CO2 and methane concentrations are highest in 800.000 years
AFP - Thursday 15 May, 18h07PARIS (AFP) -
The current concentrations of carbon dioxide (CO2) and methane (CH4) in the Earth's atmosphere are the highest since 800.000 years, according to the results of glacial drilling carried out by researchers whose work is published in the scientific journal Nature.
Apart from water vapor, they are the two main greenhouse gases responsible for global warming.
Core drilling, carried out as part of the EPICA project, was carried out to a depth of 3.270 meters in the ice cap covering the Antarctic continent, near the Franco-Italian Concordia base (Dome C).
The analysis of gas bubbles trapped in the ice made it possible to establish the content of the atmosphere in carbon dioxide and methane over a period of 800.000 years, against 650.000 years for a previous drilling.
This work "confirms, while extending it, the close correlation observed between temperatures recorded in Antarctica in the past and atmospheric CO2 and CH4 levels", according to a press release from the National Center for Scientific Research (CNRS).
"Never, over the last 800.000 years, have greenhouse gas contents as high as today", underline the French researchers who participated in this work, including the climatologist Jean Jouzel and the glaciologist Jérôme Chappellaz.
On one million molecules in the air, 380 is currently carbon dioxide, against only 172 667.000 years ago, which corresponds to the lowest concentration ever recorded, according to the researchers' records.
Methane, whose greenhouse effect is greater than that of CO2 but the lower concentration and shorter lifespan in the atmosphere, for its part exhibits "rapid fluctuations on a millennial scale, recurrent over the course of every glaciation ". This climatic variation would be linked to large-scale fluctuations in the water masses which participate in the redistribution of heat on earth (thermohaline current).
A large multi-disciplinary study, also published this week in the scientific journal Nature, also confirms the findings of the UN-mandated Intergovernmental Panel on Climate Change (IPCC) on the origin and impact of global warming.
She points out that "significant changes" are underway on all continents and most oceans. "These changes in natural systems since at least the 70s have taken place in regions where temperature increases have been observed" which "cannot be explained by natural climatic variations alone," the study continues.
“Humans influence the climate through increased greenhouse gas emissions and global warming impacts physical and biological systems,” writes Cynthia Rosenzweig, of the Goddard Institute for space studies by NASA and the Columbia Climate Systems Research Center.
Rosenzweig and researchers from ten other institutions around the world have analyzed hundreds of publications and data collected since the 70 years.
According to the IPCC, most of the observed increase in the average temperature of the planet since the middle of the 20th century is "very likely" due to the observed increase in greenhouse gases emitted by man (more than 90% certainty). At the end of the century, temperatures are expected to increase by +1,8 to 4 ° from 1980-1999
source Yahoo news