Climate change: the level of carbon dioxide in the atmosphere is the highest in three million years

"Our results show that the level of CO2 has not been as high as it has been for at least three million years now," says scientist Matteo Willeit, of the US. German institute Potsdam for research on the impact of climate, one of the co-authors of the document that roll back global warming to the one. "The study itself lasted a few years, but the development phase of the model to make these simulations possible required nearly two decades of work," he said.

The model was based on astronomical and geological data on the physics and chemistry of the Earth, took into account orbital cycles and established different scenarios on the evolution of the climate on our planet, based on the bottom sediment data. oceanic.

The specialist explained that "a series of previous studies had attempted to reconstruct CO2 concentrations in the atmosphere using different methods." In the last 800,000 years, the level of carbon dioxide Carbon is well known thanks to Antarctic ice core measurements, but for the previous period, reconstructions were of relatively low quality. "

"Our contribution to understanding past variations is different because it relies on model simulations such as ocean temperature and overall ice volume in marine sediment cores," said Willeit.

The study reveals that the beginning of the ice age and ice cycles was mainly due to a drop in CO2 levels. "In our simulations, the decrease in these levels has led to the beginning of glacial-interglacial cycles, resulting in significant growth and degradation of the ice cap in the northern hemisphere there are about 2.7 million. years, "he added.

The results also show the high sensitivity of the Earth system to relatively small changes in atmospheric CO2. "What the study reveals is that the current increase in carbon dioxide is very fast, it's not natural and unprecedented, even when we observe a very long history climate change, "he warned.

"It also shows that relatively small variations in long-term emissions have resulted in substantial changes in climate change," the scientist concluded.

CO2 emissions, related to fossil fuels such as coal and oil, recorded in 2018 the largest increase in seven years. According to the annual report presented on the sidelines of the UN climate summit held in Poland last December, they increased by 2.7% compared to 2017.

At the same time, the Intergovernmental Panel on Climate Change warned that an unprecedented number of storms, forest fires, droughts, heatwaves and heatwaves have been reported. floods have occurred during the last decade.

If emissions are not reduced, the experts said that at this rate, the dreaded 2 ° C increase in temperature could be reached in just 11 years and almost certainly in 20 years. In any case, no action will have immediate effect: it is estimated that every kilogram of CO2 released into the atmosphere over the last 100 years will continue to retain heat for centuries.

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