Introduction – How does the climate narrative work?

The development of the climate narrative is difficult to understand. 

How is it possible to bring all the important universities, including the most renowned ones such as Harvard, MIT and Stanford, Oxford, Cambridge and Heidelberg, onto the same consensus line? How can the most famous journals such as Nature and Science, but also popular science journals such as Spektrum der Wissenschaft, only accept a single understanding without obviously ruining their reputation?

It cannot work without a solid scientific foundation that cannot be disputed without embarrassment. Those who do so anyway are easily identified as “climate deniers” or “enemies of science”. 

On the other hand, the predictions and, in particular, the political consequences are so misanthropic and unrealistic that not only has a deep social divide arisen, but many people are asking themselves what kind of science it is that produces such absurd results.

In the course of my own analyses of the climate issue, I have found a pattern that runs like a red thread through all aspects. I would like to illustrate this pattern using 4 key points that are important in climate research.

The pattern is that there is always a correct observation or a valid law of nature at the core. In the next step, however, the results of this observation are either extrapolated into the future without being checked, the results are exaggerated or even distorted in their meaning. Other, relevant findings are omitted or their publication is suppressed.

Always with the result that the worst possible outcome threatens the respective sub-aspect of the climate. The combination of several such components then leads to the catastrophic horror scenarios that we are confronted with on a daily basis. As the statements usually relate to the future, they are generally almost impossible to verify.

The entire chain of reasoning typically takes the following form:

1. Anthropogenic emissions are growing – exponentially.
2. Atmospheric concentration increases with emissions as long as emissions are not completely reduced to zero
3. The increase in the concentration of CO₂ in the atmosphere leads to a – dramatic – increase in the average temperature
4. In addition, there are positive feedbacks when the temperature rises, and even tipping points beyond which reversal is no longer possible.
5. Other explanations such as hours of sunshine or the associated cloud formation are ignored, downplayed or built into the system as a feedback effect.
6. The overall effects are so catastrophic that they can be used to justify any number of totalitarian political measures aimed at reducing global emissions to zero.

My study of the subject has led me to the conclusion that each of these points shows the pattern described above, namely that there is always a kernel of truth that is harmless in itself. The aim of this paper is to work out the kernel of truth and the exaggerations, false extrapolations or omissions of essential information.

1.    Anthropogenic emissions are growing – exponentially?

Everyone knows the classic examples of exponential growth, e.g. the chessboard that is filled square by square with double the amount of rice. Exponential growth always leads to disaster. It is therefore important to examine the facts of emissions growth.

Figure 1 shows the relative growth in global anthropogenic emissions over the last 80 years.

Figure 1 Relative growth in global emissions

To understand the diagram, let’s remember that constant relative growth means exponential growth. In principle, a savings account with 3% interest grows exponentially. Accordingly, we find exponential growth in emissions with a growth rate of around 4.5% between 1945 and 1975. This phase was once known as the “economic miracle”. After that, emissions growth fell to 0 by 1980. This period was known as the “recession”, which resulted in changes of government in the USA and Germany.

A further low point in the growth of emissions was associated with the collapse of communism around 1990, with a subsequent rise again, mainly in the emerging countries. Since 2003, there has been a deliberate reduction in emissions growth as a result of climate policy.

It should be noted that emissions growth has currently fallen to 0.

Recently, Zeke Hausfather of CarbonBrief found that global anthropogenic emissions have been constant within the measurement accuracy since 2011, shown in Figure 2.

As a result, current emissions are no longer expected to be exceeded in the future. The longer-term extrapolation of the current planned future emissions, the so-called “Stated Policies” scenario (from 2021), expects constant global emissions until 2030 and a very slight reduction of 0.3% per year thereafter.

Figure 2  Anthropogenic emissions have been constant since 2011

Figure 3  STEPS scenario (States Policies Scenario) of the IEA, almost constant emissions.

As a result, the two future scenarios most frequently used by the IPCC (RCP 8.5 and RCP6.2) are far removed from the reality of actually possible emission scenarios. Nevertheless, the extreme scenario RCP8.5 is still the most frequently used in the model calculations.

The IPCC scenario RCP4.5 and the similar IEA scenario “Stated Policies” shown in Figure 3 (p. 33, Figure 1.4) are the most scientifically reliable.

This means that if the realistic emission scenarios are recognized without questioning the statements about the climate disseminated by the IPCC, a maximum emission-related temperature increase of 2.5°C compared to pre-industrial levels remains. 

