By Andy May
The moist‑adiabatic theory (Durran & Klemp, 1982) is one of the central organizing ideas in atmospheric thermodynamics, and it is used—both explicitly and implicitly—throughout modern climate models, especially in the tropics where it works best. It stems from thermodynamics and says that a rising parcel of humid air cools more slowly than a dry parcel because cooling causes condensation of water vapor which releases latent heat that warms the parcel. Adiabatic simply means that the strict theory requires, unrealistically, that no heat enters or leaves the air parcel being modeled from the environment around it, that is, the air surrounding the parcel.
Climate models use this concept, along with an estimate of the amount of “outside” air that mixes with the modeled air parcel over time to construct a vertical atmospheric temperature gradient. The theory is used mostly to evaluate and quantify greenhouse gas feedbacks (Feldl et al., 2026) in the lower latitudes. Inevitably, this modeling procedure has flaws, especially in the very active troposphere. The most obvious flaw is the tropical mid-troposphere model “hot spot” made famous by John Christy and Ross McKitrick as I have previously discussed here. You can see the climate model “hot spot,” in a tropospheric cross section of the Canadian Climate Model output in figure 3 here. Most models have a tropical hot spot, yet the spot does not show up in weather balloon or satellite observations, as conclusively shown by McKitrick and Christy (McKitrick & Christy, 2020 & 2018). This climate model flaw is serious and freely admitted in BAMS State of the Climate (Blunden & Arndt, 2020, p. S109), IPCC AR5 (IPCC, 2013, p. 892), and AR6 reports (IPCC, 2021, p. 444).
Christy pointed out this model flaw when he reviewed early drafts of the IPCC AR5 report in 2012 (pers. communication) and the IPCC published a figure, with little comment, illustrating the problem in Chapter 10 of the AR5 report on page 892. The AR5 illustration (shown on the right in figure 1) suggests that if the CO2 effects are not included in climate model runs the erroneous tropical “hot spot” is reduced or eliminated.
The problem has not gone away, and seems to have gotten worse with time, as shown in the AR6 graph to the left in figure 1 (note the x axis scale change between AR5 and AR6). Christy first reported the climate model problem in the tropical troposphere more than thirteen years ago and yet it has not been fixed in two IPCC iterations. This raises the question, “Why?”
Usually, any model can be fixed to eliminate such an obvious problem given enough time and effort. So why does the problem still exist? Is it due to some fundamental problem in the climate model structure? I think so. In my opinion, it seems that the root cause is the reliance of models on the moist adiabatic theory. I don’t think this theory can be used to recreate the critical tropospheric tropical lapse rate.
The Moist Adiabat and RAE
As explained by Timothy Cronin and Malte Jansen (Cronin & Jansen, 2016), the lapse rate in higher latitudes increases dramatically with surface temperature, relative to both the mid-latitudes and the tropics. This is illustrated in figure 2. This plays a role in polar amplification of warming. However, Cronin & Jansen show that, regardless of the pattern in figure 2, the lapse rate in the higher latitudes is more stable in the sense it is less sensitive to surface temperature vertically than in the tropics. The middle latitudes lie between these extremes.
The climate processes in the higher latitudes are fundamentally different than in the tropics. While the moist-adiabatic theory can get in the ballpark of the deep tropical lapse rate as shown later in this post, the higher latitudes are clearly in a different domain. Cronin and Jansen call this the radiative-advective equilibrium or RAE. The high latitudes are very sensitive to season and climate processes are not a function of surface temperature, but of a variety of forcings including changes in clouds, water vapor, surface albedo, and the variable transport of thermal energy and water vapor from the lower latitudes (see the Winter Gatekeeper Hypothesis).
In its simplest form, Cronin and Jansen state that RAE is a high latitude tug of war between two strong forces, radiative cooling to space and horizontal heat transport from the lower latitudes. Equilibrium is only achieved when these two forces balance. Thus, surface temperature plays a much smaller role in driving climate changes in the high latitudes. This post doesn’t address RAE, here we will discuss the limitations in the moist adiabatic theory in its wheelhouse, the deep tropics, where seasonal effects are minimal.
The tropospheric lapse rate
In the deep tropics (0-20°N/S) vertical convection is vigorous, and the environmental or actual lapse rate (Γ_env) is expected to relax toward Γₘ (the moist adiabatic lapse rate) because convection mixes the troposphere and should drive the lapse rate toward a moist adiabatic temperature profile. The middle latitudes have more dry air and Γenv < Γₘ. As discussed above, there is very little deep convection in the high latitudes and Γenv << Γₘ. The tropical lapse rate is closer to the moist adiabatic lapse rate, and the high latitude lapse rate is much farther from it. This is generally what is observed, as shown in figure 3.
In figure 3 the moist adiabatic lapse rate is computed using IGRA2 weather balloon and radiosonde data using the standard equation (Durran & Klemp, 1982). The actual lapse rate is computed directly from the IGRA2 temperature and height data. In this plot, as in the others in post, the IGRA data are run through a QC function that eliminates anomalous data. The function checks for reverse trends in the data and other anomalies.
