{"id":393075,"date":"2025-08-05T15:14:59","date_gmt":"2025-08-05T13:14:59","guid":{"rendered":"https:\/\/climatescience.press\/?p=393075"},"modified":"2025-08-05T15:15:21","modified_gmt":"2025-08-05T13:15:21","slug":"why-current-ghg-effect-is-simply-not-scary","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=393075","title":{"rendered":"Why Current GHG Effect is Simply Not\u00a0Scary"},"content":{"rendered":"\n
\"A<\/figure>\n\n\n\n

<\/p>\n\n\n\n

From Science Matters<\/a><\/p>\n\n\n\n

By\u00a0Ron Clutz<\/a><\/p>\n\n\n

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\"A<\/figure>\n<\/div>\n\n\n

Donald Rapp makes things clear and concise in his 2024 paper How Increased CO2 Warms the Earth-Two Contexts for the Greenhouse Gas Effect. <\/strong><\/a> Excerpts in italics with my bolds, exhibits and some added images.<\/p>\n\n\n\n

Physicist Donald Rapp retired from the Jet Propulsion Laboratory and has authored many books including Ice Ages and Interglacials: Measurements, Interpretation and Models; Assessing Climate Change: Temperatures, Solar Radiation and Heat Balance; and Use of Extraterrestrial Resources for Human Space Missions to Moon or Mars<\/strong> (Astronautical Engineering). Most recently he published Revisiting 2,000 Years of Climate Change (Bad Science and the \u201cHockey Stick\u201d)<\/strong><\/p>\n\n\n\n

Abstract<\/em><\/h4>\n\n\n\n

The widespread\u00a0explanations of the greenhouse effect<\/strong>\u00a0taught to millions of schoolchildren are\u00a0misleading<\/strong>. The\u00a0objective<\/strong>\u00a0of this work is to clarify how increasing CO2 produces warming in current times. It is found that there are\u00a0two contexts<\/strong>\u00a0for the greenhouse gas effect. In\u00a0one context,<\/strong>\u00a0the fundamental greenhouse gas effect, one\u00a0imagines a dry Earth starting with no water or CO2 and adding water and CO2<\/strong>\u00a0. <\/em><\/p>\n\n\n\n

This leads to the familiar\u00a0\u201cthermal blanket\u201d that strongly inhibits IR transmission<\/strong>\u00a0from the Earth to the atmosphere. The Earth is much warmer with H2O and CO2. In the\u00a0other context<\/strong>, the current greenhouse gas effect,\u00a0CO2 is added to the current atmosphere<\/strong>. <\/em><\/p>\n\n\n\n

The thermal blanket on IR radiation hardly changes. But the\u00a0surface loses energy primarily by evaporation and thermals<\/strong>.\u00a0Increased CO2<\/strong>\u00a0in the upper atmosphere carries\u00a0IR radiation to higher altitudes.<\/strong>\u00a0The Earth radiates to space at higher altitudes where it is cooler, and the\u00a0Earth is less able to shed energy.<\/strong>\u00a0<\/em><\/p>\n\n\n\n

The\u00a0Earth warms to restore the energy balance.<\/strong>\u00a0The \u201cthermal blanket\u201d is mainly irrelevant to the current greenhouse gas effect. It is concluded that almost all discussions of the greenhouse effect are based on\u00a0the fundamental greenhouse gas effect<\/strong>, which\u00a0is a hypothetical construct,<\/strong>\u00a0while the\u00a0current greenhouse gas effect is what is happening now in the real world.<\/strong><\/em><\/p>\n\n\n\n

Adding CO2 does not add much to a \u201cthermal blanket\u201d but instead,
drives emission from the Earth to higher, cooler altitudes.<\/strong><\/em><\/p>\n\n\n\n

Background<\/strong><\/em><\/p>\n\n\n\n

Were it not for the Sun, the Earth would be a frozen hulk in space. <\/em><\/p>\n\n\n\n

The Sun sends a spectrum of irradiance to the Earth, the Earth warms, and the Earth radiates energy out to space. <\/em><\/p>\n\n\n\n

