From Science Matters

By Ron Clutz

The latest comes from Australia by way of John Ray at his blog Methane cuts on track for 2030 emissions goal.  Excerpts in italics with my bolds and added images.

Australia’s methane emissions have decreased over the past two decades, according to a new report by a leading global carbon research group.

While the world’s methane emissions grew by 20 per cent, meaning two thirds of methane in the atmosphere is from human activity, Australasia and Europe emitted lower levels of the gas.

It puts Australia in relatively good stead, compared to 150 other signatories, to meet its non-binding commitments to the Global Methane Pledge, which aims to cut methane emissions by 30 per cent by the end of the decade.

The findings were revealed in the fourth global methane budget, published by the Global Carbon Project, with contributions from 66 research institutions around the world, including the CSIRO.

According to the report, agriculture contributed 40 per cent of global methane emissions from human activities, followed by the fossil fuel sector (34 per cent), solid waste and waste­water (19 per cent), and biomass and biofuel burning (7 per cent).

Pep Canadell, CSIRO executive director for the Global Carbon Project, said government policies and a smaller national sheep flock were the primary reasons for the lower methane emissions in Australasia.

“We have seen higher growth rates for methane over the past three years, from 2020 to 2022, with a record high in 2021. This increase means methane concentrations in the atmosphere are 2.6 times higher than pre-­industrial (1750) levels,” Dr Canadell said.

The primary source of methane emissions in the agriculture sector is from the breakdown of plant matter in the stomachs of sheep and cattle.

It has led to controversial calls from some circles for less red meat consumption, outraging the livestock industry, which has lowered its net greenhouse gas emissions by 78 per cent since 2005 and is funding research into methane reduction.

Last week, the government agency advising Anthony Albanese on climate change suggested Australians could eat less red meat to help reduce emissions. And the government’s official dietary guidelines will be amended to incorporate the impact of certain foods on climate change.

There is ongoing disagreement among scientists and policymakers about whether there should be a distinction between biogenic methane emitted by livestock, which already exists in a balanced cycle in plants and soil and the atmosphere, and methane emitted from sources stored deep underground for millennia.

“The frustration is that methane, despite its source, gets lumped into one bag,” Cattle Australia vice-president Adam Coffey said. “Enteric methane from livestock is categorically different to methane from coal-seam gas or mining-related fossil fuels that has been dug up from where it’s been stored for millennia and is new to the atmosphere.

“Why are we ignoring what modern climate science is telling us, which is these emissions are inherently different?”  Mr Coffey said the methane budget report showed the intense focus on the domestic industry’s environmental credent­ials was overhyped.

“I think it’s based mainly on ideology and activism,” Mr Coffey said.

This concern about methane is nonsense.
Water vapour blocks all the frequencies that methane does
so the presence of methane adds nothing

Technical Background

Methane alarm is one of the moles continually popping up in the media Climate Whack-A-Mole game. An antidote to methane madness is now available to those inquiring minds who want to know reality without the hype.

Methane and Climate is a paper by W. A. van Wijngaarden (Department of Physics and Astronomy, York University, Canada) and W. Happer (Department of Physics, Princeton University, USA) published at CO2 Coalition November 22, 2019. Below is a summary of the more detailed publication. Excerpts in italics with my bolds.

Overview

Atmospheric methane (CH4) contributes to the radiative forcing of Earth’s atmosphere. Radiative forcing is the difference in the net upward thermal radiation from the Earth through a transparent atmosphere and radiation through an otherwise identical atmosphere with greenhouse gases. Radiative forcing, normally specified in units of W m−2 , depends on latitude, longitude and altitude, but it is often quoted for a representative temperate latitude, and for the altitude of the tropopause, or for the top of the atmosphere.

For current concentrations of greenhouse gases, the radiative forcing at the tropopause, per added CH4 molecule, is about 30 times larger than the forcing per added carbon-dioxide (CO2) molecule. This is due to the heavy saturation of the absorption band of the abundant greenhouse gas, CO2. But the rate of increase of CO2 molecules, about 2.3 ppm/year (ppm = part per million by mole), is about 300 times larger than the rate of increase of CH4 molecules, which has been around 0.0076 ppm/year since the year 2008.

So the contribution of methane to the annual increase in forcing is one tenth (30/300) that of carbon dioxide. The net forcing increase from CH4 and CO2 increases is about 0.05 W m−2 year−1 . Other things being equal, this will cause a temperature increase of about 0.012 C year−1 . Proposals to place harsh restrictions on methane emissions because of warming fears are not justified by facts.

