Home world The CO2 concentration has never been this high for 3 million years

The CO2 concentration has never been this high for 3 million years

The concentration in the atmosphere of CO2, the most important greenhouse gas responsible for the greenhouse effect, is at the highest level in three million years, making the dramatic rise in the temperature of the earth and oceans within a few centuries inevitable, the researchers warns.

Scientists have estimated the current level of carbon dioxide (CO2currently more than 400 parts per million (ppm) was no more important than 800,000 years ago, during a period characterized by cycles of warming and cooling Earth that would continue today without the warming associated with human activities. but ice and sediment the coldest place on earth now shows that the 400 ppm mark was actually exceeded for the last time three million years ago, during the Pliocene. Temperatures were then 3 to 4 ° C higher, trees were growing Antarctica and the ocean level was 15 meters higher.

These analyzes are confirmed by a new one climate model developed by the Potsdam Institute for Climate Impact Research (COCK). "The end of the Pliocene is relatively close to us in terms of levels of CO2AFP researcher Matteo Willeit told AFP and lead author of a study published this week. Our models suggest that there was no glacial cycle on the Pliocene or large ice sheets in theNorthern Hemisphere. the CO2 was too high and the climate too warm to allow it.

The aim of the Paris 2015 climate agreement is heating of the planet at + 2 ° C, or + 1.5 ° C, compared to the pre-industrial era. But in 2017, emissions from greenhouse gases exceeded all records in human history, and the commitments of the signing states of the Paris Agreement would bring the world to + 3 ° C.

Lessons from the Pliocene

For researchers who met in London this week, lessons can be learned from the Pliocene. "The global temperatures were 3 to 4 ° C higher than today and the sea level 15 to 20 meters higher", says Martin Siegert, professor of geosciences at theImperial College from London. Today, with 1 ° C more than in pre-industrial times, the earth is already experiencing the effects of it climate changefrom flooding the drought.

For Siegert, have exceeded 400 ppm CO2 (in 2013) does not mean that the sea level will rise with the size of that of the Pliocene soon, but unless people can remove the CO2 of theatmosphere large-scale consequences are sooner or later inevitable.

Based on CO concentrations2Glaciologists predict an increase in the level of the oceans between 50 centimeters and one meter at the end of this century, the researcher says. "It would be hard to be more because of it melting takes time. But it doesn't stop at 2100, it goes on.

Scientists released in October IPCC were photographing call alarm: to stay below 1.5 ° C, CO would be needed2 almost 50% by 2030. But despite the promises, these emissions related to fossil energies and toAgriculture inevitably increase. "At 400 ppm we remain on the trajectory of a climate comparable to the Pliocene", warns Tina van De Flierdt, professor of isotope geochemistry in theImperial College. The Greenland ice sheet, which contains enough water to raise the sea level by seven meters, had disappeared. And that of West Antarctica, "That contains about five meters, was probably gone".

Towards global warming from 3 to 4 ° C

Researchers estimate that the atmosphere has previously experienced CO levels2 well above 400 ppm but the gas had taken millions of years to accumulate. In turn, emissions related to human activity have increased carbon dioxide levels by more than 40% in just a century and a half. With a concentration of 412 ppm and an increase, some experts believe that global warming of 3 to 4 ° C is probably inevitable.


"What we have been doing for 150 years is digging up and returning it to the atmosphere. It's a crazy experience. "

The last time the CO2 was also present in the atmosphere, he was then captured by trees, plants, animals and then buried with them at their death. "And what we have been doing for 150 years is digging up and returning it to the atmosphere, says Siegert. It's a crazy experience ».

What to remember

  • The current CO2 level in the atmosphere is the same as that of the Pliocene.
  • If we burn all available reserves of oil, gas and coal on Earth, the speed could reach 2000 ppm (before the industrial age it was 280 ppm).
  • With the same speed in the Triassic, the consequences were less because the Sun was less light.

Towards a CO2 level that has never been observed for 200 million years

Article from Xavier Demeersman Published on April 13, 2017

If we burn all reserves fuels fossils to the last drop, the CO rate2 in the atmosphere could go up to 2,000 ppm in 2250 researchers warn. Never seen it on earth Trias. The problem is that today, the such a shines more than at the moment.

In his study just published in Nature communication, a team of researchers from the University of Southampton (UK) warns that if nothing is done to slow down or better stop our fossil fuel consumption in 2015 & # 39; s (36). , 3 billion tonnes), the carbon dioxide (CO2) in our atmosphere in 200 to 300 years will be unprecedented since at least the Triassic! It can go up to 2000 particles per million (ppm) in 2250.

Remember that in theknife of the industrial revolution concentration was only 280 ppm. Two and a half centuries later it has flown, now more than 400 ppm, even in the most remote parts of the world (this has not happened for 3.5 million years). The result of the increased presence in the atmosphere is a known greenhouse effect that causes one global warming on a global scale. With a progression of up to 400 ppm, we have already gained almost one degree in a century.

