sources, an accurate accounting is necessary to get a full picture of where climate-warming gases come from.

A team of ecologists went sniffing for tree farts in ghost forests, which form when saltwater from rising sea levels poisons a woodland, leaving behind a marsh full of standing dead trees. These phantom ecosystems are expected to expand with climate change, but it’s unclear exactly how they contribute to the world’s carbon budget.

“The emergence of ghost forests is one of the biggest changes happening in response to sea level rise,” says Keryn Gedan, a coastal ecologist at George Washington University in Washington, D.C., who was not involved in the work. “As forests convert to wetlands, we expect over long timescales that’s going to represent a substantial carbon sink,” she says, since wetlands store more carbon than forests. But in the short term, dead trees decay and stop taking up carbon dioxide through photosynthesis, “so that’s going to be a major greenhouse gas source.”

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To better understand how ghost forests pass gas into the atmosphere, the researchers measured greenhouse gases wafting off dead trees and soil in five ghost forests on the Albemarle-Pamlico Peninsula in North Carolina. “It’s kind of eerie” out there, says Melinda Martinez, a wetland ecologist at North Carolina State University in Raleigh.

But Martinez ain’t afraid of no ghost forest. In 2018 and 2019, she measured CO2, methane and nitrous oxide emissions from dead trees using a portable gas analyzer she toted on her back. “I definitely looked like a ghostbuster,” she says.

Wetland ecologist Melinda Martinez totes a portable gas analyzer on her back to measure the “tree farts” emitted by a ghost forest tree. A tube connects the gas analyzer to an airtight seal around the trunk of the tree.M. Ardón

Soils gave off most of the greenhouse gases from the ghost forests. Each square meter of ground emitted an average 416 milligrams of CO2, 5.9 milligrams of methane and 0.1 milligrams of nitrous oxide per hour. On average, dead trees released about 116 milligrams of CO2, 0.3 milligrams of methane and 0.04 milligrams of nitrous oxide per square meter per hour — totaling about one-fourth the soil’s emissions.

Measuring greenhouse gases from the trees is “kind of measuring the last breath of these forests,” says Marcelo Ardón, an ecosystems ecologist and biogeochemist at North Carolina State University. The dead trees “don’t emit a ton, but they are important” to a ghost forest’s overall emissions.

Ardón coined the term “tree farts” to describe the dead trees’ greenhouse gas emissions. “I have an 8-year-old and an 11-year-old, and fart jokes are what we talk about,” he explains. But the analogy has a biological basis, too. Actual farts are caused by microbes in the body; the greenhouse gases emitted by ghost forests are created by microbes in the soil and trees.

In the grand scheme of carbon emissions, ghost forests’ role may be minor. Tree farts, for instance, have nothing on cow burps (SN: 11/18/15). A single dairy cow can emit up to 27 grams of methane — a far more potent greenhouse gas than CO2 — per hour. But accounting for even minor sources of carbon is important for fine-tuning our understanding of the global carbon budget, says Martinez (SN: 10/1/19). So it would behoove scientists not to turn up their noses at ghost tree farts.   More

Winter usually kills most forest fires. But in the boreal woods that encircle the far North, some fires, like zombies, just don’t die. 

The first broad scientific look at overwintering “zombie fires” reveals these rare occurrences can flare up the year after warmer-than-normal summers and account for up to 38 percent of the total burn area in some regions, researchers report online May 19 in Nature. As climate change accelerates in boreal forests, the frequency of zombie fires could rise and exacerbate warming by releasing more greenhouse gases from the region’s soils, which may house twice as much carbon as Earth’s atmosphere (SN: 4/11/19).

Zombie fires hibernate underground. Blanketed by snow, they smolder through the cold, surviving on the carbon-rich fuel of peat and boreal soil and moving very slowly — just 100 to 500 meters over the winter. Come spring, the fires reemerge near the forest they previously charred, burning fresh fuel well before the traditional fire season starts. Until now, these zombie fires have remained relatively mysterious to science, known mostly from firefighter anecdotes.

Strange coincidences on satellite images, however, got the attention of earth systems scientist Rebecca Scholten and her colleagues. “My adviser noticed that some years, new fires were starting very close to the previous year’s fire,” says Scholten, of Vrije University Amsterdam. This is unusual, she says, since boreal fires are usually sparked by random lightning or human activity. Local fire managers confirmed that these were the same fires, prompting the researchers to wonder just how often fires overwinter.

