Scientists from the Intergovernmental Panel on Climate Change (IPCC), meeting in Paris until February 2, will issue a report affirming with "a very high degree of confidence" that human activity since 1750 has provoked the global warming. This is what appears in the latest version of the Summary for Policymakers that IPCC specialists began discussing on Monday, January 29. Written in English, this working text, of which Le Monde was able to obtain a copy, has 14 pages. Before being adopted, it will be reread line by line and discussed by the roughly 500 delegates who represent the governments of around 120 countries. At the same time, an exhaustive report detailing the knowledge on climate change acquired since the previous text of the IPCC, in 2001, will be adopted.
A crucial passage in the draft Summary reads: "The average warming expected if carbon dioxide concentrations [in the atmosphere] were to be 550 ppm [parts per million] is probably in the range of 2-4,50 ° C above pre-industrial values, with a central estimate of 30 ° C. This warming is very unlikely to be less than 1,50 ° C. Values significantly above 4,50 ° C cannot be excluded. " The importance of this projection is measured if we know that the concentration of carbon dioxide in the atmosphere currently exceeds 380 ppm and increases by more than 2 ppm per year. In addition, the level of 20 ° C is often presented as a threshold beyond which the climate machine could get carried away.
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