Imminent Gulf Stream system collapse?
January 11, 2017
There's nothing quite like an out-there climate prediction to elicit a looming end-of-the-world scenario from the doomsday press. The findings from recent research into what is known as the Atlantic Meridional Overturning Circulation (AMOC) - or the Gulf Stream system - have presented just such an opportunity.
The study, which was published in Science Advances, explores the possibility that the Gulf Stream system could collapse under climate change, bringing with it a period of "prominent cooling" that would have significant implications for life as we know it.
And the way we know it is this: the Gulf Stream brings warm water from the tropics all the way to the North Atlantic, where its warmth is released into the atmosphere, thereby helping to regulate global climate and weather patterns. As the water loses its heat, it becomes denser, making it sink and eventually circulate back to the warmer climes of the tropics to eventually begin its voyage again.
The existence of the Gulf Stream makes possible the relatively temperate climates in Europe and parts of North America.
If, however, carbon dioxide emissions continue to rise - and as a consequence, heat the air around the North Atlantic - the water in the Gulf Stream system would not be able to cool down, so would not be able to sink and circulate back to the tropics.
And that, says the study, could lead to a complete collapse of the regulatory flow "300 years after the atmospheric CO2 concentration is abruptly doubled from the 1990 level."
Meaning, parts of the northern hemisphere would be looking at temperature drops of up to 7 degrees Celsius (almost 13 degrees Fahrenheit). And that takes us back to the doomsday predictions.
Not looking at an ice age scenario
"When you tell people there is a risk of cooling, they talk about an 'end of the world ice age,'" Stefan Rahmstorf, head of Earth System Analysis at the Potsdam Institute for Climate Research (PIK) in Berlin told DW, adding that while that kind of talk is "extremely exaggerated," there is definite cause for concern.
Though we are not looking at an overnight, or even an over-the-course-of-a-human-lifetime scenario, Rahmstorf, who is among the world's leading climatologists, stresses that the study's prediction of 300 years "is not the final word."
"No way," he says. Not least because the model the scientists used for the study doesn't factor in meltwater from Greenland, which could speed up the process of any collapse.
Author Wei Liu of Yale University acknowledges he is in the early stages of his work. "This is just a first step," he told DW, adding that he and his colleagues are already planning further research that he hopes will deliver more detailed results.
"The 300-year collapse, and extent and degree of North Atlantic cooling, may be subject to change for different models and different warming scenarios."
He says the model he used for this study was based on a "moderate" one, but that it has "opened a window" for further research.
Prevention is the cure
Rahmstorf, whose own research over the past two decades has led him to believe there is "quite a serious" risk that global warming will cause a slowdown in the Gulf Stream system, says Lui's research serves two main purposes.
"To make the wider climate modeling community aware of a potential risk that has not been properly evaluated, and to inform the public that there are risks of tipping points in the climate system that are poorly understood, and that may well have been underestimated in the past."
Exactly what that translates to in terms of the future face of northern Europe in particular, is, Rahmstorf adds, impossible to predict.
"If it were to break it down, it would imply such a massive change that I would be hard-pressed to make specific forecasts on human society."
And, like other scientists, he says that to alert rather than alarm the world. Rahmstorf means it as a call to action of sorts - a chance to prevent any doomsday scenario spun to make headlines, from becoming a reality. And as Liu also points out, there is one way to insure that doesn't happen.
"A collapse of AMOC would be triggered by global warming, by the CO2 increase that warms the water in the North Atlantic - so if we want to prevent this collapse and reduce this possibility, we have to decrease the level of CO2."