Climate

The deadly heat wave that baked the Pacific Northwest in late June would have been “virtually impossible” without human-caused climate change, an international team of scientists announced July 7.

In fact, the temperatures were so extreme — Portland, Ore., reached a staggering 47° Celsius (116° Fahrenheit) on June 29, while Seattle surged to 42° C (108° F) — that initial analyses suggested they were impossible even with climate change, Geert Jan van Oldenborgh, a climate scientist with the Royal Netherlands Meteorological Institute in De Bilt, said at a news conference to announce the team’s findings. “This was an extraordinary event. I don’t know what English word covers it.”

Climate change due to greenhouse gas emissions made the region’s heat wave at least 150 times more likely to occur, the team found. As emissions and global temperatures continue to rise, such extreme heat events could happen in the region as often as every five to 10 years by the end of the century.  

It’s not just that numerous temperature records were broken, van Oldenborgh said. It’s that the observed temperatures were so far outside of historical records, breaking those records by as much as 5 degrees C in many places — and a full month before usual peak temperatures for the region. The observations were also several degrees higher than the upper temperature limits predicted by most climate simulations for the heat waves, even taking global warming into account.

Coming just about a week after the heat wave broke, the new study is the latest real-time climate attribution effort by scientists affiliated with the World Weather Attribution network. Van Oldenborgh and University of Oxford climate scientist Friederike Otto founded the group in 2014 to conduct quick analyses of extreme events such as the 2020 Siberian heat wave (SN: 7/15/20).

In the current study, 27 researchers focused on how the observed temperatures from June 27 to June 29 compared with annual maximum temperatures over the last 50 years for locations across the northwestern United States and southwestern Canada. The team then used 21 different climate simulations of temperatures to analyze the intensity of such a heat wave in the region with and without the influence of greenhouse gas warming.

Earth has already warmed by about 1.2 degrees C relative to preindustrial times. That warming, the researchers determined, increased the intensity of the heat wave by about 2 degrees C. Once global warming increases to 2 degrees C, future heat waves may become even more intense (SN: 12/17/18). Those heat waves could be another 1.3 degrees C hotter, the researchers found.

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That poses a real danger. The late June heat wave took a painful toll (SN: 6/29/21), killing several hundred people — “almost certainly” an underestimate, the researchers say. On June 29, Lytton, a small village in British Columbia, set an all-time Canadian temperature record of 49.6° C (121.3° F). The heat may have exacerbated wildfires that, a day later, swept through British Columbia’s Fraser Canyon region, burning 90 percent of the village, according to local officials. Meanwhile, the U.S. West and southwestern Canada are already bracing for another round of soaring temperatures.

One possible reason for the startling intensity of this heat wave is that, while climate change amped up the temperatures, what happened was still a very rare, unlucky event for the region. How rare isn’t easy to say, given that the observed temperatures were so far off the charts, the researchers say. Under current climate conditions, simulations suggest that such a heat wave might occur once every 1,000 years — but these events will become much more common in future as the climate changes.

By the end of June 2021, more than 40 wildfires burned across Canada’s British Columbia, exacerbated by extreme dryness and the intense heat. One fire burned 90 percent of the town of Lytton, which had set a new temperature record for the country the day before. The fire also generated a massive storm-producing plume of smoke called a pyrocumulonimbus cloud.NASA

Another possibility is grimmer: Climate simulations may not accurately capture what really happens during extreme heat waves. “Climate science has been a bit complacent” about simulating heat waves, assuming that heat wave temperatures would increase linearly along with rising global temperatures, Otto said. But now, Earth’s climate system may have entered a new state in which other climatic factors, such as drier soils or changes to jet stream circulation, are exacerbating the heat in more difficult-to-predict, less linear ways.

The new study didn’t seek to determine which of these possibilities is true, though the team plans to tackle this question over the next few months. However, many scientists have already noted the inability of current climate models to capture what’s really going on.  

