New Year’s Resolution – Methane Response
Roger Caiazza
I am announcing my New Year’s resolution here in hopes of getting feedback and to spur others to provide their resolutions when we hear yet another climate talking point.
When I hear anyone say that methane is more potent than carbon dioxide because the radiative forcing produced is greater, I resolve to say that is only true in the laboratory on a molecular basis. In the atmosphere where it counts methane is not nearly as potent.
Discussion
I have heard the methane scare story all over but my primary concern is New York. As part of New York’s Climate Leadership and Community Protection Act (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. To respond I have developed a page that consolidates reason why methane should not be vilified. I included the following arguments.
Clyde Spender explained that changes to radiation effects occur on a molecule-by-molecule basis in the atmosphere in an article here 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.
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.
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
I would love additional arguments why methane is not to be feared, would appreciate any corrections to my arguments, and would like to hear ways to edit my resolution for more impact.
It would also be useful to me and probably others if WUWT readers would provide similar resolutions for publication.
Happy New Year
Roger Caiazza blogs on New York energy and environmental issues at Pragmatic Environmentalist of New York. More details on the Climate Leadership & Community Protection Act are available here and an inventory of over 370 articles about the Climate Act is also available. This represents his opinion and not the opinion of any of his previous employers or any other company with which he has been associated.