Trends in atmospheric CH4

[gerontocrat]

& here is the graph

click image to enlarge

[gerontocrat]

& a science paper explaining the cause of the spike in methane 2020-2022.

The root cause was La Nina.

https://www.pnas.org/doi/10.1073/pnas.2402730121  - open access

Inverse modeling of 2010–2022 satellite observations shows that inundation of the wet tropics drove the 2020–2022 methane surge

Significance
Atmospheric methane growth has accelerated over the past decade, including record-high increases in 2020–2022. We show that the decadal growth has been driven by the wet tropics while methane emissions at northern mid-latitudes have decreased. We attribute the 2020–2022 surge to large-scale inundation in Africa and Equatorial Asia associated with La Niña conditions and consistent with terrestrial water storage data. The dominance of the wet tropics in driving the methane trend has important implications for finding a pathway to decrease atmospheric methane and mitigate near-term climate change.

Abstract
Atmospheric methane concentrations rose rapidly over the past decade and surged in 2020–2022 but the causes have been unclear. We find from inverse analysis of GOSAT satellite observations that emissions from the wet tropics drove the 2010–2019 increase and the subsequent 2020–2022 surge, while emissions from northern mid-latitudes decreased. The 2020–2022 surge is principally contributed by emissions in Equatorial Asia (43%) and Africa (30%). Wetlands are the major drivers of the 2020–2022 emission increases in Africa and Equatorial Asia because of tropical inundation associated with La Niña conditions, consistent with trends in the GRACE terrestrial water storage data. In contrast, emissions from major anthropogenic emitters such as the United States, Russia, and China are relatively flat over 2010–2022. Concentrations of tropospheric OH (the main methane sink) show no long-term trend over 2010–2022 but a decrease over 2020–2022 that contributed to the methane surge.

[Sublime_Rime]

& a science paper explaining the cause of the spike in methane 2020-2022.

The root cause was La Nina.

https://www.pnas.org/doi/10.1073/pnas.2402730121  - open access

Makes sense considering the timing of the deceleration over the past 18 months as the El Nino has dominated. If there is a lag of 3-4 months as with temperature than we can expect emissions to begin to increase when Sept-Oct global data becomes available (if setting May as when El Nino had fully shifted to neutral).

[Stephan]

NOAA has delivered the latest monthly global CH₄.

July 2024:       1921.33 ppb
July 2023:       1913.60 ppb
July 2014:       1815.3 ppb
Last updated: Nov 05, 2024

The annual increase is at 6.1 ppb based on the July 2023 value I noted in November 2023. A corrected value for July 2023 gives an increase of 7.7 ppb/a which is one of the lowest increase rate since February 2018. It seems to be sure that the period of high increase rates of 2021 and 2022 is now over.

I set an index = 100 for the 1980 average [1601.2 ppb]. July 2024 is at 120.0 compared to that index.

[gerontocrat]

& here is the graph - it is starting to bend from the relatively low recent monthly increases

click images to enlarge

[kiwichick16]

https://www.rnz.co.nz/news/world/534034/tropical-wetlands-are-releasing-a-methane-bomb-threatening-climate-plans

another report on methane emissions , mainly focused on emissions from tropical wetlands.

However the report makes no mention of what appears to me to be the obvious outcome of a warming planet; that every area of the planet that has been cool/cold in the past is now warming, leading to increasing methane release from every temperate, sub polar and polar area on the planet.

Thawing Permafrost is just the poster child for warming/ thawing in every previously cool/cold climate area .....every sq metre of lost ice and snow will result in the subsequent growth of moss/lichen/sedges/grasses/bushs/trees , all initially absorbing CO2 , but subsequently providing a basis for microbial life , which then releases more methane. Not to mention the dramatically reduced albedo.

the article also talks about the short life of methane in the atmosphere, however they fail to explain that methane breaks down to H2O and more CO2

Methane is IMO far more dangerous than many people seem to think ; more Methane means more H2O and CO2 after the Methane breaks down.

[trm1958]

I read NO2 is highest in human history, CO2 highest since Pliocene, and SF6 highest since Theia collided with Earth and made the moon. How long has it been since CH4 was this high?

[Freegrass]

<>
the article also talks about the short life of methane in the atmosphere, however they fail to explain that methane breaks down to H2O and more CO2

Methane is IMO far more dangerous than many people seem to think ; more Methane means more H2O and CO2 after the Methane breaks down.

I don't understand why they keep using 20 years for the warming potential of methane. It only stays up in the air for around 12 years. I used to read numbers of 220 in the first year, and 150 in 10 years. So what are the right numbers? They're very hard to find these days, like there was a plan to make methane sound less bad than it really is.

[kiwichick16]

@  freegrass   ......almost like its "fake news "

[Renerpho]

That number of 12 years refers to the lower troposphere, right? I think stratospheric methane survives a lot longer.

[kiwichick16]

as this article states .....Methane adds ozone, water vapour and Co2 to the atmosphere 

previous estimates for the warming effect of Methane were 20 - 25 % too low

the water vapour is especially good at trapping heat   .....cool

https://en.wikipedia.org/wiki/Atmospheric_methane

[Freegrass]

as this article states .....Methane adds ozone, water vapour and Co2 to the atmosphere 

previous estimates for the warming effect of Methane were 20 - 25 % too low

the water vapour is especially good at trapping heat   .....cool

https://en.wikipedia.org/wiki/Atmospheric_methane

Again, they use 20 and 100 years. What happened to 10 or 12 years? If we stop emitting methane today, it'll almost all be gone in 12 years from now.

The global warming potential (GWP) for methane is about 84 in terms of its impact over a 20-year timeframe, and 28 in terms of its impact over a 100-year timeframe.

