It’s urgent. Global warming caused by human activities has reached an “unprecedented rate” and the window to limit the rise in temperatures to 1.5°C is already almost closed, warn dozens of renowned researchers in a study published Wednesday 5 June.
“Human-caused warming has increased at an unprecedented rate in instrumental measurements, reaching 0.26°C in 2014-2023,” these scientists indicate.
This observation, published in the journal Earth System Science Data, is the fruit of the work of nearly sixty renowned researchers who rely on the methods of the IPCC, the climate experts mandated by the UN. The interest of the study is to provide updated indicators based on the latter’s report, without waiting for the next cycle several years from now.
Compared to the pre-industrial era, this human-caused warming has reached 1.19°C over this decade, which shows a clear increase compared to the figures in the last report published a year ago (+ 1.14°C over 2013-2022).
For the year 2023 alone, warming attributable to human activity reached 1.31°C. The total warming observed reached 1.43°C – because natural climate variability also played a role, starting with the El Niño phenomenon.
Record emissions
Scientists intend to provide up-to-date data each year, to feed the COP negotiations and the political debate, while the current decade is considered decisive for saving the objectives of the 2015 Paris agreement, which aims to contain global warming well. below 2°C and if possible at 1.5°C.
This publication comes at a time when representatives from around the world are meeting in Bonn to advance climate negotiations before COP29 scheduled for Baku at the end of the year (November 11-22).
Warming is the result of greenhouse gas emissions – caused mainly by the massive use of fossil fuels (oil, gas, coal) – which are at record levels: some 53 billion tonnes of CO2 equivalent per year. year over 2013-2022. They were 55 billion for the year 2022 alone. Another effect also played a role, the scientists point out: less cooling caused by polluting particles in the air, which reflect the sun and allow the formation of certain clouds.
“The main reason is air pollution control, first in Europe and the United States, and more recently in Asia, particularly in China,” Glen Peters of the Center for International Climate Research told AFP. from Oslo.
Some researchers highlight the role of recent stricter regulations for maritime transport. But the reduction of sulfur dioxide emissions, particularly in the coal sector, began in the 1980s, underlines Glen Peters.
“A little optimism”
The residual carbon budget – the margin for maneuver, expressed in the total quantity of CO2 that could still be emitted while maintaining a 50% chance of limiting global warming to 1.5°C – is melting away. This “budget” is only around 200 billion tonnes, the equivalent of some five years of emissions at the current rate, compared to another 250 billion in the last edition of the study a year ago. .
“This is a critical decade,” the authors write. “A global warming of 1.5°C could be expected to be reached or exceeded in the next 10 years,” in the absence of cooling caused by a major volcanic eruption. “But this is also the decade when we would expect global emissions to peak and begin to decline substantially,” they point out.
Despite the record levels reached, the rate of increase in CO2 emissions has in fact slowed down this decade compared to the 2000s. The report contains “a little optimism”, judges Piers Forster, of the University of Leeds, author principal of the study. “Greenhouse gas emissions are increasing less quickly than in 2000, but they are still increasing”, so their “concentrations continue to increase and so does warming”, explains Pierre Friedlingstein, from the University of Exeter. “They must go down to net zero emissions,” he stressed.