From KlimaNachrichten

By KlimaNachrichten Redakteur

As the chart above shows, the global mean temperature in June fell slightly compared to the previous month. The deviation from the long-term average of the satellite measurements is now 0.48 degrees Celsius. At the beginning of July, global temperatures continued to fall significantly. Nevertheless, panic was spread in Germany by public media. The Greens even called for a work-free heat-free on days above 25 degrees Celsius. A maximum temperature of 25 degrees is the definition for a summer day in Germany. We now have about 40 – 50 of them per year, in the 50s it was still 20-30 days. But what is the cause of this? Does CO2 heat up the summer days? That is more than questionable.

There is heat panic in Germany – but temperatures are falling

globally For the media as well as left-wing and green parties, it was the dominant topic last week: the summer heat. It was now very clear: the climate change narrative was confirmed by the heat panic in Germany.
If you look at the temperature development of recent years in the next graph, you can see a significant increase in 2023, a persistence at a high level in 2024 and a clear downward trend since January 2025. Globally, we are currently more than half a degree Celsius below the summer of 2024. We are heading for zero degrees Celsius for the Copernicus data, the average value from 1991 to 2020 Copernicus.eu. 

None of the quality media considered it necessary to relax the scaremongering in Germany by saying that there is no sign of extraordinary global warming worldwide in 2025.
Climate researchers are puzzled as a whole about what may have caused the particular warming of 2022-2024. Their models are based on the fact that the thermal radiation emitted by the Earth is reflected back more strongly with an increase in CO2 (greenhouse effect, see next image).
However, the main cause of the particular warming of 2022-24 was not CO2, but a strong El Nino – a natural phenomenon – and an increase in direct solar radiation caused by the decrease in aerosols caused by the ban on sulfur-containing diesel on ships in 2021. And indeed, direct sunlight (yellow on the left in the next image) has increased and the thermal radiation (red on the right) emitted into space has also increased. (Source: M.Lackner according to IPCC)

And this is true not only for the last 3 years, but for the last 25 years.
If one examines the measurements of NASA’s CERES satellites, one finds that the warming of the last 25 years is mainly due to an increase in direct short-wave solar radiation and less to the greenhouse effect of the increased CO2 content of the air. Why 25 years? That’s how far back the measurements of NASA’s CERES satellite program go. The evaluation of the satellite measurements showed that 80% of the warming is due to the thinning of the clouds and the resulting increase in direct short-wave solar radiation. This leaves 20% of the warming for the CO2 greenhouse effect. It gets interesting when we trace the connection further back. And here is an informative graph from the German Weather Service about the change in sunshine duration in Germany.

You can clearly see the decrease in sunshine duration from 1950 to 1980 and the subsequent increase until today. At the same time, the temperature in Germany decreased slightly between 1960 and 1980. The sulphur and dust particles in the air have an influence on the duration of sunshine and cloud development. They rose sharply between 1950 and 1980 – not only in Germany – and aerosol dust and sulfuric acid particles are ideal cloud formers. They form cloud nuclei where the moist air condenses into clouds. After the introduction of exhaust gas purification in Germany and the USA for industrial plants and power plants in the 1980s, and later for motor vehicles, as well as the collapse of heavy industry in Eastern Europe in 1989, aerosol pollution in the air decreased, which led to less cloud formation. In addition, clean air also leads to less reflection of solar radiation on the dust particles. After 2000, China also made progress with exhaust gas purification programs, so that the trend towards cleaner, aerosol-free air has continued to prevail to this day.

In the meantime, the fact that the clouds are receding is also being noted by the climate mainstream. In order to be able to adhere to the theory of CO2, the sole climate-determining greenhouse gas, the following line of retreat is now being established: CO2 warms the air through the greenhouse effect. This warming leads to a change in the cloud regime, so that more short-wave direct sunlight can then come to Earth.
Here is the weak point of this argumentation: Until now, it has always been claimed that warming is a consequence of the increase in long-wave radiation reflected back to Earth. So far, the models have not resulted in an increase in short-wave radiation. Worse still, fewer clouds mean that the greenhouse effect is weakened and more long-wave thermal radiation can be radiated into space. So the measurements contradict the models. In other words, the models are inadequate. However, these models are the basis of politics in Europe and Germany with their devastating climate policy, according to which net zero CO2 would have to be achieved by 2045.

However, it is possible that a warming of the oceans can change the clouds. This applies to the limited greenhouse effect of CO2 (see above), but it also applies to the natural warming and cooling of the oceans. For hundreds of years, the oceans have oscillated in a cycle of warm and cold phases of about 60-70 years (AMO – Atlantic Multidecadal Oscillation). And now it gets exciting: The clouds dance in the same beat. At high sea temperatures, the clouds are permeable, at low temperatures they allow less sunlight to reach the earth. They run in exactly opposite directions. In the next diagram we can see the course of sunshine duration and AMO.

A publication in Nature scientific reports also points to this connection. (Lüdecke, Plath, Lüning). The authors examined the AMO with the sunshine duration in Copenhagen, Krakow, Potsdam, De Bilt (Holland), Vienna, Zugspitze and Trieste. In all cases, the duration of sunshine follows the cycles of Atlantic temperatures (AMO). Here is the comparison of Potsdam. (Note the different time scales)

What conclusions can we draw
from this

1. Analysis of NASA data on solar radiation and radiation shows that the models are
useless for political decisions on climate issues

2. There is a connection between aerosols in the air and cloud formation and thus solar radiation

3. It cannot be ruled out that CO2 also makes a minor contribution.

In a few years, we will know what the main drivers of cloud change are. The potential of aerosols has been exhausted and the decrease in air pollution cannot be increased much further. The AMO, which has declined significantly since the beginning of this year, remains the key to this still unsolved mystery. If the AMO enters its negative phase, the cloud cover will in all probability increase again. Then there will be a decrease in direct solar radiation and thus a decrease in the increase in warming. And the role of CO2 as a limited effective greenhouse gas would have to be redefined.

Sincerely,

Fritz Vahrenholt