Happy New Year!
I wrote an article for Watts Up With That that described my New Year’s resolution: I resolve that when I hear anyone say that methane is more potent than carbon dioxide because the radiative forcing produced is greater, I will say that is only true in the laboratory on a dry molecular basis. In the atmosphere, where it counts, methane is not nearly as potent. I had hoped to get feedback and recommendations and I was not disappointed. This post provides the rationale for my resolution.
I have followed the Climate Leadership and Community Protection Act (Climate Act) since it was first proposed, submitted comments on the Climate Act implementation plan, and have written over 380 articles about New York’s net-zero transition. The opinions expressed in this post do not reflect the position of any of my previous employers or any other organization I have been associated with, these comments are mine alone.
Rationale
I have heard the methane scare story everywhere but my primary concern is New York. As part of New York’s Climate Act methane is irrationally disparaged as part of the war on natural gas. The rationale used always revolves around the potency of methane relative to CO2. I believe that the preponderance of information shows that the argument is incorrect. I have developed a page that consolidates reasons why methane should not be vilified and updated it based on comments made. The following summarizes my rationale.
Clyde Spencer explained that changes to radiation effects occur on a molecule-by-molecule basis in the atmosphere in an article titled The Misguided Crusade to Reduce Anthropogenic Methane Emissions. The Climate Act tracks emissions by weight. In the atmosphere CO2 is more than two orders of magnitude more abundant than CH4 on a molecular basis. The Climate Act uses the global warming potential that estimates the mid-range, long-term warming potential of CH4 is 32 times that of CO2. However, that equivalence is for equal weights of the two gases! Using a molecular basis (parts per million-volume mole-fraction) to account for the lighter CH4 molecule reveals that the annual contribution to warming is a fraction of that claimed for CO2. Methane emissions on a molecular basis are increasing at a rate of 0.58% of CO2 increases. Therefore, changes in methane emissions have insignificant effects.
Several commenters pointed out that that methane and water vapor affect the same area of the spectrum of outgoing radiation thus reducing the effect of any changes in methane concentrations. .Rud Istvan explained that:
Methane is a potent GHG in the lab because the lab uses a standard dry atmosphere. I”n the real world methane’s two main infrared absorption bands (at about 3.5 and 8 microns) are completely overlapped by two of the several broader and much stronger water vapor absorption bands, specifically those from about 2.5-4 and 6-9 microns. In a world averaging about 2% specific humidity, any methane effect is literally swamped by water vapor effect.
Cyan quantified the effect of the spectral overlap “Water vapor reduces the potency of methane by about 82 percent at 80%RH. At 46% RH (from the US Standard Atmosphere) the reduction is less, at 75%.”
Andy May’s excellent summarization of Wijngaarden and Happer’s important paper “Dependence of Earth’s Thermal Radiation on Five Most Abundant Greenhouse Gases” takes a slightly different approach. He explains that the greenhouse effect of methane is not only related to the effect on longwave radiation itself but also the concentration in the atmosphere. Because the atmospheric concentration of methane is so small doubling concentrations change the “outgoing forcing by less than one percent”. In other words, doubling emissions or cutting emissions in half of methane will have no measurable effect on global warming itself. A comment by “It does not add up” pointed out that Wijngaarden and Happer also produced a separate paper concentrating specifically on methane.
Ralph B. Alexander describes another molecular consideration ignored in the Climate Act. Each greenhouse gas affects outgoing radiation differently across the bell-shaped radiation spectrum One of the reasons that CO2 is considered the most important greenhouse gas is that its effect coincides with the peak of the bell shape. On the other hand, the effect of CH4 is down in the tail of the bell shape. As a result, the potential effect of CH4 is on the order of only 20% of the effect of CO2.
The residence time of the two gases is different. Methane only has a lifetime of about 10-12 years in the atmosphere. The “consensus” science claim is that 80% of the anthropogenic CO2 emissions are removed within 300 years. (Note however that there are other estimates of much shorter residence times.) This means that CO2 is accumulating in the atmosphere. CH4 is converted to CO2 and is then counted in the monthly CO2 measurements as part of the CO2 flux. Because methane does not accumulate the same way as CO2 it should be handled differently. However, the Climate Act doubles down. Climate Act authors claimed it was necessary to use 20-year global warming potential (GWP) values because methane is estimated to be 28 to 36 greater than carbon dioxide for a 100-year time horizon but 84-87 greater GWP over a 20-year period.
Conclusion
The Climate Act uses explicit language to magnify the accounting for methane emissions that make the use of natural gas more expensive. Last spring I described legislation that was proposed and endorsed by the Hochul Administration that would have changed the accounting to be consistent with the Intergovernmental Panel on Climate Change, the Environmental Protection Agency, and most other jurisdictions. The climate activist community went nuts and the legislation never progressed.
The problem is that I show here that the basis for their indignation is flawed as I point out in my resolution. Methane does not have greater impacts than carbon dioxide and should not be treated as mandated by the Climate Act. My recent article about righteous risks noted that the activists who push the evil methane narrative are driven more by moral idealism than pragmatic concerns. In this instance, their demand for different treatment means that the proposed New York Cap-and-Invest program cannot join other jurisdictions because the emissions accounting will be different. New York will have to develop all the infrastructure and regulations for its program on its own.
Pragmatic Environmentalist of New York 