“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, human-caused warming increased to an unprecedented level of more than 0.2°C per decade,” write some 50 renowned researchers in the journal Earth System Science Databased on the methods of the Intergovernmental Panel on Climate Change (IPCC), climate experts mandated by the United Nations (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 UN conference of the parties negotiations and policy debate, as the current decade is seen as critical to salvaging the goal of the 2015 Paris Agreement .
“This is a stark reality check on the urgency of reducing global CO2 emissions.2 and methane, to help limit global warming and the resulting intensification of risks,” French paleoclimatologist Valérie Masson-Delmotte, who participated in the study, told reporters.
“Critical” decade
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.
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 study calculations.
Scientists warn that humanity is facing a ‘critical’ decade when the 1.5°C threshold could be reached or exceeded within the next 10 years.
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.
Not “to scale”
“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.
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 [protoxyde d’azote, lié aux engrais] and other greenhouse gases,” says Pierre Friedlingstein, while CO emissions2 related to the 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.