Imagine we detect a large asteroid heading straight for Earth. We are able to intervene and prevent disaster, but instead we cut the funding needed to track it. A few million dollars, it was argued, was too expensive to have a chance to save society.

While this scenario isn’t real, the metaphor is alarmingly accurate. In Europe, we spend €1bn to monitor space for asteroids, even if the actual risk of a civilisation-ending asteroid strike is close to zero.

But governments don’t commit to spend a fraction of that amount to adequately monitor a threat that is more imminent, more likely, and located here on Earth: a major change in the Atlantic Meridional Overturning Circulation (Amoc).

The Amoc is a vast system of ocean current that moves heat from the south to north in the Atlantic Ocean, thereby playing a crucial role in regulating global climate upon which modern civilisation is built – from agriculture, through infrastructure to health, prosperity and culture. Changes in Amoc can impact food security, coastal flooding, storms, energy demand, migration, infrastructure planning, etc.

Under current climate change, the Amoc is projected to weaken enough to radically change the weather and cause sea level rise in Europe. However, there is little consensus on when and how fast this will occur. Projections of the future Amoc vary between climate models, and while scientists continue to improve the ability of models to represent the real ocean, progress is hampered by insufficient understanding of the physics of the Amoc.

Consequently, this complicates matters for policymakers to implement adaptive strategies to reduce financial loss and impact on human lives. It is even more astonishing, then, that today’s minimal monitoring of the Amoc, our best hope of understanding what lies ahead, is now under acute threat of being discontinued. This will leave us unaware, unprotected and unprepared.

Worse, there is potential for Amoc weakening to become a collapse. In that specific scenario ,Europe would experience climate change up to 10 times faster than today. Considering that current climate change is already hard to keep up with as a society, we can’t begin to imagine what impact an Amoc collapse could have on our daily lives.

Further confusion is sown by an avalanche of new studies that bring a different interpretation of whether the Amoc has already weakened. This is because many new studies are based on approximations of Amoc strength that attempt to fill a gap caused by the lack of past direct measurements, for example by using historical sea surface temperature data.

The subsequent scientific debate may appear like disagreement, but it is really reflecting high levels of uncertainty because of the scarcity of data.

Underlying these high levels of uncertainty is the absence of long-term Amoc observations that allow us to describe past changes and understand how the Amoc works. We are in a situation where are trying to understand a planetary-scale system with very little direct observation.

Systematic monitoring of the Amoc began only two decades ago when a handful of visionary researchers in different countries patched together individual nationally funded research projects within the competitive science domain.

Yet, these measurements are now a benchmark for climate models and have critically improved our understanding of the Amoc. The extreme vulnerability of funding for Amoc observing has been confirmed by a recent assessment that showed how funding issues have already reduced Amoc observing capabilities.

Several Amoc monitoring initiatives are at a risk of being defunded and could be discontinued at any moment. While we can’t go back in time to do more observations, we can improve our observation strategy for the future.

Instead, the Trump administration has proposed budget cuts to Nasa, NOAA and NSF – agencies that together provide about 50% of the total Amoc monitoring budget. Last week the US announced the descoping of the Ocean Observing Initiative which was part of a programme observing the Amoc.

The recently launched European OceanEye initiative has allocated €50m for ocean observations and is a great incentive to continue Amoc observations. However, before OceanEye is up and running, the research vessels that service the present-day observing systems will already have to be financed, planned and packed.

In short: monitoring, understanding and forecasting the Amoc is at risk. Without sustained Amoc observations, we cannot know what lies ahead. An Amoc collapse may be imminent, a century away, or, if we act boldly to limit climate change, it might be averted altogether.

For too long, understanding and monitoring the Amoc was viewed as an academic pursuit. Instead, it should now be treated as what it truly is: an urgent, global priority. There is an acute and essential need to construct an alternative international funding strategy to secure long-term Amoc monitoring that realises a robust, continuous and open-access Amoc monitoring program to provide the knowledge to build a safer and more resilient world.

The cost of all Amoc monitoring adds up to about €25m a year. Meaning that for five cents per person per year, the EU can maintain one of the world’s most important climate monitoring systems that impacts our everyday lives and improves resilience to the climate crisis.

We therefore urge the EU, the UK and other international partners to step up, make haste, get organised and collaborate to assure long-term continuation of Amoc monitoring before it is lost.

• Penny Holliday is chief scientific officer of the National Oceanography Centre and has been researching ocean circulation for 30 years

• Dr M Femke de Jong is senior scientist at the Royal Netherlands Institute for Sea Research (NIOZ) and has been researching the Atlantic circulation for 23 years

• Dr Sjoerd Groeskamp is senior scientist at the Royal Netherlands Institute for Sea Research (NIOZ) studying ocean physics and thermodynamics

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