Who from the “Last Generation” knows Milutin Milanković?

_ Prof. Dr. Christian Seidl, professor emeritus of public finance, Christian-Albrechts-University. Kiel, 6 January 2022.

A constitutive element of any democracy are protest demonstrations, provided they move within the legal framework. Yet before engaging in protest demonstrations, one should first find out about the underlying facts of any given issue. It seems to me questionable whether the demonstrators of the “Last Generation” are at least somewhat familiar with the work of Milutin Milanković.

Milutin Milankovic (1879–1958)

was a Serbian mathematician. He studied civil engineering at the Technical University in Vienna until 1902. In 1909 he received a chair in applied mathematics at the University of Belgrade. There he turned to basic astronomical and mathematical research. In 1914 Milanković was interned in Budapest at the beginning of the First World War because of his Serbian nationality. There he was able to work in the library of the Hungarian Academy of Sciences and the Hungarian Institute of Meteorology on the influence of astronomical cycles on the earth’s climate, where his first manuscript on this topic was written. His research was influenced by the work of the British autodidact James Croll (1821-1890), who studied the influence of gravity from other planets in the solar system on the Earth’s orbital parameters, including the associated ice age issue.

In 1920 Milanković published the work « Théorie mathématique des phénomènes thermiques produits par la radiation solaire » at Gauthier-Villars in Paris 1920. In 1941 he crowned his life’s work with the book “Canon of Earth Irradiation and its Application to the Ice Age Problem” (Royal Serbian Academy of Sciences , Belgrade), in which he summarized his findings. Milanković did not receive the recognition he deserved during his lifetime. Only after his death was his theory generally confirmed and generally accepted.

The orbital cycles

With Kepler and Galilei, the realization that the earth revolves around the sun prevailed. However, this movement is not uniform, but it is the result of three cyclic earth orbital components, which influence the solar radiation and thus the earth’s climate. This relationship, particularly in relation to the ice ages, is the subject of Milanković’s theory. These components are eccentricity, obliquity of the ecliptic and precession.

Eccentricity measures how far Earth’s orbit deviates from a perfect circle. This is due to the influence of the gravitational pull of the two giant gas planets, Jupiter and Saturn. The more elliptical the Earth’s orbit, the more pronounced the seasons, since more solar radiation reaches the Earth at the point closest to the Sun and less at the farthest point. The cycle lasts about 100,000 years. Currently, the eccentricity is more circular with less pronounced seasons.

The obliquity of the ecliptic describes the angle at which the axis of rotation of the earth is tilted as it orbits the sun. Over the past million years, the tilt angle has varied between 22.1 and 24.5 degrees. The greater the angle of inclination, the more extreme our seasons, since each hemisphere receives more solar radiation in summer (and less in winter) when it is more inclined (tilted from the sun). This cycle extends over approximately 41,000 years. Skewness was at its maximum about 10,700 years ago and will reach its minimum inclination in about 9,800 years. This leads to milder winters and milder summers.

The earth also wobbles slightly on its axis. This is their axial precession, which results from tidal forces from gravitational influences from the sun and moon. The earth bulges at the equator, affecting its rotation. The cycle of axial precession extends for just over 25,700 years. It makes the seasonal contrasts more extreme in one hemisphere and less extreme in the other. It is currently making summers hotter in the southern half and more moderate in the northern half. In about 13,000 years this pattern will be reversed (more extremes in the northern hemisphere and fewer in the southern). There is also an apsidal precession. In addition to the Earth’s axis, the Earth’s orbital ellipse also wobbles due to its interaction with Jupiter and Saturn. Their cycle spans about 112,000 years. Both precession effects together describe an overall recession cycle of 23,000 years on average.

Earth history

The primeval atmosphere of our planet about 4 billion years ago had no oxygen, but consisted of carbon dioxide, methane and water vapor. Despite less solar radiation, temperatures were around 50 degrees Celcius. The primeval ocean was formed by cooling. Carbon dioxide was dissolved from the atmosphere and bound in sediments; this was reinforced by weathering of the stones. After the growth of vegetation, carbon dioxide was removed from the atmosphere by photosynthesis. Some of the sediments penetrated into the earth’s interior and was melted. Carbon dioxide is released back into the atmosphere by volcanism.

