Study Shows Tricky New Methane Math

December 17, 2022

Phys.org:

A mysterious surge in planet-heating atmospheric methane in 2020 despite COVID lockdowns that reduced many human-caused sources can be explained by a greater release from nature and, surprisingly, reduced air pollution, scientists said Wednesday.

Methane stays in the atmosphere only a fraction as long as carbon dioxide, but is far more efficient at trapping heat and is responsible for roughly 30 percent of the global rise in temperatures to date.

Released from the oil and gas, waste and agriculture sectors, as well as through biological processes in wetlands, the powerful greenhouse gas is a key target for efforts to curb global warming. 

But a new study published in the journal Nature suggests that cutting methane may be even more of a challenge—and more urgent—than is currently understood. 

Researchers in China, France, the US and Norway found that efforts to reduce CO2 emissions and air pollution will affect the atmospheric process that scrubs methane from the air. That means the planet-heating gas will linger longer and accumulate faster.

f the world is to meet the challenge of keeping warming to under 2 degrees Celsius since the pre-industrial era, “we will have to act even more quickly and even more strongly to reduce methane”, said Philippe Ciais who co-led the research at France’s Laboratory for the Sciences of Climate and Environment (LSCE).

The researchers focused on the mystery of the concentrations of methane in the atmosphere in 2020, which had their biggest increase on record even as COVID-19 lockdowns saw carbon dioxide emissions fall.

‘Bad news’

What they found is potentially two pieces of “bad news” for climate change, said co-author Marielle Saunois of (LSCE). 

Firstly, they looked at inventories to assess fossil fuel and agricultural methane emissions and found that human sources of methane did indeed fall slightly in 2020.

Then they used ecosystem models to estimate that warmer and wetter conditions over parts of the northern hemisphere caused a surge in emissions from wetlands.

That confirms other research and is worrying because the more methane released, the more warming, potentially creating a feedback loop largely outside of human control. 

But that is only half of the story, the researchers found.

Researchers also looked at changes in atmospheric chemistry, because this provides a “sink” for methane, effectively cleaning it out of the air in a relatively short period by converting it to water and CO2 when it reacts with the hydroxyl radical (OH).

These hydroxyl radicals are present in tiny quantities and have a lifetime of less than a second, but they remove about 85 percent of methane from the atmosphere. 

They are the “Pac-Man of the atmosphere”, said Ciais: “As soon as they see something they eat it and then disappear.”

The researchers simulated changes in OH using human sources of carbon monoxide, hydrocarbons and nitrogen oxide emissions that altogether affect the production and loss of hydroxyl radicals in the atmosphere. 

They found that OH concentrations decreased by around 1.6 percent in 2020 from the year before, largely because of a fall in nitrogen oxide (NOx) emissions caused by the COVID lockdowns. Nitrogen oxide is emitted into the air primarily from burning fuel. 

A 20 percent reduction in NOx could increase methane twice as fast, Cias told a press briefing, adding: “This has surprised us greatly.”

The researchers said their study helps to solve the riddle of the rise in methane in the atmosphere in 2020.

But they acknowledged that more work would have to be done to answer the next mystery: why the rise in methane concentrations hit a new record in 2021. 

Ciais said lower nitrogen oxide emissions from transport in the United States and India, as well as continued low levels of air travel due to the pandemic may have played a part. 

Euan Nisbet, a professor of Earth Sciences at Royal Holloway University who was not involved in the research, said the jump in methane in 2020 was a “major shock”. 

“Even more worrying is the rise in methane in 2021—this was after the major Coronavirus shutdowns when the economy was recovering,” he told AFP. 

“As yet we don’t have detailed studies but something very dramatic seems to be going on.”

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5 Responses to “Study Shows Tricky New Methane Math”

  1. rhymeswithgoalie Says:

    Longer-term pattern:

  2. Gingerbaker Says:

    “That means the planet-heating gas will linger longer and accumulate faster.”

    But methane does not actually accumulate, because it is (still) scrubbed from the atmosphere too fast. Which means that the increase in atmospheric concentration is caused by an increase in methane production. So, where is that increase in methane production coming from?

    No doubt, we are seeing an increase in methane release from permafrost melting. The amount of wetlands we have is, iirc, decreasing. The global numbers of pigs and chickens have risen considerably since 1960, not surprisingly as our human population has risen considerably in that same time frame. And we have seen a huge increase in fracking, methane use as fuel, and methane leakage from the natural gas industry. Every time we have looked at that we have been shocked at the increases there and we still have no idea of the true amount.

