The concentration of carbon dioxide in the atmosphere, the main cause of climate change, is at its highest level in three million years, which makes the increase in the temperature of the planet and the level of the oceans inevitable, the researchers warn.
To date, scientists estimated that the current level of CO2, somewhat higher than 400 parts per million (ppm), was no more important than 800,000 years ago, in a period marked by cycles of warming and cooling the Earth.
But samples of ice and marine sediments extracted from the coldest place on the planet now reveal that the level of 400 ppm was exceeded for the last time three million years ago , during the Pliocene. The temperatures were then 3 to 4 °C higher, the trees grew in the Antarctic and the level of the oceans was 15 meters higher.
These analyzes are corroborated by a new climate model developed by the Potsdam Institute for Climate Impact Research (PIK).
The end of the Pliocene is relatively close to us in terms of CO2 levels,”
said Matteo Willeit, PIK researcher and lead author of a study published this week.
The Paris Climate Agreement of 2015 seeks to limit global warming to + 2 °C , or even + 1.5 °C, compared to the pre-industrial era.
But in 2017, greenhouse gas emissions exceeded all records in the history of humanity, and, taking into account the commitments of the States that signed the agreements, the trend points towards + 3 °C.
Currently, with 1°C more than in pre-industrial times, the Earth is already affected by the impacts of climate imbalance, from floods to droughts.
Based on the concentrations of CO2, glaciologists predict an increase in the level of the oceans between 50 cm and one meter, between now and the end of the century, says the researcher.
It will be difficult it gets higher, because the thaw takes time. But this does not stop at 2100, this continues.”
In October, the group of experts on climate change GIEC warned that to stay below 1.5 ° C, CO2 emissions would have to be reduced by around 50% by 2030.
But, despite the promises, these emissions, caused by fossil fuels and agriculture, keep increasing.
Researchers estimate that the atmosphere has previously known CO2 levels well above 400 ppm, but the gas had taken millions of years to accumulate. In contrast, emissions due to human activity triggered CO2 levels by more than 40% in a century and a half.
The last time that CO2 was so present in the atmosphere, it was then captured by trees, plants and animals, and buried with them after their death.
And what we’ve been doing for 150 years is digging it up and sending it back into the atmosphere,”
said scientists.