All things being equal – Watts Up With That?

By Andy May

The interesting way Debate on Linkedin between Tinus Pulles and myself, the two topics that came up were related and too complex to comment on. The first is Tinus’ question, “Would the amount of CO in the atmosphere be more₂all other variables being equal, results in higher surface temperatures.”

The second question arose when I quoted the following from the IPCC AR6 report:

“As a result, much longer-lived non-condensable greenhouse gases act as ‘control knobs’, regulating planetary temperature, with water vapor concentration as a feedback effect (Lacis et al., 2010, 2013).” (IPCC, 2021, p. 179).

And this comment from AR5:

“Currently, water vapor has the largest greenhouse effect in the Earth’s atmosphere. However, other greenhouse gases, mainly CO₂, is necessary to maintain the presence of water vapor in the atmosphere. … Thus, greenhouse gases other than water vapor provide the temperature structure that maintains the current level of water vapor in the atmosphere. So even though CO₂ As the main man-made control on climate, water vapor is a powerful and rapid feedback that amplifies any initial forcing by a typical factor of two to three. Water vapor is not a significant initial force but is still a fundamental contributor to climate change.” (IPCC, 2013, p. 667).

Oddly, Tinus does not think that the IPCC takes seriously Lacis et al.’s view that CO₂ is a surface temperature control knob and he doesn’t seem to agree with it. His reasoning is that in the first quote, “control knob” is in quotes and the second is in a colored box, identifying it as an answer to a “FAQ” or Question common 8.1 (chapter 8, pages 666-667).

But both reports explicitly cite Lacis et al. (2010 & 2013) and use the language of Lacis et al and agree with them. We can comfortably assume that the IPCC AR5 and AR6 reports agree with Lacis et al., despite Tinus’ objections.

What’s interesting is that these two points are closely related in an interesting way. Tinus’s first question is a leading one with the underlying assumption that CO₂ climate control. He knew, as everyone does, that if infrared radiation hits pure CO₂ In the laboratory, it absorbs some of the substance and heats up. The laboratory experiment is the “all things being equal” he is talking about.

Outside of the lab and in the real world, there are a number of other factors that need to be addressed that could change the results, this is why the question Tinus asked comes out on top, the question is framed to come to a specific answer. Often, the way questions are asked can lead to wrong answers, so we need to avoid answering leading questions.

Now we come to the second problem, calling the CO₂ climate “control knob”. Lacis et al. explains this idea and is clearly supported by the IPCC:

“Abundant physical evidence shows that carbon dioxide (CO₂) is the most important climate-related greenhouse gas in the Earth’s atmosphere. This is because CO₂, like ozone, N2O, CH4 and chlorofluorocarbons, do not condense and precipitate from the atmosphere at current climate temperatures, while water vapor can and does. Non-condensable greenhouse gases, which account for 25% of the total greenhouse effect on earth, thus play a role in providing a stable temperature structure to maintain the current levels of water vapor and clouds in the atmosphere through Feedback processes account for the remaining 75% of the greenhouse effect. There is no radiation force provided by CO₂ and other non-condensing greenhouse gases, terrestrial greenhouses will collapse, pushing the global climate into a frozen state on Earth.” (Lacis, Schmidt, Rind, & Ruedy, 2010)

Lacis et al. estimates that water vapor is responsible for about 75% of the overall greenhouse effect, which is within the range of other estimates, but no one knows for sure because the impact of clouds is unknown. Clouds have a large positive (warming) greenhouse effect at night, trapping heat, and a large negative albedo (cooling) effect during the day because they are bright white and reflect a lot of incoming sunlight. . Furthermore, clouds change over time and by location (more on clouds This And This).

This means that the greenhouse effect varies over time and by region. In the tropics, where it is always wet, the greenhouse effect is very large, and in the deserts and polar regions in winter, the greenhouse effect is very small, even negative in the poles during most of the winter. In the polar regions in winter and in the desert, the sky is often cloudless.

As Lacis et al. for example, water vapor condenses and is unevenly distributed over the Earth’s surface. That is the crux of their argument that CO₂ and other non-condensable greenhouse gases are the “control knob” on climate, and water vapor is a significant but relatively unimportant “feedback” for doing what the advanced greenhouse gases tell it to do.

Is that argument correct? The pun is completely intentional. As Wim Röst said (in a very good presentation in June 2023 at Hillegom, the Netherlands), water, snow and water vapor govern the greenhouse effect, cooling the surface through evaporation, releasing much of their latent heat enters space and determines all weather. Various processes driven by water in the troposphere control the amount of incoming and outgoing radiation by changing both the position and motion of clouds and latent heat.

Wyatt and Curry [ (Wyatt & Curry, 2014), (Wyatt M. G., 2012c), (Wyatt M., 2014)] have shown that multiple ocean and atmospheric oscillations move across the Earth’s surface in a coordinated manner, which they call “stadium waves,” forming a climate cycle or oscillation of about 65-70 year. This fluctuation can be seen in global average temperatures as shown in (May & Crok, 2024) in figure 1 below.

As Figure 1 shows, the trendless global mean surface temperature (HadCRUT4) agrees well with the trendless AMO index. This correspondence is better, at least visually, than the correspondence between CO₂ and temperature. AMO is not the leading oscillator in stadium waves, but it is an important component of it. The correspondence of the AMO with global mean surface temperatures opens up the possibility that water and water vapor are not “feedbacks” but drivers of climate change. CO₂ and other non-condensable greenhouse gases may have some impact on climate change, but overall it is very small and it is doubtful that they play a major role.

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