Volcanoes on the ocean floors flare up in regular cycles, ranging from two weeks to 100,000 years.
The study suggests that these seafloor volcanoes might have helped trigger natural climate swings in the past.
The idea is that the volcanic cycles might be tied to cycles in Earth’s orbit – the Milankovitch cycles – and to changing sea levels.
The volcanoes give off carbon dioxide (CO2), and they change how much CO2 is in the air.
The graph shows that highest value of CO2 produced in this way is around 280 parts per million of air.
There is no direct link to current climate change in this discovery, as the air now contains around 400 parts per million of carbon dioxide.
The extra carbon dioxide in the air now has been produced by burning fossil fuels.