The points in the graph are IGRA2 weather balloon stations and the computed global means of 10° latitude bins. The values are the computed moist adiabatic lapse rate subtracted from the actual. Generally, the value is negative, meaning that the moist adiabatic lapse rate (Gamma_m or Γₘ) is larger than the actual lapse rate (Γenv), the exception is the lower troposphere from about 25°S to 10°N, where the mean actual lapse rate is higher than the moist adiabatic lapse rate suggesting vertical instability.
In the tropics, deep convection tends toward the moist adiabat (Cronin & Jansen, 2016), relative to the middle latitudes, it even exceeds it in the deep tropics as shown in figure 3. If the actual lapse rate is higher than the fully saturated moist adiabatic lapse rate, then air parcels cannot cool themselves naturally and accelerated vertical convection will occur, it initiates spontaneously. This is one way cloud towers form in the tropics and during thunderstorms.
It is easier to see what is happening if we compare the moist adiabatic lapse rate to actual, as shown in figure 4.
As illustrated in Figure 4, Γₘ is the cooling rate of a normally rising saturated air parcel, expressed in °C/km. The dry adiabatic lapse rate is about 9.8 °C/km, while the moist adiabatic lapse rate typically ranges from 3 to 7 °C/km, depending strongly on temperature and humidity. The actual lapse rate is strongly dependent upon latitude and varies from near zero in the polar regions to over six °C/km in the tropics. As noted above, when Γ_env is less than or equal to Γₘ, the atmosphere is stable or neutral: a rising saturated parcel cools as fast or faster than its surroundings and therefore does not accelerate upward. But when Γ_env exceeds Γₘ, a saturated parcel cools more slowly than the environment, becomes warmer and lighter than the surrounding air, and accelerates spontaneously. This conditionally unstable state triggers vertical overturning and deep convection.
AR6 tells us that:
“In the tropics, the vertical temperature profile is mainly driven by moist convection and is close to a moist adiabat.” (IPCC, 2021, p. 969).
The IGRA data reveal that while this statement is true, the story is more complex. AR6 relies on the relationship between the moist-adiabatic lapse rate and the actual lapse rate to evaluate feedbacks quantitatively, this includes water vapor feedback and aerosol feedback. While warming attributed to greenhouse gases alone is about one degree per doubling, the effect of feedbacks is estimated (by the IPCC) to exceed two degrees, so the evaluation of feedbacks is important, especially when combined with radiative-advective equilibrium or RAE (Feldl et al., 2026).
Deep convection in the lower troposphere intensifies rapidly once sea surface temperatures (SSTs) approach 30 °C, as shown in Figure 5. This is a natural thermostat or an atmospheric air conditioner that prevents surface temperatures from exceeding 30°C for any length of time over the oceans (Sud et al., 1999) & (Newell & Dopplick, 1979). For those interested, the first mention of the 30 °C limit is probably (Riehl & Malkus, 1958). Over land and close to shore there is no real limit.
The rapid acceleration of rising warm air when Γ_env > Γₘ causes many weather features like tropical thunderstorms and the ITCZ. The ITCZ is the most visible evidence of the effect and generally it lies between 10°N and 10°S, it is comprised of deep convective cloud towers.
The moist adiabatic theory and reality.
Figure 6 shows the observed tropospheric temperature between 10°N and 10°S in black and the moist adiabatic temperature in blue. The red line removes the “adiabatic” restriction on heat flow and allows some heat transfer between the “environment” and each air parcel, thus it lies between measured air temperature and the moist adiabatic temperature, I call it “T_entrain.”
Discussion
After making the model to entrain some of the surrounding environmental air into the moist adiabatic parcels (red line), I noticed that the shape of the moist adiabatic profile (blue) and the entrained profile were substantially different than the shape of the actual temperature curve. The relationship reminded me of the shape of the measured data, shown in black in figure 1, as compared to the AR5 and AR6 models shown in color. I do not think it is possible to adjust the simple air mixing parameter so that the entrained curve will match reality. In my opinion, this means we are missing something important. The moist adiabatic theory, alone, is not enough, even in the tropics.
Besides entrainment of surrounding air into a moist adiabatic air parcel, the environmental lapse rate is also affected by detrainment or the loss of humidity and heat to the environment. It is also affected by lateral winds bringing in dry air, cloud formation and destruction, possible air subsidence, cloud-radiative interactions, vertical wind shear, and inversions due to cloud formation. There are probably other factors as well that I can’t think of right now.
This is only considering the tropics; the higher latitudes are in a different world with regard to climate change. Nicole Feldl and Timothy Merlis (Feldl & Merlis, 2023) have proposed a composite model that blends the moist adiabatic theory in the tropics and the radiative-advective equilibrium theory for the higher latitudes. It supposedly allows climate changes to be a better function of only surface temperature. The IGRA2 data, as studied here, suggests that this sort of model will be an improvement to existing models, but will still be flawed, both in the tropics and in the higher latitudes. The bottom line is that climate change is not solely a function of surface temperature, there are other factors that play significant roles.
