Are the Gulf and Jet Streams Collapsing? Here’s what the Science Says

11 September 2021 0 By Bambam

If you read the headlines you could not be faulted for believing that the jet stream and the Gulf Stream are on the cusp of imminent collapse. These dire predictions claim to be derived from research but closer scrutiny reveals that they are getting way ahead of the science. This is a story about the dangers of overstating the evidence.

The collapse of the Gulf Stream and the jet stream are valid concerns. Tipping points like these are being investigated by scientists because they could trigger a cascade of impacts that will be irreversible and could contribute to the collapse of civilization as we know it. While such tipping points are indeed dangerous, so are inaccurate characterizations of the scientific literature. Catastrophic narratives that are not corroborated by science provide fodder for pessimists who argue that it is too late to do anything to avert the worst impacts of the climate crisis. Sensationalistic media coverage also undermines the credibility of scientists and the perceived veracity of science.

As reviewed in the 6th assessment IPCC report (AR6) there is much that we know with considerable certainty including the scientific consensus that anthropogenic climate change is real and left unchecked will augur calamity. However, when it comes to feedback loops and tipping points there is much we do not know. In the absence of a clear scientific consensus, some have interjected fatalistic predictions that are not supported by the evidence. The latest IPCC report concluded that although the Gulf Stream is weakening it is not on the verge of imminent collapse and recent studies have found that Arctic warming may not be altering the jet stream as some had theorized.

Gulf Stream 

The Gulf Stream is a huge ocean current that plays a part in regulating the northern hemisphere’s climate. There has been a loss of stability of the Gulf Stream over the last century that has been interpreted to suggest that it could be shutting down. If it were to collapse it could augur “severe impacts on the global climate system” that has been described as a “calamitous climate catastrophe” for millions of more people around the world. If this were to happen it would have devastating global impacts that would include altering precipitation patterns that could disrupt agricultural production in places like India, South America, and West Africa. It could also increase storms, raise sea levels and further imperil both the Amazon rainforest and Antarctic ice sheets.

The Gulf stream is typically 100 kilometers (62 mi) wide and 800 meters (2,600 ft) to 1,200 meters (3,900 ft) deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 meters per second (5.6 mph). The Gulf Stream stream is part of a larger current called the Atlantic Meridional Overturning Circulation (AMOC) which is one of the world’s biggest ocean circulation systems. It originates in the Gulf of Mexico and carries warm, salty water through the upper layers of the Atlantic, passing Newfoundland and Labrador to the Nordic seas off the coast of Scandinavia and the U.K. where it cools and becomes saltier until it sinks north of Iceland, which in turn pulls more warm water from the Caribbean. 

Global warming induced melting of Greenland’s ice sheet and sea ice from glaciers in the north is causing an influx of freshwater that is slowing the process down. There are concerns that if it collapses Europe could go into a deep freeze as it did at the end of the last ice age (13,000 years ago) when melting North American ice sheets caused an influx of freshwater weakening ocean currents. 

The Gulf Stream is already moving more slowly than at any point in at least 1,000 years.  Stefan Rahmstorf, of the Potsdam Institute for Climate Impact Research, who co-authored the study said: “We risk triggering [a tipping point] in this century, and the circulation would spin down within the next century” However, he added, “It is extremely unlikely that we have already triggered it.”

Niklas Boers is the Scientist behind a recently published study that documented signs that these currents could collapse in the next few decades. His research concluded that “Significant early-warning signals are found in eight independent AMOC indices” suggesting the stream might be close to “a critical transition to its weak circulation mode.”

Other scientists are not convinced that AMOC is nearing a tipping point. As noted above, the latest IPCC report concluded that the Gulf Stream is not on the verge of imminent collapse. The report expressed “medium confidence” that AMOC has weakened in 2004–2017 relative to 1850–1900. The report concluded that AMOC is projected to weaken during the 21st century but “It is very unlikely that the AMOC will undergo an abrupt transition or collapse in the 21st century”. 

Jet stream

The jet stream is a narrow variable band of very strong predominantly westerly air currents encircling the globe several miles above the earth. There are typically two or three jet streams in each of the northern and southern hemispheres. Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some planets, including Earth.  

Researchers have theorized that warmer Arctic air associated with global warming is altering the jet stream, but other studies suggest that this may not be the case.  The theory is that arctic warming is causing “blocking” which is a slow-moving and persistent weather pattern, that stops or slows the jet stream by putting a high-pressure weather system in the way. This deflects weather or causes it to remain stationary resulting in longer periods of dry weather or longer periods of wet weather.

This hypothesis is being challenged by research, including the most comprehensive polar modeling study to date. As reviewed in a Washington Post article by meteorologist and journalist Bob Henson, concerns about the collapse of the jet stream arose after climate scientists Jennifer Francis and Stephen Vavrus published a paper in 2012. They studied Arctic amplification (warming) which leads to depleted sea ice that forces the jet stream to dip farther south.  The Francis-Vavrus hypothesis is corroborated by a 2020 study by Zachary Labe and more recent research by Doug Smith. 

