In 1896, the Swede Svante Arrhenius estimated that a doubling of the CO2 content of the atmosphere would increase temperatures by around 5-6 ° C depending on the latitude. This hypothesis of the doubling of CO2 (in 3,000 years for Arrhenius, at the rate of his time) has become the common thread of research on climate change and its modeling.
In the 5 reports of the Intergovernmental Panel on Climate Change (IPCC), published in 1990, 1995, 2001, 2007 and 2013, the ranges of forecasts for 2100 have changed, still under the assumption of doubly: 2-5 ° C; 1-3.5 ° C; 1.4-5.8 ° C; 1.1-6.4 ° C and 1.5-4.8 ° C. Uncertainties have not been reduced, and improved forecasts can only come from even more explicit manifestations of climate change …
Climatologists work from models, this modeling work is used to feed the IPCC. The first model dates from 1950 (it was tested on the first existing computer, the Eniac). At the date of the 4th report, in 2007, the number of independent models used by laboratories around the world was 23. Today, there are around forty models, including two French. Subject to an increase in the CO2 concentration, all these models simulate a warming. On the other hand, the amplitude of this warming varies according to the models, between 2.5 ° C and 4.5 ° C for a doubling of the CO2 concentration. There are uncertainties, which concern climatic feedbacks, which are not taken into account in the same way by the models.
In the 19th century, the level of CO2 in the atmosphere was around 280 parts per million by volume (ppm). In 1958, when the first measurements were taken at the Mauna Loa site in Hawaii, it reached 315 ppm. On May 12, 2019, it was 415.4 ppm: + 100 ppm in 61 years. A record since Humanity has existed, long before the first measurements which date back to 1880. And growth is not linear, but exponential: +3 ppm between 2018 and 2019. At this rate, the doubling should occur, on a linear model, in 2067: it will occur much earlier. And at + 5 ° C, is it compatible with human life on Earth? If so, at what cost of demographic decline? Let us not forget, that during the Pliocene, three million years ago, the temperature was +3 to +4 ° C compared to today, trees grew in Antarctica and the ocean level was 15 m higher than today. Obviously we will not succeed, because the melting of the ice sheets takes time, but we can count on 50 cm to 1 m depending on the model, by 2100. And that will not stop at 2100, be sure of it. .
For a doubling of the CO2 content compared to pre-industrial times, the results of the most recent modeling work are mentioned in an issue of the journal Science of April 19, 2019. Until now, the models aimed at a warming between 2 and 4.5 ° C. As part of the preparation of the next IPCC report, in 2021, the models developed by the most recognized American, English, Canadian and French research centers, lead to disconcerting results: a much more severe warming, reaching at least 5 ° C.
The results are discussed, scientists are skeptical, the modelers themselves wonder, but the trend is considered very real and definitive. Would the worst be sure? One of the modelers, Andrew Gettelman, of the National Center for Atmospheric Research, Boulder, Colo., Seems to fear it: “The frightening part is that these models might be relevant.”
During that time, in the European elections, we only talk about the REM vs. the RN, migration and the role of Europe… Derisory. Isn’t the stake elsewhere?
Chris is an avid outdoorsman and has been contubuting to The Camping Canuck for 2 years.