A three-dimensional portrait of methane concentrations around the world is helping researchers to understand the complex gas, which constitutes the second largest contributor to greenhouse gas (GHG) warming after carbon dioxide.
Methane is an important GHG that is emitted during the production and transport of coal, natural gas and oil as well from agricultural practices like rice cultivation and the raising of livestock, according to the U.S. Environmental Protection Agency (EPA). Once lofted into the atmosphere, high-altitude winds can transport methane far beyond its source, disproportionately impacting communities around the world.
"There's an urgency in understanding where the sources are coming from so that we can be better prepared to mitigate methane emissions where there are opportunities to do so," said research scientist Ben Poulter at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
During extraction processes, if methane leaks into the air before being used, a single molecule can trap the sun's heat and warm the atmosphere, according to the Environmental Defense Fund. The largest source of man-made methane production is attributed to the oil and gas industry; about 10 percent of all GHG emissions from fossil fuels in the U.S. can be attributed to methane. Though methane has a shorter lifetime with lower concentrations in the atmosphere than carbon dioxide, the gas is eighty-four times more potent and needs to be considered when evaluating the impact of global climate change.
"It is estimated that up to 60 percent of the current methane flux from land to the atmosphere is the result of human activities," said Abhishek Chatterjee, a carbon cycle scientist with Universities Space Research Association based at Goddard.
"Similar to carbon dioxide, human activity over long time periods is increasing atmospheric methane concentrations faster than the removal from natural 'sinks' can offset it. As human populations continue to grow, changes in energy use, agriculture and rice cultivation [and] livestock raising will influence methane emissions. However, it's difficult to predict future trends due to both lack of measurements and incomplete understanding of the carbon-climate feedbacks."
To determine methane's role on Earth's carbon cycle and its impact on the climate system, researchers at NASA combined multiple data sets from self-reported fossil fuel producers, government overseers and satellite observations. These were put into a high-resolution computer model to simulate the global movement of methane emissions based on known processes in certain environments while accounting for weather models and natural processes that break down the gas.
Methane's global movements through space and landscapes are complex and can vary depending on many factors. Of note, the impacts of methane are felt disproportionately around the planet.
Europe was shown to be the only region to show a decrease in methane emissions over the last two decades, which may largely be due to measures prioritizing the use of renewable energy in a shift from fossil fuels like coal.
In South America, the Amazon River Basin and its associated wetlands flood seasonally, which creates oxygen-deprived environments that contribute a significant source of methane. Researchers estimate that around 60 percent of wetland methane emissions come from the tropics.
In Asia, more than 85 percent of methane emissions comes from human activities, with rice cultivation and livestock being the driving sources. Additionally, China's economic expansion and increasing population have driven the demand for energy and resources.
"Agriculture is responsible for about 20% of global methane emissions and includes enteric fermentation, which is the processing of food in the guts of cattle, mainly, but also includes how we manage the waste products that come from livestock and other agricultural activities," said Poulter.
Arctic and high-latitude regions account for about one-fifth of global methane emissions.
"What happens in the Arctic doesn't stay in the Arctic," said Ott, adding that the region is not currently a strong pulse of methane but "that could change dramatically over time."
The findings will help to inform future field and satellite missions, as well as policy decisions.
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By David Konisky
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By Katherine Kornei
Clear-cutting a forest is relatively easy—just pick a tree and start chopping. But there are benefits to more sophisticated forest management. One technique—which involves repeatedly harvesting smaller trees every 30 or so years but leaving an upper story of larger trees for longer periods (60, 90, or 120 years)—ensures a steady supply of both firewood and construction timber.
A Pattern in the Rings
<p>The <a href="https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/coppice-standards-0" target="_blank">coppice-with-standards</a> management practice produces a two-story forest, said <a href="https://www.researchgate.net/profile/Bernhard_Muigg" target="_blank">Bernhard Muigg</a>, a dendrochronologist at the University of Freiburg in Germany. "You have an upper story of single trees that are allowed to grow for several understory generations."</p><p>That arrangement imprints a characteristic tree ring pattern in a forest's upper story trees (the "standards"): thick rings indicative of heavy growth, which show up at regular intervals as the surrounding smaller trees are cut down. "The trees are growing faster," said Muigg. "You can really see it with your naked eye."</p><p>Muigg and his collaborators characterized that <a href="https://ltrr.arizona.edu/about/treerings" target="_blank">dendrochronological pattern</a> in 161 oak trees growing in central Germany, one of the few remaining sites in Europe with actively managed coppice-with-standards forests. They found up to nine cycles of heavy growth in the trees, the oldest of which was planted in 1761. The researchers then turned to a historical data set — more than 2,000 oak <a href="https://eos.org/articles/podcast-discovering-europes-history-through-its-timbers" target="_blank" rel="noopener noreferrer">timbers from buildings and archaeological sites</a> in Germany and France dating from between 300 and 2015 — to look for a similar pattern.</p>A Gap of 500 Years
<p>The team found wood with the characteristic coppice-with-standards tree ring pattern dating to as early as the 6th century. That was a surprise, Muigg and his colleagues concluded, because the first mention of this forest management practice in historical documents occurred only roughly 500 years later, in the 13th century.</p><p>It's probable that forest management practices were not well documented prior to the High Middle Ages (1000–1250), the researchers suggested. "Forests are mainly mentioned in the context of royal hunting interests or donations," said Muigg. Dendrochronological studies are particularly important because they can reveal information not captured by a sparse historical record, he added.</p><p>These results were <a href="https://www.nature.com/articles/s41598-020-78933-8" target="_blank">published in December in <em>Scientific Reports</em></a>.</p><p>"It's nice to see the longevity and the history of coppice-with-standards," said <a href="https://www.teagasc.ie/contact/staff-directory/s/ian-short/" target="_blank">Ian Short</a>, a forestry researcher at Teagasc, the Agriculture and Food Development Authority in Ireland, not involved in the research. This technique is valuable because it promotes conservation and habitat biodiversity, Short said. "In the next 10 or 20 years, I think we'll see more coppice-with-standards coming back into production."</p><p>In the future, Muigg and his collaborators hope to analyze a larger sample of historic timbers to trace how the coppice-with-standards practice spread throughout Europe. It will be interesting to understand where this technique originated and how it propagated, said Muigg, and there are plenty of old pieces of wood waiting to be analyzed. "There [are] tons of dendrochronological data."</p><p><em><a href="mailto:katherine.kornei@gmail.com" target="_blank" rel="noopener noreferrer">Katherine Kornei</a> is a freelance science journalist covering Earth and space science. Her bylines frequently appear in Eos, Science, and The New York Times. Katherine holds a Ph.D. in astronomy from the University of California, Los Angeles.</em></p><p><em>This story originally appeared in <a href="https://eos.org/articles/tree-rings-reveal-how-ancient-forests-were-managed" target="_blank">Eos</a></em> <em>and is republished here as part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story.</em></p>Earth's ice is melting 57 percent faster than in the 1990s and the world has lost more than 28 trillion tons of ice since 1994, research published Monday in The Cryosphere shows.
By Jewel Fraser
Noreen Nunez lives in a middle-class neighborhood that rises up a hillside in Trinidad's Tunapuna-Piarco region.