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      What the pandemic can teach us about ways to reduce air pollution

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      The COVID-19 pandemic wasn’t just a shock to the human immune system. It was also a shock to the Earth system, dramatically changing the air quality in cities around the globe.
      As countries around the globe struggled to contain the disease, they imposed temporary shutdowns. Scientists are now sifting through data collected by satellite and on the ground to understand what this hiatus in human activities can tell us about the atmospheric cocktail that generates city pollution. Much of this preliminary data was shared at the American Geophysical Union annual meeting in December.
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      It was already known that peoples’ activities were curtailed enough to result in a dramatic drop in emissions of greenhouse gases in April, as well as a dip in the seismic noises produced by humans (SN: 5/19/20; SN: 7/23/20). That quiet period didn’t last, though, and carbon dioxide emissions began to climb back upward by the summer. April 2020 saw a drop of about 17 percent in global monthly CO2 emissions from fossil fuels, but by year’s end, annual CO2 emissions for the globe were only 7 percent lower than they were in 2019. That reduction was too brief, compared with the hundreds of years that the gas can linger in Earth’s atmosphere, to put a dent in the planet’s atmospheric CO2 level (SN: 8/7/20).

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      But in addition to briefly reducing emissions of climate-warming gases, this abrupt halt in many human activities — particularly commuter traffic — also created an unprecedented experiment for scientists to examine the complicated chemistry of atmospheric pollutants in cities. By altering the usual mix of pollutants hovering over cities, the shutdowns may help scientists better understand another longstanding misery for human health: poor air quality in many cities.
      That’s not to say that the pandemic has a silver lining, says Jessica Gilman, a tropospheric chemist at the National Oceanic and Atmospheric Administration in Boulder, Colo. “Misery is no solution to our global environmental challenges.”
      But there’s now a wealth of data from cities around the globe on how the pandemic altered regional or local concentrations of the precursors of ozone, a primary component of smog. Those precursors include nitrogen oxides and volatile organic compounds — both produced by traffic — as well as methane, produced by the oil and gas industry. With satellites, scientists are also able to assess how levels of these pollutants changed around the globe.
      Building a global picture of altered city pollution is no easy task, though. Researchers are finding that the pandemic’s impact on levels of various pollutants was highly regional, affected by differences in wind and rain as well as by photochemical interactions with sunlight — the intensity of which also changes with the season.  
      That stark variety of regional effects was evident in, for example, the different post-pandemic ozone levels in Denver and New York City. Nitrogen oxide gases produced by traffic are a powerful precursor to cities’ elevated ozone levels, which can damage the lungs and trigger respiratory ailments. The United States has made strides in reducing these gases over the last few decades — but there hasn’t been a corresponding drop in ozone levels, Dan Jaffe, an environmental chemist at the University of Washington Bothell, reported at the meeting on December 9.
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      The shutdowns gave researchers some insight into why, Jaffe says. From March 15 through July 23, New York City had a 21 percent decrease in nitrogen dioxide, one of several nitrogen oxide gases, in comparison with 2019 levels. Although the shutdowns were more stringent during the spring months, it turned out that summertime reductions in nitrogen dioxide were most strongly linked to the city’s change in ozone levels, the researchers found. “We see very strong reduction in summertime ozone this year,” Jaffe said at the meeting, citing unpublished data.
      That’s because in the summer months, heat and sunlight react with the precursor gases in the atmosphere, like nitrogen dioxide, creating a toxic cocktail. This kind of insight can be a boon to policy makers in a non-pandemic year, suggesting that nitrogen oxide regulations should focus most strongly on the summer, Jaffe says. “It’s really good evidence that NOx reductions extending into July in 2020 had an important impact.”
      In Denver, however, ozone didn’t drop so consistently — possibly because wildfires were beginning to rage across the U.S. West by the end of the summer (SN: 12/21/20). The fires produce nitrogen oxides, carbon monoxide and fine particles that can also help to increase ground-level ozone.
      “There are different patterns in different cities,” Jaffe says. “There are a lot of factors to sort out, and a lot of work to be done.” Armed with a wealth of new data from 2020, scientists hope to be able to make some headway. More

