There are fixed, immutable points about how the world works. And, for that reason, reassuring ones. From school onwards, for example, we learn that the Gulf Stream originates in the Gulf of Mexico and, with its vast masses of warm water, crosses the Atlantic Ocean towards the northeast, making winters milder across western and northern Europe. But global warming is upending even this certainty. And the consequences are "unimaginable". Journalist Lorenzo Colantoni set out to investigate them – and, above all, to tell the stories of the people who will have to face them – travelling on foot, by train and by sailboat across six European countries, from the Azzorre to Svalbard. The result is Lungo la corrente, published by Laterza.

What the studies say about the collapse of the AMOC

What we know as the Gulf Stream is part of a broader system that specialists call the AMOC, an acronym for Atlantic Meridional Overturning Circulation. This system of currents is already at its weakest point in the last 1,600 years. A key role is played by greenhouse gas emissions, which have raised average global temperatures, causing the melting of Greenland's ice and Arctic sea ice. This meltwater, combined with increased precipitation, flows into the North Atlantic, making its waters fresher and less dense.

Until now, the scientific community's stance has been cautious. The Intergovernmental Panel on Climate Change (IPCC), for instance, considers that another 700 to 1,000 years remain before the AMOC risks shutting down entirely. Other studies, however, suggest that this moment may be far closer. The first, dating back to 2021, confirms the "near-complete loss of stability" of the AMOC over the past century. The second, published in July 2023 by the University of Copenhagen, estimates that – if CO2 emissions remain at current levels – the entire system could collapse between 2025 and 2095, with an intermediate estimate of 2050. A virtually immediate horizon.

Another very recent publication with US climatologist James Hansen as lead author states clearly that the United Nations is underestimating two phenomena. The first is the impact that the reduction in sulphur emissions from maritime transport has on Earth's albedo and, consequently, on the amount of heat absorbed by our planet. The second is, precisely, the collapse of the AMOC. Which could occur within the next twenty or thirty years and must be regarded as the "point of no return".

What would happen if the Gulf Stream stopped

"The main problem behind this uncertainty is that we lack the data. Research vessels can measure the current speed of the currents, or even past speeds by dredging and examining sediments, but these are always point measurements. Even the satellites of the European Space Agency attempt to gauge the speed and intensity of the currents, but they produce indirect measurements and can only see the first few centimetres of water", Lorenzo Colantoni explains to us. What's more, he continues, "we think of the current as a single flow, a sort of arrow running from Central America to northern Europe, when in reality it is made up of many sub-currents. Some of them have probably already collapsed".

In short, what lies before us is a hypothetical future in which the AMOC "switches off". We do not know if or when this will happen, but we know it would be a tipping point with literally unimaginable consequences. When the same thing happened in the past – for natural reasons, and therefore far more slowly – temperatures varied by as much as 10 degrees Celsius. "It is a more remote eventuality, but it should frighten us all the same. It is a sword of Damocles hanging over our heads, and we do not know whether it is held by a thread or a chain", comments Colantoni. Regardless of this overarching risk, we are already grappling with the potential collapse of subsystems. It cannot be ruled out that changes in the currents have influenced some of the extreme weather events of recent years, such as the drought that devastated the Amazon in the second half of 2023 or the violent hurricanes battering the coastlines of the United States. But, as is often the case when discussing climate, we cannot reconstruct a clear, definitive cause-and-effect relationship with any certainty.

Daily life in a Europe already transformed by the climate crisis

This adds complexity upon complexity. For researchers, but also for those who try to communicate these topics, bringing them out of the niche of specialists. "There are many elements to balance. You have to give voice to a scientific community that is very cautious while, at the same time, conveying to the general public the urgency of what is happening. All of this while anti-climate communication has no qualms about riding the most blatant fake news. A topic like that of the current, moreover, has an incredible level of abstraction but an extraordinary impact on everyday life", Colantoni continues.

The approach he proposes in the pages of Lungo la corrente is to start from the big themes and then bring them down to the daily reality of those who live them first-hand. Like the sprightly ladies the author meets on Sanday, one of the most remote islands of the Orkney archipelago, in Scotland. Five hundred inhabitants, two ferry connections a day in summer and two a week in winter. While serving him tea and slices of cake, the elderly women – together with their husbands – recount how, twenty years earlier, the island's residents made their land available for the installation of wind turbines, purchasing a 10 per cent stake in the plant. Since then, they have received free energy in return ("as long as there's wind, of course – but here there's always wind") and a fair payment for the surplus they sell.

The inhabitants of Orkney are not so much afraid of storms as of the anomalous heat that melts the snow protecting the fields in winter and encourages the proliferation of insects. Geese, instead of migrating south, overwinter on the islands and devastate the fields, leaving farmers without fodder. Also because of the heat, at the far north of the Scandinavian peninsula, in Lapponia, snow disappears and permafrost ice melts, cracking the ground and releasing further carbon dioxide. While some look with interest at the commercial opportunities offered by a Northwest Passage that is finally becoming navigable, others see the end of their thousand-year-old culture drawing near. Such is the case of the Sami, Europe's last indigenous people.

"We all live in a single ocean"

As we grapple with an increasingly extreme climate, we are faced with the prospect of a total or partial collapse of the Amoc, with consequences that are yet to be fully assessed. In Great Britain, according to some research, it could cause temperatures to plummet by 6 degrees Celsius. The climate would then become comparable to that of the Yukon or British Columbia — a kind of cold desert where farming is impossible without irrigation.

At first glance, one might think that Italy — not being on the Atlantic coast — is only marginally affected. But that is not the case, Colantoni stresses, because ocean currents regulate the rainfall cycle, including in the Mediterranean basin. "The issues I address in my book will turn our lives upside down, because Italy is already a climate change hotspot: partly due to its geographical position and shape, and partly due to hydrogeological instability caused by some misguided choices made in the past."

"Moreover, some recent studies show how the connection between the Mediterranean Sea and the Atlantic Ocean has an impact on how the current functions, through its contribution of salinity," Colantoni explains. "Contrary to what climate denialism claims — which is often tied to a kind of isolationism — the truth is that we all live in a single ocean. We, as Italy, have a central role and an extraordinary potential, in a positive sense. Because my work on Lungo la corrente is above all a work of hope — I want to make that clear. There is already a large, serious and committed movement seeking solutions to climate change. I'm not talking about a handful of isolated heroes, but about a new generation trying to change things. We in Italy, too, could be pioneers in renewables, in adaptation, in nature-based solutions. We simply need to choose where to invest, and which side to stand on."