Decreased Northern Hemisphere Precipitation from Consecutive CO2
Doublings Is Associated with Significant AMOC Weakening
Abstract
Previous studies found many climate properties such as northern
hemisphere (NH) surface temperature and precipitation respond
non-monotonically when CO2 is increased from 1x to 8xCO2 relative to
pre-industrial levels. Here, we explore the robustness of the
non-monotonicity in NH precipitation response in 11 coupled climate
models. Eight models show a decrease of NH precipitation under repeated
CO2 doubling beyond a critical level, which varies from 2xCO2 to 8xCO2.
These models also show a robust cooling associated with the North
Atlantic warming hole, and a prominent weakening in the Atlantic
meridional overturning circulation (AMOC) at the same critical CO2
level. The sensitivity of NH precipitation and AMOC to CO2 doublings are
positively correlated, especially when the AMOC weakens beyond 10 Sv.
Regionally, this decrease in NH precipitation is most prominent over the
North Atlantic, Europe and the tropical Pacific.