Raymond Pierrehumbert on why GeoEngineering is the wrong way to solve abrupt global warming crisis

 I doubt you've studied the quantum mechanics of abrupt human caused global warming. Try reading Professor Raymond Pierrehumbert's article in Scientific American. Weird - I can't find that article on google nor even his list of published papers. Granted SciAm is more of a magazine than a science journal. I have it on my blog though.  Oh it's in PHysics Today

https://elixirfield.blogspot.com/2020/09/professor-ray-pierrehumbert-its-time-to.html 

https://elixirfield.blogspot.com/2018/10/physics-professor-raymond-t.html

Here's his article in the journal Nature - a nice overview: "Warming the world Greenhouse effect: Fourier’s concept of planetary energy balance is still relevant today." Sorry links are strictly censored on youtube unless I'm posting on my own uploads. haha. You're gonna have to cut and paste that article title - or you could practice "willful ignorance" which is the de facto norm on the interwebs.

 There's also his "Abrupt Climate Change" in the journal Science -  

Here is another great commentary by Raymond Pierrehumbert: 

 "To understand why albedo hacking is such a bad idea, we first have to understand the practically irreversible effects that carbon dioxide emissions have on climate. Carbon dioxide is removed only very gradually from the atmosphere, first through slow uptake by the oceans (where it causes ocean acidification) and ultimately by reaction with certain continental rocks over 100,000 years or more. If we emit a trillion tons of carbon in the form of carbon dioxide before we decarbonize the economy (we’ve already emitted more than half that) it will cause about 2 degrees Celsius of warming, and most of that warming will still be around in 10,000 years. 

Worse, a trillion tons doesn’t begin to exhaust the likely amounts of fossil fuels available, or the speed with which they could be tapped by an exponentially growing, energy-hungry, wasteful economy." "In other words, once you start doing albedo modification, you need to keep doing it essentially forever. Let me reiterate: Any kind of geoengineering of the Earth’s reflectivity—such as seeding the stratosphere with crushed limestone, or spraying saltwater in the air—is not a one-time, one-off event, but something which would have to be repeated in perpetuity, on a regular basis. In other words, forever.

 This is a key concept that most mass media coverage of geoengineering seems to miss. What is the morality of committing 10,000 years of future humanity to maintaining an activity year in and year out without fail? What is our track record as a species of maintaining any technological activity for more than a century or two? Oliver Morton, in his thoughtful (but ultimately boosterish) book puts forth the vision of albedo modification as just another stage in the cycle of technological dependencies that make the life of humanity better, rather like the Haber Process for making fertilizer has allowed agriculture to support a much larger population. 

It’s an interesting point, but there remains the uncomfortable issue of whether a global-scale intervention like albedo modification is really in the same category. Or, more broadly, is our ever-expanding wave of technological dependency increasing the resilience of human society or just setting us up for a harder fall when it all becomes unsustainable? Albedo modification is sometimes thought of as something you can do to hold warming in check while “buying time” to decarbonize the economy, but this is a fundamental misconception. Each additional kilogram of carbon dioxide emitted commits the Earth to a certain amount of warming that essentially never goes away (unless we learn how to suck carbon dioxide out of the atmosphere in massive amounts quickly—a very debatable prospect). And so the need for continued geoengineering to counteract that additional warming never goes away—even after carbon dioxide emissions are eventually brought to zero. 

  Moreover, because carbon dioxide accumulates inexorably in the atmosphere so long as emissions continue, one cannot even achieve the more modest goal of slowing the rate of warming without inexorably increasing the amount of albedo modification deployed each year. It’s like drinking water contaminated with a poison like mercury that accumulates in your body, but trying to cancel out the effects with ever greater dosages of antidote. So long as there is any poison left in the water, your bodily burden increases and each year you need to take a greater daily dose of antidote. Even if the poison is removed from the drinking water supply, you have to continue taking the antidote for the rest of your life, because of the poison accumulated in your body—unless you undergo some therapy which actively removes the poison from your body, which would be analogous to sucking carbon dioxide out of the air."

https://www.realclimate.org/index.php/archives/2010/12/losing-time-not-buying-time/ 

 For example, doubling CO₂ from 300 ppm to 600 ppm yields a clear-sky radiative forcing of 4.5 W/m². Doubling methane from 1ppm to 2 ppm yields a radiative forcing of 0.8 W/m², but since we started from such a low concentration of methane, it takes many fewer molecules of methane to double methane than to double CO₂. Per molecule added, methane yields about 54 times as much radiative forcing as CO₂. Note that most of this effect has nothing much to do with any special property of methane, but arises simply because the radiative forcing for most greenhouse gases is logarithmic in concentration, so you sort of get the same radiative forcing for everybody upon doubling their concentration — but if you start with somebody whose concentration is low, it takes many fewer molecules to double. That means that the CO₂ equivalent of methane depends on what concentration you are starting with. If you started from a concentration of 10ppm, then the equivalence factor drops to 10. If you start out with equal amounts of methane and CO₂ (300 ppm), then the equivalence factor drops further to 0.5. In that sense, methane is, intrinsically speaking, a worse greenhouse gas than CO₂, though the crossover is at values that are so high they are only relevant (at most) to the Early Earth.

 Nice explanation!! Thanks Raymond Pierrehumbert

Methane oxidizes to CO₂ in about 10 years, and since we are dealing with so little methane, that extra ppm of CO₂ you get after it oxidizes adds little ongoing warming. That means that the methane concentration in the atmosphere is determined by the methane emission rate averaged over the previous ten years, and the methane component of warming disappears quickly after emissions cease. In contrast, about half of CO₂ emitted disappears into the ocean fairly quickly, while the other half stays in the atmosphere for thousands of years. Therefore, the atmospheric burden of CO₂ in any given year is determined by the cumulative emissions going back to the beginning of the Industrial Revolution, and the warming persists for thousands of years after emissions cease. Over the long term, CO₂ accumulates in the atmosphere, like mercury in the body of a fish, whereas methane does not. For this reason, it is the CO₂ emissions, and the CO₂ emissions alone, that determine the climate that humanity will need to live with for a time that stretches into the future at least as long as the time since the founding of the first Sumerian cities stretches into the past. The usual wimpy statement that CO₂ stays in the air for "centuries" doesn’t begin to convey the far-reaching consequences of the amount of CO₂ we decide to pump out in the coming several decades.

 "But the evidence is much firmer for the last 800,000 years, when ice cores show that CO2 concentrations stayed tight between 180 and 290 ppm, hovering at around 280 ppm for some 10,000 years before the industrial revolution hit."