Sometimes the best lines are throwaways. For instance Richard S. Lindzen’s recent aside about “the general expectation that long-surviving systems are dominated by negative feedbacks.” In the world of climate alarmism, of course, the feedbacks are all positive: the small warming from increasing CO2 alters water vapour in ways that increase temperature, thus releasing more CO2 from permafrost, “fire ice” or whatever you like that further alters water vapour until, in James Hansen’s memorably over-the-top warning, the “ocean ends up in the atmosphere” like Venus. Which is why they freak out on general grounds if you suggest otherwise. Thus Jim Steele recently wrote that “When I mention that CO2 has a cooling effect, I’m amazed by the hateful tirades from paranoid people who dismiss scientific truth as ‘dangerous misinformation’.”
Steele’s particular point is that “inversion layers” lead increased CO2 to increase radiation of heat to space, particularly in the stratosphere. How much exactly is a question for further research. But only if you don’t rule out a priori the very possibility of such mechanisms. Of which it is not the only one.
Indeed, Lindzen’s aside was contained in his chapter “Reflections on the Iris Effect” in Jennifer Marohasy, ed., Climate Change: The Facts 2020, on pp. 193-94. And the Iris Effect itself is another very interesting negative feedback mechanism. According to Lindzen, a vital impact of warming is that it diminishes upper-level cirrus clouds. But such clouds themselves contribute to warming. So the Iris Effect is another way that warming limits itself, a “negative-gain governor” tending to make the climate system more stable not less so… which helps explain why a viable biosphere has lasted so long.
Another chapter in that invaluable IPA book, which yes we recently read and are eagerly sharing its contents, discusses another such crucial negative mechanism. In “Tropical Convection: Cooling the Atmosphere”, Peter Ridd and Marchant van der Walt write that “Deep convection drives energy from near the earth-ocean surface, where it has accumulated due to the absorption of solar energy, to the upper atmosphere where it can be radiated to space as infra-red (IR) emissions. This is one of the energy transfer pathways that cools the surface.”
The importance of this mechanism is enormous, they say. “Deep convection ultimately reduces the surface temperature of the earth by about 45 degrees C, from what it would be if there were no air motion in the atmosphere; if the only mechanism to drive thermal energy upwards by IR radiative transport (Thomas & Stamnes 1999; Manabe & Strickler 1964). Without the air circulation caused by deep convection the Earth would be uninhabitably hot.”
Which, as an aside, would not exist if the “greenhouse effect” really did work like a greenhouse, whose glass panels prevent air from circulating in or out. And what of the feedback?
Well, say Ridd and van der Walt, “If the Earth’s temperature increases from whatever cause (natural or human influences), increased evaporation over the ocean provides more fuel to the convection heat engine, and the surface cooling effect it drives. We make this analogy with an engine and calculate that ‘the engine’ becomes more powerful by about 10% per degree rise in temperature. Therefore, in the tropics the heat engine is a very strong negative feedback mechanism, acting to counter the effects of increasing concentrations of greenhouse gases.”
These are just three mechanisms. And of course none exist, or have a powerful impact, just because someone said they did. It’s a matter for empirical investigation. But within a theoretical framework that allows the possibility that they do, which framework is arguably now lacking at least within the citadels of orthodoxy.
If climate science were real science, it would not have a dogmatic a priori assumption that there are few or no negative feedback mechanisms. On the contrary, it would incline to assume the reverse though not uncritically; since the climate has been here for a while, it stands to reason that something is holding it together. Otherwise some stochastic shock, even if not man-made, would have pushed it off a cliff or whatever metaphor you like and the planet would be all but uninhabitable.
Which is not to say that runaway processes cannot occur. Especially cooling; there are grounds for thinking the planet has periodically come close to being a snowball on which life could barely survive. And things that seem long to us, though in geological terms they are brief, show that there are several equilibria possible. But by and large the planet has tended to be at around 22°C for very long periods of time, and at the current 12 for much shorter ones that were still long. And while it is not, of course, the case that at 22 the planet was a wasteland, the main point is that something tended to make temperature settle down for long periods of time. Exactly what the alarmists, by and large, declare to be either impossible or at least dependent on keeping atmospheric CO2 way below where it normally was.
Which makes no sense.