“A harsh reality check”: warming due to human activities is now increasing at a rate of more than 0.2°C per decade, with greenhouse gas emissions at an unprecedented level, according to a large international study published Thursday.
“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, s based on the methods of the IPCC, 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. Scientists aim to provide up-to-date open data every year, to feed into COP negotiations and policy debate, as the current decade is seen as decisive in saving the goal of the 2015 Paris agreement.
“It’s a stark reality check about the urgency of reducing global CO2 and methane emissions to help limit global warming and the resulting increase in risk,” he said. to journalists the French paleoclimatologist Valérie Masson-Delmotte, who participated in the study.
1.26°C more in 2022
Representatives of all the countries are currently meeting in Bonn for technical exchanges with a view to preparing 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 Thursday also come at the midpoint of a decisive year for climate policy, with the publication expected in September of the first “global assessment” of the commitments of the various States to implement the Paris agreement, which plans to limit warming well below 2°C and if possible 1.5°C, compared to the pre-industrial period.
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However, the warming caused by human activities, essentially 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 study calculations.
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 halved
The residual carbon budget – the room for manoeuvre, expressed as the total quantity of CO2 that could still be emitted while maintaining a 50% chance of limiting global warming below 1.5°C – has been halved compared to the IPCC. This “budget” is only around 250 billion tonnes, the equivalent of a few years of emissions at the current rate.
“The carbon budget is reduced each year since we emit CO2 which accumulates in the atmosphere: we are inexorably approaching this limit of 1.5°C”, underlines Pierre Friedlingstein, researcher at the CNRS, co-author of the study. “The latest available evidence shows that actions taken at the global level are not yet on the scale necessary to bring about a significant shift in the direction of human influence on the planet’s energy imbalances and resulting warming,” write the scientists.
54 billion CO2
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 linked to emissions of methane, N2O (nitrous oxide, linked to fertilizers, editor’s note) and other greenhouse gases”, specifies Pierre Friedlingstein, while CO2 emissions linked to use of fossil fuels are more or less stable.
Warming has also been caused by a reduction in pollutant particles in the air, which have a cooling effect. This is a paradoxical and short-term effect of less use of coal.