The recent leak in California attracted mass media attention and now Canada and the US have announced reductions in methane emissions, timed to show PM Trudeau’s visit was not just window dressing. But how important is methane as an issue for the climate or the environment?
From Sea Friends (here):
Methane is natural gas CH4 which burns cleanly to carbon dioxide and water. Methane is eagerly sought after as fuel for electric power plants because of its ease of transport and because it produces the least carbon dioxide for the most power. Also cars can be powered with compressed natural gas (CNG) for short distances.
In many countries CNG has been widely distributed as the main home heating fuel. As a consequence, methane has leaked to the atmosphere in large quantities, now firmly controlled. Grazing animals also produce methane in their complicated stomachs and methane escapes from rice paddies and peat bogs like the Siberian permafrost.
It is thought that methane is a very potent greenhouse gas because it absorbs some infrared wavelengths 7 times more effectively than CO2, molecule for molecule, and by weight even 20 times. As we have seen previously, this also means that within a distance of metres, its effect has saturated, and further transmission of heat occurs by convection and conduction rather than by radiation.
Note that when H20 is present in the lower troposphere, there are few photons left for CH4 to absorb:
Even if the IPCC radiative greenhouse theory were true, methane occurs only in minute quantities in air, 1.8ppm versus CO2 of 390ppm. By weight, CH4 is only 5.24Gt versus CO2 3140Gt (on this assumption). If it truly were twenty times more potent, it would amount to an equivalent of 105Gt CO2 or one thirtieth that of CO2. A doubling in methane would thus have no noticeable effect on world temperature.
However, the factor of 20 is entirely misleading because absorption is proportional to the number of molecules (=volume), so the factor of 7 (7.3) is correct and 20 is wrong. With this in mind, the perceived threat from methane becomes even less.
Further still, methane has been rising from 1.6ppm to 1.8ppm in 30 years (1980-2010), assuming that it has not stopped rising, this amounts to a doubling in 2-3 centuries. In other words, methane can never have any measurable effect on temperature, even if the IPCC radiative cooling theory were right.
Because only a small fraction in the rise of methane in air can be attributed to farm animals, it is ludicrous to worry about this aspect or to try to farm with smaller emissions of methane, or to tax it or to trade credits.
The fact that methane in air has been leveling off in the past two decades, even though we do not know why, implies that it plays absolutely no role as a greenhouse gas.
More information at THE METHANE MISCONCEPTIONS by Dr Wilson Flood (UK) here.
The Methane Monster in the Arctic
It is clear from the above text that methane is not presently a threat, so concerns are raised about a possible outburst of methane from reserves under Arctic ice. Dave Cohen explains the the alarms from methane hydrate doomers at his blog here.
From a peer-reviewed Nature Education article here, Methane Hydrates and Contemporary Climate Change,
Carolyn D. Ruppel (U.S. Geological Survey, Woods Hole, MA) lays out the science and concludes:
Catastrophic, widespread dissociation of methane gas hydrates will not be triggered by continued climate warming at contemporary rates (0.2ºC per decade; IPCC 2007) over timescales of a few hundred years. Most of Earth’s gas hydrates occur at low saturations and in sediments at such great depths below the seafloor or onshore permafrost that they will barely be affected by warming over even 103 yr. Even when CH4 is liberated from gas hydrates, oxidative and physical processes may greatly reduce the amount that reaches the atmosphere as CH4. The CO2 produced by oxidation of CH4 released from dissociating gas hydrates will likely have a greater impact on the Earth system (e.g., on ocean chemistry and atmospheric CO2 concentrations; Archer et al. 2009) than will the CH4 that remains after passing through various sinks.
Natural Gas (75% methane) burns the cleanest with the least CO2 for the energy produced.
Leakage of methane is already addressed by efficiency improvements for its economic recovery, and will apparently be subject to even more regulations.
The atmosphere is a methane sink where the compound is oxidized through a series of reactions producing 1 CO2 and 2H20 after a few years.
GWP (Global Warming Potential) is CO2 equivalent heat trapping based on laboratory, not real world effects.
Any IR absorption by methane is limited by H2O absorbing in the same low energy LW bands.
There is no danger this century from natural or man-made methane emissions.
Give a daisy a break (h/t Derek here)