The researchers looked at variations in oxygen levels in the shells of tiny sea creatures found in samples taken from the world's ocean beds.

BBC: Climate change 'to halt ice age'

But to do so on a global scale would require turning trillions of tons of greenhouse-gas emissions into a substance that could be stored cheaply and easily underground or in ocean beds.

NEWYORKER: The Climate Fixers

The other approach is less risky, and involves removing carbon directly from the atmosphere and burying it in vast ocean storage beds or deep inside the earth.

NEWYORKER: The Climate Fixers