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To find evidence of underground fires, the researchers combined firefighter reports with satellite images of Alaska and northern Canada captured from 2002 to 2018. They looked for blazes that started close to the scars left the previous year and that began before midsummer, when lightning-sparked fires usually occur.

The team found that zombie fires are rare, accounting for 0.8 percent of the total area burned by forest fires in these regions over those 16 years, but there was lots of variability. In 2008, one zombie fire burned approximately 13,700 hectares in Alaska, about 38 percent of all burned areas that year in that state. Zombie fires were more likely to occur, and burn larger swaths of land, after warmer summers that allowed fires to reach deeper into the soil, the researchers found.

Boreal forests are warming faster that the global average and “we’re seeing more hot summers and more large fires and intense burning,” Scholten says. That might set the stage for zombie fires to play a bigger role.

“This is a really welcome advance which could help fire management,” says Jessica McCarty, a geographer at Miami University in Oxford, Ohio, who wasn’t involved in the study. Understanding when zombie fires are more likely to occur could help firefighters identify these areas early, she says, protecting fragile landscapes that house a lot of climate warming gases.

“Some of these soils are thousands of years old,” McCarty says. While “areas we thought were fire resistant are now fire prone” due to climate change, she says, better fire management can make a difference. “We’re not helpless.” More

Over the last four decades, a highly organized, well-funded campaign powered by the fossil fuel industry has sought to discredit the science that links global climate change to human emissions of carbon dioxide and other greenhouse gases. These disinformation efforts have sown confusion over data, questioned the integrity of climate scientists and denied the scientific consensus on the role of humans.

Such disinformation efforts are outlined in internal documents from fossil fuel giants such as Shell and Exxon. As early as the 1980s, oil companies knew that burning fossil fuels was altering the climate, according to industry documents reviewed at a 2019 U.S. House of Representatives Committee on Oversight and Reform hearing. Yet these companies, aided by some scientists, set out to mislead the public, deny well-established science and forestall efforts to regulate emissions.

But the effects of climate change on extreme events such as wildfires, heat waves and hurricanes have become hard to downplay (SN: 12/19/20 & SN: 1/2/21, p. 37). Not coincidentally, climate disinformation tactics have shifted from outright denial to distraction and delay (SN: 1/16/21, p. 28).

As disinformation tactics evolve, researchers continue to test new ways to combat them. Debunking by fact-checking untrue statements is one way to combat climate disinformation. Another way, increasingly adopted by social media platforms, is to add warning labels flagging messages as possible disinformation, such as the labels Twitter and Facebook (which also owns Instagram) began adding in 2020 regarding the U.S. presidential election and the COVID-19 pandemic.

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At the same time, Facebook was sharply criticized for a change to its fact-checking policies that critics say enables the spread of climate disinformation. In 2019, the social media giant decided to exempt posts that it determines to be opinion or satire from fact-checking, creating a potentially large disinformation loophole.

In response to mounting criticism, Facebook unveiled a pilot project in February for its users in the United Kingdom, with labels pointing out myths about climate change. The labels also point users to Facebook’s climate science information center.

For this project, Facebook consulted several climate communication experts. Sander van der Linden, a social psychologist at the University of Cambridge, and cognitive scientist John Cook of George Mason University in Fairfax, Va., helped the company develop a new “myth-busting” unit that debunks common climate change myths — such as that scientists don’t agree that global warming is happening.

Cook and van der Linden have also been testing ways to get out in front of disinformation, an approach known as prebunking, or inoculation theory. By helping people recognize common rhetorical techniques used to spread climate disinformation — such as logical fallacies, relying on fake “experts” and cherry-picking only the data that support one view — the two hope to build resilience against these tactics.

This new line of defense may come with a bonus, van der Linden says. Training people in these techniques could build a more general resilience to disinformation, whether related to climate, vaccines or COVID-19.

Science News asked Cook and van der Linden about debunking conspiracies, collaborating with Facebook and how prebunking is (and isn’t) like getting vaccinated. The conversations, held separately, have been edited for brevity and clarity.

