A study has found that intense global warming could shut down the ocean’s ability to soak up carbon dioxide, leading to accelerated global warming as the greenhouse gas accumulates in the atmosphere. The decline happens because of a surface layer of low-alkalinity water that emerges during extreme warming that hinders the ability of the oceans to absorb CO2. The study is based on a climate simulation configured to a worst-case emissions scenario that the researchers say must be avoided at all costs.