The paper is focused on the greenhouse effects of atmospheric methane, since there have recently been proposals to put harsh restrictions on any human activities that release methane. The basic radiation-transfer physics outlined in this paper gives no support to the idea that greenhouse gases like methane, CH4, carbon dioxide, CO2 or nitrous oxide, N2O are contributing to a climate crisis. Given the huge benefits of more CO2 to agriculture, to forestry, and to primary photosynthetic productivity in general, more CO2 is almost certainly benefitting the world. And radiative effects of CH4 and N2O, another greenhouse gas produced by human activities, are so small that they are irrelevant to climate.

Radiative Properties of Earth Atmosphere

On the left of Fig. 2 we have indicated the three most important atmospheric layers for radiative heat transfer. The lowest atmospheric layer is the troposphere, where parcels of air, warmed by contact with the solar-heated surface, float upward, much like hot-air balloons. As they expand into the surrounding air, the parcels do work at the expense of internal thermal energy. This causes the parcels to cool with increasing altitude, since heat flow in or out of parcels is usually slow compared to the velocities of ascent of descent.

If the parcels consisted of dry air, the cooling rate would be 9.8 C km−1 the dry adiabatic lapse rate[12]. But rising air has usually picked up water vapor from the land or ocean. The condensation of water vapor to droplets of liquid or to ice crystallites in clouds, releases so much latent heat that the lapse rates are less than 9.8 C km−1 in the lower troposphere. A representative lapse rate for mid latitudes is dT/dz = 6.5 K km−1 as shown in Fig. 2.

The tropospheric lapse rate is familiar to vacationers who leave hot areas near sea level for cool vacation homes at higher altitudesin the mountains. On average, the temperature lapse rates are small enough to keep the troposphere buoyantly stable[13]. Tropospheric air parcels that are displaced in altitude will oscillate up and down around their original position with periods of a few minutes. However, at any given time, large regions of the troposphere (particularly in the tropics) are unstable to moist convection because of exceptionally large temperature lapse rates.

The vertical radiation flux Z, which is discussed below, can change rapidly in the troposphere and stratosphere. There can be a further small change of Z in the mesosphere. Changes in Z above the mesopause are small enough to be neglected, so we will often refer to the mesopause as “the top of the atmosphere” (TOA), with respect to radiation transfer. As shown in Fig. 2, the most abundant greenhouse gas at the surface is water vapor, H2O. However, the concentration of water vapor drops by a factor of a thousand or more between the surface and the tropopause. This is because of condensation of water vapor into clouds and eventual removal by precipitation. Carbon dioxide, CO2, the most abundant greenhouse gas after water vapor, is also the most uniformly mixed because of its chemical stability. Methane, the main topic of this discussion is much less abundant than CO2 and it has somewhat higher concentrations in the troposphere than in the stratosphere where it is oxidized by OH radicals and ozone, O3. The oxidation of methane[8] is the main source of the stratospheric water vapor shown in Fig. 2.

Future Forcings of CH4 and CO2

Methane levels in Earth’s atmosphere are slowly increasing.  If the current rate of increase, about 0.007 ppm/year for the past decade or so, were to continue unchanged it would take about 270 years to double the current concentration of C {i} = 1.8 ppm. But, as one can see from Fig.7, methane levels have stopped increasing for years at a time, so it is hard to be confident about future concentrations. Methane concentrations may never double, but if they do, WH[1] show that this would only increase the forcing by 0.8 W m−2. This is a tiny fraction of representative total forcings at midlatitudes of about 140 W m−2 at the tropopause and 120 W m−2 at the top of the atmosphere.

The per-molecule forcings P {i} of (13) and (14) have been used with the column density Nˆ of (12) and the concentration increase rates dC¯{i}/dt, noted in Fig. 7 and Fig. 8, to evaluate the future forcing (15), which is plotted in Fig. 9. Even after 50 years, the forcing increments from increased concentrations of methane (∆F = 0.23 W m−2), or the roughly ten times larger forcing from increased carbon dioxide (∆F = 2.2 W m−2) are very small compared to the total forcing, ∆F = 137 W m−2, shown in Fig. 3. The reason that the per-molecule forcing of methane is some 30 times larger than that of carbon dioxide for current concentrations is “saturation” of the absorption bands. The current density of CO2 molecules is some 200 times greater than that of CH4 molecules, so the absorption bands of CO2 are much more saturated than those of CH4. In the dilute“optically thin” limit, WH[1] show that the tropospheric forcing power per molecule is P {i} = 0.15 × 10−22 W for CH4, and P {i} = 2.73 × 10−22 W for CO2. Each CO2 molecule in the dilute limit causes about 5 times more forcing increase than an additional molecule of CH4, which is only a ”super greenhouse gas” because there is so little in the atmosphere, compared to CO2.

Methane Summary

Natural gas is 75% Methane (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, in the past 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.  (From Sea Friends (here):

More information at The Methane Misconceptions by Dr. Wilson Flood (UK) here.

Climatists Aim Forks at Our Food Supply