Adding to concerns about how the world is managing climate change, World Meteorological Organization, external says that greenhouse gas concentrations have reached a record high in 2023.

Last year’s increase was higher than in the past 12 months, thanks to record wildfires in Canada and the emergence of the El Niño weather phenomenon, all adding to continued emissions from fossil fuels.

But WMO scientists also say they have seen some evidence that as the world warms, trees are not able to absorb the same level of CO2 as they used to.

The data indicate that the southeastern Amazon has now transformed from a carbon sink to a source.

“In the Amazon, deforestation means you lose the forest,” said Dr. Oksana Tarasova of the WMO.

“Then the temperature started to rise, then the air circulation pattern changes. There’s less precipitation, less absorption of CO2, which means more CO2 remains in the atmosphere.”

The Amazon is an example of what scientists call a climate feedback—where rising temperatures can act on natural systems to increase the causes of warming.

So if forests and oceans become less able to absorb CO2, global warming could accelerate faster.

“We see some clear signals. We can’t say it’s 100% climate feedbacks because there is substantial variability due to El Niño and La Niña weather events, but we see something happening in the system,” said Oksana Tarasova.

The WMO says the last time Earth experienced a comparable concentration of carbon in the atmosphere was 3-5 million years ago – when average temperatures were 2-3°C warmer than they are now and sea levels were 10-20 meters higher.