By Andy May
In an interesting linkedin debate between Tinus Pulles and me, two subjects came up that are related to one another and too complicated for a comment. First is Tinus’ question, “Will more atmospheric CO2, all other variables being equal, lead to a higher surface temperature.”
The second question arose when I quoted the following from the IPCC AR6 report:
“As a result, non-condensing GHGs [greenhouse gases] with much longer residence times serve as ‘control knobs’, regulating planetary temperature, with water vapour concentrations as a feedback effect (Lacis et al., 2010, 2013).” (IPCC, 2021, p. 179).
And this comment from AR5:
“Currently, water vapour has the largest greenhouse effect in the Earth’s atmosphere. However, other greenhouse gases, primarily CO2, are necessary to sustain the presence of water vapour in the atmosphere. … So greenhouse gases other than water vapour provide the temperature structure that sustains current levels of atmospheric water vapour. Therefore, although CO2 is the main anthropogenic control knob on climate, water vapour is a strong and fast feedback that amplifies any initial forcing by a typical factor between two and three. Water vapour is not a significant initial forcing, but is nevertheless a fundamental agent of climate change.” (IPCC, 2013, p. 667).
Oddly, Tinus doesn’t think the IPCC is serious about Lacis, et al.’s idea that CO2 is a control knob for surface temperature and he apparently disagrees with it. His excuse is that in the first quote “control knob” is in quotes and in the second is in a colored box, which identifies it as an answer to a “frequently asked question” or FAQ 8.1 (chapter 8, pp 666-667).
But both reports clearly cite Lacis, et al. (2010 & 2013) and use Lacis et al.’s language and agree with them. We can comfortably assume that the IPCC AR5 and AR6 reports agree with Lacis et al., regardless of Tinus’ objections.
The interesting thing is that these two points are intimately related to one another in an interesting way. Tinus’ first question is a leading question with the underlying assumption that CO2 controls the climate. He knows, as everyone does, that if infrared radiation is shined on pure CO2 in a laboratory, it will absorb some of it and warm up. The laboratory experiment is the “all things equal” he is talking about.
Outside the laboratory and in the real world there are a number of other factors that need to be dealt with that can change the result, this is why the question Tinus is asking is leading, the question is framed to get at a particular answer. Often, the way a question is framed can result in an answer that is incorrect. We must avoid answering leading questions.
Now we come to the second issue, calling CO2 the climate “control knob.” Lacis et al. explains this idea, which the IPCC clearly supports:
“Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere. This is because CO2, like ozone, N2O, CH4, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.” (Lacis, Schmidt, Rind, & Ruedy, 2010)
Lacis et al. estimate that water vapor supplies about 75% of the overall greenhouse effect, which is in the ballpark of other estimates, but no one knows for sure because the effect of clouds is unknown. Clouds have a large positive (warming) greenhouse effect at night, keeping heat in and a large negative (cooling) albedo effect during the day because they are bright white and reflect a lot of incoming sunlight. Further, clouds vary over time and with location (more on clouds here and here).
This means that the greenhouse effect changes both temporally and areally. In the tropics where it is humid all the time the greenhouse effect is very large and in deserts and in the polar regions in the winter it is very small, even negative at the poles over much of the winter. In the polar regions in winter and in deserts the skies are usually cloud free.
As Lacis, et al. say, water vapor condenses, and is unevenly distributed over Earth’s surface. That is the crux of their argument that CO2 and other non-condensing GHGs are the “control knob” for climate and water vapor is a significant, but relatively unimportant, “feedback” that does what the superior GHGs tell it to do.
Does that argument hold water? The pun is fully intended. As Wim Röst has said (in a very good June, 2023 presentation in Hillegom, The Netherlands) water, snow, and water vapor dominate the greenhouse effect, cool the surface through evaporation, release much of their latent heat to space, and determine all weather. The various water-driven processes in the troposphere control the amount of incoming and outgoing radiation by varying both the location and movement of clouds and latent heat.
Wyatt and Curry [ (Wyatt & Curry, 2014), (Wyatt M. G., 2012c), (Wyatt M., 2014)] have shown that numerous ocean and atmospheric oscillations move across Earth’s surface in a coordinated manner, that they call the “stadium wave,” that forms a roughly 65-70-year climate cycle or oscillation. This oscillation can be seen in global average temperature as shown in (May & Crok, 2024) in figure 1 below.
As figure 1 shows the detrended global average surface temperature (HadCRUT4) conforms very well to the detrended AMO index. This correspondence is better, at least visually, than the correspondence between CO2 and temperature. The AMO is not the leading oscillation in the stadium wave, but it is an important component of it. The correspondence of the AMO to the global average surface temperature opens the possibility that water and water vapor are not a “feedback,” but a driver of climate change. CO2 and other noncondensing greenhouse gases probably have some effect on climate change, but by all accounts, it is small, and it is doubtful that they are in the driver’s seat.
Download the bibliography here.
Water condenses but it also evaporates so won’t the water cycle function with our without non condensing greenhouse gases?
