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    Climate change made Siberia’s heat wave at least 600 times more likely

    The intense heat wave that gripped Siberia during the first half of 2020 would have been impossible without human-caused climate change, a new study finds. Researchers with the World Weather Attribution Network report that climate change made the prolonged heat in the region at least 600 times more likely — and possibly as much as 99,000 times more likely.
    “We wouldn’t expect the natural world to generate [such a heat wave] in anything less than 800,000 years or so,” climate scientist Andrew Ciavarella of the U.K. Met Office in Exeter, England, said July 14 in a news conference. It’s “effectively impossible without human influence.”
    The new study, posted online July 15, examined two aspects of the heat wave: the persistence and intensity of average temperatures across Siberia from January to June 2020; and daily maximum temperatures during June 2020 in the remote Siberian town of Verkhoyansk.

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    Tiny Verkhoyansk made international headlines when it logged a record high temperature of 38° Celsius (100.4° Fahrenheit) on June 20 (SN: 6/23/20). The record was just one extreme amid a larger and longer event in the region that has led to a series of human and natural disasters (SN: 7/1/20). Those include wildfires across Siberia, the collapse of a fuel tank in the mining city of Norilsk due to sagging permafrost, and heat health effects (SN: 4/3/18).
    Using observational data from Verkhoyansk and other Siberian weather stations, the researchers first assessed the rarity of the observed temperatures and determined temperature trends. Then they compared these observations with hundreds of climate simulations using different greenhouse gas warming scenarios. 

    Had such a hot spell occurred in 1900 instead of 2020, it would have been at least 2 degrees cooler on average, the researchers found. In Verkhoyansk, climate change amped up June temperatures by at least 1 degree relative to 1900. And such heat waves are likely to become more common in the near future, the scientists found: By 2050, temperatures in Siberia could increase by between 2.5 degrees to as much as 7 degrees compared to the year 1900, the report finds. More

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    Agriculture and fossil fuels are driving record-high methane emissions

    Methane levels in the atmosphere are at an all-time high. But curbing emissions of that potent greenhouse gas requires knowing where methane is being released, and why. Now, a global inventory of methane sources reveals the major culprits behind rising methane pollution in the 21st century.
    Agriculture, landfill waste and fossil fuel use were the primary reasons that Earth’s atmosphere absorbed about 40 million metric tons more methane from human activities in 2017 than it did per year in the early 2000s. Expanding agriculture dominated methane release in places like Africa, South Asia and Oceania, while increasing fossil fuel use heightened emissions in China and the United States, researchers report online July 14 in Environmental Research Letters.
    Methane “is one of the most important greenhouse gases — arguably the second most important after CO2,” says Alexander Turner, an atmospheric scientist who will join the University of Washington in Seattle in 2021.
    Although there is far less methane than carbon dioxide in the atmosphere, methane can trap about 30 times as much heat over a century as the same amount of CO2. Tallying methane sources “is really important if you want to understand how the climate is going to evolve,” says Turner, who wasn’t involved in the new study. It can also help prioritize strategies to quell pollution, like consuming less meat to cut down on emissions from cattle ranches and using aircraft or satellites to scout out leaky gas pipelines to fix (SN: 11/14/19).  

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    Marielle Saunois, an atmospheric scientist at the Pierre Simon Laplace Institute in Paris, and colleagues cataloged global methane pollution in 2017 — the most recent year with complete data — using atmospheric measurements from towers and aircraft around the world. The isotope, or type of carbon, in methane samples contained clues about its source — such as whether the methane was emitted by the oil and gas industry, or by microbes living in rice paddies, landfills or the guts of belching cattle (SN: 11/18/15). The team compared the 2017 observations with average annual emissions from 2000 to 2006.
    In 2017, human activities pumped about 364 million metric tons of methane into the atmosphere, compared with 324 million tons per year, on average, in the early 2000s. About half of that 12 percent increase was the result of expanding agriculture and landfills, while the other half arose from fossil fuels. Emissions from natural sources like wetlands, on the other hand, held relatively steady.
    Emissions rose most sharply in Africa and the Middle East, and South Asia and Oceania. Both regions ramped up emissions by 10 million to 15 million metric tons. Agricultural sources, such as cattle ranches and paddy fields, were responsible for a 10-million-ton rise in emissions from South Asia and Oceania and a surge almost as big in Africa, the authors estimate. Emissions swelled by 5 to 10 million tons in China and North America, where fossil fuels drove pollution. In the United States alone, fossil fuels boosted methane release by about 4 million tons.

    One region that did not show an uptick in methane was the Arctic. That’s curious, because the Arctic is warming faster than anywhere else in the world, and is covered in permafrost — which is expected to release lots of methane into the air as it thaws, says Tonya DelSontro, an aquatic biogeochemist at the University of Geneva not involved in the work (SN: 7/1/20).
    The new findings could mean that the Arctic has not bled much methane into the atmosphere yet — or that scientists have not collected enough data from this remote area to accurately gauge its methane emission trends, DelSontro says (SN: 12/19/16). 
    The new methane budget may track emissions only through 2017, but “the atmosphere does not suggest that anything has slowed down for methane emissions in the last two years,” says study coauthor Rob Jackson, an environmental scientist at Stanford University. “If anything, it’s possibly speeding up.” By the end of 2019, the methane concentration in the atmosphere reached about 1,875 parts per billion — up from about 1,857 parts per billion in 2017, according to the U.S. National Oceanic and Atmospheric Administration. More

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    Earth’s annual e-waste could grow to 75 million metric tons by 2030

    The planet’s hefty pile of discarded electronics is getting a lot heavier, a new report finds. In 2014, the world collectively tossed an estimated 44.4 million metric tons of unwanted “e-waste” — battery-powered or plug-tethered devices such as laptops, smartphones and televisions. By 2030, that number is projected to grow to about 74.7 million tons, […] More

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    4 ways to put the 100-degree Arctic heat record in context

    On June 20, a remote Siberian town called Verkhoyansk logged a temperature of 38° Celsius (100.4° Fahrenheit), likely setting a new high-temperature record for the Arctic Circle (SN: 6/23/20). But that new record didn’t occur in a vacuum: It’s part of a long-term trend of historically hot temperatures in Siberia linked to climate change, and […] More

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    Smoke from Australian fires rose higher into the ozone layer than ever before

    Australia’s most recent wildfire season was so severe that smoke from the fires reached new heights in the atmosphere — and showed some very weird behavior while it was up there. A particularly intense series of bushfires in southeastern Australia from December 29 to January 4 spurred the formation of huge pyrocumulonimbus, or pyroCb, clouds […] More

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    How giving cash to poor families may also save trees in Indonesia

    Last year marked the third year in a row of when Indonesia’s bleak rate of deforestation has slowed in pace. One reason for the turnaround may be the country’s antipoverty program. That initiative is associated with a 30 percent reduction in tree cover loss in villages, researchers report June 12 in Science Advances. In 2007, […] More

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    Rapid sea level rise could drown protective mangrove forests by 2100

    Mangrove forests can only take so much. The famously resilient, salt-tolerant and twisty trees have so far managed to keep pace with rising sea levels, providing a valuable buffer to coastal communities against pounding storm surges. Now, researchers have found the forests’ limit.  Mangroves cannot survive in seas rising faster than about 7 millimeters per […] More