There has been plenty of hypothesizing that global warming could cause destabilization of key ocean currents that have determined the character of the world’s regional climates over the last few millennia or so, i.e. human history. This new paper is the first I am aware of (but I am not even close to an expert on this subject or oceanography more generally) to find empirical evidence that the the AMOC current (which I believe includes the Gulf Stream) could be nearing a tipping point.
The Atlantic Meridional Overturning Circulation (AMOC), a major ocean current system transporting warm surface waters toward the northern Atlantic, has been suggested to exhibit two distinct modes of operation. A collapse from the currently attained strong to the weak mode would have severe impacts on the global climate system and further multi-stable Earth system components. Observations and recently suggested fingerprints of AMOC variability indicate a gradual weakening during the last decades, but estimates of the critical transition point remain uncertain. Here, a robust and general early-warning indicator for forthcoming critical transitions is introduced. Significant early-warning signals are found in eight independent AMOC indices, based on observational sea-surface temperature and salinity data from across the Atlantic Ocean basin. These results reveal spatially consistent empirical evidence that, in the course of the last century, the AMOC may have evolved from relatively stable conditions to a point close to a critical transition.
Nature Climate Change
This would seem to have major consequences to (1) where and how much food we can grow in the world, and (2) the location of our actual physical coastlines and the coastal cities that house much of the world’s human population. Adjusting to gradual long-term changes in these things will be a challenge. A sudden, major shift might be something our civilization can’t adjust to. The consequences are unimaginably dire. The risk is unknown but this study suggests it is real. Logic and risk management principles suggest that we need to be cautious here and actually do what we can to avoid this. Let’s hope “a point close to a critical transition” is not really all that close in human terms, and we have time for our civilization, with its flawed geopolitical and economic systems, to come to its senses.