2. atmospheric CO₂ concentration increases continuously — unless emissions are reduced to zero?

The question is how anthropogenic emissions affect the CO₂ concentration in the atmosphere.  It is known and illustrated in Fig. 4 by the International Energy Agency that by no means all the CO₂ emitted remains in the atmosphere, but that a growing proportion of it is reabsorbed by the oceans and plants.

Figure 4 Sources and sinks of CO₂

The statistical evaluation of anthropogenic emissions and the CO₂ concentration, taking into account the conservation of mass and a linear model of the natural sinks oceans and biosphere, shows that every year just under 2% of the CO₂ concentration above the pre-industrial natural equilibrium level is absorbed by the oceans and the biosphere.  This is currently half of anthropogenic emissions with an increasing trend, as shown in Figure 5. 

 Figure 5 CO₂ balance and linear sink model

The most likely global future scenario of the International Energy Agency – the continuation of today’s political regulations (Stated Policies Scenario STEPS) shown in Fig. 3 – includes a gentle decrease (3%/decade) in global emissions to the 2005 level by the end of the century. These emission reductions are achievable through efficiency improvements and normal progress.

If we take this STEPS reference scenario as a basis, using the linear sink model leads to an increase in concentration of 55 ppm to a plateau of 475 ppm, where the concentration then remains.   

Figure 6  Measured and predicted CO₂ concentration with 95% error bar

It is essential that the CO₂ concentration does not rise to climatically dangerous levels.   Article 4.1 of the Paris Climate Agreement literally states that
countries must reach their maximum emissions as soon as possible “in order to achieve a balance between anthropogenic emissions of greenhouse gases and their absorption by sinks in the second half of this century“. The Paris Climate Agreement therefore by no means calls for complete decarbonization. 

The net-zero balance between emissions and absorption will be achieved in 2080 by extrapolating today’s behavior without ruinous climate measures. 

Without going into the details of the so-called sensitivity calculation, the following can be simplified for the further temperature development:

If we assume that the CO₂ concentration is fully responsible for the temperature development of the atmosphere, then in 2020 the CO₂ concentration was 410 ppm, i.e. (410-280) ppm = 130 ppm above the pre-industrial level. Until then, the temperature was about 1° C higher than before industrialization. In the future, we can expect the CO₂ concentration to increase by (475-410) ppm = 65 ppm based on the above forecast. This is just half of the previous increase. Consequently, even if we are convinced of the climate impact of CO₂ , we can expect an additional half of the previous temperature increase by then, i.e. ½° C. This means that by 2080, the temperature will be 1.5° C above pre-industrial levels, meeting the target of the Paris Climate Agreement, even without radical emission reductions. 

3.    Atmospheric CO₂ concentration causes – dramatic?  — temperature rise

Having discussed the possible quantities of CO₂ that we will have to deal with in the future, we now want to look at the core climate issue, the greenhouse effect of CO₂ . 

The possible influence of CO₂ on global warming is that its absorption of thermal radiation causes this radiation to be attenuated when it reaches outer space. The physics of this process is radiative transfer. As this topic is fundamental to the entire climate debate on the one hand, and challenging and difficult to understand on the other, I would like to cover it in detail here, but leave out the complicated physical formulas.

In order to be able to measure the greenhouse effect, the infrared radiation emitted into space must be measured. However, at 0.2 W/m² per decade, the expected greenhouse effect is so tiny that it is not directly detectable with today’s satellite technology, which has a measurement accuracy of around 10 W/m² .

 We therefore have no choice but to make do
with mathematical models of the physical radiative transfer equation. However, this is not valid proof of the effectiveness of this CO₂  greenhouse effect in the real, much more complex atmosphere.

 There is a widely recognized simulation program MODTRAN, with which the radiation of infrared radiation into space and thus also the CO₂ greenhouse effect can be physically correctly simulated:

Figure 7 Comparison between measured infrared spectrum and infrared spectrum simulated with MODTRAN

Figure 7 shows that the MODTRAN reconstruction of the infrared spectrum is in excellent agreement with the infrared spectrum measured from space. We can thus justify the applicability of the simulation program and conclude that the simulation can also be used to describe hypothetical constellations with sufficient accuracy.

With this simulation program we want to check the most important statements regarding the greenhouse effect.

To start in familiar territory, we first try to reproduce the commonly published “pure CO₂ greenhouse effect” by allowing the solar radiation, which is not reduced by anything, to warm the earth and its infrared radiation into space to be attenuated solely by the CO₂ concentration. The CO₂ concentration is set to the pre-industrial level of 280 ppm.

