Assessment of the state of the climate | “We are on red alert”

The World Meteorological Organization (WMO) unveiled its most recent assessment on the state of the climate on Tuesday. A report which sounds like an acknowledgment of failure since greenhouse gas emissions, surface temperature and ocean temperature have set new records in 2023.

New records for CO₂ and methane

In 2022, the last year where consolidated figures are available, CO concentrations₂ (417.9 parts per million) and methane (1923 parts per billion) in the atmosphere have set new records, thus worsening the greenhouse effect which influences the global climate. These values ​​unfortunately continued to increase in 2023 and 2024, setting new records in the process. Philippe Gachon, professor of hydroclimatology at UQAM, is particularly concerned about methane, a “time bomb” which has a warming power 20 to 30 times greater than CO₂. “Methane can also promote the reaching of tipping points which will completely modify the state of equilibrium of the climate,” underlines the researcher.

Gaps that worry scientists

The year 2023 was the hottest year on record, recalls the WMO in its report entitled State of the Global Climate. The average temperature on Earth was thus 1.45 degrees higher than the level established at the start of the pre-industrial era. What particularly worries scientists is the gap with the previous record, established in 2016 (1.29 degrees). Figures, let us remember, which constitute an average on a global scale. Worryingly, WMO experts also predict that 2024 could beat the 2023 record. “Since the start of the year, new records have been established,” recalls Philippe Gachon. This indeed points to a record year. It depends on when the El Niño effect will fade. »

The oceans are warming

The oceans represent 70% of the surface area of ​​our planet. They also absorb 90% of the heat generated by increased GHG emissions. With such a volume of water, the oceans are warming much more slowly than the surrounding air, but they are still warming, to levels never before observed. By the end of 2023, more than 90% of the oceans had experienced heat waves, reports the WMO. “It’s much easier to evaporate hot water than cold water, it takes less energy. The more the ocean warms, the more there are enormous transfers of humidity that go into the atmosphere, causing extreme weather events,” explains Philippe Gachon. What is particularly worrying according to him is that we are also observing a warming of the oceans up to 2000 meters deep.

Sea level rise accelerates

The planet is warming just like the oceans, which is causing sea levels to rise, which reached a new record in 2023. Between 2014 and 2023, ocean levels increased by 4.77 mm per year, or more double the annual level observed between 1993 and 2002 (2.13 mm). Two phenomena are at the origin of this increase, namely the melting of ice and the increase in water temperature, leading to thermal expansion, i.e. a greater volume of water. “The global meteorological community is warning the whole world and sounding the alarm: we are on red alert,” declared Celeste Saulo, Secretary General of the WMO, when presenting her organization’s report. .

Less and less ice at sea and on land

Drop an ice cube into a cup of hot water and it will obviously melt. This is what is happening with sea ice in the Arctic and Antarctica. In February, the extent of sea ice in Antarctica broke a new record with an area 1 million square kilometers less than the previous record. The ice cover in Greenland is also shrinking year after year. Ice, like snow, helps reflect the sun’s rays; However, the disappearance of these white surfaces amplifies warming, thereby accelerating the melting of the ice. If the world became carbon neutral today, “it would certainly take decades, even several centuries, before the oceans cooled again,” specifies Philippe Gachon.

Read the World Meteorological Organization report