Nobel laureate Klaus Hasselmann

Critics of climate modeling include, in particular, Steven Koonin, a highly accomplished American physicist and climate scientist who once served U.S. President Barack Obama and recently published a “climate skeptic” book. He notes that climate models have failed time and again because they fail to prove human influence on global warming. Discrepancies among individual climate models showed “that the science is far from settled”.


Almost all models are running too warm. Nobody knows why. Image: Legate’s presentation Heartland 14th Climate Conference Las Vegas 15 October 2021

Data from NASA’s Ceres project used

In general, real-world data repeatedly calls into question the results of climate models and thus the tone-setting climate science. This is also the case with a study by German researchers Fritz Vahrenholt and Hans-Rolf Dübal, which has just been published in the peer-reviewed scientific journal Atmosphere.

Vahrenholt and Dübal are originally chemists, but have worked extensively on climate science in recent decades. The study is based on data from NASA’s Clouds and the Earth’s Radiant Energy System (Ceres). Ceres has been using satellites to record the radiation that reaches, and is emitted by, the Earth since 1998. The project’s goals include a better understanding of the role of clouds and the Earth’s radiation balance with respect to global warming.

Cloud cover has decreased by two percent

And it is precisely these data from Ceres that throw a wrench into the thesis of man-made climate change. Vahrenholt and Dübal conclude that it is not man-made enhancement of the greenhouse effect that is the main cause of warming over the past 20 years, but a two percent decrease in cloud cover during that period. According to Vahrenholt and Dübal, the weaker cloud cover has resulted in more shortwave radiation from the sun reaching Earth. This increase in solar radiation has been a major driver of global warming.

NASA researchers led by Norman Loeb, as well as Finnish researcher Antero Ollila, have each pointed out in a study that shortwave solar radiation increased from 2005 to 2019 due to a decrease in low clouds. Dübal and Vahrenholt have now studied radiation fluxes for the entire period from 2001 to 2020 – both near the ground and at an altitude of 20 kilometers – and related them to changes in cloud cover.

Greenhouse effect had only a small impact

In fact, the satellite data from Ceres show that the shortwave radiation emitted into space by the clouds has decreased by about two percent in both the northern hemisphere (NH) and the southern hemisphere (SH). With solar radiation remaining nearly constant, this means that more shortwave radiation has reached the Earth’s surface and contributed to warming. At the same time, the fraction of longwave radiation that is reflected back to Earth from the atmosphere has only warmed the planet to a lesser extent. This radiation back to the earth is the greenhouse effect, which has been intensified by the emission of climate gases. According to Fritz Vahrenholt and Hans-Rolf Dübal, this enhanced greenhouse effect has even been largely compensated by the aforementioned decrease in cloud cover: The decrease in clouds has resulted in more longwave radiation reaching space from the earth.

IPCC relies on model calculations instead of real data

The study results of the two German researchers contradict the claims of the Intergovernmental Panel on Climate Change (IPCC), according to which the observed warming occurred solely because the proportion of long-wave radiation reflected back to Earth from the atmosphere increased (due to the stronger greenhouse effect). The IPCC attributes 100 percent of the warming to this enhanced greenhouse effect – but justifies it with model calculations rather than real data.

“The warming of the last 20 years has been caused more by changes in clouds than by the classical greenhouse effect,” say study authors Fritz Vahrenholt and Hans-Rolf Dübal

In their study, Vahrenholt and Dübal also looked into the background of the observed stronger heat absorption by the Earth. The corresponding explanations can quickly exceed the understanding of laymen: Based on observations of the so-called enthalpy of the climate system and oceanic heat uptake, it was shown that there have been two warming periods on Earth since 1850, each lasting 20 to 30 years. A third warming period began in 1990 and continues to this day.

The onset of each of these three warming episodes was accompanied by changes in the Atlantic Multidecadal Oscillation, a natural periodic ocean current in the Atlantic that significantly determines the climate…

End of the warming period could mean end of global warming

The third warming period coincides with the observed decrease in cloud cover. Whether this warming period, like its two predecessors, will end soon must be clarified by measurement data in the coming years. If the warming period ends soon, global warming should decrease and the announced “climate catastrophe” will largely fail to materialize.

To date, it is unclear what is causing the observed cloud thinning. According to the study authors, changes in ocean currents are cited in the literature as possible causes Study authors are cited in the literature as possible causes, but also a decrease in aerosols in the air and warming due to more CO₂ in the atmosphere. However, Vahrenholt and Dübal emphasize: “The warming of the last 20 years was caused more by changes in clouds than by the classical greenhouse effect.”

The Intergovernmental Panel on Climate Change is thus challenged to review its findings.

Hat-tip: EIKE