"A harsh reminder of the facts." A vast international study published on Thursday 8 June claims that global warming is now increasing at a rate of more than 0.2°C per decade, with greenhouse gas emissions at an unprecedented level.
"Over the period 2013-2022, the warming caused by humanity has increased to an unprecedented level of more than 0.2 ° C per decade," write about fifty renowned researchers in the journal Earth System Science Data, relying on the methods of the IPCC, the climate experts mandated by the UN.
The interest of the study is to provide updated indicators from the 2021 IPCC report, without waiting for the next cycle in several years. The scientists intend to provide updated open data every year, to feed into COP negotiations and political debate, as the current decade is considered decisive in saving the goal of the 2015 Paris Agreement.
"This is a harsh reminder of the reality of the facts, in relation to the urgency of reducing global emissions of CO2 and methane, to limit global warming and the consequent intensification of risks," French paleoclimatologist Valérie Masson-Delmotte, who participated in the study, told reporters.
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The 1.5°C increase could be reached or exceeded in the next decade
Representatives of all countries are currently meeting in Bonn for technical exchanges in preparation for COP28, the major UN climate conference scheduled for the end of the year in Dubai, where the problem posed by the use of fossil fuels will be central.
These new estimates published on Thursday also come in the middle of a decisive year for climate policy, with the expected publication in September of the first "global assessment" of the commitments of the various States to implement the Paris Agreement, which plans to limit warming to well below 2 ° C and if possible to 1.5 ° C, compared to the pre-industrial period.
However, the warming caused by human activities, mainly with the use of fossil fuels (coal, oil, gas), has already reached 1.14 ° C over the period 2013-2022 and 1.26 ° C in 2022, according to the calculations of the study. Scientists warn that humanity is facing a "critical" decade when the 1.5°C threshold could be reached or exceeded in the next 10 years.
The residual carbon budget – the room for manoeuvre, expressed in total CO2, that could still be emitted while keeping a 50% chance of limiting global warming below 1.5°C – has been halved compared to the IPCC. This "budget" is now only of the order of 250 billion tonnes, the equivalent of a few years of emissions at the current rate.
"The carbon budget is reduced every year since we emit CO2 that accumulates in the atmosphere: we are inexorably approaching this limit of 1.5 ° C," says Pierre Friedlingstein, researcher at the CNRS, co-author of the study.
Actions still insufficient to "bring about significant change"
"The latest available evidence shows that global actions are not yet on the scale needed to cause a significant shift in the direction of human influence on global energy imbalances and the resulting warming," the scientists write.
This rate of warming is caused by greenhouse gas emissions at record levels, with some 54 billion tonnes of carbon dioxide equivalent per year over 2012-2021, they calculated. They reached 55 billion tonnes in 2021 alone.
"It is mainly related to methane, N2O (nitrous oxide, related to fertilizers, editor's note) and other greenhouse gases," says Pierre Friedlingstein, while CO2 emissions related to the use of fossil fuels are, for their part, more or less stable.
Warming has also been caused by a reduction in particulate pollutants in the air, which have a cooling effect. This is a paradoxical and short-term effect of less coal use.
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