We use the so-called standard atmosphere, which has proven itself for decades in calculations important for aviation, but remove all other trace gases, including water vapor. However, the other gases such as oxygen and nitrogen are assumed to be present, so that nothing changes in the thermodynamics of the atmosphere. By slightly correcting the ground temperature to 13.5°C (reference temperature is 15°C), the infrared radiation is set to 340 W/m² . This is just ¼ of the solar constant, so it corresponds exactly to the solar radiation distributed over the entire surface of the earth. 

The “CO₂ hole”, i.e. the reduced radiation in the CO₂ band compared to the normal Planck spectrum, is clearly visible in the spectrum.

Figure 8 Simulated IR spectrum: only pre-industrial CO₂

What happens if the CO₂ concentration doubles?

Figure 9 Radiative forcing in Figure 9a Temperature increase for
CO2 doubling (no albedo, compensation of radiative forcing
no water vapor)                                                                from Fig. 9.

In Fig. 9, we see that doubling the CO₂ concentration to 560 ppm reduces the heat flux of infrared radiation by 3.77 W/m² . This figure is used by the IPCC and almost all climate researchers to describe the CO₂ forcing.  In Fig. 9a, we change the ground temperature from -1.5°C to -0.7°C in order to achieve the radiation of 340 W/m² again. This warming of 0.8°C with a doubling of the CO₂ concentration is referred to as “climate sensitivity”.  It is surprisingly low given the current reports of impending climate catastrophes.

Especially when we consider that the settings of the simulation program used so far are completely at odds with the real Earth’s atmosphere:

• No consideration of the albedo, the reflection of light,
• No consideration of clouds and water vapor

We will now approach the real conditions step by step. The scenarios are summarized in the following table:

Scenario	Albedo	Irradiation (W/m )2	CO2 before (ppm)	Temperature ( °C)	CO2 after (ppm)	Drive (W/m )2	Temperature Increase for balance (°C)
Pre-industrial CO only2 , no clouds, No water vapor	0	340	280	13,7	560	-3,77	0,8
No greenhouse gases, No clouds (CO 2 from 0-280 ppm)	0,125	297,5	0	-2	280	-27	7
CO only2 , Albedo, no clouds, No water vapor	0,125	270	280	5	560	-3,2	0,7
Pre-industrial standard atmosphere	0,3	240	280	15	560	-2	0,5
Pre-industrial standard atmosphere, CO2 today Concentration	0,3	240	280	15	420	-1,1	0,3

The scenario in the first row of the table is the “pure CO₂ ” scenario just discussed.

In the second line, we go one step back and also remove the CO₂ , i.e. a planet without greenhouse gases, without clouds, without water vapor. But the Earth’s surface reflects sunlight, so it has an albedo. The value 0.125 corresponds to that of other rocky planets as well as the ocean surface. Surprisingly, in this case the surface temperature is -2°C (and not -18°C as is often claimed!). This is because, since we assume no water vapor, we also have no cloud albedo. If we now increase the CO₂ concentration to the pre-industrial level of 280 ppm, the infrared radiation is reduced by 27 W/m² . This large radiative forcing is offset by a temperature increase of 7°C.

We can see that there is a considerable greenhouse effect between the situation without any greenhouse gases and the pre-industrial state, with a warming of 7°C.

The third line takes this pre-industrial state, i.e. Earth’s albedo, 280 ppm CO₂ , no clouds and no water vapor, as the starting point for the next scenario. If the CO₂ concentration is doubled, we get a radiative forcing of -3.2 W/m² , i.e. slightly less than in the first “pure CO₂ scenario”. As a result, the warming of 0.7°C to achieve radiative equilibrium is also slightly lower here.

After these preparations, we have the pre-industrial standard atmosphere with albedo, clouds and water vapor in the 4th row.  Now we use the real, measured albedo of 0.3 and the ground temperature of 15°C associated with the standard atmosphere.  There are now several ways to adjust cloud cover and water vapor in order to achieve the infrared radiation of 340 W/m² * (1-a) = 240 W/m² corresponding to the albedo a=0.3. The exact choice of these parameters is not important for the result as long as the radiation is 240 W/m² .

In this scenario, doubling the CO₂ concentration to 560 ppm results in a radiative forcing of -2 W/m² and a compensating temperature increase, i.e. a sensitivity of 0.5°C. 