We’ve seen both misinformation and disinformation used in the climate change denial discussion. What’s the difference?

van der Linden: Misinformation is any information that’s incorrect, whether due to error or fake news. Disinformation is deliberately intended to deceive. Then there’s propaganda: disinformation with a political agenda. But in practice, it’s difficult to disentangle them. Often, people use misinformation because it’s the broadest category.

Has there been a change in the nature of climate change denialism in the last few decades?

Cook: It is shifting. For example, we fed 21 years of [climate change] denial blog posts from the U.K. into a machine learning program. We found that the science denialism misinformation is gradually going down — and solution misinformation [targeting climate policy and renewable energy] is on the rise [as reported online in early March at SocArXiv.org].

As the science becomes more apparent, it becomes more untenable to attack it. We see spikes in policy misinformation just before the government brings in new science policy, such as a carbon pricing bill. And there was a huge spike before the [2015] Paris climate agreement. That’s what we will see more of over time.

How do you hope Facebook’s new climate change misinformation project will help?

Cook: We need tech solutions, like flagging and tagging misinformation, as well as social media platforms downplaying it, so [the misinformation] doesn’t get put on as many people’s feeds. We can’t depend on social media. A look behind the curtain at Facebook showed me the challenge of getting corporations to adequately respond. There are a lot of internal tensions.

van der Linden: I’ve worked with WhatsApp and Google, and it’s always the same story. They want to do the right thing, but don’t follow through because it hurts engagement on the platform.

But going from not taking a stance on climate change to taking a stance, that’s a huge win. What Facebook has done is a step forward. They listened to our designs and suggestions and comments on their [pilot] test.

We wanted more than a neutral [label directing people to Facebook’s information page on climate change], but they wanted to test the neutral post first. That’s all good. It’ll be a few months at least for the testing in the U.K. phase to roll out, but we don’t yet know how many other countries they will roll it out to and when. We all came on board with the idea that they’re going to do more, and more aggressively. I’ll be pleasantly surprised if it rolls out globally. That’s my criteria for success.

Scientists have been countering climate change misinformation for years, through fact-checking and debunking. It’s a bit like whack-a-mole. You advocate for “inoculating” people against the techniques that help misinformation spread through communities. How can that help?

van der Linden: Fact-checking and debunking is useful if you do it right. But there’s the issue of ideology, of resistance to fact-checking when it’s not in line with ideology. Wouldn’t life be so much easier if we could prevent [disinformation] in the first place? That’s the whole point of prebunking or inoculation. It’s a multilayer defense system. If you can get there first, that’s great. But that won’t always be possible, so you still have real-time fact-checking. This multilayer firewall is going to be the most useful thing.

You’ve both developed online interactive tools, games really, to test the idea of inoculating people against disinformation tactics. Sander, you created an online interactive game called Bad News, in which players can invent conspiracies and act as fake news producers. A study of 15,000 participants reported in 2019 in Palgrave Communications showed that by playing at creating misinformation, people got better at recognizing it. But how long does this “inoculation” last?

van der Linden: That’s an important difference in the viral analogy. Biological vaccines give more or less lifelong immunity, at least for some kinds of viruses. That’s not the case for a psychological vaccine. It wears off over time.

In one study, we followed up with people [repeatedly] for about three months, during which time they didn’t replay the game. We found no decay of the inoculation effect, which was quite surprising. The inoculation remained stable for about two months. In [a shorter study focused on] climate change misinformation, the inoculation effect also remained stable, for at least one week.

John, what about your game Cranky Uncle? At first, it focused on climate change denial, but you’ve expanded it to include other types of misinformation, on topics such as COVID-19, flat-earthism and vaccine misinformation. How well do techniques to inoculate against climate change denialism translate to other types of misinformation?

Cook: The techniques used in climate denial are seen in all forms of misinformation. Working on deconstructing [that] misinformation introduced me to parallel argumentation, which is basically using analogies to combat flawed logic. That’s what late night comedians do: Make what is obviously a ridiculous argument. The other night, for example, Seth Meyers talked about how Texas blaming its [February] power outage on renewable energy was like New Jersey blaming its problems on Boston [clam chowder].

My main tip is to arm yourself with awareness of misleading techniques. Think of it like a virus spreading: You don’t want to be a superspreader. Make sure that you’re wearing a mask, for starters. And when you see misinformation, call it out. That observational correction — it matters. It makes a difference. More