Two recent scientific reports have revealed troubling news about the ability of our planet's two major natural carbon sinks to absorb CO2. To date, the land and ocean have acted as carbon sinks, absorbing more than half of all CO2 emissions humans have pumped into the atmosphere since the Industrial Revolution began. But new evidence suggests their ability to do so is declining. They could be reaching their limits. And if we don't get emissions down fast, this could create a tipping point where they collapse and become sources of accerlated emissions.
Decline of the Land and Ocean Carbon Sinks
The first report - Low Latency Carbon Budget Analysis Reveals a Large Decline of the Land Carbon Sink in 2023 - highlights a sharp drop in the land's capacity to absorb CO2. According to 16 scientists from universities in the UK, France, Germany and China, the net amount of CO2 absorbed globally by land areas fell in 2023 to its lowest level in two decades.
The second report published in Nature and from MIT - Recent Increase in Oceanic Carbon Uptake Driven by Weaker Upper-Ocean Overturning - warns of a weakening of the oceans' role in absorbing CO2. The report identifies signs and risks that the overall capacity of oceans to absorb CO2 is declining due to changes in circulation and warmer water temperatures which reduce the amount of CO2 that can be dissolved in water.
These findings are particularly alarming in the context of continued global emissions growth. Despite the role of carbon sinks to date, by 2023 the Earth has already warmed by over 1.5°C. As emissions keep growing and land and ocean sinks weaken, more CO2 will remain in the atmosphere, accelerating global warming. If land and ocean carbon sinks reach their limits, the world will need to take much more aggressive climate action to stay safe. We will no longer be able to rely on a crucial buffer that has allowed us to keep pumping out emissions.
Even more worryingly, there is a real risk that land and oceans could reach tipping points and become sources rather than sinks of CO2 emissions. The Amazon rainforest is already showing signs of becoming a carbon source rather than a sink due to deforestation and droughts. Canada's wildfires in 2023 released four times the annual emissions of the global aviation sector. Permafrost in the Arctic stores twice as much carbon as the world's atmosphere. It's thawing could release vast amounts of stored carbon and methane, significantly accelerating global warming.
The science is clear: our planet's natural defences against climate change are weakening and potentially at risk of reversing. This is reinforced by recent accelerations in atmospheric and ocean heat. Deep, immediate and sustained action is necessary to reduce greenhouse gas emissions. We must rapidly move away from fossil fuels and adopt clean renewable energy. We must protect and restore forests which are vital carbon sinks. We must invest in reforestation, afforestation and biodiversity conservation. The challenge is immense, but the risks of doing nothing are too high. We can and must do all we can to halt climate collapse.
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