Normally present in trace amounts in the Earth’s atmosphere, the CO2 level has increased considerably since the end of the 19th century. Despite the different actions taken by governments, the use of fossil fuels and global warming only worsen the phenomenon. Last month, atmospheric CO2 reached its highest level for several hundred thousand years.
Despite efforts to reduce greenhouse gas emissions, the atmospheric CO2 concentration reached a new record in April: 410 ppm by volume. This is its highest rate in 800’000 years. The data collected by the atmospheric observatory Mauna Loa (Hawaii) and modeled by the Keeling curve (graph of the evolution of terrestrial atmospheric CO2) have indeed shown a precise rate of 410.31 ppm.
“We continue to burn fossil fuels,” explains geochemist Ralph Keeling, son of Charles Keeling (author of the Keeling curve) and director of the Scripps CO2 Program, who is responsible for carrying out these measurements. “And as long as we do, carbon dioxide will continue to accumulate in the air, it’s as simple as that.”
Yet this is not the first warning sign. Last April, the carbon dioxide level reached 410.05 ppm for the first time. Although the increase this year seems small, it is symptomatic of the weakness of the efforts of the governments around the world. The Scripps CO2 Program has been measuring the amounts of atmospheric carbon dioxide at the Mauna Loa observatory since 1958. And the corresponding Keeling curve shows a gradual and disturbing increase in them. In the 1950s, Charles Keeling’s first measurements indicated a rate of 310 ppm. That is to say, currently, in 1 million kilograms of air, there are 410 kg of CO2.
In order to go back further in the history of the Earth, geochemists study the bubbles of gas trapped in ice. Such ice cores provide information on the chemical composition of the atmosphere thousands, even hundreds of thousands of years ago. The last eight ice ages spanned 800,000 years, and according to the scientists’ analysis, the CO2 level was not as high as it is now. But comparisons with the rate measured in April could be pushed even further back in time. Last year, a report by the World Meteorological Organization (WMO) suggested that CO2 concentrations were highest for at least 3 million years.
This allows researchers to show explicitly that the abnormal levels attained for 100 years are due to human activities and not to a potential terrestrial natural cycle. As the Scripps explains, before the advent of life and photosynthetic activity, the concentration of CO2 was 100,000 times higher than today, about 4.5 billion years ago. With photosynthesis and occasional episodes like the “Azolla event”, the CO2 level has been falling steadily. Chemical dating shows that, chronologically, the increase of this rate coincides with the emergence of human industrial activity.
At the same time, carbon dioxide emissions are experiencing the same trend. The use of fossil fuels, especially with the massive reopening of coal plants, accounts for the majority of measured emissions. The more CO2 accumulates in the atmosphere, the more it traps solar radiation. This phenomenon accentuates global warming, leading to the release of additional CO2 from underground sources, sea ice and permafrost. A self-perpetuating vicious cycle of carbon dioxide emissions is set up.
Currently, many projects are being developed to trap or recycle atmospheric CO2. However, the development of these technological innovations will take time and all efforts available. The Scripps calls on governments and citizens to take drastic measures, each at their own level, to minimize CO2 emissions.