The average time that a physical methane molecule is in the atmosphere is estimated to be around 9.6 years. However, the average time that the atmosphere will be affected by the emission of that molecule before reaching equilibrium – known as its 'perturbation lifetime' – is approximately twelve years.

[Renerpho]

I'm not sure what exactly you are discussing.

Tables 8.7 here gives the warming potentials (GWP₂₀~85 and GWP₁₀₀~30), based on a "perturbation lifetime" of 12.4 years, and also discusses the effect of additional CO₂ from methane oxidation. Nowhere are they saying that 20 or 100 years refer to the lifetime of the methane.

The average lifetime of CH₄ in the troposphere is about 9-12 years; but once it reaches the stratosphere (where it can do a lot of damage), that increases to about 140 years. The lifetime of stratospheric methane has actually been decreasing by something like 50% since the 19th century, due to the addition of other gases, but it is still much longer than in the lower parts of the atmosphere. (Source)

And the oxidation of CH₄ to stratospheric water vapour increases its radiative forcing by approximately 15%, an effect that has long been known. (Source)

[Richard Rathbone]

<>
the article also talks about the short life of methane in the atmosphere, however they fail to explain that methane breaks down to H2O and more CO2

Methane is IMO far more dangerous than many people seem to think ; more Methane means more H2O and CO2 after the Methane breaks down.

I don't understand why they keep using 20 years for the warming potential of methane. It only stays up in the air for around 12 years. I used to read numbers of 220 in the first year, and 150 in 10 years. So what are the right numbers? They're very hard to find these days, like there was a plan to make methane sound less bad than it really is.

They are all the right number. Which one to use depends on the context you want to use it in. If  you don't care what happens in the long term, just what happens in the next 10 years, you use  the 10 year value. If the time horizon of what you care about is 20 years, you use the 20 year value. If you are looking for what can make the biggest difference next year from immediate action,  you use the 1 year value.

There are big wins to be had next year from methane cuts now, but to maintain them, there have to be cuts next year too, and so on every year till its all gone and then the benefits of those cuts start fading away. To have the same big win in 2026 that you get in 2025 from cuts in 2024,  requires cuts in 2025 too. If you just hold steady in 2025, the benefits from the 2024 cuts start being lost. So if your time horizon is actually 10 years, you take all that fading away into account by using the 10 year value.

But just as maintaining the benefit of  the 1 year value requires cuts to continue to be made every year, maintaining the value of a decadal cut requires continued cutting every decade. So if your time horizon isn't actually 10 years, but a century, you use the 100 year value to take into account way the immediate benefits fade away over a century.

We are in a position now where GHG emissions need to stop in well under a century, so that is  too long a time horizon, and the best compromise between urgency and practicality is probably somewhere in the 10-50 year region. There's no realistic expectation that methane can be gone from the economy inside 10 years, but activists might push for it to  be gone that fast and use the 10 year value in the scenario  they were pushing. "Realists" might  think its going to be the last bit  of fossil that goes and its not going to be gone for 50 years, and use the 50 year value in  their scenario. Denialists don't want it gone at all, and use the 100 year value to make any action now look futile. 

[RoxTheGeologist]

<>
the article also talks about the short life of methane in the atmosphere, however they fail to explain that methane breaks down to H2O and more CO2

Methane is IMO far more dangerous than many people seem to think ; more Methane means more H2O and CO2 after the Methane breaks down.

I don't understand why they keep using 20 years for the warming potential of methane. It only stays up in the air for around 12 years. I used to read numbers of 220 in the first year, and 150 in 10 years. So what are the right numbers? They're very hard to find these days, like there was a plan to make methane sound less bad than it really is.

GWP 100 is used generally - its a bit like sulphates - masking the true problem

[Reginald]

CNN has a piece (video, sorry) that talks about the Environmental Defense Fund's new methane satellite, and the volumes of methane emitted from various sites.

The three leaking sites they mention are:

Appalachian Basin: 226 tonnes of methane per HOUR.
Uinta Basin (Utah): 60 tonnes of methane per HOUR.
Permian Basin: 290 tonnes of methane per HOUR.

https://www.cnn.com/2024/11/27/climate/video/edf-satellite-methane-leaks-weir-cnc-digvid

[Stephan]

NOAA has delivered the latest monthly global CH₄.

August 2024:       1926.92 ppb
August 2023:       1917.24 ppb
August 2014:       1818.9 ppb
Last updated: Dec 05, 2024

The annual increase is at 7.5 ppb based on the August 2023 value I noted in December 2023. A corrected value for August 2023 gives an increase of 9.7 ppb/a which is lower than most of the annual increase rates of the last years. It seems to be sure that the period of high increase rates of 2021 and 2022 is now over.

I set an index = 100 for the 1980 average [1601.2 ppb]. August 2024 is at 120.3 compared to that index.

[gerontocrat]

It seems to be sure that the period of high increase rates of 2021 and 2022 is now over.

I am not so sure. The CH4 graph attached consistently shows CH4 ppb rising sharply before an El Nino, sharply falling during an El Nino, and then rising again as El Nino ends. Will it happen again?

Note also......

‘Climate bomb’ warning over $200bn wave of new gas projects

New liquefied natural gas projects could produce 10 gigatonnes of emissions by the end of the decade, close to the annual emissions of all coal plants

https://www.theguardian.com/environment/2024/dec/05/climate-bomb-warning-over-200bn-wave-of-new-gas-projects

[Renerpho]

It seems to be sure that the period of high increase rates of 2021 and 2022 is now over.

I am not so sure. The CH4 graph attached consistently shows CH4 ppb rising sharply before and El Nino, sharply falling during an El Nino, and then rising again as El Nino ends. Will it happen again?

I think you're both right. The recent period of high increases is over. A new period of high increases may or may not begin very soon.