Monday, February 24, 2020
Record Antarctic temperatures fuel sea level worry
Sea levels may threaten coastal cities sooner than expected, scientists say, as ice loss speeds up and Antarctic temperatures rise.
February 20th, 2020, by Alex Kirby
https://climatenewsnetwork.net/record-antarctic-temperatures-fuel-sea-level-worry/
LONDON, 20 February, 2020 − Across the world, people now alive in coastal areas may face dangerously rising seas within their lifetimes, as record Antarctic temperatures and rapid melting of the continent’s ice drive global sea levels upwards.
Temperatures on the Antarctic Peninsula reached more than 20°C for the first time in history earlier this month, the Guardian reported: “The 20.75C logged by Brazilian scientists at Seymour Island on 9 February was almost a full degree higher than the previous record of 19.8C, taken on Signy Island in January 1982.”
The Antarctic Peninsula has warmed by almost 3°C since the start of the Industrial Revolution around 200 years ago − faster than almost anywhere else on Earth. But scientists are increasingly concerned not only about the Peninsula, but with the possibility that the entire southern continent may be heating up much faster than current estimates suggest.
Among evidence of increasing scientific effort to determine what is happening is a joint UK-US collaboration, due to report in 2023 on the chances of the collapse of the huge Thwaites glacier in West Antarctica, where from 1992 to 2017 the annual rate of ice loss rose threefold.
Big speed-up
Now a study by scientists co-ordinated by Germany’s Potsdam Institute for Climate Impact Research (PIK) says sea level rise caused by Antarctica’s ice loss could become a major risk for coastal protection in the near future.
After what they call “an exceptionally comprehensive comparison of state-of-the-art computer models from around the world”, they conclude that Antarctica alone could cause global sea level to rise by 2100 by up to three times more than it did in the last century.
“The ‘Antarctica Factor’ turns out to be the greatest risk, and also the greatest uncertainty, for sea levels around the globe,” says the lead author, Anders Levermann of PIK and Columbia University’s Lamont-Doherty Earth Observatory (LDEO) in New York.
“While we saw about 19 centimetres of sea level rise in the past 100 years, Antarctic ice loss could lead to up to 58 centimetres within this century”, he said.
“Coastal planning cannot merely rely on the best guess. It requires a risk analysis. Our study provides exactly that. The sea level contribution of Antarctica is very likely not going to be more than 58 centimetres.”
Thermal expansion of the oceans by global warming and the melting of glaciers, which so far have been the most important factors in sea level rise, will add to the contribution from Antarctic ice loss, making the overall sea level rise risk even bigger. But the ‘Antarctica Factor’ is about to become the most important element, according to the study, published in the journal Earth System Dynamics.
The range of sea-level rise estimates the scientists have come up with is fairly large. Assuming that humanity keeps on emitting greenhouse gases as before, they say, the range they call “very likely” to describe the future is between 6 and 58 cms for this century.
If greenhouse gas emissions were reduced rapidly, it would be between 4 and 37 cms. Importantly, the difference between a business-as-usual scenario and one of emissions reductions becomes substantially greater as time passes.
More robust insights
Sixteen ice sheet modelling groups consisting of 36 researchers from 27 institutes contributed to the new study. A similar study six years ago had to rely on the output of only five ice sheet models.
“The more computer simulation models we use, all of them with slightly different dynamic representations of the Antarctic ice sheet, the wider the range of results that we yield − but also the more robust the insights that we gain”, said co-author Sophie Nowicki of the NASA Goddard Space Flight Center.
“There are still large uncertainties, but we are constantly improving our understanding of the largest ice sheet on Earth. Comparing model outputs is a forceful tool to provide society with the necessary information for rational decisions.”
Over the long term, the Antarctic ice sheet has the potential ultimately to raise sea levels by many tens of metres. “What we know for certain”, said Professor Levermann, “is that not stopping the burning of coal, oil and gas will drive up the risks for coastal metropolises from New York to Mumbai, Hamburg and Shanghai.”
− Climate News Network
The Cosmic Irony of Bernie Sanders’s Rise
What makes Bernie Sanders so threatening to the Democratic establishment is that he stands for what millions of Democrats thought their party stood for all along.