Download the bibliography here.
Earth is cooler w atmos/water vapor/30% albedo not warmer.
Ubiquitous GHE balance graphics don’t + violate GAAP & LoT.
Kinetic heat transfer processes of contiguous atmos molecules (e.g. convection) render a BB surface, “extra” GHE energy & “back” radiation impossible.
GHE = bogus & CAGW = scam.
Without any atmosphere, planet Earth would have a Albedo of about 0.13 similar to the moon and be cloudless and GHG free
Using normal textbook formulae
1360/4*(1-.13) = 295.8
And 296 Watts/sq.M using SB formula at emissivity of .98 gives 270 K or about 3 degrees below freezing as its emissions temperature…which would be the surface temperature.
Since the Planet is actually about 15 C…your claim is FALSE.
Your result for an atmosphere-less moon is 270K, a figure often seen.
Actual measured Average Surface Temperature for our moon is ~197K.
Since Earth’s AST is ~288K the idea that our cold, thin atmosphere can explain the > 90K difference is beyond ridiculous.
The reason the Moon has such a low temperature is that it’s solar cycle is 29.5 times longer than Earth’s so it cools to its minimum temperature for ~14 days.
” rel=”nofollow ugc”
It also warms to maximum for a longer period also. Time is important. Averages tell one nothing without quoting both a mean AND a variance. The variance of temperatures on the moon is quite large compared to the diurnal temperatures on the earth. A larger variance is an important distinction.
Agree, but the reason is not the rotation rate but the surface compostion.
On the current moon sun warms the upper 30-50cm of the regolith to max 400K or so.
On Earth we have mostly oceans. Sun only increases the temperature of the upper few meters a few degrees. Specific heat capacity matters.
Compare the diurnal temp variation of the ocean surface with that of eg a desert on the same latitude.
But T^4 means it radiates a lot more “”hot” so averages colder. Besides, I said normal textbook formulae, which assumes a planet rotating fast enough that the daytime/nightime temp variation is small…in the solar system, even the Earth doesn’t quite cut it…
That’s why I added a temperature graph to my post.
Some modelling showed that increasing the moons rotation rate to that of our Earth would result in a 10-15K higher AST.
Then adding an atmosphere would first of all result in ~30% reflected energy iso the ~11% we currently see.
So with much less solar energy the atmosphere would have to increase the AST some 80K.
Not to mention the oceans. Coldest ocean water is ~270K. No believable mechanism that can let the cold atmosphere warm ~4km deep oceans to these temperatures.
Remove the Earth’s atmosphere or even just the GHGs and the Earth becomes much like the Moon, no water vapor or clouds, no ice or snow, no oceans, no vegetation, no 30% albedo becoming a barren rock ball, hot^3 (400 K) on the lit side, cold^3 (100 K) on the dark. At Earth’s distance from the Sun space is hot (394 K) not cold (5 K).
That’s NOT what the RGHE theory says.
EVIDENCE:
RGHE theory says “288 K (15 C) w – 255 K (-18 C) w/o = a 33 C colder ice ball Earth.” 255 K assumes w/o case keeps 30% albedo, an assumption akin to criminal fraud. Nobody agrees 288 K is GMST plus it was 15 C in 1896. 288 K is a physical surface measurement. 255 K is a S-B equilibrium calculation at ToA. Apples and potatoes.
Nikolov “Airless Celestial Bodies”
Kramm “Moon as test bed for Earth”
UCLA Diviner lunar mission data
JWST solar shield (391.7 K)
Sky Lab golden awning
ISS HVAC design for lit side of 250 F. (ISS web site)
Astronaut backpack life support w/ AC and cool water tubing underwear. (Space Discovery Center)
That’s not what RGHE theory says. You seem to think so but…255 is what high school teachers correctly came up with as an effective radiative temp at 30% albedo and other basic assumptions for a uniform surface temp planet…to demonstrate the GHE to their students…that’s a long way from what a METEO Prof is going to tell his students.
For something more closely approximating Earth on the other hand…
1360/4x(1-0.3) = 238
And 238 watts/sq.M is about the a radiative temp of -35 C…Which is the temperature of the atmosphere about 8 km up…and then lapse rate of about 6.5 degrees C per Km gets you to approximately 290 K or 17 C down at surface. So your statements are FALSE…
288, 289, 290 is irrelevant for approx surface temp calcs…only 5 watts per degree….
And outer space is -270 “in the shade”. 394 K HaHaHaHa ROFL..
Where on the oblate spheroid of Earth receives 295.8 W/m^2.
The poles?
Those BHE balance graphics are “flat earth.”
The Flat Earther Society has their own web page. 1360/4 is for a spherical Earth.
Did you not read .13 Albedo…so not Earth as we live on…one with no clouds or oceans…
Generally Accepted Accounting Practices (GAAP) do not apply to balancing equations in science.
