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Comment by Brakenshire | Hacker News Reader

And then it breaks down to CO2. That is a basic and well understood part of climate science, that’s how the calculations are made which show an 80 fold higher impact for Methane per unit mass than for CO2 over a 20 year period, and 20 fold higher impact over a 100 year period.

As the climate scientist says in the article, this doesn’t disprove mainstream climate science, and the calculations are correct but banal, and just presented in a way to give a misleading impression of a smaller impact. The author is quite open about preparing the paper specifically to give ammunition to efforts to roll back Oil and Gas regulations.

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Methane is 16.04 g/mol and CO2 is 44.01 g/mol. PPM of CO2 is 415 and PPM of Methane is something like 1.8 PPM.

Increase in CO2 is something like 15PPM/decade. Increase in Methane is 0.1PPM/decade (or less).

So in absolute terms, the relative effect of Methane compared to CO2, using the 80x figure is (1.8 * 16 * 80) / (415*44.01) = 12.6%.

And in growth terms, the relative effect of Methane is 19%.

However, since methane is limited by total land under cultivation, and it has actual hit a stable PPM in the last decade (unlike CO2 which grows exponentially), CO2 is by far the larger component in any climate models projecting into the future.

In conclusion, Former White House adviser can actually math while your 80x figure needed to be put into context. I do not know where you get your information from, but I expect that it is from someone trying to make a tendentious environmental case against cows more than it's about someone trying to present unbiased facts.

since methane is limited by total land under cultivation

This isn't true. There have been numerous stories of methane stores (e.g. Siberia) that have begun leaking in recent years.

Don't get your news from the places peddling that stuff. Here is what CH4 has been doing since 1985 (notice ppb, not ppm):

https://imgur.com/gaKEU3g

Historical data can't refute an argument about future melting permafrost...

An argument without any data can't refute an argument with historical data, either.

You don't disagree with me on the science. Methane has a limited half life, this is well understood and built into the models. You are repeating the science as if it were different, and then drawing different conclusions from it.

I don't see what the absolute numbers have to do with whether or not oil or gas installations should be able to vent a particular quantity of methane.

Or why it matters that another unrelated source of Methane is limited. If cattle produced a similar but different molecule that would reduce the Methane absolute numbers dramatically, but in reality would have no impact on the question at hand. This is all like saying that driving a car in North Dakota matters less than in California, because North Dakota has lower total absolute emissions. It is sophistry.

To summarize your comment, you're calculating that methane contributes around 12% to atmospheric heat trapping (when only considering methane and CO2), and conclude that it is therefore irrelevant.

I don't think your own calculation supports that conclusion.

CO2 is growing exponentially. CH4 is not. If CO2 were stuck at the current level forever, nobody would care about global warming. It's future expected doublings that are driving the danger scenarios.

Let me make it extremely simple: there are future expected doublings of CO2 ppm, but there are none for CH4. The share of warming for CH4 compared to CO2 is low and will only get lower.

The NOAA Global Greenhouse Gas Reference Network [1, 2] is a great resource for this. Their data on methane goes back to 1984, so I compared methane and CO2 concentrations in the 1984-2019 time frame. In this time frame, the atmospheric CO2 concentration grew by 19.7% (from 344 to 412 ppm), the concentration of methane grew by 14.7% (from 1630 to 1870 ppb).

So, you're right that CO2 is growing a bit faster, but the difference really is rather small.

In addition to this, there are highly nonlinear effects that may occur in the future that others have alluded to, such as the clathrate gun hypothesis [3]. Even in the absence of such dramatic effects, you would expect methane levels to further increase with increasing meat consumption in countries that are getting wealthier (e.g. in India, China).

Edit: I should also point out that the claim that only future doublings in CO2 concentration matter is totally wrong. Even in the IPCC report's worst case scenario, CO2 concentrations will grow to ca. 1000 ppm by 2100, just over a single further doubling [4]. In the best case scenario, they stabilize a bit under 500 ppm, which is just another 20% increase from today. In that best case scenario (B1), global temperatures are still expected to rise by slightly more than 1.5°C by 2100 [5]!

[1] https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/

[2] https://www.esrl.noaa.gov/gmd/ccgg/trends/

[3] https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis

[4] https://en.wikipedia.org/wiki/File:Projected_changes_over_th...

[5] https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg1-chap... (Fig. 10.4)

  CO2 is growing exponentially.

No, it isn't. 68 parts per million in 35 years isn't remotely "exponential" growth. It's roughly half a percentage point a year.

Meaningful, yes. Exponential, not hardly.

Saying it is a few percent per year is proof that it is an exponential growth, per its definition.

"per unit mass" is the operative term since there is far far less methane being emitted.

Methane was only relevant because it was such a strong greenhouse gas. As CO2, it becomes just a drop in the bucket.

It becomes in combination 80 fold higher over 20 years and 20 fold higher over 100 years, per unit mass.

Incidentally the reaction from Methane to CO2 produces 2.5 times more mass of CO2 than the Methane it starts with, which is one reason why the impact remains quite high. And of course everyone knows Methane emissions are relatively low, otherwise given their potency their effect on GHG warming would be a lot more than the 15% of thereabouts which it is at the moment.

This is all like attacking an IPCC claim that the sea level is going to rise by 1m over 100 years by saying it won’t rise by 5m, but by on average 1cm a year for 100 years. We know that already.

What exactly are you trying to say with this? The tone of your comment sounds as if you're trying to disagree with your parent comment or somehow put it in perspective, when in fact you're just stating a related fact that is totally compatible with it.

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