This process continues until the\u00a0Earth warms enough to radiate about as much energy to space as it receives from the Sun, reaching an approximate steady state.<\/strong>\u00a0If for some reason, the Earth is unable to radiate all the energy received from the Sun, the Earth will warm until it can radiate all the energy received. It is widely accepted that rising CO2 concentration reduces the ability of the Earth to radiate energy to space. <\/em><\/p>\n\n\n\n

In a dynamic situation where the CO2 concentration is continually increasing with time, the Earth will continuously warm as it tries to \u201ccatch up\u201d to the effect of increasing CO2 and reestablish a steady state. It is a conundrum that\u00a0while it is widely accepted that rising CO2 concentration produces global warming, the exact mechanism<\/strong>\u00a0by which warming is induced\u00a0in the current atmosphere<\/strong>\u00a0by rising CO2 is\u00a0not widely understood<\/strong>. The concept of a\u00a0\u201cthermal blanket\u201d<\/strong>\u00a0imposed by greenhouse gases to warm the Earth has merit in some contexts but is mainly\u00a0irrelevant to<\/strong>\u00a0the question of\u00a0how adding CO2 to the current atmosphere produces warming.<\/strong><\/em><\/p>\n\n\n\n

Before attempting to deal with the question of how rising CO2 concentration affects the current Earth\u2019s climate, it is appropriate to first discuss the Earth\u2019s energy budget. The exact values for each energy flow are not important, but the relative values are important to show which processes dominate.<\/strong><\/em><\/p>\n\n\n\n

Finally, we provide an explanation of how adding CO2 to the current atmosphere<\/strong> produces global warming in the current atmosphere<\/strong>. The mechanism is not widely known and is likely to be surprising to some. Warming<\/strong> does not occur by increasing the thickness of the thermal blanket but instead occurs by raising the altitude at which the Earth radiates to space.<\/strong><\/em><\/p>\n\n\n\n

IR radiation<\/strong><\/em><\/h4>\n\n\n\n

A fundamental law of physics states that\u00a0all bodies emit a\u00a0spectrum of radiant power proportional to the fourth power\u00a0of their absolute temperature<\/strong>.<\/em><\/p>\n\n\n\n

A body at absolute temperature\u00a0T (K) emits power per unit area:\u00a0P = \u03c3 T\u00a04\u00a0= 5.67 x 10\u00a0-8\u00a0T\u00a04\u00a0(W\/m\u00a02).\u00a0<\/em><\/p>\n\n\n\n

For example, a body at T = 280 K is said to emit 348 W\/m\u00a02.\u00a0<\/em><\/p>\n\n\n\n

However, this law of physics is academic and not directly\u00a0applicable to real-world experience.<\/strong>\u00a0<\/em><\/p>\n\n\n\n

In the real world, we\u00a0never have a single isolated body emitting radiation<\/strong>, instead,\u00a0we deal with pairs of bodies where the warmer one radiates\u00a0a net flux to the cooler one. (If you stand next to a body at\u00a0280 K, you don\u2019t feel an incoming heat \u03d0lux of 348 W\/m\u00a02).\u00a0<\/em><\/p>\n\n\n\n

For example, if there is one body at 280 K and a second body\u00a0at 275 K, the warmer body will radiate through a vacuum\u00a0to the cooler body at a net of 24 W\/m\u00a02. <\/em><\/p>\n\n\n\n

That is a real-world\u00a0parameter that can be measured. But the academic model\u00a0involves\u00a0calculating the emission of the warm body as 348\u00a0W\/m\u00a02\u00a0and the emission of the cooler body as 324 W\/m<\/strong>, and\u00a0subtracting, the net transfer from the warm body to the cool\u00a0body is 24 W\/m\u00a02. But the calculated values are academic\u00a0and cannot be measured in the real world with 348 W\/m\u00a02\u00a0in\u00a0one direction\u00a0and 324 W\/m\u00a02\u00a0in the opposite direction.\u00a0Those values are only of academic use to infer the measurable net of\u00a0about 24 W\/m\u00a02.<\/strong>\u00a0<\/em><\/p>\n\n\n\n

See the simple model in Figure 1 presented\u00a0here for illustration.<\/em><\/p>\n\n\n