SETH ACKERMAN
https://jacobinmag.com/2020/02/democratic-primary-electability-bernie-sanders?utm
When I look at the Democratic primaries, I see an ideological struggle pitting Bernie Sanders against the party establishment.
But that probably isn’t what most Democratic primary voters see. They’ve been watching a totally different contest: a months-long televised audition to find a qualified, appealing leader who can win in November. Ideological differences aren’t foremost in their minds; in fact, many voters probably find them difficult to parse. The candidates are all Democrats, aren’t they? What more is there to say?
Voters do see differences, of course. But they’re mainly differences of style and temperament: some candidates are dealmakers, others are scrappers. Some are outsiders, others power brokers. And of course there are differences of age and gender. As for Bernie, probably everyone recognizes him as the pugnacious outsider in the race, the kind of politician who errs more on the side of principle than expediency (whether they’re into that sort of thing or not).
But that’s not the same as a fundamental ideological difference. My hypothesis is that when Sanders condemns the depredations of the “billionaire class,” or calls for a major power shift from corporations to workers, a majority of the party faithful assume he’s just saying out loud what popular Democrats like Barack Obama truly believe in their hearts but are, perhaps, a little too politically prudent to state so baldly.
Why would loyal Democrats labor under such illusions about their party leaders? Because those leaders go to great lengths to cultivate those illusions — and for the most part they succeed. Many of us on the Left tend to tune out the stump-speech platitudes of mainstream Democrats, which makes it easy to lose sight of the fact that, to the ideologically unarmored, those platitudes can make a speaker sound a lot like someone who shares the values of, say, a Bernie Sanders.
As a result, there are millions of loyal Democrats whose loyalty stems from a touching belief that the Democratic Party exists to stand up to powerful interests on their behalf. The public personas of Obama and Sanders may differ wildly along a hundred different dimensions, but ideologically, tens of millions of Democrats see Bernie Sanders as Barack Obama, only more so.
This hypothesis can help make sense of some otherwise inexplicable facts.
Take the confounding pattern of voters’ first and second candidate choices. How can it be that the top second choice of Biden supporters is Sanders? Aren’t Biden and Sanders polar opposites politically?
Yes — in reality. But in the perception of many rank-and-file Democrats, the two probably resemble each other quite a bit. Both are old-school, rough-around-the-edges, snowy-haired “Democrats” who are all about standing up for the little guy. That’s the image Biden strives to project — “Middle-Class Joe” is his self-fashioned sobriquet — even as he (for example) works to strip bankruptcy protections from desperate debtors to please his funders at Delaware banks.
Or take the unshakable conviction of so many pundits that Bernie is a “factional candidate” with a “hard ceiling” of support due to his “extreme” political stances. That may be how the world looks to you when you’re surrounded by people who know their Yglesiases from their Kleins. (Though the actual Yglesias and Klein probably know better.)
But in the real world of ordinary Democrats, Bernie simply isn’t seen as a marginal radical:
He has the highest favorability of any candidate in the race.
When Democrats are asked which candidates’ positions “align with your personal political views,” they rate Bernie’s views as second closest to their own, right behind Biden’s; those who say his views align with theirs “very closely” outnumber those saying “not closely at all” by a 2-to-1 margin.
When YouGov asked Democratic primary voters if there were any candidates they’d be disappointed to see win the nomination, fewer named Sanders (23%) than Biden (28%) or Bloomberg (27%).
And now we’ve learned that when Democrats are presented with head-to-head primary matchups, Bernie beats every other candidate in the race.
It’s not hard to see how this puts the Democratic elite in an agonizing bind. There is an ideological struggle going on within the party, even if many ordinary Democrats hardly notice it. But it’s a struggle that dare not speak its name. Whatever popular legitimacy the party possesses depends on its followers’ belief that it hews to the very principles now most closely associated with Bernie Sanders. That makes it excruciatingly difficult to craft an effective anti-Bernie appeal.
The obvious solution, of course, is to resort to electability arguments. Indeed, if Sanders once seemed to have a ceiling of support, it wasn’t because Democratic voters were alienated by his “extremism” or turned off by his “rabid fanbase” (a hilariously solipsistic explanation that doubles as a diagnostic test for Terminal Onlineness). They worried about whether he could beat Trump.
