Methane Explained

February 21, 2020

I suspect most readers here will have seen reports on new research showing that atmospheric methane concentrations are increasing, and that oil and gas extraction, not burps from the arctic, are a much larger driver than previously thought.

New York Times:

Oil and gas production may be responsible for a far larger share of the soaring levels of methane, a powerful greenhouse gas, in the earth’s atmosphere than previously thought, new research has found.

The findings, published in the journal Nature, add urgency to efforts to rein in methane emissions from the fossil fuel industry, which routinely leaks or intentionally releases the gas into air.

“We’ve identified a gigantic discrepancy that shows the industry needs to, at the very least, improve their monitoring,” said Benjamin Hmiel, a researcher at the University of Rochester and the study’s lead author. “If these emissions are truly coming from oil, gas extraction, production use, the industry isn’t even reporting or seeing that right now.”

Atmospheric concentrations of methane have more than doubled from preindustrial times. A New York Times investigation into “super emitter” sites last year revealed vast quantities of methane being released from oil wells and other energy facilities instead of being captured.

Zeke Hausfather Twitter Thread:

When we emit a ton of methane (CH4), about 80% is removed from the atmosphere via chemical reactions with hydroxyl (OH) radicals within 20 years. (above) CO2, on the other hand, is not removed by chemical reactions; it has to be absorbed by land and ocean sinks.

Forty years after its been emitted nearly all methane is gone, while nearly 50% of the CO2 remains in the atmosphere (assuming current carbon sink behavior; a warming world will likely reduce the efficacy of the carbon sink resulting in more CO2 remaining in the atmosphere). 

In practice, this means that the long-term atmospheric CO2 concentration is a function of cumulative emissions, while atmospheric CH4 is a function of the rate of emissions. One ton per year of CO2 increases atmospheric CO2 by ~40 tons by 2100. For methane its only 12 tons.

To put it another way, if we stop increasing CH4 emissions, atmospheric CH4 will stop increasing. But if we stop increasing CO2 emissions atmospheric CO2 will continue to increase until we reduce CO2 emissions close to zero.

This raises a few important points: 

First, CO2 is the primary driver of longer-term warming. In future baseline emissions scenarios (e.g. where we don’t mitigate emissions) CO2 drives around 90% of the additional 21st century warming.  

Second, reducing warming by cutting methane is a lot easier than CO2. Cutting methane results in near-immediate temperature declines, while cutting CO2 only slows the rate of warming until you go to near-zero. 

Third, methane can be cut at any point and have a large effect on temperatures. CO2 on the other hand is cumulative; waiting to cut CO2 emissions locks in warming in a way thats not the case for methane. 

Finally, the prioritization of CO2 and CH4 mitigation depends on short-term vs long-term prioritization. If you think we are close to climate tipping points CH4 cuts are a way to quickly reduce warming. If you care more about 2050 or 2070 temps than CO2 cuts matter more. 

3 Responses to “Methane Explained”

  1. indy222 Says:

    Right.

    Now, take that methane curve and add on similar ones each starting 1 year later, to get a feel for what an increasing thaw rate of the permafrost will do, and what a 44:1 amplifying methane emission rate vs temperature rise in wetlands, and you see that methane increases too. In addition to our own leaky nat gas lines, or just plain negligence by Big Oil money in not bothering trying to harness nor flare some nat gas. Then add that CO2e onto the thaw rate derived CO2 only, from MacDougall et al 2012 and 2016 for the current best estimate ECS=5C.

    It’s quite scary.

    See graphs in my public talk… https://www.youtube.com/watch?v=aYxrTNSG2E0&feature=youtu.be


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