    And there is little doubt in my mind who will be blamed for this rise in methane concentration: cattle. Specifically, American beef. Whose numbers have actually dramatically decreased since 1960, and therefore are not to blame for the situation. I will be shocked if the hydroxyl radical deficit is not used to call for a reduction in the consumption of American beef. Anyone want to bet?

    “Methane stays in the atmosphere only a fraction as long as carbon dioxide, but is far more efficient at trapping heat and is responsible for roughly 30 percent of the global rise in temperatures to date.”

    That 30% figure is almost certainly based on the GWP100 timeframe which hugely exaggerates the contribution of non fossil fuel methane and hugely underestimates the contribution of fossil fuel methane. If the calculation was done rationally, we would see that it is the fossil fuel industry leakages that are truly important to the proper calculus, because they alone introduce exogenous carbon – previously sequestered for millions of years – to the carbon cycle.

  3. Mark Mev Says:

    “Specifically, American beef. Whose numbers have actually dramatically decreased since 1960”
    I’m done searching. I can’t find any charts that back up that statement. Can you point me to the data? Thanks.

    • Gingerbaker Says:

      “Since 1977, the average carcass
      weight per animal has increased from
      274 kg to 351 kg, thus decreasing the
      number of animals within the national
      herd required to meet the demand for
      beef products (Capper 2011). Average
      growth rate increased from 0.71 kg/day
      to 1.16 kg/day between 1977 and 2007,
      which decreased the average number of
      days required to reach slaughter weight
      from 609 to 485.”

      and

      “Modern beef production requires considerably fewer resources than the equivalent system in 1977, with 69.9% of animals, 81.4% of feedstuffs, 87.9% of the water, and only 67.0% of the land required to produce 1 billion kg of beef. :

      from Capper, J. L. 2011. The environmental impact of
      beef production in the United States: 1977
      compared with 2007. J Anim Sci 89:4249–
      4261.

      —————————————————————–

      See Also from “Our world in data: https://www.flickr.com/photos/96198796@N05/48744134058/in/album-72157714202939482/

      ——————————————————————

      If you want a deep-dive into livestock food science, see:

      Click to access CAST_Issue_Paper_53_Feed_vs_1FAEEE311471D.pdf

  4. John Oneill Says:

    NOx, or nitrogen oxides, is generally used as a generic term for all the compounds of nitrogen and oxygen, which confusingly have quite different chemistry, effects, and lifetime in the atmosphere. There’s nitric oxide, NO, nitrous oxide, NO2, and nitrogen dioxide, N2O.
    Nitrogen dioxide is the acrid gas associated with air pollution from burning fuel, coming from the high temperatures inside the cylinders of internal combustion engines, especially diesels, and from propane burners. It’s production could be greatly reduced by the drop-in replacement of dimethyl ether, CH3-O-CH3, for both liquid petroleum gas (propane and butane), and for diesel. DME has no carbon-carbon bonds, so it does not produce soot or particulates when burnt, and the oxygen connecting the two carbons greatly reduces NOx formation. DME as a synthetic fuel has much more desirable qualities than either ammonia or hydrogen. It’s far less toxic than ammonia, and has about double the energy density. Unlike hydrogen, it can be stored at room temperature and moderate pressure, the same as LPG. It is not a greenhouse gas, having only a brief lifetime in the atmosphere, though it does of course form two moles of CO2 per mole when burnt.
    Nitric oxide, NO, has only a single atom of nitrogen and oxygen, and is much less stable than NO2; it reacts with ozone to form nitrogen dioxide, and then with water to form nitric acid, hence acid rain.
    Nitrous oxide, N2O, is safe enough to give to pregnant women in childbirth – it’s the well-known ‘laughing gas’. It would probably be one of the more harmless drugs, except for its potent greenhouse effect. It combines the ability of methane to intercept infrared, and the longer lifetime of carbon dioxide. It also reacts with ozone to attack the ozone layer. About 40% of N2O in the atmosphere is believed to be of human origin, mostly from breakdown of nitrogen fertilisers – though the unexplained heavy use in the hospital here, about 5x higher than would be expected, has had to be included in the hospital’s carbon budget.


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