Global warming 55 million years ago shifted ocean currents

An extraordinary burst of global warming that occurred around 55 million years ago dramatically reversed Earth’s pattern of ocean currents, a finding that strengthens modern-day concern about climate change, a study says. The big event, the Palaeocene/Eocene Thermal Maximum (PETM), saw the planet’s surface temperature rise by between five and eight degrees C (nine and 16.2 F) in a very short time, unleashing climate shifts that endured tens of thousands of years.

The increase was predicted according to scenarios of atmospheric carbon dioxide (CO2), ranging from 540 to 970 parts per million (ppm). That compares with 280ppm for pre-industrial times and around 380ppm today, which is already the highest concentration of CO2 for 650,000 years.

The study, which appears on Thursday in the British journal Nature, comes on the heels of research published in November which suggests that global warming is slowing the Atlantic current that gives western Europe its mild climate.

physorg