However, climate researchers James Screen and Russell Blackport, published an article in April that indicates the link may not be as strong as originally thought. This study and others suggest the observed data may be due to temporary large-scale changes in atmospheric circulation.  Conversely, wavier jet streams, extreme weather events, and blocking may be regional, short-term responses. Another study revealed how the observed temperature record also contradicts Francis-Vavrus’prediction with cold-air outbreaks decreasing in both frequency and severity in most locations in the Northern Hemisphere midlatitudes, 

In 2018 research published by climate scientist Michael Mann and his colleagues suggest that stuck summertime patterns that cause prolonged heat waves or flooding, may be related to resonant jet stream modes induced by global warming. In Mann an email reported by the Post, Mann recently summarized the state of research on the jet stream saying:

“I think the jury is still very much out. And I applaud both ‘camps’ for continuing to examine the best available data and models to get to the bottom of this. Eventually, this work will converge toward a scientific consensus. It’s not easy, but it’s how the gears of science turn, and it’s how we move forward toward a better physical understanding of the world.” 

What we must do

The Gulf Stream and the jet stream may not be on the verge of imminent collapse but they and the plethora of other known climate impacts illustrate the pervasive effects of global warming and the need for action. The only way to minimize the most serious impacts is to reduce warming and the best way to do that is by eliminating anthropogenic greenhouse gas (GHG) emissions.  

Boers acknowledges that he does not know for sure if a warming climate will cause the Gulf Stream to collapse, but, he sensibly argues that we should do everything we can to minimize GHGs to keep warming at a minimum. Boers explained, “the only thing to do is keep emissions as low as possible. The likelihood of this extremely high-impact event happening increases with every gram of CO2 that we put into the atmosphere”. Rahmstorf echoed these sentiments saying, “if we do not stop global warming, it is increasingly likely that we will trigger [collapse]”. 

Alongside more research, we also need to improve basic scientific literacy so that the public can understand statements of probability and appreciate the difference between experimental data and a hypothesis. We cannot afford to allow public misapprehensions to skew the scientific debate.  We must investigate the facts in a rigorous and methodological fashion whether they support a theory or refute it. We must help the public to understand that replicated peer-reviewed science is the best method we have to advance our understanding.

How we confound the facts

The tendency of some to embrace dark predictions says a great deal about how humans are wired to pay attention to catastrophe and the media’s propensity to pander to these proclivities. Sensationalist headlines like “A Crucial System of Ocean Currents Is Faltering” (New York Times), “A critical ocean system may be heading for collapse” (Washington Post), and “When Jet and Gulf Streams Run Amok, We’re In For It” (Bloomberg) illustrate how journalists are racing ahead of the facts. Such headlines are ubiquitous because they garner a lot more viewers (and advertisers) than carefully worded statements that are restricted to the known science.

These sentiments also reflect the well-warranted general mood of many climate observers. It is hard not to be pessimistic when we are confronted with the multi-dimensional perilousness of the climate crisis. However, we cannot afford to lose our heads. While we can understand the emotion, and may even be burdened with it ourselves, the way forward demands that we carefully examine the facts. 

While both streams warrant close scrutiny the science is by no means settled. Uncertainty may be frustrating, but is not a weakness, in fact, contrary to the criticisms from some quarters, remaining true to the observed data is a credit to the methodology of science and the rigor of scientists. Being cautious gives them credibility, so when they unequivocally say anthropogenic climate change is real, it carries weight.

Scientific methodology minimizes the biases that confound our understanding. Confirmation bias leads people to assign events to the observed phenomena. We should be careful when we try to connect two events even if they fit into a plausible narrative. People have a tendency to cherry-pick information to vindicate their beliefs while science strives to stay rooted in what can be experimentally demonstrated. 

Why getting ahead of science is dangerous

The story of these two streams rebukes those who fault climate scientists for being too conservative in their assessments. Scientists should submit their theories to research and go where the evidence takes them. This is the method by which we find and prioritize solutions. This is the scientific method.  Getting ahead of the research can erode public confidence in both the published research and the scientists who perform that research.

Media coverage and the social media discourse on the Gulf Stream and the jet stream illustrate what happens when we stray from the scientific literature and allow ourselves to get ahead of the facts. Contrary to the prognostications of the doomists research does not support the view that either the jet stream or the Gulf Stream is in danger of imminent collapse.  However, that should not be interpreted as they will not collapse if we continue to overheat the planet with GHGs. While we still have time to minimize the worst impacts of the climate crisis (a point corroborated by the latest IPCC report) the situation is critical and our time is running short. If we countenance pessimistic narratives that say it is too late, then is unlikely that people will be motivated to do what they must in the time we have.  We have reason to be optimistic we know what we must do, but we risk not getting it done if we allow science to be misconstrued. 

The tale of these two streams reinforces the importance of climate education and basic scientific literacy. Projection and interpolation will not deliver us to the scientific guidance we need to help us to forge policies. Nor will we be able to marshal popular support and craft effective policy if we fall prey to sensationalism or succumb to pessimism. 

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