Factor ten
Well, until now…”What we observe in past developments are simply increases of 10 ppmcontinues the paleoclimatologist. Even taking these extremely rapid increases, we are ten times slower than the current increases in CO2 linked to human activity! Past increases are relatively small compared to current (increases in) concentrations caused by anthropogenic activities, where in a century, we go from around 300 to 400 ppm, therefore 100 ppm more! This allows us to highlight the comparison between the two eras, both in terms of speed and amplitude. There is a factor of 10 at least between the two! Currently, we are not on a leap at all, in fact. These jumps have nothing to do in terms of amplitude and speed with what we experience today. Currently, we are seeing a release of CO2 linked to the combustion of fossil fuels (oil and gas). And with a jump, we have a beginning and an end. Here, we don’t know when it will end… Which is all the more worrying.”
This marine current worries scientists because its loss could lower temperatures by 30°C in Europe: “Winters like in Canada”
The study, published in Nature Climate Changeis also interested in the causes of these CO2 jumps in the past, which are not linked to humans but have natural causes. These jumps mainly occur when two situations are encountered: the first criterion is the fact that the Earth’s axis is tilted more than average. Indeed, this inclination varies naturally over periods of approximately 41,000 years. A “high (or strong) obliquity” allows the Sun’s energy to be distributed equitably between the Equator and the poles, and not mainly on the Equator and little at the poles. Besides this “high obliquity”, the second criterion is the fact that the Earth is recording a collapse of the Amoc, the famous ocean current which brings (among other things) warm waters from the Equator to the European continent and which plays a major role the role of driver of the earth’s climate.
Ecosystem change
The team of researchers carried out modeling to understand this association. “It seems that at high obliquity, when the Earth has its head particularly tilted forward towards the Sun, carbon sources such as grasslands and forests are located in certain particular places, notably in Africa and the Middle East. And that, in connection with the cessation of Amoc ocean circulation, these sources cause a massive release of carbon.” Indeed, we can imagine that with the effect of the end of Amoc on the global climate (decrease in rain or increase in temperature in certain regions, etc.), we observe a change in ecosystems: Forests disappear, meadows become more arid… These new habitats can no longer play a role as carbon sinks or become emitters.
Currently, precisely, the Earth finds itself, as during the jumps of the past, in a period of high obliquity. This has been the case for thousands of years, which explains why we do not see any effect on our ecosystems. But at the same time, some scientists fear that the Amoc is slowing down due to global warming (we are indeed measuring a slight slowdown, which could however correspond to natural variability), which could ultimately lead to a collapse .
A CO2 jump to be feared now?
Consequence “A jump in CO₂ could therefore occur”, explain the authors of the study. “This would release the equivalent of 4 years of human-caused greenhouse gas emissions over a period of a century. This would add to the CO₂ that humans already emit, accentuating the global greenhouse effect” . But in addition to this ultimately relative increase, the collapse of Amoc would have many other consequences, these “catastrophic”recognizes Etienne Legrain. “There would be consequences for the climate on a global scale. This would shut down the main engine of the climate. We would be entering the unknown.” Scientists had recently estimated that in winter, Europe would be on average below zero from November to April (which does not currently happen) while in summer the average temperature would drop to 15°C (instead of 20°C). C). In February, we could lose up to 30°C in Scandinavia and the north of Great Britain and around 10°C in Belgium. European winters would therefore resemble those of Canada. However, many uncertainties remain about Amoc, whether in the past (notably its causes), currently or for the future.