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      Plastic drinking water pipes exposed to high heat can leak hazardous chemicals

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      In August, a massive wildfire tore through the San Lorenzo Valley north of Santa Cruz, Calif., destroying almost 1,500 structures and exposing many others to extreme heat. Before the fire was even out, lab tests revealed benzene levels as high as 9.1 parts per billion in residential water samples — nine times higher than the state’s maximum safety level.
      This isn’t the first time the carcinogen has followed wildfires: California water managers found unsafe levels of benzene and other volatile organic compounds, or VOCs, in Santa Rosa after the Tubbs Fire in 2017, and in Paradise after the Camp Fire in 2018.
      Scientists suspected that, among other possibilities, plastic drinking water pipes exposed to extreme heat released the chemicals (SN: 11/13/20). Now, lab experiments show that’s possible.  
      Andrew Whelton, an environmental engineer at Purdue University in West Lafayette, Ind., and colleagues subjected commonly available pipes to temperatures from 200° Celsius to 400° C. Those temperatures, hot enough to damage but not destroy pipes, can occur as heat radiates from nearby flames, Whelton says.
      A plastic water pipe (left) and meter box (right) recovered from homes in Paradise, Calif., after the Camp Fire scorched the community in 2018 reveal the degree to which plastics can melt when exposed to high temperatures.Andrew Whelton/Purdue University (CC-BY-ND)
      When the researchers then submerged the pipes in water and cooled them, varying amounts of benzene and VOCs — more than 100 chemicals in some tests — leached from 10 of the 11 types of pipe into the water, the team reports December 14 in Environmental Science: Water Research & Technology.
      “Some contamination for the past fires likely originated from thermally damaged plastics,” says Whelton. It’s impossible to do experiments in the midst of a raging fire to pinpoint the exact source of the contamination, he says, but inspecting damaged pipes after the fact can suggest what temperatures they may have experienced.
      Benzene exposure can cause immediate health problems, including skin and throat irritation, dizziness, and longer-term effects such as leukemia. The team suggests testing drinking water if fire comes anywhere near your property and, if possible, replacing any plastic in a home’s water system with heat-resistant metal. More

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      A new iron-based catalyst converts carbon dioxide into jet fuel

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      Today, airplanes pump a lot of climate-warming carbon dioxide into the atmosphere. But someday, carbon dioxide sucked from the atmosphere could be used to power airplanes.
      A new iron-based catalyst converts carbon dioxide into jet fuel, researchers report online December 22 in Nature Communications. Unlike cars, planes can’t carry batteries big enough to run on electricity from wind or solar power. But if CO2, rather than oil, were used to make jet fuel, that could reduce the air travel industry’s carbon footprint — which currently makes up 12 percent of all transportation-related CO2 emissions.
      Past attempts to convert carbon dioxide into fuel have relied on catalysts made of relatively expensive materials, like cobalt, and required multiple chemical processing steps. The new catalyst powder is made of inexpensive ingredients, including iron, and transforms CO2 in a single step.
      When placed in a reaction chamber with carbon dioxide and hydrogen gas, the catalyst helps carbon from the CO2 molecules separate from oxygen and link up with hydrogen — forming the hydrocarbon molecules that make up jet fuel. The leftover oxygen atoms from the CO2 join up with other hydrogen atoms to form water.
      Tiancun Xiao, a chemist at the University of Oxford, and colleagues tested their new catalyst on carbon dioxide in a small reaction chamber set to 300° Celsius and pressurized to about 10 times the air pressure at sea level. Over 20 hours, the catalyst converted 38 percent of the carbon dioxide in the chamber into new chemical products. About 48 percent of those products were jet fuel hydrocarbons. Other by-products included similar petrochemicals, such as ethylene and propylene, which can be used to make plastics. More

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      Wildfires, heat waves and hurricanes broke all kinds of records in 2020

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      2020 was a year of unremitting extreme climate events, from heat waves to wildfires to hurricanes, many of which scientists have directly linked to human-caused climate change (SN: 8/27/20). Each event has taken a huge toll in lives lost and damages incurred. As of early October, the United States alone had weathered at least 16 climate- or weather-related disasters each costing more than $1 billion. The price tags of the late-season hurricanes Delta, Zeta and Eta could push the final 2020 tally of such expensive disasters even higher, setting a new record.
      With the COVID-19 pandemic dominating the news, some of these events may have already faded into memory. Here, Science News takes a look at this year of climate extremes.