Sanders is old, he’s strident, he’s Jewish. He calls himself a socialist and speaks with what is easily the least presidential accent of any nominee since Al Smith. He isn’t anyone’s textbook image of electability. That gave Democratic elites an opening: “We would love to see a President Sanders,” they implied, “but nominating Bernie will just give us another four years of Trump.”
But that argument has a fatal weakness: it can be tested at the ballot box. When Bernie triumphed in Iowa and New Hampshire, Democrats received it as a clarion signal that he could win, and right away the electability argument began a self-propelled collapse. The more Bernie wins, the more he seems viable; the more viable he seems, the more he will win.
For professional Democrats and pundits, this must be nothing short of maddening. Don’t these voters realize? There’s a huge difference between winning a Democratic primary, where a liberal electorate seeks a liberal nominee, and winning a nationwide general election, where the voter pool includes millions of deeply conservative, often religious, people, out there in the hinterland. Bernie Sanders can win a Democratic primary, fine. But that tells you nothing about whether he can win in November.
Except — that’s not at all how most Democratic primary voters see things. Remember, they don’t see the primaries as an ideological contest. To them, what happened in Iowa and New Hampshire was that thousands of Democrats spent months scrutinizing the candidates to find the one with the best chance of beating Trump. And if half a million Democrats — or even just a plurality of them — came out of that process thinking Bernie was the most electable, why wouldn’t other Democrats take that as a sign that this guy’s probably got a good shot?
Incredibly, it’s the very ideological innocence of ordinary Democrats, their partisan loyalty and trust in their leaders — the very factors that once gave those leaders a free hand to run the party as they please — that now, like an infernal machine, work inexorably against them.
For decades, those leaders propagated the conceit that intra-party disagreements are never about ends, only means; that they’re merely differences over how best to realize the ideals that everyone in the party supposedly shares: ideals of justice, compassion, defense of the little guy. Now, to their horror, they realize that this conceit has left their flock wholly susceptible to the charms of any politician who can speak with evident sincerity about justice, compassion, and defense of the little guy — and they are powerless to stop it without destroying the conceit.
Not for the first time in history, they who have put out the people’s eyes reproach them of their blindness. And now they’re getting their comeuppance.
Sunday, February 23, 2020
Greenhouse gases have a puzzling double effect
February 21st, 2020, by Tim Radford
Lustier plant growth as greenhouse gases climb should counter global heating and atmospheric carbon build-up. But it’s not quite so simple.
https://climatenewsnetwork.net/greenhouse-gases-have-a-puzzling-double-effect/
LONDON, 21 February, 2020 – The Arctic is getting greener as greenhouse gases abound and the global thermometer rises. The vegetation of the high latitudes is moving further north, growing taller, becoming more substantial, more abundant and budding earlier, according to new studies by 40 scientists from 36 European and US institutions.
And the whole planet is getting greener too, according to a separate study in a second journal, as more carbon dioxide in the atmosphere – the chief cause of global heating – also acts as a fertiliser to stimulate plant growth.
It is as if researchers have finally identified a genuine negative feedback effect: as the world warms because of higher levels of greenhouse gases, the plant world responds by absorbing more of the carbon in the atmosphere and modifying the overall impact.
But both studies identify problems with what might be a comforting conclusion: it isn’t clear why in some Arctic regions the green things are getting greener, while in others the vegetation cover is becoming poorer.
And worldwide, it might be that much of the global greening can be attributed to human action – the advance of industrial-scale agriculture and commercial forest plantation – in which case most of the absorbed carbon dioxide will be returned to the atmosphere sooner or later.
Both studies confirm the value of a closer look at the evidence so far – and the need for further study.
In the journal Nature Climate Change, scientists report that they checked the big picture of polar greening based on four decades of data from large-scale satellite observation against more detailed evidence over smaller sample regions collected by sensors mounted on drones and on aircraft, as well as direct examination on the once-frozen ground.
The Arctic is the fastest-warming region of the planet: it is warming twice as fast as the globe as a whole. Snow melts earlier, plants leaf sooner. Shrubs that once stayed close to the slushy snow surface are now taller, and new species are colonising once hostile terrain.