Moreover, if our thirst for oilgas, coal is by no means closed – politicians are even watchingArctic with envy – if we continue to burn all our fossil fuel reserves buried in the basement to the last drop, we are on our way to a speed of 2000 ppm on the horizon of the mid-XXIII centurye century! Never seen it on earth for at least 200 million years!

High CO2 and a sun that shines more

Focused on climate change, the authors made no less than 1,241 estimates of CO2 via 112 published studies. They were able to cover 420 million years thanks to the indications in various fossils of plants, shellssoil samples from different periods, etc. Like many of their fellow climatologists and paleoclimatologists, they have discovered that the current ongoing climate change caused by human activities is happening at a rapid pace, without a known equivalent.

Most importantly, the researchers point out that in the past, during the Trias or the Devonian (400 million years ago), even when the speed of carbon dioxide in the atmosphere was very high, the effects of warming remained less strong than today (or in our near future) with similar values. Why? Because our sun was less clear then (he Brightness continue to increase naturally, this is part of the cycle of evolution of stars). They are also concerned about what can happen to our world at a speed of CO2 that does not stop climbing and a sun brighter. To prevent a future that is to be heated (too much), the remedy is therefore the reduction of mass greenhouse gas emissions.

CO content2 studied for 2 million years

Article from Jean-Luc Goudet published on 25/06/2009

By analyzing the remains of planktonic marine animals, American researchers have reconstructed 2.1 million years of history of the concentration of carbon dioxide in the atmosphere. Conclusion: it is in the last ice age for nothing but the current level is a record.

Until now, only ice cores were able to measure previous carbon dioxide levels (or carbon dioxide) of the Earth's atmosphere. Caught in the bubbles stuck in the ice, theair can be analyzed. But this memory can only be traced back to the moment 850,000 years. An American team has found a way to do better.

These researchers have studied small single-cell planktonic organisms, globigerins, that belong to the huge family of foraminifera, great success of the evolution of the last five hundred million years. These little creatures are surrounded by a thin shield limestone, which is called test (and not shell). The team showed the ratio of two isotopes of the boron (11B and 12B) in this test depends on the acidity of the seawater at the time of manufacture. However, this acidity is directly related to the amount of carbon dioxide dissolved in water and therefore the atmospheric content. Moreover, it is known that the pH of seawater has a direct influence on the production of shells and lime tests by marine animals. The current acidification, due to the increase in the concentration of carbon dioxide, is apparently already Is it? diluted foraminifera tests.

By dating the tests from Globigerinoides sacculifer in sediments from the bottom of the North Atlantic Ocean, a thousand kilometers from the African coast, Bärbel Hönisch, a geochemist Lamont-Doherty Earth Observatory (LDEO) and his colleagues were able to follow the evolution of atmospheric CO2 for 2.1 million years, which had never been done so precisely.

The ice ages remain mysterious

Several lessons have already been learned from this new panorama about the history of the Earth's atmosphere. The first is the importance of the current amount of carbon dioxide. Thanks to the ice cores we already knew it CO content2 has never been 850,000 years stronger. This last figure can now be increased to 2.1 million years. During this period, the concentration of this gas fluctuated strongly, but the observed maxima are on average 280 ppm (parts per million), compared to 385 today.

Moreover, the authors believe that their results are the link between CO2 and the global climate, but the ice ages experienced by the earth during this period are not explained by significant reductions in carbon dioxide. Previous studies have already indicated that the amount of CO2 Not much had changed during the last twenty million years, but the resolution of the data was not sufficient to conclude whether there was a connection with the successive colds.

The rhythm of this ice ages remains a mystery. Two million years ago the Earth had every 41,000 years ago. Changes in the axis of rotation of the planet can then explain such a periodicity. But somewhere in the middle of it Pleistocenebetween 500,000 years and one million years this pace has slowed down and ice age occurs every 100,000 years.

A significant change in the carbon dioxide content in the atmosphere seemed a good explanation, with an ice age that began with the decrease in this greenhouse gas. According to the authors, this hypothesis must be forgotten. Others are in the running, such as the progression of huge glaciers in the territory of present-day Canada, which would have peeled the land for them and settled permanently on the rocky bed.

This lighting during the last two million years of the atmosphere brings answers but also raises new questions …

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It will also interest you

The circulation of CO2 in the atmosphere as you have never seen it before In this NASA video, it is possible for the first time, with an impressive level of detail and in three dimensions, to visualize the cycle of carbon dioxide (CO2) in the atmosphere over a year. In order to better predict the long-term evolution of climate change, scientists need to collect as much data as possible about the circulation of this greenhouse gas that is massively emitted by our human activities.



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