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\"Illustration
Figure 1: Radiant heat transfer between warm and cool bodies<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

The two contexts of the greenhouse effect<\/strong><\/em><\/p>\n\n\n\n

We are all aware of the widely discussed greenhouse effect<\/strong> that warms the Earth as the concentration of greenhouse gases increases. But just how does it work?<\/strong> Here, we define two contexts for greenhouse gas effects:<\/em><\/p>\n\n\n\n

\"Diagram<\/figure>\n\n\n\n

1) The\u00a0fundamental greenhouse gas effect<\/strong>\u00a0can be described\u00a0by a \u201cgedanken experiment\u201d in which one imagines\u00a0a dry Earth starting with no water or CO\u00a02\u00a0and begins\u00a0adding water and CO\u00a02. The\u00a0original atmosphere, lacking\u00a0water and CO\u00a02, will transmit IR radiation completely<\/strong>.\u00a0As a result, the Earth will be quite cool.\u00a0As H\u00a02\u00a0O and\u00a0CO\u00a02\u00a0are added<\/strong>\u00a0to the atmosphere, the\u00a0transmission of\u00a0IR radiation from the Earth\u2019s surface is increasingly\u00a0inhibited, and the Earth warms.<\/strong>\u00a0As the Earth warms,\u00a0evaporation and thermals transmit more energy from\u00a0the Earth to the atmosphere. By the time\u00a0H\u00a02\u00a0O and\u00a0CO\u00a02<\/strong>\u00a0levels reach\u00a0current levels<\/strong>,\u00a0the atmosphere is\u00a0almost opaque to IR radiation,<\/strong>\u00a0and a \u201cthermal blanket\u201d\u00a0greatly reduces IR transmission from the Earth to the\u00a0atmosphere. The Earth cools primarily by evaporation\u00a0and thermals, and it is much warmer than if CO\u00a02\u00a0and\u00a0water were absent. The notion of a\u00a0\u201cthermal blanket\u201d\u00a0of IR absorbing gases warming the Earth has validity\u00a0in this context<\/strong>\u00a0starting with a transmitting atmosphere\u00a0and adding greenhouse gases.\u00a0However, once the\u00a0thermal blanket is established with ~ 400 ppm CO\u00a02,\u00a0adding more CO\u00a02\u00a0has only a small effect on reducing IR\u00a0radiation from the surface.<\/strong><\/em><\/p>\n\n\n\n

2) The\u00a0current greenhouse gas effect<\/strong>\u00a0deals with the\u00a0question:\u00a0How does the addition of CO\u00a02\u00a0to the\u00a0atmosphere affect the global average temperature in\u00a02024 and beyond, with CO\u00a02\u00a0around 400+ ppm?<\/strong>\u00a0It was\u00a0shown previously that starting with no water or CO\u00a02,\u00a0adding H\u00a02\u00a0O and CO\u00a02\u00a0to the atmosphere generates a\u00a0\u201cthermal blanket\u201d for radiation. But once that \u201cthermal\u00a0blanket\u201d is well established and the lower atmosphere is\u00a0very opaque to IR radiation, what is the effect of adding\u00a0even more CO\u00a02? Dufresne, et al. provide a detailed\u00a0technical analysis to show how the current greenhouse\u00a0effect works<\/strong>\u00a0[7]. However, this reference is complex\u00a0and written for expert specialists in IR transmission\u00a0through the atmosphere.\u00a0In the sections that follow, a\u00a0simpler, qualitative interpretation will be presented.<\/strong><\/a><\/em><\/a><\/p>\n\n\n

\n
\"Diagram
Figure 3: Energy flows in the Earth\u2019s system. (Based on LTWS references).<\/figcaption><\/figure>\n<\/div>\n\n\n

Energy budget of the earth<\/strong><\/em><\/h4>\n\n\n\n

Energy transfer in the Earth system can take place by thermal transfers (\u201cthermals\u201d)<\/strong> where winds carry warm air up to colder regions, evaporation<\/strong> from the surface (removes heat), and condensation<\/strong> in the atmosphere (deposits heat) and radiation<\/strong> (further discussion follows).<\/em><\/p>\n\n\n\n

