The concentration of greenhouse gases in the atmosphere reached a record level in 2023, which will inevitably cause temperatures to rise in the coming years, the UN has warned.
Levels of the three main greenhouse gases that contribute to global warming – carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) – rose last year, according to the World Meteorological Organization (WMO).
This UN agency mainly observed that carbon dioxide is accumulating faster than ever in the atmosphere, with rates that have increased by more than 10% in two decades.
"Another year, another record. It should raise alarm bells among decision makers. It is clear that we are falling short of the Paris Agreement targets," said Celeste Saulo, WMO Secretary-General.
Based on the Paris Agreement, Governments would have to take action to limit the increase in the Earth's temperature to less than 2°C compared to the pre-industrial era.
The WMO's annual report on greenhouse gases was released just days before COP29, the UN climate summit, which will be held from November 11 to 22 in Baku, Azerbaijan.
As long as emissions continue, greenhouse gases will continue to build up in the atmosphere, raising the Earth's temperature, the WMO said.
Already global temperatures at the surface of the Earth and the sea were in 2023 "the highest recorded since 1850".
Given the lifetime of carbon dioxide in the atmosphere, current temperature levels will be maintained for decades even if greenhouse gas emissions are rapidly reduced to zero.
"CO2 is accumulating in the atmosphere faster than at any other time in human existence," the WMO warned.
The Earth experienced such high CO2 concentrations 3 to 5 million years ago, when the temperature was 2 to 3 degrees Celsius higher and the sea level 10 to 20 meters higher than today, he recalled.
Just under half of CO2 emissions remain in the atmosphere, while the rest is absorbed by ecosystems.
But today "we are facing a potentially vicious cycle," warned Ms Barrett, WMO Deputy Secretary-General.
Climate change could "drive ecosystems to become the largest producers of greenhouse gases," he said.
Forest fires may cause more carbon dioxide to be released into the atmosphere, while warmer oceans may absorb less. As a result, more CO2 may remain in the atmosphere and accelerate global warming, he noted.
