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Since when "do scientists know" for climate change ?

September 2003

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Considering the passionate articles that we sometimes read in the paper on the reliability - or honesty - of the scientists that study our future climate, it is tempting to consider that science there leans on very recent and precarious results that need to be confirmed before we do anything. But in reality part of the scientific basis was not discovered yesterday...and is even quite old !

I offer below a little "chronology of climate change", with some important dates liked to this file.



End of the 18th century: Horace Bénédict de Saussure, a swiss naturalist, builds a device composed of 5 glass boxes included one in another (that is each glass box contains a smaller one, and so on 4 times), and puts a thermometer in each box. He notes that when this structure is exposed to the sun, the temperature in each box increases when going towards the smaller box (the one most inside). He understands that glass "traps" solar energy, and suggests the atmosphere behaves the same.

1824: Joseph Fourier, a french physicist, publishes "Remarques générales sur les températures du globe terrestre et des espaces planétaires" (general remarks on the temperatures of the Earth globe and the planetary spaces), where he exposes that the ground temperature on Earth is increased by the existence of the atmosphere, that lets better go through sun rays than infrared terrestrial radiation (see physical aspects of the greenhouse effect), and names this process "greenhouse effect", on the basis of de Saussure's works.

1838: Claude Pouillet, a french physicist, attributes the natural greenhouse effect to water vapour and carbon dioxide. He concludes that any variation in the quantity of water vapour or of carbon dioxide in the atmopshere should result in a climate change.

1860: optical and radiative properties of the atmospheric gases are studied by John Tyndall, an irish physicist, who confirms that the molecules mostly responsible of this greenhouse effect are water vapour and carbon dioxide.

1896: Svante Arrhenius, a sweedish chemist (he will be awarded the Nobel Prize in 1903 for having discovered the electrolytic properties of acids and bases) comes by calculation to the conclusion that a doubling of CO2 in the air will lead to a global increase of 4°C of the ground temperature, and predicts as a consequence that the industrial age will generate a global warming.

In a book published in 1910 and named "L'évolution des mondes" (title in french !), he writes: "would the carbonic acid [name then given to CO2, NDR] double in quantity, we would gain 4 degrees ; it should increase fourfolds to have 8 °C extra. In the same time its diminution would increase the heat and climatic differences between the various parts of the globe ; its increase would on the opposite equalize the temperature [this means that he understood that in a global increase the poles would heat faster than the tropics, NDR].

1902: The existence of stratosphere is anounced by Léon Teisserenc de Bort, during a speech at the french Académie des Sciences. His discovery results from the perfection of sounding balloons, of which he will launch close to 300. His works will help to understand that ozone absorbs sunlight (actually ultraviolets).

1920: Lewis Fry Richardson, an english physicist, attempts a first experience of climate modelling on the grounds of the sole equations of physics (without any computer, of course !). He can't make it and concludes that he would have required thousands of people in order to do the corresponding elementary calculations.

1947: though the first expeditions designed to take samples of marine sediments took place around 1850, two major episodes happen: the sweedish expedition on the Albatross, and the american expeditions of Maurice Ewing. These samplings have played a major role in the reconstitutions of past climates.

1950: Julius Charney, director of the Institute for Advanced Study of Princeton University (United States) develops, with a mathematicien named John von Neumann (a world famous pionneer in computer science), the first numeric model for meteorological forecast. This is allowed by the setting up, in 1946, of the first computer that ever existed : the Electronic Numerical Integrator and Calculator (ENIAC).

1950: creation of the World Meteorological Organization (WMO).

1958: this year, baptised "international geophysics year", is the start of spatial exploration, with the launch of the first articifial satellites ever (among which Explorer 1 and the followers of the same kind allowed the discovery of the Van Allen Belts), and also the beginning of the continuous measurement of the atmospheric carbon dioxide concentration at the Manau Loa observatory (Hawaï), what allowed to prove the continuous increase of this concentration, year after year, since then.

1966: Some american scientists perform the first ice drilling in Greenland and extract and ice core more than a kilometer long. Many others will follow, including the Vostok drilling in Antarctica, done by a american/russian/french team (the scientific work is essentially russian and french on this precise drilling, the Americans having mostly provided the logistics), that will lead to the publication of a curve now world famous on the simultaneous variations of CO2 and temperature for the last 400.000 years.

70's & 80's: the progressive rise of computers and satellites enables a fast development of climate simulation. The first models took only the atmosphere into account.

1980's: numerous international research programs on the past climates are launched, that aim at favorizing collaborations between teams and comparing the results: World Climate Research Program (WCRP), CLIMAP, PCMDI (intermodel comparison), and many others....

1987: Creation of the International Panel on Climate Change (IPCC), set up jointly by the World Meteorological Organization and the United Nations Environment Programme. The mission of the IPCC is to periodically assess and synthetize the scientific work done on human-induced climate change (see the page describing this organism in detail).

1990: The IPCC publishes its first assessment report, which concludes that there is a body of evidence that suggests that the climate will change under man's influence, and has probably begun to do so.

1990's: Beginning of simulations coupling oceanic and atmospheric models.

1992: Signing, during the Rio Summit, of the "Framework Convention on Climate Change", that will be ratified by almost every country in the world. This convention proposes to "stabilize the atmospheric concentrations of greenhouse gases at a level that prevents any dangerous anthropic perturbation of the climate system" and stipulates that the "parties" (that is the countries that signed the convention) will periodically meet (once a year presently) to implement this objective.

1992: The French government creates the Mission Interministérielle de l'Effet de Serre, which has two main missions : preparing the international negociations and setting up the french national plan for fighting against climate change.

1997: Signing of the Kyoto Protocol, during the third "conference of the parties" (COP in short).

2001: The IPCC publishes its third assessment report (the second was published in 1996), representing three 800 page volumes. The scientific basis report confirms that our massive greenhouse gases emissions will modify the climate, and that part of the temperature rise that happened during the 20th century is most probably the beginning of this change. The next assessment report is scheduled for 2005/2006.

2007: The IPCC publishes its fourth assessment report. The conclusions once valid are still valid...


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