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Schriftenreihe des Europa Institutes Budapest, Band 28:33–42.


Main Trends of the Changing European Climate


In order to understand the climate of the Balkans and of the Mediterranean region as well as its expected changes it is expedient at first to survey in brief the operational mechanisms of the climate of the entire northern hemisphere.

The decisive factor of the Earth’s climatic system is the tropical heat surplus. It means the surplus of incoming sunshine per unit of surface compared to the higher latitudes (mostly to the region of the poles). As it is well known, the reason for this is that the Earth’s axis of rotation is tilted (23.5° away from the perpendicular to its orbital plane, Figure 1).

The heat surplus developing in the tropics has to be distributed and spread in the less warm areas according to the basic rules of thermodynamics. It is the driving force originating from the surplus in the tropical regions as well as from other physical quantities (such as the impulse momentum, the rotation quantity) that serves as the ’engine’ of the functioning climatic system (Figure 2).

The hot tropical air warmed along the equator, hence expanding and rising, would set out high up towards the poles and (studying the northern hemisphere) it reaches near the 30th latitude, landing in the Sahara region, causing tremendous aridity there. Part of the air near the soil would start back towards the equator where once again it warms up and goes upward. This closed cycle is called Hadley cell or Hadley circulation (Figures 3 and 4).

It can be said that it is this heat transfer that plays as transmission mechanism the role of the driving belt in the functioning of the climatic system.

Without going into detail it should be mentioned that after the subsiding branch of the Hadley cell the air is unable to develop yet another closed cell circulation. No more closed cells are found between the subtropical and the temperate zones (more or less in the domain between latitudes 30 and 60), and here we enter the turbulent zone. As its name indicates, here the cyclones of the temperate zone are the main implementers of transporting energy, impulse and impulse momentum. It can be said that the cyclones are the driven wheels of the climatic system (Figures 5 and 6).

The characteristic track of cyclones, the location of their appearance, the duration of their existence as well as the energy carried by them are the basic, decisive factors determining the weather (cold and heat fronts, rains, rainstorms) in the temperate zone.

Therefore it is a question of fundamental importance with respect to the future of Europe’s climate whether the intensity and track of the temperate zone cyclones could change?

In this respect let me present two examples: a historical and a current one. There is a grinding stone on the frontispiece of R. S. Bradley’s book entitled Quaternary Paleoclimatology1 which was used by an ancient culture to grind cultivated seeds. The author adds the following commentary to the picture: “A grindstone, formerly used by Neolithic people for crushing grain, is all that remains of an agricultural community that once flourished in what is today one of the most inhospitable regions on Earth. In this part of the Algerian Sahara, the climate has changed radically during mid- to late-Holocene time — from at least seasonally moist, to extremely arid.”

On this basis we may infer that the downward branch of the Hadley cell got closer to the equator, it was ’narrower’ at the end of the last glacier period some 8 to 10 thousand years ago, therefore the rainy zone appeared already on the territory of present-day Algeria.

This raises the possibility that as a result of global warming a contrary process may also take place, in other words, the cell may ’widen’, and its borderline may be pushed further north. And truly, according to the most recent researches2: Within the context of the long-term global warming, …, evidence is found for the intensification of the Hadley cell since 1950. The Hadley cell change is consistent, including a strengthening of westerly atmospheric flow and an intensification of midlatitude cyclones.”

The theoretical antecedents of the phenomenon have been known for long. I would mention by way of an example the university textbook written by Rudolf Czelnai, published in 1979, which says that with the warming of the poles the difference of temperature between the tropics and the poles is decreasing, as a result of which the number and migratory track of the temperate zone cyclones may be modified.

Actually any change of the cyclone tracks would radically alter the weather of Europe. The main danger of climatic change is due to this fact and not to gradual warming (Figure 7).

The consequences of change include, as it is stated in the 2007 IPCC (Intergovernmental Panel on Climate Change) Assessment Report 4:

1. The typical western zonal current is expected to move northwards, therefore

– Western Europe (South Germany, the Czech Republic) may get more

– Central and South-Eastern Europe may get less precipitation.

2. The subtropical and desert effects may spread to the present Mediterranean (causing summer heat and aridity), while

– the Mediterranean influence may move up to South and Central Hungary.

According to the models run on computer providing the basis of the report in question the following can be expected in the coming period:

1. Further warming, which would be significant*

– in winter in Northern and Eastern Europe,

– in summer in Southern and Central Europe.

2. The minimum and maximum temperatures would change more than the average (mean) temperature.

3. The annual quantity of precipitation would grow in Northern Europe (mostly in winter), and would be less in Southern Europe (mostly in summer).

4. The daily extremes of precipitation would grow everywhere, even in places where the total of the annual precipitation would be less. All this, however, is not only the future. The domestic consequences of the slight global warming which has been taking place in the past century up to now (0.7 to 0.8 °C) can already be sensed (Figures 8, 9 and 10).

The models run by computer give the values for temperature changes by season for Europe as seen on Figures 11, 12, 13 and 14. Changes in precipitation are less unambiguous, but even there an annually decreasing trend may be regarded as probable (Figure 15).

Finally, I would like to call the attention of historian colleagues to the fact that the topic is not at all new! For instance, a book first published in 1910, and afterwards repeatedly, Wilhelm Bölsche’s Eiszeit und Klimawechsel (Ice Age and Climate Change) deals with the same problems we are currently engaged in: how much was humanity’s carbon dioxide emission and in which year, how much is the actual carbon dioxide content of the atmosphere. “The quantity of carbon gas in the atmosphere [today, in 1910] is 0.03 volumepercent. Emission was 140 million tons in 1860, 510 in 1890, 550 in 1894, 690 in 1899, 890 in 1904 and 110 million tons in 1910 [today]”

He also points out that a warming by 5 to 6 °C would bring coconut palms to Germany (Figure 16).

My conclusion is that we haven’t got another eighty years to draw conclusions!



Published by Unwin Hyman, Boston, 1985.


Bradley et al., 2004.