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      Australia’s ‘black summer’
      The bushfires that burned southeastern Australia between July 2019 and March 2020 scorched roughly 11 million hectares and killed dozens of people. Climate change made those devastating fires at least 30 percent more likely to occur, researchers reported (SN: 3/4/20). The primary reason: a prolonged and severe heat wave that baked the country in 2019 and 2020, which itself was exacerbated by climate change.
      The intensity of Australia’s fires produced some striking sights. A particularly intense fire led to the formation of towering pyrocumulonimbus clouds that launched hundreds of thousands of metric tons of smoke into the stratosphere (SN: 6/15/20).
      One massive plume of smoke, wrapped in rotating winds, ascended to a record 31 kilometers in the atmosphere, deep into Earth’s protective ozone layer. Although it’s not clear what chemical scars it left, such a large smoke plume has the potential to trigger chemical reactions that destroy ozone.
      This injured koala, cared for at the Kangaroo Island Wildlife Park in January, was among the countless animals harmed or killed by the bushfires that blazed across Australia this year.Lisa Maree Williams/Getty Images
      The West on fire
      Record-setting wildfires in the U.S. West also produced heartbreaking images: raging blazes, orange skies, destroyed homes, neighborhoods enveloped in acrid smoke (SN: 9/18/20). By mid-November, more than 9,200 fires in California had burned about 1.7 million hectares — more than double the acreage burned in 2018, the state’s previous record fire year. Meanwhile, Colorado battled three of the largest wildfires in the state’s history. Combined, those fires burned more than 219,000 hectares.
      The role of climate change in these blazes is multipronged. From California to Colorado, rising temperatures due to climate change have led to earlier spring snow melting, resulting in drier vegetation by summer. In California, that extremely dry vegetation combined with a record-breaking heat wave primed the landscape for runaway fires (SN: 8/17/20).
      Climate change is increasing the frequency of extreme climate conditions. California’s average heat and dryness in both summer and autumn have become more severe, dramatically increasing the number of days each year prone to extreme fire weather conditions (SN: 8/27/20). Simulations of future climate change project increasing dryness over at least the next few decades — which means 2020’s fire records aren’t likely to stand for long.
      Siberian meltdown
      From January through July, Siberia was in the grips of a powerful heat wave that led to record-breaking temperatures (SN: 6/23/20), unprecedented wildfires in the Arctic and thawing permafrost, which in turn may have led to the collapse of a fuel storage tank that flooded nearby rivers with diesel fuel (SN: 7/1/20).
      A worker takes part in cleanup operations at a fuel spill in northern Russia. A heat wave thawed permafrost, which may have caused the collapse of a fuel tank in May that released about 20 million liters of diesel fuel.Denis Kozhevnikov/TASS/Getty Images
      Such heat in Siberia — with temperatures as high as 38° Celsius (about 100° Fahrenheit) — would have been impossible without climate change (SN: 7/15/20). Human influence made the heat wave at least 600 times as likely — and possibly as much as 99,000 times as likely, scientists reported. Moreover, the carbon dioxide churned into the atmosphere by this year’s Arctic wildfires also smashed the previous record for the region, set in 2019 (SN: 8/2/19). That CO2 can beget further warming, and the fires can also speed up permafrost thaw, which could add more of another greenhouse gas, methane, to the atmosphere.
      This year also saw the second-lowest extent of Arctic sea ice on record. Meanwhile, a roughly Manhattan-sized chunk of Canada’s Milne ice shelf — close to half of what had been the country’s last intact ice shelf — suddenly collapsed into the Arctic Ocean in August, carrying an ice-observing station away with it.
      Supercharged hurricanes
      As early as April, scientists predicted that the Atlantic hurricane season, which lasts from June 1 through November 30, would be busy, with about 18 named storms, compared with an average of 12 (SN: 4/16/20). By August, scientists upped their predictions to as many as 25 (SN: 8/7/20). But 2020 surpassed those expectations too: By mid-November, there were 30 named storms, eclipsing a record set in 2005 (SN: 11/10/20).
      Hurricane Laura (shown whipping up the waves near Galveston, Texas, on August 26) rapidly intensified into a Category 4 storm before making landfall on August 27 in Louisiana.Thomas B. Shea/Getty Images
      It’s difficult to link climate change to the number of storms that form in a given year. Very warm ocean waters, such as in the Atlantic Ocean this year, foster tropical cyclone formation. It’s true that those warm waters are linked to climate change, as the surface ocean swallows up excess heat from the atmosphere. But other factors are also involved in hurricane formation, including wind conditions, making it difficult to establish a link.
      But there are established links between warming oceans and increasing hurricane intensity, as well as rainfall (SN: 9/13/18). Warm Atlantic waters gave a boost to the intense storms of the 2017 hurricane season, for example (SN: 9/28/18). The warm waters can also provide enough energy to give hurricanes extra staying power even after landfall (SN: 11/11/20).
      And, as the world saw in 2020, very warm ocean waters can also speed up how quickly a storm strengthens — leading to dangerous, difficult-to-predict, suddenly supercharged storms. Such rapid intensification is defined as sustained wind speeds increasing by at least 55 kilometers per hour within just 24 hours. 2020 saw that in abundance, with 10 Atlantic storms rapidly intensifying in the region’s bathlike waters before making landfall. More