The 1st Law of Thermodynamics applies to thermal energy, not electromagnetic (Kirchhoff’s Law) but the principle of energy balance is defined, identically, in both.
Having dealt with material sciences, it is valid that all solid surfaces emit electromagnetic energy (not just IR) based on surface temperature. Water “skin” also acts as a surface.
There are a lot of thing wrong with those overly simplified graphics, which I have posted about many times.
GHE is bogus. CAGW = scam. Both statements are correct.
Albedo is a term that has been pirated and redefined.
It is now incorrectly used as “surface reflectivity.”
Bond albedo is the correct term and it is defined as how “bright” a surface appears from a distance (includes emissions and reflected energy)..
Geometric albedo is the term used when the view point is on the nadir vector from the source.
If one applies electromagnetic theory to the issue (which modelers avoid), one can calculate the surface reflectivity and EM energy absorption, base on geometry and angle of incidence.
“GHE is bogus” is 0/10 on your midterm. CAGW = tax collection excuse so 7/10 on the remainder.
How about ‘ambiguous’ rather than ‘bogus’?
“The phrase “greenhouse effect,” often abbreviated as “GHE,” is very ambiguous. It applies to Earth’s surface temperature, and has never been observed or measured, only modeled. To make matters worse, it has numerous possible components, and the relative contributions of the possible components are unknown.”
https://andymaypetrophysicist.com/2021/09/20/the-greenhouse-effect-a-summary-of-wijngaarden-and-happer/
Andy, thank you for this excellent and detailed analysis. Your discussion of the limitations of the moist-adiabatic theory — especially the persistent mismatch between modeled and observed tropical tropospheric temperatures (the missing “hot spot”) — highlights a fundamental issue in how climate models handle vertical structure and convection.
I’ve been working on a related but distinct framework called the Dew-Point Anchor Hypothesis (DPAH). It proposes that the dew-point lifting condensation level (LCL) acts as a primary thermodynamic “anchor” in the atmosphere. Instead of treating moisture as a passive byproduct of surface air temperature (SAT), DPAH elevates dew-point temperature to an independent state variable that helps constrain the vertical structure and preferred equilibrium states of the tropical atmosphere.
In this approach:
Early results and documentation are available in two open-access Zenodo deposits:
• DPAH Markov Model – Proposal #1: Dew-Point Lifting Condensation Level (LCL) as a Thermal Anchor in a Markov Chain Atmospheric Model
• DPAH Markovian Matrix: A Probabilistic Two-Regime Model of Tropical Atmospheric Circulation – Interim Report
I’d be very interested in your thoughts on whether this LCL-anchoring concept could complement or help refine the moist-adiabatic and radiative-advective ideas you discuss. The core idea is that the atmosphere isn’t purely driven by surface temperature gradients but is significantly governed by moisture thresholds.
Thanks again for the thoughtful post this kind of careful examination of foundational assumptions is exactly what’s needed.
Thanks Phillip, I downloaded the material and will look it over. I think we are circling the same thing, water vapor is not a “feedback,” it is the driving force behind climate change and its reverse, climate stability. Surface temperature is a minor player and heavily constrained by water vapor driven processes.
Andy,
Thanks for engaging in this issue. Here is some background on the Dew-Point Anchor Hypothesis (DPAH) for the general WUWT reader. From first principles physics has universal applicability. Geologists typically start their analysis by studying the large scale big picture and then work down in size from there. In the case of Earth’s planetary atmosphere, it is instructive to move out further and include in the study other terrestrial planet’s atmospheres in a process called comparative planetology. By approaching climate studies at this multi-planet scale, we can identify physical commonality. What I found was that there is a process by which a planet’s condensing atmospheric volatile determines the atmospheric component of Bond albedo. I identified the following planetary condensing volatiles: for Venus – Sulfuric Acid; for Earth – Water; for Mars – Carbon Dioxide gas; for Titan – Methane; and now I have added to the list for Pluto – Nitrogen gas.
Using my prior experience with Markov chain analysis for my master’s Dissertation on the Trees of Epping Forest. I engaged Grok in the mathematical process of studying climate from an inverse modelling perspective using Markov chains, with simple python code software that I can run on my Dell PC. Modelling is ultimately a process that matches a mathematical model to data. The results of modelling are only validations of a concept but not proof. My exploratory studies are ongoing with interim results published on Zenodo.
The climate processes in the higher latitudes are fundamentally different than in the tropics.
Are you sure about that?
Mysterious cold blob will ‘disrupt life as we know it’ across Europe
I was just getting over the green blob with therapy and it looks like I’ll be back on the medication again with the blues blob
When water vapor condenses into water droplets, heat is released and this heat causes the air to expand and become less dense.
At the same time, water droplets are denser than the previous water vapor.
That the thermal expansion dominates is demonstrated by the existence of thunderstorms.
My question is, how much does the condensation of water decrease the extra lift created by the release of heat caused by condensation?
