Thermohaline Circulation, the Achilles Heel of Our Climate System: Will Man-Made CO ₂ Upset the Current Balance?

TLDR

Earth’s climate has historically experienced frequent large, abrupt global changes linked to the thermohaline circulation’s ability to operate in multiple modes, as evidenced by glacial records and ancient sedimentary evidence. Orbital cycles causing antiphasing of polar insolation may trigger thermohaline circulation reorganizations. If rising atmospheric CO₂ triggers another reorganization, it could jeopardize global food security for 11–16 billion people.

Abstract

During the last glacial period, Earth's climate underwent frequent large and abrupt global changes. This behavior appears to reflect the ability of the ocean's thermohaline circulation to assume more than one mode of operation. The record in ancient sedimentary rocks suggests that similar abrupt changes plagued the Earth at other times. The trigger mechanism for these reorganizations may have been the antiphasing of polar insolation associated with orbital cycles. Were the ongoing increase in atmospheric CO2 levels to trigger another such reorganization, it would be bad news for a world striving to feed 11 to 16 billion people.