This is expected to destabilise the Arctic tundra, the region of year-round permafrost that masks a vast reservoir of carbon buried in the frozen soils.
Natural response
So botanists and climate scientists in the high latitudes now have to begin some tricky calculations in their pursuit of reliable estimates of the global carbon budget. How much carbon will the new green growth absorb and store? And how much carbon buried for the last 100,000 years or so will escape into the atmosphere with the advance of the northern greenery and the thawing of the soils?
But at least, according to a paper in the journal Nature Reviews Earth and Environment, the observed greening of the Arctic is a natural response to rising average temperatures and greater carbon dioxide fertilisation as a consequence of ever-higher levels of greenhouse gas emissions and consequent climate change.
Svalbard in the high Arctic is almost 2°C warmer in summer than it was in 1986, and at least 30% greener. But the Arctic is a region with limited human settlement and low industrial investment.
A team of researchers from China, the US, France and Norway combed through 250 earlier studies, and revisited satellite data, climate models and field observations, to make sense of the evidence of a planet that has grown a lot greener: half of all the world’s vegetated lands are leafier than they once were.
And they concluded that it was possible that the growth of global greening in the last 40 years may have slowed the rate of global heating by as much as 0.25°C.
Human footprint
But the same greening can be seen as evidence of rapid human impact on the planet as a whole: much of it can be explained by more intensive use of farmland and forest plantation, especially in the world’s most populous countries, India and China.
“It is ironic that the very same carbon emissions responsible for harmful changes to climate are also fertilising plant growth, which in turn is somewhat moderating global warming,” said one author, Jarle Bjerke of the Norwegian Institute for Nature Research.
And his co-author Phillipe Ciais, of France’s Laboratory of Climate and Environmental Sciences, said: “Plants are actively defending against the dangers of carbon pollution by not only sequestering carbon on land but also by wetting the atmosphere through transpiration of ground water and evaporation of precipitation intercepted by their bodies.
“Stopping deforestation and promoting sustainable, ecologically sensible afforestation could be one of the simplest and most cost-effective, though not sufficient, defences against climate change.” – Climate News Network
Empathy can be detected in people whose brains are at rest
Findings may help health care professionals better assess those with autism, schizophrenia
https://www.sciencedaily.com/releases/2020/02/200218152307.htm
February 18, 2020
University of California - Los Angeles Health Sciences
Researchers have found that it is possible to assess a person's ability to feel empathy by studying their brain activity while they are resting rather than while they are engaged in specific tasks.
UCLA researchers have found that it is possible to assess a person's ability to feel empathy by studying their brain activity while they are resting rather than while they are engaged in specific tasks.
Traditionally, empathy is assessed through the use of questionnaires and psychological assessments. The findings of this study offer an alternative to people who may have difficulty filling out questionnaires, such as people with severe mental illness or autism, said senior author Dr. Marco Iacoboni, professor of psychiatry and biobehavioral sciences at the David Geffen School of Medicine at UCLA.
"Assessing empathy is often the hardest in the populations that need it most," Iacoboni said. "Empathy is a cornerstone of mental health and well-being. It promotes social and cooperative behavior through our concern for others. It also helps us to infer and predict the internal feelings, behavior and intentions of others."
Iacoboni has long studied empathy in humans. His previous studies have involved testing empathy in people presented with moral dilemmas or watching someone in pain.
For the current study, published in Frontiers in Integrative Neuroscience, researchers recruited 58 male and female participants ages 18 to 35.
Resting brain activity data were collected using functional magnetic resonance imaging, or fMRI, a noninvasive technique for measuring and mapping brain activity through small changes in blood flow. Participants were told to let their minds wander while keeping their eyes still, by looking at a fixation cross on a black screen.
Afterward, the participants completed questionnaires designed to measure empathy. They rated how statements such as "I often have tender, concerned feelings for people less fortunate than me" and "I sometimes try to understand my friends better by imagining how things look from their perspective" described them on a five-point scale from "not well" to "very well."
Researchers wanted to measure how accurately they could predict the participants' empathic disposition, characterized as the willingness and ability to understand another's situation, by analyzing the brain scans.