In addition to the scenario of a doubling of the CO₂ concentration, it is of course also interesting to see where we stand today with regard to the greenhouse effect. The current CO₂ concentration of 420 ppm is just in the middle between the pre-industrial 280 ppm and double that value.

In the 5th row of the table, we find the radiative forcing of -1.1 W/m² and the temperature increase of 0.3°C required to compensate for the increase from 280 ppm to 420 ppm.   Based on this result, it can therefore be said that since the beginning of industrialization, the previous increase in CO₂ concentration was responsible for a global temperature increase of 0.3°C.

This is much less than the average temperature increase we measure.  The question therefore arises as to how the “remaining” temperature increase can be explained.

There are several possibilities:

• Positive feedback effects that intensify CO₂ -induced warming. This is the direction of the Intergovernmental Panel on Climate Change and the topic of the next chapter.
• Other causes such as hours of sunshine or cloud albedo. This is the topic of the next but one chapter
• Random fluctuations. In view of the chaotic nature of weather events, randomness is often invoked.  We will leave this open in this paper.

4.    Positive feedback leads to — catastrophic?  — consequences

The maximum possible climate sensitivity in the previous chapter, i.e. temperature increase with a doubling of the CO₂ concentration, is 0.8°C, under real conditions rather 0.5°C.

It was clear early on that such low climate sensitivity could not seriously worry anyone in the world. In addition, the measured global warming is greater than predicted by the radiative transfer equation.

This is why feedbacks were brought into play; the most prominent publication in this context was by James Hansen et al. in 1984: “Climate Sensitivity: Analysis of Feedback Mechanisms“. It was James Hansen who significantly influenced US climate policy with his appearance before the US Senate in 1988.

The high sensitivities published by the IPCC for a doubling of the CO₂ concentration between 1.5°C and 4.5°C arose with the help of the feedback mechanisms.

In particular, the question arises as to how a small warming of 0.8°C can lead to a warming of 4.5°C through feedback without the system getting completely out of control?

By far the most important feedback in this context is water vapor feedback. That is why we want to take a closer look at it here.

How does water vapor feedback work?

The water vapor feedback consists of a 2-step process:

• If the air temperature rises by 1°C, the air can absorb 6% more water vapor.  Usually a value of 7% is given, but the 7% is only possible from an altitude of 8 km, so we carry out the calculation here with 6%, but the use of 7% would make little difference to the result.

It should be noted that this percentage is the maximum possible water vapor content. Whether this is actually achieved depends on whether sufficient water vapor is available.

• The radiation transport of infrared radiation depends on the relative humidity:
  Additional humidity reduces the emitted infrared radiation due to absorption by the additional water vapor.

The reduced infrared radiation is a negative radiative forcing. The temperature increase compensating for this attenuation is the sought-after primary feedback g (“gain”). This must be less than 1 to avoid a so-called tipping point, at which the system becomes unstable.

The total feedback f results as a geometric series due to the recursive application of the above mechanism:

f = 1+ g + g2 + g3… = 1/(1-g).  

This relationship is described by James Hansen in his work from 1984. A total feedback of e.g. f=4, which causes a warming of 3.2°C from a greenhouse effect of 0.8°C, would result from a primary feedback of g=0.75.

To calculate the primary feedback, the calculation of the radiation transport due to the change in humidity is still missing.

Determination of radiation transport from changes in air humidity

In order to determine the dependence of radiation transport on air humidity, we again use the MODTRAN simulation program under conditions that are as close as possible to today’s conditions on the one hand, and that allow upward and downward changes in relative air humidity (“Water Vapor Scale”) on the other. This is achieved here with the setting Water Vapor Scale = 0.8, i.e. relative humidity 80%.  At a floor temperature of 15°C, this results in a radiation of around 245 W/m² .

  Figure 10 Simulation of the initial state for measuring the radiative forcing when the air humidity changes

If the relative humidity is increased by 6% to 86%, the infrared radiation is reduced by 0.69 W/m² (Fig. 11). This radiative forcing is compensated by a temperature increase of 0.185°C (Fig. 11a):

 Figure 11  Radiative forcing at 6%                        Figure 11a Temperature to compensate for
increase in humidity                                   the radiative forcing of Fig. 11

If you believe that other initial settings lead to significantly different results, you can try this yourself with the publicly available simulation program. 

In summary, the original temperature increase of 1°C results in a 6% increase in the absorption capacity for water vapor.  If this possibility actually takes place, then this leads to a temperature increase of about 0.19°C. The initial feedback is therefore g=0.19. Due to the recursion, this results in a maximum total feedback of f= 1/(1-0.19) = 1.23. 

