Introduction
Some recent measurements conducted by sensors stationed across the North Atlantic have picked up a potentially worrying signal: The grand northward stream of water that moves heat from the tropics towards the Arctic region has been slowing down. If that slowing-down were to continue and deepen, it could bring severe changes in sea level and weather around the ocean basin. That flow is an essential part of the grander circulation of water, heat and nutrient in the oceans around the globe. Since the 1980s, there has been a prevalent concern among scientists in the field that rising global temperatures could throw a wrench in the Atlantic meridional overturning circulation (AMOC), which could consequently lead to stark implications on the climate.
Such concerns were subdued over the last decades as climate models suggested this branch of the ocean circulation was not likely to see a rapid slow down. But new studies suggest the recent weakening observed by ocean sensors is not just a passing phase, as some had thought, but part of a long-term decline that has put the circulation at its weakest state in centuries (Rahmstorf, 2015). The results indicate that climate models might have been missing key elements and that ill effects could be on their way. However, the question of what these distorted or missing elements in climate models are could determine how distressing this development is. If these models are not responsive enough to the changes going on in the North Atlantic, it puts us further in trouble.