The predictions were made by looking into resting activity in specific brain networks that earlier studies demonstrated are important for empathy. Researchers used a form of artificial intelligence called machine learning, which can pick up subtle patterns in data that more traditional data analyses might not.
"We found that even when not engaged directly in a task that involves empathy, brain activity within these networks can reveal people's empathic disposition," Iacoboni said. "The beauty of the study is that the MRIs helped us predict the results of each participant's questionnaire."
The findings could help health care professionals better assess empathy in people with autism or schizophrenia, who may have difficulties filling out questionnaires or expressing emotion.
"People with these conditions are thought to lack empathy," he said. "But if we can demonstrate that their brains have the capability for empathy, we can work to improve it through training and the use of other therapies."
Furthermore, said lead author Leonardo Christov-Moore, a postdoctoral fellow currently at USC's Brain and Creativity Institute, this technique may be expanded to improve treatment as well as diagnosis.
"The predictive power of machine learning algorithms like this one, when applied to brain data, can also help us predict how well a given patient will respond to a given intervention, helping us tailor optimal therapeutic strategies from the get-go."
The study adds to a growing body of research suggesting that brains at rest are as active as brains engaged in a task, and that brain networks in the resting brain may interact in a similar fashion as when they are engaged in a task.
Iacoboni said future, larger studies may help identify other regions of the brain associated with empathy.
Story Source:
Materials provided by University of California - Los Angeles Health Sciences. Original written by Marrecca Fiore. Note: Content may be edited for style and length.
Journal Reference:
Leonardo Christov-Moore, Nicco Reggente, Pamela K. Douglas, Jamie D. Feusner, Marco Iacoboni. Predicting Empathy From Resting State Brain Connectivity: A Multivariate Approach. Frontiers in Integrative Neuroscience, 2020; 14 DOI: 10.3389/fnint.2020.00003
Methane emitted by humans vastly underestimated
https://www.sciencedaily.com/releases/2020/02/200219113746.htm
Date: February 19, 2020
Source: University of Rochester
Summary: Researchers measured methane levels in ancient air samples and found that scientists have been vastly underestimating the amount of methane humans are emitting into the atmosphere via fossil fuels. The researchers indicate that reducing fossil fuel use is a key target in curbing climate change.
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FULL STORY
Methane molecules illustration (stock image).
Credit: © vchalup / Adobe Stock
Methane is a powerful greenhouse gas and large contributor to global warming. Methane emissions to the atmosphere have increased by approximately 150 percent over the past three centuries, but it has been difficult for researchers to determine exactly where these emissions originate; heat-trapping gases like methane can be emitted naturally, as well as from human activity.
University of Rochester researchers Benjamin Hmiel, a postdoctoral associate in the lab of Vasilii Petrenko, a professor of earth and environmental sciences, and their collaborators, measured methane levels in ancient air samples and found that scientists have been vastly underestimating the amount of methane humans are emitting into the atmosphere via fossil fuels. In a paper published in Nature, the researchers indicate that reducing fossil fuel use is a key target in curbing climate change.
"Placing stricter methane emission regulations on the fossil fuel industry will have the potential to reduce future global warming to a larger extent than previously thought," Hmiel says.
Two Types of Methane
Methane is the second largest anthropogenic -- originating from human activity -- contributor to global warming, after carbon dioxide. But, compared to carbon dioxide, as well as other heat-trapping gases, methane has a relatively short shelf-life; it lasts an average of only nine years in the atmosphere, while carbon dioxide, for instance, can persist in the atmosphere for about a century. That makes methane an especially suitable target for curbing emission levels in a short time frame.
"If we stopped emitting all carbon dioxide today, high carbon dioxide levels in the atmosphere would still persist for a long time," Hmiel says. "Methane is important to study because if we make changes to our current methane emissions, it's going to reflect more quickly."
Methane emitted into the atmosphere can be sorted into two categories, based on its signature of carbon-14, a rare radioactive isotope. There is fossil methane, which has been sequestered for millions of years in ancient hydrocarbon deposits and no longer contains carbon-14 because the isotope has decayed; and there is biological methane, which is in contact with plants and wildlife on the planet's surface and does contain carbon-14. Biological methane can be released naturally from sources such as wetlands or via anthropogenic sources such as landfills, rice fields, and livestock. Fossil methane, which is the focus of Hmiel's study, can be emitted via natural geologic seeps or as a result of humans extracting and using fossil fuels including oil, gas, and coal.