More clarity is available over the last 500 million years. For the first 100 million years, the carbon dioxide content of the atmosphere was between 4,000 and 6,000 ppm (parts per million). In the period from 400 to 250 million years ago, carbon dioxide levels were similar to today and there was an ice cover down to about 30 degrees latitude. In the period from 250 to 100 million years ago, the carbon dioxide content was well over 1,000 ppm again. That was the period of the dinosaurs with temperatures 8 percent higher than today.

The last 65 million years are called the Cenozoic or Cenozoic Era. In their first 30 million years, the carbon dioxide content was around 1,000 ppm; about 50 million years ago it even exceeded the value of 1,500 ppm; the average temperature was 12 degrees Celcius above today. Temperatures gradually fell as carbon dioxide concentrations dropped to 300 ppm, until Antarctica began to freeze 35 million years ago. 7-8 million years ago the northern half also began to freeze and the Greenland ice sheet formed. These developments were caused by plate tectonic shifts of continents.

Ice Age, present and “Last Generation”

2.5 million years ago the Ice Age began, in which we still live today. Its beginning is probably due to the closure of the Central American land bridge, which diverted the ocean currents far into the North Atlantic. Antarctic ice cores are available for the past 720,000 years and represent an excellent database.

Milanković was particularly concerned with the Ice Age. He calculated the combined effect of the three orbital cycles (of which he considered the obliquity of the ecliptic to be the most important sub-cycle), with which he calculated the ice ages. Their cycle was about 41,000 years in the last few hundred thousand years (although about 800,000 years ago they were extended to 100,000 years for a few hundred thousand years). These ice age cycles have an asymmetrical sawtooth-like progression. They develop relatively slowly in the direction of an ice age. After reaching its peak, a significant warming occurs after a relatively short time. The last ice age ended around 10,000 years ago. The warm period that followed about 6,000 years ago not only brought about a growing season in the Sahara; by then all the glaciers in the Alps had melted. Since then, we’ve been moving towards a new ice age, but the concentration of carbon dioxide in the earth’s atmosphere has increased from about 280 ppm to 412 ppm since the beginning of the industrial age, especially in the last 20 years. This has diverted the climate development in the direction of a warm period. Apparently, the cooling trend that began about 6,000 years ago has not continued.

Is that already the catastrophe or would a new ice age not also be a catastrophe against which we have inadvertently protected ourselves? If the dinosaurs hadn’t already died out as a supposed result of a massive meteorite impact, they might have frozen to death due to the present climate being 8 degrees Celsius colder. The Milanković cycles did not run smoothly. About 1,000 years ago there was a warm period in which the Vikings settled in Greenland and advanced to what is now Canada. Around 700 to 800 years ago, the coast of Greenland cooled down so much that the descendants of the Vikings could not survive there. From a European point of view, America was also lost again.

Current warming is due to us burning more fossil fuels than their carbon emissions can be absorbed. The fossil fuels were formed millions of years ago and neutralized in the ground. We’re releasing them now, restoring the carbon dioxide-laden atmosphere that existed back then.

In my opinion, the “Last Generation” did not understand that fossil fuels cannot be fully replaced by sustainably generated energies, but carbon dioxide emissions can be reduced to a level that can be absorbed by the oceans and vegetation. Superfluous carbon dioxide emissions must be prevented. For example, a great deal of travel is undertaken to attend competitive sporting events, as if there were no television on which to artificially superimpose the screams of the fans. Recreational holidays can also be relaxing in your own country. Wars and military activities in general are sources of significant carbon dioxide emissions. Currently, the gas that Russia does not supply is flared. It would be much better for both the environment and for us if we could continue to use it, since less fracking gas would then have to be extracted and burned.

Our planet is currently inhabited by 8 billion people. In a few decades it will be 10 billion. Our planet can only feed and accommodate this mass of people under austerity conditions, at least for significant population masses. This can only be avoided through strict birth control, which unfortunately is associated with temporary aging. Nuclear power has even been touted by the EU as a way out. That would be nice if it wasn’t for the nuclear waste that should be stored for 1 million years. This is probably a crude statement, but it is important to note that about 1 million years ago (12 million years according to others) the prehominids split into four subclasses: gorillas, chimpanzees, orangutans and homo sapiens.

The knowledge presented in this paper is publicly available. Why does the “Last Generation” deny reality and blame high-quality works of art for climate change? Why have the climate activists spared Beuys so far?

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