Typo – with or without
I think the water cycle will function without CO2 and I think clouds will exist without CO2. But I don’t remember reading that anywhere else. It is the weakest part of Lacis’ hypothesis in my opinion.
loucksda8e9eb4118: “so won’t the water cycle function with or without non condensing greenhouse gases?”
WR: The Water Cycle reacts to temperature. Temperature is set by a lot of factors, the most important is the Water Cycle itself. Think about the highly dynamic temperature-dependent evaporative cooling of the surface, about abundant water vapor which at relatively low temperatures enables the start of surface heat removing convection, think about the formation and disappearance of clouds, about the role of sea-ice covering polar oceans and in this way strongly diminishing polar ocean heat losses. Think also about the low and high-pressure areas caused by local differences in water vapor and temperature, the wind directions, and the wind strengths caused by the strength and position of those pressure areas, think about the changes in oceanic behavior those winds and evaporation are causing. All changes affect Weather and Weather Patterns which in turn change the oceans, changes that in turn are affecting Weather and Weather Patterns, etc. etc..
The end result of all Water Cycle actions is…. a certain surface temperature.
And my point is that Lacis et al are only looking at half the story, the condensing half, and ignoring the evaporative half. Therefore their argument is invalid.
For those interested in the full LinkedIn discussion, please read: https://drive.google.com/file/d/1vTDySgA5t575PgOUCfLor_NgpqUCnt-h/view?usp=drive_link
We can see that AMO and ENSO are generally in ‘resonance’, which suggests that solar intensity is the common factor, combined in random mode by the modulations of surface states linked to the defusing of both the Atlantic and Pacific trade winds.
Over the last 40 years, the reduction in sulphur aerosols has led to a rise in the TSI at the end of the Maunder Minimum, with its effect on reducing cloud density and leading to a significant increase in the energy accumulated by the oceans and returned to the atmosphere during the warm ‘phase’ of the SST.
Slightly tangentially; If one look at the SST in the area 40N to 60N -40E to -10E , ERSST V.5
(e.g https://climexp.knmi.nl/select.cgi?id=someone@somewhere&field=ersstv5)
The AMO is clear without there being any residual or trend.
The standalone statistics package “PAST” from the University of Oslo has ‘Sum-of sinusoids’ fitting.
(Model->Sum-of-sinusoids ,click the tic-box that says ‘Fit periods’) the residuals from a fit are displayed and can be pasted back into PAST’s spreadsheet-style environment and tested for a trend with Model->Linear …
It gets 69.6 years as the highest amplitude wave ~0.3 C and 21.6 years as the second wave ~0.18C
-Pretty close to 22 years
Cool! Thanks
PAST statistics package: https://www.nhm.uio.no/english/research/resources/past/
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My overall impression here – a LOT of people talk about climate change is if this were a simple subject. Unfortunately, this is a monstrously complex subject. It encompasses physics, chemistry, studies of the sun, geology, paleontology, dendrology – it is literally the most cross disciplinary subject known to the human race. And no one understands every little piece of it.
I wrote my master’s thesis on paleo climate science, back in the stone age. I’ve been listed as a climate expert and written various summary documents for the government. And I will say – I would need to spend every waking hour of every day till I die reading and studying to understand it. That said, my overall sense is, 80% of the papers, models, and projections are pure speculation. Absolute scientific bilgewater. So many studies that get published are what I call confirmational studies – the study was planned with an expected result in the data, that it would match what is known about climate change. If the results don’t, the data is adjusted until they do.
That said, I think Andy May brings up a great many interesting and important objections and observations, which, are certainly worth a fair discussion. I have, myself, noted the weird correspondence of the ADO and PDO to climate change temperatures. It seems unlikely to be coincidental and suggests a lot of what we assign to climate change might not be solely due to that source. But I don’t have a clue, because I have yet to hear a convincing explanation for what causes the AMO and PMO.
AMO changes could be due to atmospheric circulation, which induce changes in clouds, atmospheric dust and surface heat flux. Freshwater influx may also be responsible. So, climate change could drive the AMO, hence the graph would then match the AMO. But I have always assumed the drivers for the AMO were a lot more complicated than simple warming.
More simply, does warming drive the AMO, or does the AMO drive the warming? I do recall that the prevalent theory of the Younger Dryas was a huge release of freshwater to the oceans. That caused a break or pause in the AMO. That caused an abrupt cooling in the northern hemisphere. The AMO then would act to buffer out the effects of climate change – as the poles melt, more freshwater enters the ocean, that causes the AMO and PMO to slow down, causing cooling, and the glaciers reform? That would make perfect sense to me, as a control knob for climate. Better yet, not a control knob, a thermostat. It keeps the climate in the northern hemisphere within certain boundaries.
I would appreciate your insights.
I’m unclear what drives the AMO or what caused the Younger Dryas. I see lots of ideas about both but no one has convinced me they know either. I am pretty sure that changes in CO2 concentration did not cause either, but beyond that conclusion, I don’t know.