Scientists are able to accurately quantify the total amount of methane emitted to the atmosphere each year, but it is difficult to break down this total into its individual components: Which portions originate from fossil sources and which are biological? How much methane is released naturally and how much is released by human activity?
"As a scientific community we've been struggling to understand exactly how much methane we as humans are emitting into the atmosphere," says Petrenko, a coauthor of the study. "We know that the fossil fuel component is one of our biggest component emissions, but it has been challenging to pin that down because in today's atmosphere, the natural and anthropogenic components of the fossil emissions look the same, isotopically."
Turning to the Past
In order to more accurately separate the natural and anthropogenic components, Hmiel and his colleagues turned to the past, by drilling and collecting ice cores from Greenland. The ice core samples act like time capsules: they contain air bubbles with small quantities of ancient air trapped inside. The researchers use a melting chamber to extract the ancient air from the bubbles and then study its chemical composition.
Hmiel's research focused on measuring the composition of air from the early 18th century -- before the start of the Industrial Revolution -- to the present day. Humans did not begin using fossil fuels in significant amounts until the mid-19th century. Measuring emission levels before this time period allows researchers to identify the natural emissions absent the emissions from fossil fuels that are present in today's atmosphere. There is no evidence to suggest natural fossil methane emissions can vary over the course of a few centuries.
By measuring the carbon-14 isotopes in air from more than 200 years ago, the researchers found that almost all of the methane emitted to the atmosphere was biological in nature until about 1870. That's when the fossil component began to rise rapidly. The timing coincides with a sharp increase in the use of fossil fuels.
The levels of naturally released fossil methane are about 10 times lower than previous research reported. Given the total fossil emissions measured in the atmosphere today, Hmiel and his colleagues deduce that the manmade fossil component is higher than expected -- 25-40 percent higher, they found.
Climate Change Implications
The data has important implications for climate research: if anthropogenic methane emissions make up a larger part of the total, reducing emissions from human activities like fossil fuel extraction and use will have a greater impact on curbing future global warming than scientists previously thought.
To Hmiel, that's actually good news. "I don't want to get too hopeless on this because my data does have a positive implication: most of the methane emissions are anthropogenic, so we have more control. If we can reduce our emissions, it's going to have more of an impact."
This study was supported by the US National Science Foundation and the David and Lucille Packard Foundation.
Story Source:
Materials provided by University of Rochester. Note: Content may be edited for style and length.
Journal Reference:
Benjamin Hmiel, V. V. Petrenko, M. N. Dyonisius, C. Buizert, A. M. Smith, P. F. Place, C. Harth, R. Beaudette, Q. Hua, B. Yang, I. Vimont, S. E. Michel, J. P. Severinghaus, D. Etheridge, T. Bromley, J. Schmitt, X. Faïn, R. F. Weiss, E. Dlugokencky. Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions. Nature, 2020; 578 (7795): 409 DOI: 10.1038/s41586-020-1991-8
FULL STORY
Methane molecules illustration (stock image).
Credit: © vchalup / Adobe Stock
Methane is a powerful greenhouse gas and large contributor to global warming. Methane emissions to the atmosphere have increased by approximately 150 percent over the past three centuries, but it has been difficult for researchers to determine exactly where these emissions originate; heat-trapping gases like methane can be emitted naturally, as well as from human activity.
University of Rochester researchers Benjamin Hmiel, a postdoctoral associate in the lab of Vasilii Petrenko, a professor of earth and environmental sciences, and their collaborators, measured methane levels in ancient air samples and found that scientists have been vastly underestimating the amount of methane humans are emitting into the atmosphere via fossil fuels. In a paper published in Nature, the researchers indicate that reducing fossil fuel use is a key target in curbing climate change.
"Placing stricter methane emission regulations on the fossil fuel industry will have the potential to reduce future global warming to a larger extent than previously thought," Hmiel says.