The density increase from the condensed water reduces the extra buoyancy gained from latent heat release by only a small fraction — typically 10–25% in typical thunderstorm updrafts, and even less in the early stages. The thermal expansion effect strongly dominates, which is exactly why thunderstorms can grow explosively to the tropopause.
Why the Net Effect Still Strongly Favors Upward MotionWhen water vapor condenses:
Important observation: Small cloud droplets (typically 10–20 microns) remain suspended in the updraft and contribute to the loading. However, once droplets grow large enough to become raindrops (usually >0.5 mm), they fall out of the parcel as precipitation. This process (known as the pseudo-adiabatic approximation in meteorology) removes much of the liquid water mass while leaving the released latent heat behind in the rising air.
This is why:
A typical strong updraft might temporarily hold 2–8 grams of liquid water per kg of air. This loading reduces buoyancy by an amount equivalent to roughly 0.5–2.5 °C of cooling. Meanwhile, the latent heat released in the same process can warm the parcel by several degrees to over 10 °C cumulatively.
Result: Net buoyancy remains strongly positive. That’s why you see towering cumulonimbus instead of the cloud collapsing under its own weight.
Bottom LineYour observation is spot on: thermal expansion from latent heat dominates. The fact that raindrops fall out (while tiny cloud droplets do not) further tilts the balance in favor of strong upward motion. If the droplet mass penalty were stronger than the heating effect, deep moist convection (thunderstorms, tropical cyclones, the ITCZ) simply couldn’t exist at the scale we observe.
“Condensate loading: The newly formed liquid droplets add mass to the parcel.”
If a parcel of air contains moisture that converts to liquid droplets, how can the mass increase? Where did the additional material come from within the parcel of air to increase its mass?
Steve: Here is my DPAH collaborator Grok’s Reply:
The confusion is understandable but easily cleared up.
No additional mass is created. The total mass of the air parcel (dry air + water) stays exactly the same. The water simply changes phase from vapor to liquid droplets.
Condensate loading refers to the fact that, after condensation, the same water mass now exists as tiny liquid droplets that occupy almost zero volume. These suspended droplets increase the density (mass per unit volume) of the parcel slightly, creating a small downward force.
Meanwhile, the latent heat released warms and expands the air, strongly reducing its density.
The net result is still strongly positive buoyancy — which is why thunderstorms exist. The heat-driven expansion wins decisively over the modest loading effect from the droplets (especially once rain falls out and removes much of the liquid mass).
Think of convective clouds as bubble clouds which have an observable flat level base. Each rising thermal is like a warm, moist bubble of air. When it reaches the lifting condensation level (LCL), condensation kicks in: latent heat is released, the bubble gets even warmer and more buoyant, and it accelerates upward — just like a hot-air balloon or a soap bubble rising in still air. Glider pilots often experience this directly: they get “sucked into” these powerful bubbles, sometimes rising at 1,000–2,000 feet per minute or more once inside a well-developed cumulus cloud.
This phase-change buoyancy dynamic is exactly why the Dew-Point Anchor Hypothesis (DPAH) treats the lifting condensation level (LCL) as a key thermodynamic boundary.
At the LCL, the switch from vapor to liquid (with its associated latent heat release) suddenly activates powerful net upward buoyancy in moist air parcels. This is not just a minor local effect — it fundamentally shapes the vertical temperature and moisture structure of the entire tropospheric column in convecting regions. By anchoring the DPAH inverse stochastic model at this observable physical threshold (rather than assuming moisture is a passive slave to surface temperature), DPAH provides a natural constraint on the preferred equilibrium states of the atmosphere. It helps explain the transition into deep moist convection and the emergence of stable large-scale regimes such as the moist ascent (ITCZ-like) and drier descent branches of tropical circulation.
In short, the LCL is where the powerful thermodynamics you correctly identified — dominant heat-driven expansion versus modest condensate loading — becomes the dominant organising principle for the tropical troposphere. /Grok
I have a small problem with this. In a given volume, whether the mass is in vapor or liquid form, the mass remains the same. If the volume remains the same, then the density of that volume does not change.
This I understand and agree with. What I see occurring is that the density of the liquid is larger than the density of the expanded original volume and therefore does not rise as the less dense air surrounding the liquid drops rises farther.
In other words, it is the release of the latent heat from the water vapor that causes the expansion and further increase in height of the parcel of air. This should be a continuing process as not all water vapor will condense at once so some will continue upward and condense at higher and higher altitudes.
CO2 has nothing to do with this process. It is why water vapor and latent heat is the predominant heat regulation substance.
“These suspended droplets increase the density (mass per unit volume) of the parcel slightly, creating a small downward force.”
“At the LCL, the switch from vapor to liquid (with its associated latent heat release) suddenly activates powerful net upward buoyancy in moist air parcels.”
Help me understand. When does condensation increase density, and when does it reduce density?
Good question and Phillip can correct me here, but air parcel volumes are not constant. If they were, your argument would be valid. The volume expands and contracts with environmental conditions.