If we assume a greenhouse effect from radiative transfer of 0.8°C, then, together with the maximum possible feedback, this results in a temperature increase of
0.8°C * 1.23 = 0.984 °C  1°C, with the sensitivity determined here 0.5°C * 1.23 = 0.62 °C. 

These values are lower than the lowest sensitivity of 1.5°C of the models used by the IPCC.

The warming that has occurred since the beginning of industrialization is therefore 0.3°C * 1.23 = 0.37°C, i.e. significantly less than 0.5°C, even with feedback.

This proves that even the frequently invoked water vapor feedback does not lead to exorbitant and certainly not catastrophic global warming.

5.    But isn’t it warming up? – Effects of hours of sunshine and clouds.

To stop at this point will leave anyone who has studied the climate issue a little dissatisfied with the obvious question: “But the earth is warming, and more than would be possible according to the revised greenhouse effect including feedback?”.

This is why we are looking at the effects of the number of hours of sunshine and the associated cloud formation, which until recently have received little attention in the climate debate.

Study of the hours of sunshine in Germany

I currently have no worldwide data available for the number of hours of sunshine, so I will limit my calculations to Germany.

The German weather service not only provides measured temperatures, but also the number of hours of sunshine.

The following simple analysis by the German Weather Service shows that the number of hours of sunshine has increased by around 1.5% per decade for over 70 years (
(168.5/7.2)/1554 = 0.015)

This is almost 20 times greater than the relative increase in CO₂ radiative forcing in 10 years of (0.2 W/m² )/(240 W/m² ) = 0.08%.

                                      Figure 12 Hours of sunshine from 1951-2023

The question naturally arises as to the cause of the change in hours of sunshine.

The State Agency for Nature, Environment and Nature Conservation in North Rhine-Westphalia writes: “The 1950s to 1980s reflect the period of “global dimming”, in which the intensity of daylight and sunlight was reduced due to high levels of air pollution. Since the 1980s, increased filtering of exhaust gases and pollutants from the air has reduced the “global dimming”, which can also be seen in the increase in hours of sunshine.”

This correlation can also be seen in various regions around the world

In a statistical analysis I carried out myself, I analyzed the two possible influencing factors

• Latitude-weighted hours of sunshine
• CO₂ -concentration

for the average monthly temperature over the last 65 years:

Figure 13 Monthly temperature profile in Germany and modeling with solar radiation

The surprising result was that over 90% of the total temperature changes, including the increasing long-term trend, could be explained by solar radiation approximated by hours of sunshine, but the CO₂ concentration had to be excluded as a non-statistically significant explanation.

Investigation of changes in global cloud cover

Jay R Herman from NASA has calculated and evaluated the average reflectivity of the Earth’s cloud cover with the help of satellite measurements over a period of more than 30 years:

Figure 14 Cloud reflectivity between 1979 and 2011

He identified a clear trend of decreasing cloud cover. From this he calculated,

how this affects the affected components of the global energy budget: 

Figure 15 Change in the energy budget due to the change in cloud reflectivity

The result was that due to the reduced cloud cover, solar radiation increased by 2.33 W/m² in 33 years. That is 0.7 W/m² of radiative forcing per decade.

In contrast, the decrease in radiation due to the increase in CO₂ concentration amounted to a maximum of 0.2 W/m² per decade.

According to this study, at 78% the influence of clouds on the climate is at least 3.5 times greater than that of CO₂ , which therefore has an influence of 22% at most. 

 

Conclusion – there is no impending climate catastrophe

Let us summarize the stages of these observations on the deconstruction of the climate narrative once again:

1. There is no exponential growth in CO₂ emissions. There used to be such a phase, but it is long gone and global emissions have been on a plateau for 10 years.
2. The CO₂ concentration is still growing despite constant emissions, but its growth has already slowed down and will stop in the second half of the century
3. The physically plausible greenhouse effect of CO₂ is much lower than is usually claimed, the justifiable sensitivity is only 0.5°C
4. Estimating the maximum possible feedback effect of water vapor results in an upper limit of the feedback factor of 1.25. This does not justify temperature increases of 3°C or more
5. There are plausible simple explanations for the earth’s temperature development. The most important of these is that, as a result of various air pollution control measures (reduction of wood and coal combustion, catalytic converters in cars, etc.), aerosols in the atmosphere have decreased over the last 70 years, which has led to a reduction in cloud formation and therefore to an increase in solar radiation.