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Tree rings, ice cores and sediment deposits could see changes in pollution during the global shutdown due to the pandemic.
In 2017, researchers from several universities used advanced laser-based technology to look inside ice cores mined high in the Alps. They found the Black Death.
The ice core record showed that during the past 2,000 years, annual levels of lead in the atmosphere suddenly decreased only once. That period ran from 1349 to 1353, roughly coinciding with one of the worst pandemics in human history: when the bubonic plague killed one-third to one-half of Europe's population. All that death collapsed economic activity, including lead mining and smelting. Fewer tiny lead particles floated in the air and settled on alpine glaciers, where snow compressed them into ice that dropped the record for each year in a core.
A new pandemic is now burning around the world. Recent studies show that various types of pollution have decreased significantly as people have stopped driving, planes have stopped flying, and factories have been closed. Nitrogen dioxide emitted by vehicles decreased by 40 to 60 percent in Chinese cities, compared to a similar period last year. Carbon monoxide concentrations above New York City have fallen to half their 2019 levels. Global carbon dioxide emissions have decreased by 17 percent from a year ago, and analyzes suggest that 2020 will see the biggest annual drop in those emissions, at around two billion metric tons, or 5.5 percent of the 2019 total.
But are these massive disruptions in our collective pollution production large enough to be captured in tree rings, ice cores, and sediment deposits? Will the planet "remember" the COVID-19 crisis?
If we envision a researcher 100 years from now drilling into the ice, the most likely marker to be found would be aerosols, says Paul Mayewski, director of the Institute for Climate Change at the University of Maine and lead author of the Black Death paper. Aerosols are ultrafine particles that can float in the atmosphere for days or weeks before hitting the ground. Pollutants, such as lead, cadmium, and sulfur, arise from factory and power plant smokestacks, vehicle exhausts, mining and smelting operations, and other sources.
"Ice cores can rebuild aerosols with monthly resolution in some cases, so the COVID-19 signal should appear," says Christo Buizert, a paleoclimatologist at Oregon State University who specializes in ice cores and abrupt climate change. . With lockdowns in large portions of the industrialized world now reaching two to three months and a global economic slowdown still under way, a drop in cadmium ice or sulfur deposits seems likely.
Another important aerosol that Buizert says could show up on ice cores is soot - specifically, particles 2.5 microns in diameter or smaller, known as PM2.5. These particles mainly come from coal and natural gas power plants, as well as vehicle exhausts and stoves. And they aggravate human health around the world. PM2.5 levels over Wuhan, China, where the pandemic is believed to have originated, fell 44 percent during the city's closure. Meanwhile, Delhi had a 60 percent reduction and Los Angeles had a 31 percent decrease.
Our 2120 paleoclimatologist could also find the pandemic in the tree rings. As trees grow, they absorb sulfur, nitrogen oxides, and metals such as cadmium deposited from the atmosphere in soil and water. Scientists can use mass spectrometry to analyze how levels vary from year to year. Rings can provide an even better record than ice cores because the trees are much closer to cities and industrial centers than the average glacier. Studies show that even particles that stay in the air for short periods of time can circulate quite far. For example, the burning of fossil fuels in the United States and Europe is a primary source of soot particles that cover ice and snow in the Arctic.
Other markers of the pandemic could involve higher levels of certain materials than average rather than less of them. Kim Cobb, a paleoclimatologist at the Georgia Institute of Technology, believes that the growing mountain of plastic personal protective equipment, or PPE, that is being discarded, could appear in layers of sediment in waterways. "You would probably see them in river deltas, in coastal sedimentary sequences and, I imagine, in some lake systems, especially if they are adjacent to large cities," he says. Many metric tons of plastics already find their way into these sediments, but the addition of billions of gloves, masks, and other single-use items could create a pulse, a thicker and perhaps even distinct layer that represents a rich cataclysm. in plastics. "It would be a marker, a chronological layer, that would be something fascinating for future geologists," says Cobb.
In 3020, an intrepid researcher could still discern that layer, given the long time many plastics take to degrade. A dendrochronologist could also be in the business with recording aerosols on some long-lived trees. The ice cores would certainly retain their markers, if some glaciers and ice sheets still existed.
Ice would tell the same story 100,000 years from now. The oldest cores that reveal our past climate span millions of years. "Ice cores don't lie," says Mayewski. "They capture, as best they can, everything that is transported in the atmosphere."
However, across all of these records, pandemic-related changes in CO 2 emissions would be more difficult to detect. The gases are exchanged between the atmosphere and the snow until it is compressed into ice. If the drop in emissions lasts for only a few months before recovering, that period is likely not long enough to leave a noticeable shift. Of course, if the pandemic lasts longer than we all expect, the ice would register the fall.
Perhaps humanity can view the decline in the use of fossil fuels during the pandemic as an opportunity to truly part ways with them and intensively mitigate climate change. If that response occurs, 2020 could end up looking like a tipping point. Cobb says he imagines a scenario “where thousands of years from now, 2020 will mark the year of maximum emissions, and therefore maximum atmospheric CO 2 concentrations, because we come to value science and our collective responsibility among ourselves on a planet. little".
