UN report: climate change has weakened the ocean's CO2 uptake by about 6 percent
The seas absorb about 30 percent of human-caused CO2 – but the sink is weakening. Ahead of COP31, UNEP and the UN climate secretariat call for more monitoring and protection of mangroves.
Symbolic image · Photo: Terpsichores / Wikimedia Commons, CC BY-SA 3.0 (cropped and resized)
The oceans are losing strength as a climate buffer, according to a new UN report. According to the report by the UN Environment Programme (UNEP) and the UN climate secretariat (UNFCCC), presented by UN News on Wednesday ahead of the COP31 climate conference in November, the seas absorb around 30 percent of human-caused CO2 emissions and about 90 percent of the excess heat trapped by greenhouse gases. Climate change, however, has already reduced their capacity to take up carbon by about 6 percent, driven by rising temperatures and changes in ocean chemistry, circulation and ecosystems.
"For a long time the ocean has been doing us an enormous climate service, but that service is under increasing pressure," lead author Sara Traerup told UN News, warning the process could accelerate in the foreseeable future. Reliable data are lacking above all for the Southern and Indian Oceans, the Arctic and many coastal regions. "What we don't know, we cannot manage and protect," Traerup said. The report calls monitoring networks, sensors and models the most mature and most urgently needed technology.
As a second lever it points to so-called blue carbon ecosystems: mangroves, seagrass meadows and salt marshes already sequester around 407 million tonnes of CO2 a year, and restoring them could add considerably more. Marine carbon dioxide removal technologies, by contrast, are described as potentially promising but highly uncertain; they should complement rather than replace emissions cuts – "not a shortcut", Traerup stressed. Small island states, which emit less than 1 percent of global emissions, should get easier access to finance and technology.