“I agree that it is virtually impossible that the [Pacific Northwest] heat wave would have occurred with the observed intensity in the absence of climate change,” Michael Mann, a climate scientist at Penn State who wasn’t involved in the attribution study, commented via e-mail. “But the models used don’t capture the jet stream phenomenon … that WE KNOW played an important role in this event.”

Disproportionate warming of the Arctic region alters temperature gradients high in the atmosphere, which can lead to a wavier jet stream, Mann wrote in the New York Times June 29. That waviness can exacerbate and prolong extreme weather events, such as the heat dome centered over the Pacific Northwest in late June.

This recent heat wave wasn’t just a major disaster, but also posed major scientific questions, van Oldenborgh said. Such an event “would have been judged impossible last year. All of us have just dialed down our certainty of how heat waves behave,” he added. “[We] are much less certain of how the climate affects heat waves than we were two weeks ago.” More

Like a lid on a steaming pot, a high-pressure system is sitting over the U.S. Pacific Northwest and British Columbia, Canada, sending temperatures in the region soaring to unprecedented heights.

From a historic perspective, the event is so rare and extreme as to be a once in a millennium heat wave. But one consequence of Earth’s rapidly changing climate is that such extreme events will become much more common in the region in future, says Larry O’Neill, a climate scientist at Oregon State University in Corvallis.

Temperatures in Portland, Ore., reached 115° Fahrenheit (46° Celsius) on June 29, the highest temperature recorded there since record-keeping began in 1940; average high temperatures for this time of year are about 73° F (23° C). Similar records were notched across the region and more are expected to be set as the high pressure system slowly slides east.

The heat was so extreme it melted transit power cables for Portland’s cable cars and caused asphalt and concrete roads in western Washington to expand and crack. Such high temperatures are particularly dangerous in a normally cool region little used to or prepared for it, raising the risk of heat-related deaths and other health hazards (SN: 4/3/18). Ground-level ozone levels, for instance, also reached the highest seen yet in 2021, the chemical reactions that form the gas amped up by a potent mix of high heat and strong ultraviolet light.

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O’Neill talked to Science News about three things to know about the heat wave.

1. The heat wave is linked to a stalled kink in the jet stream.

Jet streams, fast-moving currents of air high in the troposphere, encircle both poles, helping to push weather systems around Earth’s surface.  The current isn’t smooth and straight; it can meander and form large swirls, peaks and troughs surrounding zones of high- and low-pressure.

Occasionally, these weather patterns stall, becoming stationary “blocking events” that keep a particular spate of weather in place for an extended period of time. One such stalled-out high-pressure zone — basically a large dome of hot, dry weather — is now sitting atop the Pacific Northwest.

The punishing heatwave has an incredible jet stream pattern.The dome of heat will be encircled by the polar jet and this helps lift a sub-tropical jet branch almost into the Canadian Arctic. pic.twitter.com/uIWIIINlSc— Scott Duncan (@ScottDuncanWX) June 25, 2021
London-based meteorologist Scott Duncan tweets about the unusual heat (top) and the jet stream pattern (bottom) that created that heat dome over the Pacific Northwest. In the jet stream image, hot, dry air (in orange) swirls around and maintains a high-pressure system over the region from June 24 to June 29, locking that hot, dry air in place.

Historically, similar high-pressure patterns have brought heat waves to the region, O’Neill says. But this one is different. A typical severe heat wave in the past might lead to temperatures of about 100 °F, he says, “not 115 °F.”

2. Climate change is making the heat wave more severe.

Baseline temperatures were already higher than in the past, due to Earth’s changing climate. Globally, Earth’s average temperatures are increasing, with 2016 and 2020 tied for the hottest years on record (SN: 1/14/21).

Those changes are reflected in what’s now officially considered “normal.” In May, for example, the U.S. National Oceanographic and Atmospheric Administration reported that the country’s new baseline reference temperature, or “climate normal,” will be the period from 1991 to 2020 — also now the hottest 30-year period on record for the country (SN: 5/26/21).