An air parcels mass is usually fixed and so is its composition. This last bit is problematic because, obviously, water vapor is a component, and it does change. As it changes the density changes.
This may seems like a dodge, but we are getting deep into the weeds here and rather than derail Andy’s thread with the high level meteorology that Grok is punching out, I recommend that you take up this question directly with the AI (this is a huge rabbit hole).
It is a good thing heat of vaporization is so large that the rising vapor easily overcomes other factors that would hinder its upward motion. The presence of CO2 is utterly unimportant. It just goes along for the ride.
With all that water, all forms, the impact of CO2 is so close to zero that the difference isn’t meaningful.
About the only impact CO2 has is that it makes the air slightly denser, though once again, the fraction of CO2 is so low that the difference is barely measurable.
CH4 atomic weight 16
H2O atomic weight 18
N2 atomic weight 28
O2 atomic weight 32
CO2 atomic weight 44
Those are ‘molecular’ weights not ‘atomic’, the third most common gas is omitted: Argon atomic weight 40.
I had forgotten about the impact of droplet formation.
Is that not because the cooling behavior of a parcel of air is driven by the absolute humidity until it reaches saturation? The Clausius-Clapeyron relationship establishes an upper-bound (saturation) on the potential humidity increase, dependent on temperature, but the actual humidity is generally supply-limited over the continents, which is why so much of the interior west of the Mississippi is arid or desert. Also, air can become supersaturated if there is a lack of sufficient condensation nuclei. That means the lapse rate varies locally with both temperature, evapotranspiration, and mixing.
Grok’s Reply to Clyde Spencer:
Clyde, you raise a very good point — the standard moist-adiabatic theory is insufficient on its own, even in the tropics, and your observation about humidity supply and local variability is part of the reason.
The moist adiabatic lapse rate assumes a parcel that remains saturated as it rises (i.e., it follows the Clausius-Clapeyron relationship perfectly). In reality, the cooling behavior of a real air parcel is governed by its actual absolute humidity (not just the saturation vapor pressure) until it reaches the Lifting Condensation Level (LCL). Only after condensation begins does the release of latent heat start to modify the lapse rate.
Important Distinction in the Tropics vs. Continents
However, even in the deep tropics, the simple moist-adiabatic assumption breaks down because real parcels experience entrainment of drier air, variable condensation nuclei, occasional supersaturation, precipitation fallout, and ice processes higher up. This is why Andy’s analysis shows the observed temperature profile diverging from the pure moist adiabat.
This is exactly where the Dew-Point Anchor Hypothesis (DPAH) tries to add value. Instead of assuming moisture is always a passive slave to surface temperature (following C-C perfectly), DPAH treats the dew-point temperature and the LCL as a primary, observable thermodynamic anchor. It recognizes that the actual moisture content sets a real physical boundary condition that constrains the vertical structure and preferred equilibrium states of the tropical atmosphere — not just the theoretical saturation limit.
By using a probabilistic (Markovian) approach anchored at the LCL, it naturally produces two stable regimes (moist ascent and drier descent) while still respecting energy balance and local supply variations. This helps explain why the pure moist-adiabatic theory falls short and why the tropical “thermostat” around 30°C is so robust.
Your point about local variability in lapse rates due to actual humidity, mixing, and nuclei is spot on — these are exactly the kinds of real-world complications that simpler theories miss. Anchoring at the dew point/LCL provides a practical way to incorporate them without losing physical transparency.
Well said, Clyde. /Grok
Thank you for going to the trouble of validating my ruminations.
Clyde
Super saturation in free atmosphere is not possible as the parcel increases altitude, given that atmospheric temperature and pressure both reduce simultaneously.
Yes, increased available nuclei improves the formation of droplets at lower saturation levels. Heavy rain is super saturation of the atmosphere, but the droplets are descending at a reasonable speed.
Yes these cold droplets may attract some heat as cold water is more receptive to heat adsorbsion, but that heat is secured within the water as it descends due to atmospheric pressure increase.
Regards
Ozone, supersaturation is normal inside clouds, in fact it is required for them to form. When deep tropical convection occurs, super saturation is the norm. Updrafts often exceed 5-10 m/s, cooling is very rapid, and condensation cannot keep up.
Some day I may get around to writing an article about it, but after reading a Discover Magazine article (The Clouds Are Alive, April 2012) about the role of microbes in clouds, I realized that the contribution of fugitive antibiotics may also play a role in the debate about the role of Man in affecting weather and climate. There is so much we don’t know about Nature, which is generally ignored by those who have already decided that CO2 from fossil fuels controls everything.
Thanks
It is missing from models but it is now well known, The tropical oceans surface temperature is regulated. It cannot sustain more than 30C.