After analyzing the data in the LTWS references (see Section 1.2), a rough estimate of key energy flows<\/strong> per unit time in the Earth system is given as follows. The exact numbers are not critical; only their relative values are important for this <\/strong>discussion.<\/strong><\/em><\/p>\n\n\n\n

These results can be visualized in Figure 3<\/strong> which is based on the references LTWS. As shown in Figure 3, incoming solar irradiance (341 W\/ m 2 ) is partly reflected by the lower atmosphere back out to space (79 W\/m 2 ), partly reflected by the Earth\u2019s surface back out to space (23 W\/m 2 ), partly absorbed by the lower atmosphere (76 W\/m 2 ), and finally about 163 W\/m 2 is absorbed by the surface.<\/em><\/p>\n\n\n\n

Radiation from the Earth\u2019s surface to the lower atmosphere <\/strong>requires further discussion.<\/strong> The LTWS references show high up and down radiation flows. For example, Trenberth, et al<\/strong>. did not show radiation transfer between the Earth\u2019s surface as a simple 25 W\/m 2 net radiative transfer from the surface to the lower atmosphere. Instead, they showed 356 W\/m <\/strong>2 radiated upward from the surface and 333 W\/m 2 of \u201cback <\/strong>radiation\u201d from the atmosphere to the surface<\/strong> [2]. The figure 356 W\/m 2 <\/strong>radiated upward<\/strong> from the surface corresponds to <\/strong>the theoretical radiation from a blackbody at 281.5 K.<\/strong> The claimed downward figure is difficult to explain. But both of <\/strong>these figures are academic.<\/strong> What is happening is that the warm Earth is radiating upward through an optically thick gas <\/strong>of H 2 O and CO 2 <\/strong>absorbers, and the radiant transfer through that thick gas is estimated to be only a mere ~25 W\/m <\/strong>2<\/strong> . This is the \u201cthermal blanket\u201d so often referred to in discussions of global warming. The thermal blanket is real. But the problem with so many discussions of the greenhouse effect is that there is a preoccupation with radiant energy transfer<\/strong> between the Earth and the atmosphere (which is \u201cblanketed\u201d) while neglecting the more important transfers of energy to the atmosphere by processes other than radiation.<\/strong><\/em><\/p>\n\n\n

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\"Graph
Figure 4: Pressure, temperature, and relative humidity vs. altitude [8].<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

The terms \u201clower atmosphere\u201d and \u201cupper atmosphere\u201d are defined next. Following Miscolczi, Figure 4 shows that the demarcation between upper and lower atmospheres occurs at <\/strong>an altitude of roughly 12 km<\/strong> above which H 2 O is frozen out and the temperature roughly stabilizes [8].<\/em><\/p>\n\n\n\n

Energy transfer in the lower atmosphere takes place by conduction,
convection, and radiation. Energy transfer in the upper atmosphere
takes place primarily by radiation.<\/strong><\/em><\/p>\n\n\n\n

The greenhouse effect<\/strong><\/em><\/h4>\n\n\n\n

The greenhouse effect can only be fully understood by comprehensive modeling of upward energy flows<\/strong> in the Earth system. Excellent studies by Dufresne, et al. and Pierrehumbert provide detailed physics [7,9]. Here, we interpret these results <\/strong>qualitatively.<\/strong><\/em><\/p>\n\n\n\n

Within the Earth system of land, ocean, atmosphere, and clouds, energy transfer is taking place continuously. There is a net energy flow upward toward higher altitudes. From the surface of the Earth, much of the upward flow of energy in the lower atmosphere is through evaporation and convection. The lower atmosphere is almost opaque to IR radiation due to <\/strong>water vapor and CO 2.<\/strong><\/em><\/p>\n\n\n

\n
\"Diagram
Figure 5: Qualitative sketch to show radiation is dominant at the highest altitude. By adding CO2 to the atmosphere, radiative energy transport is carried to a higher altitude where it is colder, reducing the radiant power emitted by the upper atmosphere.<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