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      Plastic waste forms huge, deadly masses in camel guts

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      Marcus Eriksen was studying plastic pollution in the Arabian Gulf when he met camel expert Ulrich Wernery. “[Ulrich] said, ‘You want to see plastic? Come with me.’ So we went deep into the desert,” Eriksen recalls. Before long, they spotted a camel skeleton and began to dig through sand and bones.
      “We unearthed this mass of plastic, and I was just appalled. I couldn’t believe that — almost did not believe that — a mass as big as a medium-sized suitcase, all plastic bags, could be inside the rib cage of this [camel] carcass,” says Eriksen, an environmental scientist at the 5 Gyres Institute, a plastic pollution research and education organization in Santa Monica, Calif.
      “We hear about marine mammals, sea lions, whales, turtles and seabirds impacted” by plastic waste, Eriksen says (SN: 6/6/19). But “this is not just an ocean issue. It’s a land issue, too. It’s everywhere.”
      About 390,000 dromedary camels (Camelus dromedarius) live in the United Arab Emirates. Now in a study in the February 2021 Journal of Arid Environments, Eriksen, Wernery and colleagues estimate that plastic kills around 1 percent of these culturally important animals.
      Of 30,000 dead camels that Wernery, a veterinary microbiologist at the Central Veterinary Research Laboratory in Dubai, and his team have examined since 2008, 300 had guts packed with plastic ranging from three to 64 kilograms. The researchers dubbed these plastic masses “polybezoars” to distinguish them from naturally occurring hair and plant fiber bezoars.
      When camels eat plastic, it accumulates into enormous, stomach-clogging masses called polybezoars. Researchers found these polybezoars — the biggest of which weighs almost 64 kilograms — inside dead camels in the desert near Dubai.M. Eriksen et al/J. Arid Enviro. 2021
      When camels eat plastic, it accumulates into enormous, stomach-clogging masses called polybezoars. Researchers found these polybezoars — the biggest of which weighs almost 64 kilograms — inside dead camels in the desert near Dubai.M. Eriksen et al/J. Arid Enviro. 2021
      As dromedaries roam the desert looking for food, they munch on plastic bags and other trash that drift into trees and pile up along roadsides. “From the camel’s perspective … if it’s not sand, it’s food,” Eriksen says.
      With a stomach full of plastic, camels don’t eat because they don’t feel hungry, and they starve to death. Plastic can also leach toxins and introduce bacteria that poison the one-humped mammals, Wernery says.

