Climate: the last seven years are the hottest on record – Le Monde

Climate change offers no real respite. Although global average temperatures temporarily dropped last year, 2021 remains one of the seven hottest years on record. The last seven years are all part of this disastrous classification, according to the final report of the World Meteorological Organization (WMO), published Wednesday, January 19. Global warming is expected to continue, warns the UN agency, due to record levels of greenhouse gases present in the atmosphere, due to human activities and in particular the combustion of fossil fuels (coal, oil and gas).

This situation is all the more exceptional as 2021 was marked by two episodes of La Niña, a cooling of surface waters in the central and eastern equatorial Pacific which lowers the global temperature of the planet. “The year 2021 has been warmer than those influenced by La Niña in the recent past”, says WMO Secretary-General Petteri Taalas, noting that long-term human-caused warming is now “much more pronounced” than the variability caused by natural climatic factors.

In 2021, the average temperature on the planet was higher by about 1.1 ⁰C in the pre-industrial era (1850-1900). This value exceeds by 1 ⁰C pre-industrial levels for the seventh consecutive year. Since the 1980s, each decade has been warmer than the previous one.

Synthesis of six international datasets

To establish the temperature assessment, the WMO synthesizes six international data sets, such as those from NASA, the British Met Office or the European Copernicus service for monitoring climate change. Copernicus has rated 2021 as the fifth hottest year on record, very slightly ahead of 2015 and 2018. The United States Ocean and Atmospheric Administration and Berkeley Earth placed it in sixth position, the British tied for sixth and the Japanese meteorological service seventh.

In the end, the WMO could not set an overall ranking for 2021 because the slight differences between the datasets “are within the margin of error of the calculation of the mean global temperature”, says the agency. The only certainty: the year 2016, marked by an El Niño episode of exceptional intensity – which accentuates the warming – remains the hottest on record, neck and neck with 2019 and 2020.

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