Of the 37.4 billion tonnes of carbon dioxide we emitted into the atmosphere in 2024 from burning fossil fuels, about half was sequestered by the planet’s oceans, soils, forests and other natural processes. But evidence is suggesting a weakening of this service, some of which is related to heat—and 2024, was the hottest year ever recorded since we were a Homo species inhabiting Earth. Among other factors, photosynthesis—the process that plants use to convert atmospheric carbon dioxide into sugars and an oxygen byproduct—begins to slow when temperatures rise too high, until it stops at 45°C. Consequently, certain areas of the planet sequestered absolutely no CO₂ in 2023.

“We’re seeing cracks in the resilience of Earth’s systems. We’re seeing massive cracks on land—terrestrial ecosystems are losing their carbon store and uptake capacity, but the oceans are also showing signs of instability,” says Johan Rockström, director of the Potsdam Institute for Climate Impact Research (“Are Earth’s Carbon Sinks Collapsing?” by Patrick Greenfield, The Guardian Weekly, October 25, 2024). “Nature has so far balanced our abuse. This is coming to an end.” Should this happen, we will be unable to meet any of our climate goals.