This explanation comes from MS Copilot:
The role of ice in the tropical atmosphere
In the deep tropics, the emission of outgoing longwave radiation (OLR) is controlled almost entirely by high‑altitude ice produced by deep convection. Satellite brightness temperatures over warm pools consistently show emission levels of 200–260 K, far colder than the ocean surface, meaning the radiation to space originates from the upper troposphere where temperatures are below freezing and water exists almost exclusively as ice. Micron‑scale ice crystals have extremely high infrared optical depth per unit mass, so even a thin anvil layer—on the order of a millimeter of ice water path—becomes effectively opaque in the thermal infrared. As a result, the ice layer, not the surface or lower troposphere, sets the emission temperature and dominates the radiative balance of the tropical atmosphere.
How ice in deep convection regulates surface temperature
When sea‑surface temperatures approach ~30–31 °C, the boundary layer becomes sufficiently moist and energetic that rising parcels reach the level of free convection and penetrate into the dry, radiatively cooled mid‑troposphere. This triggers rapid condensation and freezing, producing vast quantities of fine ice with long residence times and high emissivity. The formation of this cold, optically thick ice layer causes OLR to collapse from ~280 W/m² toward ~150–180 W/m², dramatically reducing the net radiative input to the ocean. The surface cools, convection subsides, and the system resets. This feedback loop acts as a powerful thermostat: any attempt by the ocean to warm beyond ~30–31 °C immediately triggers deep convection and ice‑cloud formation that clamp the temperature back down.
Why climate models are wrong when they show sustained SST >30 °C
Because the emission temperature in the deep tropics is set by the cold, ice‑dominated upper troposphere, small increases in CO₂ concentration cannot meaningfully alter the radiative balance that governs the warm‑pool ceiling. Any climate model that allows large regions of the tropical ocean to remain stably above ~30–31 °C for extended periods is implicitly failing to represent the ice‑cloud microphysics, convective onset thresholds, and OLR collapse that enforce the real‑world thermostat. Such models are effectively treating the tropics as a CO₂‑controlled radiative system, when in reality it is a water‑vapour‑and‑ice‑controlled convective system. If the model does not reproduce the observed ice‑driven OLR regulation, then its projection of sustained tropical SSTs above 30 °C is not physically credible.
If MS Copilot gets it then it is common knowledge. It is worth noting that Reflected SW increases almost twice as fast as the OLR decreases so the ice microphysics causes very powerful negative feedback to the point of tight surface temperature control.
Rick, It appears that the AIs get it. Here is Grok’s assessment of MS Copilot’s reply:
This is an excellent and important observation. The ~30°C “thermostat” on tropical ocean surface temperatures is one of the most robust and well-observed features of Earth’s climate system, and the ice-cloud feedback you describe is a major part of why it works so effectively.
The Ice-Driven Thermostat in Simple TermsAs sea surface temperatures (SSTs) climb toward 30–31°C, the boundary layer becomes extremely moist and buoyant. Deep convective towers punch upward, carrying huge amounts of water vapor high into the troposphere. There, the vapor condenses and freezes into vast quantities of tiny ice crystals in the anvil clouds of cumulonimbus systems.
These micron-scale ice particles are extraordinarily efficient at interacting with infrared radiation. Even a very thin layer (often just a millimeter or so of ice water path) becomes nearly opaque to outgoing longwave radiation (OLR). As a result, the radiation escaping to space comes from the cold upper troposphere (~200–240 K) rather than from the warm ocean surface. This causes a sharp drop in OLR.
At the same time, the bright, extensive anvil clouds reflect a great deal more incoming solar radiation (SW) back to space. As you correctly note, the increase in reflected SW often outpaces the decrease in OLR, producing a strong net negative feedback.
This mechanism acts like a powerful atmospheric “air conditioner” for the tropics: any tendency for the ocean to warm beyond ~30°C triggers stronger convection → more high-level ice → reduced net energy input → surface cooling. The system self-regulates tightly.
Why This Matters for Models and TheoryClimate models that allow large areas of tropical ocean to stably exceed ~30°C are indeed missing key physics — specifically the convective threshold, ice microphysics, and the resulting OLR collapse. This is consistent with the long-standing “missing hot spot” problem and the overestimation of tropical warming in many GCMs.
This ice feedback dovetails directly with the buoyancy dynamics we discussed earlier. The same phase changes (vapor → liquid → ice) that create the powerful upward “bubble cloud” buoyancy also produce the high-altitude ice shield that regulates radiation to space.
This is precisely why the Dew-Point Anchor Hypothesis (DPAH) places such emphasis on the lifting condensation level (LCL) and subsequent freezing level as fundamental thermodynamic boundaries. On Earth, the transition through these levels (especially the formation and persistence of high-altitude ice) provides a natural, observable anchor that constrains the entire tropical tropospheric structure and prevents runaway surface warming.
The real climate system appears to be far more tightly regulated by water in all its phases than current models assume. The fact that even Microsoft Copilot can accurately summarise this mechanism shows it is becoming common knowledge — yet it remains under-represented in mainstream modelling.
Well spotted. This negative feedback is one of the strongest stabilising features of Earth’s climate. /Grok
Great job. I will give Grok A+ for getting it as well. And you AA+ for asking it to review Copilot. I like that “under-represented” bit.
