Milutin Milanković

Milutin Milanković (Serb: МилутинМиланковић) is a Serb theorist (astronomer and mathematician) (born with Dalj, in the empire Austro-Hungarian (today part of Croatia) 1879 and died in 1958).

1904 : doctorate in technical sciences at the Institute of technology of Vienna.
1909: assisting in mathematics applied to the university of Belgrade.
1914: captive fact taken by the Austro-Hungarian army (released in 19.?).
1920 - 1941: its work undertakes on its theory of change of climate to the quaternary one.

The theories of Milankovic were largely allowed only with beginning of the year 70. This was due to a certain number of factors including/understanding mainly:

nonsatisfactory dating of the icecaps;
enormous times concerned in the accumulation of the layers of ice;
nature complexes various radiations and their reports/ratios with the climate.

These factors provided far too many alternative explanations to the climate changes to retain only one of them (that of Milankovic) so tempting is it.

Did Milankovic have very early (perhaps in captivity?) intuition that the seasonal variations and athwartship of solar energy received by the Earth were the cause of the climate changes. To show this intuition, bases its theory, it undertook as from 1920, of research, very mathematical, on the astronomical determinants of the climate. This research was to lead in 1941. It then published its astronomical Théorie of the climate , concerning the total sunning, together with tables, always of use at present. Considering the time this publication passed almost unperceived and it was necessary to wait the Seventies so that successors (such Jean Robert) leave it the shade so that it is really taken into account.

It highlighted, in this work the existence of climatic cycles (in particular glacial) dependant on astronomical conditions (see below).

As from 1976, the examination of the deep oceanic cores confirm the theory of Milankovitch and its real correlation to the cycles of environmental change: “… the orbital variations remain the mechanism most completely examined climate change on scales of time of tens of thousands of years and are by far the direct effect most clearly of the variations of insolation on the terrestrial atmosphere…” (National Research Council, National council of Research, 1982 - < www.earthobservatory.nasa.gov >)

Data

See also the article Parameters of Milanković devoted.

For a certain time, of the researchers had understood that on the reduction, slow but inexorable, of the average temperature of the Earth (since million years) other factors are superimposed which should be tried to model, in order to be able to integrate them in a total forecast of the climate changes.

In 1911, Milankovitch, decides to draw up a chart the glacial periods of the Pléistocène, together with tables, always of use at present (pleistocene is the geological time going from 1,8 million years to 11.500 years, approx.). It was characterized by prolonged glacial periods, the glaciers covering of the continents, stopped by short interglacial periods, with the moderate climate. Milankovitch made all its calculations with the hand, and it remade them during the thirty years to come. It incorporated new information there on small variations of the slope of the axis of the Earth, and on small orbital changes caused by the sudden traction of the another planet gravity. Each one of these orbital variations has its own scale of time, and consequently they act one on the other in various manners, but each one is regular. Going up up to 600.000 years behind in its calculations, it measured carefully, the effect of these factors on the solar radiation entering through the Scandinavian hemisphere. The diagrams and the tables of Milankovitch created at the time are still employed today. Finally, the mathematician arrived at a complete astronomical theory of the glaciations.
Thus, two long cycles of glaciation of 413.000 and 100.000 years are correlated with two cycles " courts" from 40.000 and 21.000 years, according to the variations (known) of the terrestrial orbit (slope, nutation, precession). But, the largest planets of the solar system, Jupiter and Saturne also disturb the orbital movements of the Earth.

But the large telluric explosions can they also (as the explosion of the 26.12.2004) make deviate the axis of rotation whereas the important volcanic eruptions decrease the quantity of heat received on the ground.

In the same way solar activities, natural (activity of the plants and the animals), anthropic (industrial, agricultural…), even meteoritic as many factors of disturbance represents…

The astronomical component

Milankovitch thus showed, that the Cycle of glaciation finds, primarily, its origin in two types of periodicity:

of the long periods, 413.000/100.000 years,
of the periods " courtes" from 40.000 years and 21.000 years.
These periodicities are characteristic respectively:

#des variations of the eccentricity of the Terrestrial orbit;
# of the slope of the axis of rotation of the Earth (the Nutation);
#de its Precession (or rotation of this axis).
Wurms, the last great glaciation knew its maximum 18.000 years ago, the temperatures were lower by approximately four degrees than those current and one can expect a return of the ice in several tens of thousands of years. Since the end of the latter great glaciation, approximately ten thousand years ago, the climate is more lenient and relatively stable, in the long run. This softness allowed the primitive companies hunters - gatherers sédentariser and to develop agriculture and the breeding (passage of the Paléolithique to the Neolithic ).

Attention, according to the cycles of Milankovitch, one can expect a return of the ices in a few tens of thousands of years…

Other factors of the climate change

The solar activity

Acts, they also in two manners: - a maximum of sunspots involves a strong followed radiative activity, in a short amount of time (a few hours at a few days), of a rise correlated of the temperature on Earth;

them successive changes of polarity of the magnetic axis of the sun, could be in the beginning “small Age Ice” t.q that known at the end of the reign of Louis XIV (the sun king).

The activity meteoritic

The falls, random, of large meteors (Asteroid S or Comet S) modify obviously, not only the living conditions but also the climatic conditions of our Planet.

The terrestrial activity

A intensive volcanicity

Exploded large, it acts in two manners:

of the important lâchers of ashes can occult the rays of the Sun (with reduction in the quantity of received heat, modification of the albedo…) and thus to cause a glacial Era such as that which seems to have taken place during the Riss.

the force of the explosion, near to the million megatons, can in it even " bousculer" the terrestrial axis of rotation.

The surface activity

Terrestrial activities:

that they are natural (continuous reduction in the average temperature of the Earth activity of the plants and the animals, phenomena weather…) ;

or anthropic (industrial, agricultural…), they represent as many factors of disturbance to be started with the Greenhouse effect but also with a possible modification of the Albédo.

How to combine all these components of the climate?

The spot seems very difficult because so certain components (astronomical, solar…) are partly prédictibles, others are it only while being based on scenarios (like the greenhouse effect), others finally (meteors, volcanicity…) are for the moment primarily random.

One could thus distribute these components in three series:

component prédictibles, undoubtedly most important;

component " semi-prédictibles" (" scénarisables") ;

component nonprédictibles (random). What gives the broadth of the task (even if these last series of components are additional compared to the first).

NASA, in order to obtain " a Modeling of the climate " however made some attempts in this direction (by taking only some of these components); it has to give up in front of the length of the computing times, in spite of the use of the most powerful computers currently.

See too

Climatologist
Parameters of Milanković

External bonds

August 1st

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