Radiation energy transfer will persist out toward a\u00a0high altitude until the CO\u00a02\u00a0concentration diminishes. Each\u00a0CO\u00a02\u00a0molecule that absorbs an IR photon can reradiate in all\u00a0directions, but\u00a0in a thin atmosphere, some upward IR radiation\u00a0will be lost, and on a net basis, this allows the Earth to radiate\u00a0out to space.<\/strong>\u00a0The presence of an IR transmitting\/absorbing\u00a0gas (CO\u00a02\u00a0) will allow energy transport to higher altitudes. The\u00a0highest altitude where there is enough thin gas to maintain\u00a0radiation<\/strong>\u00a0is the region of the atmosphere that\u00a0mainly radiates\u00a0energy outward to space.<\/strong>\u00a0This is illustrated on the left side\u00a0of Figure 5. Figure 5 was created here to illustrate how the\u00a0predominant energy transfer mechanisms gradually change\u00a0to IR radiation at higher altitudes, and the presence of CO\u00a02\u00a0carries the IR radiation to higher altitudes.<\/em><\/a><\/p>\n\n\n\n

\"Infographic<\/figure>\n\n\n\n

Conclusion<\/strong><\/em><\/h4>\n\n\n\n

There are two different contexts for discussion of the effect of greenhouse gases on the Earth\u2019s climate.<\/em><\/p>\n\n\n\n

In one context, one can imagine an Earth with no water vapor or CO 2 in the atmosphere. This Earth can radiate effectively to space and is relatively cold. As water vapor and CO 2 are added to the atmosphere, the IR-opacity of the atmosphere increases and the Earth system warms. The greenhouse gases act as a <\/strong>\u201cthermal blanket\u201d to warm the Earth by impeding upward <\/strong>IR radiation<\/strong>. This is labeled the fundamental greenhouse gas effect. However, once<\/strong> the thermal blanket is established, <\/strong>adding more CO 2 has only a minimal effect on the thermal <\/strong>blanket,<\/strong> and reduced upward IR radiation from the surface does not produce significant warming. This is referred to by Dufresne, et al. [7] as the \u201csaturation paradox\u201d.<\/strong><\/em><\/p>\n\n\n\n

In the other context<\/strong>, we are concerned with the effect of <\/strong>adding more CO 2 <\/strong>to the current atmosphere<\/strong> where the CO 2 concentration is already 400+ ppm, and the thermal blanket <\/strong>is already in place,<\/strong> restricting upward IR-radiation. This is labeled the current greenhouse gas effect, and it is quite different from the fundamental greenhouse gas effect. In the current atmosphere, energy transfer from the Earth to the <\/strong>atmosphere is primarily by evaporation and thermals<\/strong>, and IR-radiant energy transfer is significantly impeded by an almost opaque lower atmosphere. The \u201cthermal blanket\u201d is in place, but it doesn\u2019t change much as CO 2 is added to the atmosphere. Adding CO <\/strong>2 to the current atmosphere slightly increases the opacity of the lower atmosphere but this is of <\/strong>little consequence.<\/strong><\/em><\/p>\n\n\n\n

In the upper atmosphere, CO 2 is the major means of energy transport by IR radiation. The greatest effect of adding CO 2 to the current atmosphere is to extend the upward range of IR-radiant transmission to higher altitudes. The main region where the Earth radiates to space is thereby extended to higher altitudes where it is colder, and the Earth <\/strong>cannot radiate as effectively as it could with less CO <\/strong>2<\/strong> in the atmosphere. The Earth warms<\/strong> until the region in the upper atmosphere where the Earth radiates to space is warm enough <\/strong>to balance incoming solar energy.<\/strong><\/em><\/p>\n\n\n\n

My Comment:<\/strong><\/h4>\n\n\n\n

The explanation above is clear and understandable in qualitative terms.\u00a0 It does not reference empirical evidence regarding a GHG effect from a raised effective radiating level (ERL).\u00a0 Studies investigating this theory find that the effect is too small to appear in the data.<\/p>\n\n\n

\n
\"Schematic<\/figure>\n<\/div>\n\n\n
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Refresher: GHG Theory and the Tests It Fails<\/a><\/blockquote>