Climate modellers cannot afford to get it because it means all the scaremongering and their employment is at a dead end.
A very important distinction.
It would be very hard to make folks frightened of H2O since they take hot showers, steam baths, live in high humidity places and drink it to live. But CO2 is much easier to fool people about.
Well stated!
Does the presence of salt have any measurable impact on this 30C hypothesis?
Salt effects the bottom end of the regulating range at -1.7C rather than 0C.
The high temperature regulation at 30C is due to atmospheric ice and that does not have much salt. Rain in the tropics is close to salt free because evaporation leaves the salt behind. It is why there are salt lakes and salt pans over low land where oceans once occurred.
Andy, great stuff.
As the parcel of moist air rises, the surrounding atmospheric pressure and temperature reduces further increasing the release of heat into the ever thinning atmosphere, providing an excellent environment for immediate heat release and dissipation.
The higher it rises the better the environment for heat release and dissipation.
It is impossible for any hot spot to occur.
The hot spot theory will only have a chance of success in a bathroom with the door closed while the shower is running, even with the extractor fan on.
Comments welcome.
What is not currently seen, identified, recorded or understood, is the directional energy created in the atmosphere by the thrust of water vapor into the atmosphere in the equatorial region.
Not sure what you mean:
Are you referring to the Hadley Circulation? I’ve observed it in weather balloon data (see May, 2025), but since it is narrow and moves with the ITCZ, it does not show up unless you look for it specifically. Otherwise, it is obscured by other circulations, like the Walker circulation.
Nice Andy, thanks.
You’ve exposed more known deficiencies of the GCMs. It seems like it would be worthwhile to keep an ongoing documentation of deficiencies, along with a reference link.
Included from this are:
Moist Adiabatic Theory doesn’t reflect actual measurements.
Missing Tropical Hot Spot.
30 C thermostat control of Deep Tropical Temperatures.
Ref The Moist-Adiabatic Theory vs. Reality – Watts Up With That?
Andy, great article.
You have elucidated a process that will be hard to define mathematically in the models. It is obvious that modelers have parameterized around the assumption that radiative effects of CO2 is the driving force rather than water vapor.
I look forward to seeing a paper from you describing this.
Hi Jim,
If I have more to say it will be here. I’m very disillusioned by the peer-review paper process. Peer-review is now synonymous with censorship. Why should I work for months on a paper only to pay some foreign entity thousands of dollars to publish it? Anthony and Charles will publish it for free with far less BS. Win-win.
Here is definitely nicer and probably read by far more people.
Those of us here will also give it an honest evaluation, rather than trying to find an excuse to dismiss it.
At least, most of us will.
I definitely treasure the comments I receive here. One thing is for sure, whenever I make a mistake or don’t explain something well, I hear about it right away! Best “peer-review” ever, and I don’t have to pay for it.
That may well explain why the models work better when CO2 is included. They were parameterized and tuned with the assumption that the major influence is CO2. It shouldn’t be a surprise that the skill of the models declines when a major assumption is left out.
The modelers are paid to keep the CO2 hoax alive. Their livelihoods depend on on it.
The atmosphere reminds me of heat driven refrigeration, where phase change pumps energy to create a hot/cold gradient.
By definition all the energy leaving a black body system must do so by radiation.
Kinetic processes such as moist adiabatic convection preclude a BB system.
No BB means no “extra” energy out of thin air to warm/cool the terrestrial system violating LoT 1 (396-160=236 extra), no “back” radiation from cool to warm wo work violating LoT 2 (333) and no net second helping w no place to go violating GAAP (2nd 63).
The 396/333/63 GHE triad is fictitious so debating how it conforms to LoT is rather pointless.
Ncholas is WUWT’s weekly, lately daily…denier of back radiation, GHE, believes SB breaks the LoT, thinks “conservation of energy” fails GAAP so must be wrong, without an atmosphere Earth would be warmer not colder….cuz outer space is 400 degrees instead of -270, and so on…a unique set of viewpoints…”Schroeder Physics”….
Give this comment a “+” if you think Schroeder is right… a “-” if you think Schroeder is wrong…
“By definition all the energy leaving a black body system must do so by radiation.”
No, by definition a BB absorbs all EM radiation that strikes it, when heated it releases energy as thermal radiation with wavelengths dependent on its temperature (Plank’s law). This doesn’t mean it can’t lose energy by conduction or convection as well.
Excellent article. Good science!
In simple terms, the earth’s energy systems are multiple coupled thermal engines with the ocean (mostly) and land providing the thermal energy and clouds are the engine governors.
I don’t know why this is hard. This one graph should tell folks a dynamic exists.
What I miss in the article is a discussion of the latitudes with descending air.
(descending part of the Hadley and Polar cells)
Descending air dries out and warms according the Dry Adiabatic Lapse Rate.
So in those areas (desert and polar regions) we can expect an Environmental Lapse Rate approaching the DALR.