That changing reference makes it tough to place such an unprecedented heat wave in any kind of historical context. “We have a historical data record that’s 100 years long,” O’Neill says. Saying that the heat wave is a once-in-a-millennium event means that “you would expect that, at random chance, this would occur once every 1,000 years. But we’ve never observed this. We have no basis to say this,” he adds. “This is a climate that we’re not accustomed to.”

3. Climate change is likely to make such extreme events more common in the future.

A week before the onset of the heat wave, forecasters were predicting such unprecedented temperatures for the region that many people dismissed those predictions as “being ridiculous,” O’Neill says. “Turns out, [the forecasters] were right.”

Future climate change attribution studies may shed some more light on the ways in which this particular heat wave may be linked to climate change (SN: 7/15/20). Overall, it’s known that climate change is likely to make such extreme events more common in the future, O’Neill says. “We’re seeing these highs form more frequently, and more persistently.” Extreme heat and extreme drought in the U.S. West, for example, can create a reinforcing cycle that exacerbates both (SN: 4/16/20).  

And that poses many dangers for the planet, not least for human health (SN: 4/3/18). In May, scientists reported in Nature Climate Change that 37 percent of heat-related deaths between 1991 and 2018 were attributable to human-caused climate change.  

“When we talk about climate change, often the conversation is a little more abstract,” O’Neill says. “We’re experiencing it right now (SN: 11/25/19). And this question about whether we adapt and mitigate — that’s something we have to figure out right now.” More

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

Rivers ravaged by a lengthy drought may not be able to recover, even after the rains return. Seven years after the Millennium drought baked southeastern Australia, a large fraction of the region’s rivers still show no signs of returning to their predrought water flow, researchers report in the May 14 Science.

There’s “an implicit assumption that no matter how big a disturbance is, the water will always come back — it’s just a matter of how long it takes,” says Tim Peterson, a hydrologist at Monash University in Melbourne, Australia. “I’ve never been satisfied with that.”

The years-long drought in southeastern Australia, which began sometime between 1997 and 2001 and lasted until 2010, offered a natural experiment to test this assumption, he says. “It wasn’t the most severe drought” the region has ever experienced, but it was the longest period of low rainfall in the region since about 1900.

Peterson and colleagues analyzed annual and seasonal streamflow rates in 161 river basins in the region from before, during and after the drought. By 2017, they found, 37 percent of those river basins still weren’t seeing the amount of water flow that they had predrought. Furthermore, of those low-flow rivers, the vast majority — 80 percent — also show no signs that they might recover in the future, the team found.

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Many of southeastern Australia’s rivers had bounced back from previous droughts, including a severe but brief episode in 1983. But even heavy rains in 2010, marking the end of the Millennium drought, weren’t enough to return these basins to their earlier state. That suggests that there is, after all, a limit to rivers’ resilience.

What’s changed in these river basins isn’t yet clear, Peterson says. The precipitation post drought was similar to predrought precipitation, and the water isn’t ending up in the streamflow, so it must be going somewhere else. The team examined various possibilities: The water infiltrated into the ground and was stored as groundwater, or it never made it to the ground at all — possibly intercepted by leaves, and then evaporating back to the air.

But none of these explanations were borne out by studies of these sites, the researchers report. The remaining, and most probable, possibility is that the environment has changed: Water is evaporating from soils and transpiring from plants more quickly than it did predrought.

Peterson has long suggested that under certain conditions rivers might not, in fact, recover — and this study confirms that theoretical work, says Peter Troch, a hydrologist at the University of Arizona in Tucson. Enhanced soil evaporation and plant transpiration are examples of such positive feedbacks, processes that can enhance the impacts of a drought. “Until his work, this lack of resilience was not anticipated, and all hydrological models did not account for such possibility,” Troch says.

“This study will definitely inspire other researchers to undertake such work,” he notes. “Hopefully we can gain more insight into the functioning of [river basins’] response to climate change.”

Indeed, the finding that rivers have “finite resilience” to drought is of particular concern as the planet warms and lengthier droughts become more likely, writes hydrologist Flavia Tauro in a commentary in the same issue of Science. More