Two Types of Methane
Methane is the second largest anthropogenic -- originating from human activity -- contributor to global warming, after carbon dioxide. But, compared to carbon dioxide, as well as other heat-trapping gases, methane has a relatively short shelf-life; it lasts an average of only nine years in the atmosphere, while carbon dioxide, for instance, can persist in the atmosphere for about a century. That makes methane an especially suitable target for curbing emission levels in a short time frame.
"If we stopped emitting all carbon dioxide today, high carbon dioxide levels in the atmosphere would still persist for a long time," Hmiel says. "Methane is important to study because if we make changes to our current methane emissions, it's going to reflect more quickly."
Methane emitted into the atmosphere can be sorted into two categories, based on its signature of carbon-14, a rare radioactive isotope. There is fossil methane, which has been sequestered for millions of years in ancient hydrocarbon deposits and no longer contains carbon-14 because the isotope has decayed; and there is biological methane, which is in contact with plants and wildlife on the planet's surface and does contain carbon-14. Biological methane can be released naturally from sources such as wetlands or via anthropogenic sources such as landfills, rice fields, and livestock. Fossil methane, which is the focus of Hmiel's study, can be emitted via natural geologic seeps or as a result of humans extracting and using fossil fuels including oil, gas, and coal.
Scientists are able to accurately quantify the total amount of methane emitted to the atmosphere each year, but it is difficult to break down this total into its individual components: Which portions originate from fossil sources and which are biological? How much methane is released naturally and how much is released by human activity?
"As a scientific community we've been struggling to understand exactly how much methane we as humans are emitting into the atmosphere," says Petrenko, a coauthor of the study. "We know that the fossil fuel component is one of our biggest component emissions, but it has been challenging to pin that down because in today's atmosphere, the natural and anthropogenic components of the fossil emissions look the same, isotopically."
Turning to the Past
In order to more accurately separate the natural and anthropogenic components, Hmiel and his colleagues turned to the past, by drilling and collecting ice cores from Greenland. The ice core samples act like time capsules: they contain air bubbles with small quantities of ancient air trapped inside. The researchers use a melting chamber to extract the ancient air from the bubbles and then study its chemical composition.
Hmiel's research focused on measuring the composition of air from the early 18th century -- before the start of the Industrial Revolution -- to the present day. Humans did not begin using fossil fuels in significant amounts until the mid-19th century. Measuring emission levels before this time period allows researchers to identify the natural emissions absent the emissions from fossil fuels that are present in today's atmosphere. There is no evidence to suggest natural fossil methane emissions can vary over the course of a few centuries.
By measuring the carbon-14 isotopes in air from more than 200 years ago, the researchers found that almost all of the methane emitted to the atmosphere was biological in nature until about 1870. That's when the fossil component began to rise rapidly. The timing coincides with a sharp increase in the use of fossil fuels.
The levels of naturally released fossil methane are about 10 times lower than previous research reported. Given the total fossil emissions measured in the atmosphere today, Hmiel and his colleagues deduce that the manmade fossil component is higher than expected -- 25-40 percent higher, they found.
Climate Change Implications
The data has important implications for climate research: if anthropogenic methane emissions make up a larger part of the total, reducing emissions from human activities like fossil fuel extraction and use will have a greater impact on curbing future global warming than scientists previously thought.
To Hmiel, that's actually good news. "I don't want to get too hopeless on this because my data does have a positive implication: most of the methane emissions are anthropogenic, so we have more control. If we can reduce our emissions, it's going to have more of an impact."
This study was supported by the US National Science Foundation and the David and Lucille Packard Foundation.
Story Source:
Materials provided by University of Rochester. Note: Content may be edited for style and length.
Journal Reference:
Benjamin Hmiel, V. V. Petrenko, M. N. Dyonisius, C. Buizert, A. M. Smith, P. F. Place, C. Harth, R. Beaudette, Q. Hua, B. Yang, I. Vimont, S. E. Michel, J. P. Severinghaus, D. Etheridge, T. Bromley, J. Schmitt, X. Faïn, R. F. Weiss, E. Dlugokencky. Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions. Nature, 2020; 578 (7795): 409 DOI: 10.1038/s41586-020-1991-8
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