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      “If 1 percent mortality due to plastic is verified by future and more detailed studies, then plastic pollution will certainly represent a reason of concern for [camels],” says Luca Nizzetto, an environmental scientist at the Norwegian Institute for Water Research in Oslo, who was not involved with the research. “These types of studies are relevant to raise social awareness about this pollution.”
      Banning plastic bags and single-use plastics is crucial for protecting camels and other wildlife, Eriksen says. “Plastic bags are escape artists. They blow out of garbage cans, out of landfills, out of trucks and out of people’s hands. They travel for hundreds of miles.” More

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      In the past 15 years, climate change has transformed the Arctic

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      Fifteen years of grading warming’s impact on the Arctic has made one thing abundantly clear: Climate change has drastically altered the Arctic in that short time period.
      Breaking unfortunate records is “like whack-a-mole,” says Jackie Richter-Menge, a climate scientist at the University of Alaska Fairbanks and an editor of the 2020 Arctic Report Card, released December 8 at the virtual meeting of the American Geophysical Union. From sea ice lows to temperature highs, records keep popping up all over the place. For instance, in June, a record-high 38° Celsius (100.4° Fahrenheit) temperature was recorded in the Arctic Circle (SN:6/23/20). And in 2018, winter ice on the Bering Sea shrank to a 5,500 year low (SN:9/3/20).
      “But quite honestly, the biggest headline is the persistence and robustness of the warming,” Richter-Menge says. In 2007, only a year after the first Arctic Report Card, summer sea ice reached a record low, shrinking to an area 1.6 million square kilometers smaller than the previous year. Then, only five years later, the report card noted a new low, 18 percent below 2007. In 2020, sea ice didn’t set a record but not for lack of trying: It still was the second lowest on record in the last 42 years.  
      “The transformation of the Arctic to a warmer, less frozen and biologically changed region is well under way,” the report concludes. And it’s changing faster than expected when researchers launched the report card in 2006. The annual average air temperature in the Arctic is rising two to three times faster than the rest of the globe, Richter-Menge says. Over the last 20 years, it’s warmed at a rate of 0.77 degrees C per decade, compared with the global average of 0.29 degrees C per decade.

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      Improvements in research techniques over the last 15 years have helped researchers more thoroughly observe warming’s impact and how different aspects of Arctic climate change are linked to one another, she says. These improvements include the ability to measure ice mass via gravity measurements taken by the Gravity Recovery and Climate Experiment (GRACE) satellite. Other satellites have provided additional observations from above while on-the-ground measurements, such as by the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), have provided up-close sea ice measurements (SN:4/8/20). The report has also begun to include on-the-ground observations of the Arctic’s Indigenous people, who experiences these changes directly (SN:12/11/19).
      The changes have revealed few bright spots but one is the rebound of bowhead whales, which were hunted almost to extinction around the turn of the 20th century. While researchers are careful to note that the whales are still vulnerable, the four populations of the whales (Balaena mysticetus) now range from 218 in the Okhotsk Sea to around 16,800 in the Bering, Chukchi and Beaufort seas. Researchers suggest that the whales’ rebound is due, at least in part, to the warming that has occurred over the last 30 years. Earlier sea ice melting and warmer surface water means more krill and other food for these baleen feeders.
      In a rare bit of good news from the Arctic, researchers report that bowhead whales are on the rebound. Unfortunately, the same warming that has aided the whales has melted ice sheets and increased hardships for Indigenous hunters.Nature Picture Library/Alamy Stock Photo
      But don’t be fooled. The potential good news is overshadowed by the bad news. There’s been “this accumulation of knowledge and insights that we’ve gained over 15 years,” says Mark Serreze, a climate scientist at the National Snow and Ice Data Center in Boulder, Colo., who wasn’t involved in this year’s report. The 2020 research is “an exclamation point on the changes that have been unfolding,” he says. “The bowhead whales are doing OK, but that’s about it.” More