667 per centimeter : climate science, quantitative biology, statistics, and energy policy

When chasing political solutions to mitigating climate disruption, it’s long been tempting to go after relatively easy quick wins in the short term rather than facing up to the real problem: Emissions of Carbon Dioxide. So, in a world where lack of progress in the UNFCCC as evidenced in the recent COP26 seems a failure of international and national politics, the idea of focusing upon reducing Methane emissions and other short-lived climate pollutants is an easy branch to grasp as we are falling from the horse. John Broder at The New York Times reports on how the United States is doing just that.

Another Times journalist, Andrew Revkin, summarized the scientific consensus on why this focus is misplaced, even bad in his “Scientist’s View: In Climate Action, No Shortcuts Around CO2.” His article quoted James Hansen, Susan Solomon, Ken Caldeira, and Ray Pierrehumbert, linking to Professor Pierrehumbert’s piece at RealClimate (“Losing time, not buying time”), one which included the following figure:

And this one:

Yes, this is a long game, one where Methane is a bit player.

What’s also concerning is measures to curtail some short-lived climate pollutants, notably the hydrofluorocarbons, will result in more Carbon Dioxide emissions in the long run. While there are substitutes available for hydrofluorocarbons, at present none are as effective as the originals and, in an example of the engineering trade-offs (*) which riddle through all solutions to climate disruption, they are key components of geothermal and air source heat pumps, devices which replace natural gas and oil furnaces, particularly in northern climes. Zero CO₂ emissions there, and no emissions of hydrofluorocarbons when the units are properly maintained.

I’ve blogged about Methane before, quoting some of the same sources. Professor Pierrehumbert has a more detailed technical review article presenting the arguments why the focus should and must be Carbon Dioxide, as politically and economically difficult as that might seem (**). And he keeps trying to make that point.

Quoting Professor Pierrehumbert’s RealClimate article:

Let’s suppose, however, that we decide to go all-out on methane, and not do anything serious about CO₂ for another 30 years. To keep the example simple, we’ll think of a world in which methane and CO₂ are the only anthropogenic climate forcing agents. Suppose we are outrageously successful, and knock down anthropogenic methane emissions to zero, which would knock back atmospheric methane to a pre-industrial concentration of around 0.8 ppm. This yields a one-time reduction of radiative forcing of about 0.9W/m². Because we’re dealing with fairly short-term influences which haven’t had time to involve the deep ocean, we translate this into a cooling using the median transient climate sensitivity from Table 3.1 in the NRC Climate Stabilization Targets report, rather than the higher equilibrium sensitivity. This gives us a one-time cooling of 0.4ºC. The notion of “buying time” comes from the idea that by taking out this increment of warming, you can go on emitting CO₂ for longer before hitting a 2 degree danger threshold. The problem is that, once you hit that threshold with CO₂, you are stuck there essentially forever, since you can’t “unemit” the CO₂ with any known scalable economically feasible technology.

While we are “buying” (or frittering away) time dealing with methane, fossil-fuel CO₂ emission rate, and hence cumulative emissions, continue rising at the rate of 3% per year, as they have done since 1900. By 2040, we have put another 573 gigatonnes of carbon into the atmosphere, bringing the cumulative fossil fuel total up to 965 gigatonnes. By controlling methane you have indeed kept the warming in 2040 from broaching the 2C limit, but what happens then? In order to keep the cumulative emissions below the 1 trillion tonne limit, you are faced with the daunting task of bringing the emissions rate (which by 2040 has grown to 22 gigatonnes per year) all the way to zero almost immediately. That wasn’t very helpful, was it? At that point, you’d probably like to return the time you bought and get a refund (but sorry, no refunds on sale items). More realistically, by the time you managed to halt emissions growth and bring it down to nearly zero, another half trillion tonnes or so would have accumulated in the atmosphere, committing the Earth to a yet higher level of long-term warming.

(Some emphasis added in the above.)

Accordingly, all the United States position on Methane and other gases means is that leadership has been lost, and if that’s all there is, the COP26 is indeed a failure. Without more political and economic ambition on the part of developed countries to reduce their CO₂ emissions, it can’t be anything else.

I’m not suggesting sackcloth and ashes here, and I’m not even suggesting reducing consumption. I am suggesting that those with means, who consume the most, need to rejigger their kit, switching to EVs on their own dime, putting PV panels everywhere they can, installing home batteries, and demanding their suburbs generate sufficiently electricity on the lands they have and control to supply all their needs. They have the wealth to do this, comparatively speaking, without hardship. The tools to do this are here, now, and they do not require some unproven future technology to achieve. In my opinion, there is no need for degrowth.

Update, 2021-11-15

There was a lot of back in forth in the comments of another forum to which I contributed (***). This concerned whether or not the so-called Global Warming Potential (GWP) in particular with respect to Methane was meaningful for policy purposes. I got a bit wrong, because I did not realize infrared absorption spectra were built into the definition of GWP. With help from an expert advisor (****), I discovered that the GWP of a substance is the warming contributed by a one tonne pulse of the substance contributed to atmosphere over a hundred year interval relative to the effect of a one tonne pulse of Carbon Dioxide. This seemed to be widely accepted, even if it has some dark corners which I won’t get into here.

However, while doing some reading on this I discovered:

Allen, Myles R., Jan S. Fuglestvedt, Keith P. Shine, Andy Reisinger, Raymond T. Pierrehumbert, and Piers M. Forster. "New use of global warming potentials to compare cumulative and short-lived climate pollutants." Nature Climate Change 6, no. 8 (2016): 773-776.

Allen, et al point out there are shortcomings to using GWP and, in fact, there are alternatives, including one called Global Temperature Potential or GTP. What this means for methane and black Carbon (soot) is illustrated by the following figure:

I strongly recommend the article to see what some of the problems are with GWP.

(*) Land use for solar and wind farms versus aesthetics and appearance, even though the forests are unhealthy. Land use for traditional agriculture versus land use for agrivoltaics. Sea areas for wind farms versus preserving traditional fishing and shrimping spots. Fossil fuel industry jobs despite impact upon health, the climate, and its economic inefficiency versus wind+solar+storage+electrolyzed Hydrogen. Highly reliable EVs versus ICEs which support employment at gas stations, auto repair jobs, and the auto assembly lines. Discounting the harms to future generations in OECD countries and harm which is occuring to the non-OECD versus taking the moral responsibility to effectively pay for the harms done to the climate. There are many others.

(**) The fault, in my opinion, isn’t Republican versus Democrat, since parties have historically done nothing substantial to fix greenhouse gas emissions, as reported by James Gustave Speth in They Knew: The Us Federal Governments Fifty-Year Role in Causing the Climate Crisis (2021). The fault is to a great degree Western culture and a collective refusal to acknowledge how our quality of life is do primarily to our exploitation of the resources of the planet.

(***) Alas, despite searching, I could not locate this discussion. I think it was at Peter Sinclair’s Climate Denial Crock of the Week.

(****) Dr Alan S Levy, or ClimateAdam