Almost everywhere on earth is warming, almost.

So what makes this small patch of water in the North Atlantic different?

It turns out this anomaly might actually be a sign that one of our major systems that regulates our climate could be approaching a tipping point with impacts so disastrous.

They've even made a blockbuster movie about it.

All these lines of evidence, they point to the same direction.

The present day AMOC is likely weakening, so that means that we're heading in the direction of a tipping point.

That's Rene Van Westen.

He studies the Atlantic Meridional Overturning Circulation, or AMOC, a system of Atlantic current so enormous that it helps regulate climate all around the world.

And it's in trouble.

Usually when scientists use the term, "tipping point", they're referring to a threshold, a point of no return where a large sudden shift in our environment is inevitable.

And in climate science, that threshold is typically global temperature.

But what if for the AMOC, that's the wrong approach?

Now, there's lots of AMOC coverage out there, including some of our own.

But Rene's research completely changed how I think about this tipping point.

We're closer to it than ever before, and yet, we may have more control over what happens next than we thought.

For the AMOC, the present day warming rate matters, so therefore the responsibility is now and not in the future.

All right, let's start with this ominous blue spot.

What's going on here?

There's this small patch south of Greenland, and this is the only patch over the entire globe that is actually showing a cooling trend in a warming world.

This is the cold blob, or North Atlantic warming hole.

And it's become one of the most striking clues that something is changing in the Atlantic.

But to understand why, we first need to understand a bit more about how the AMOC works.

Scientists often describe it as a giant conveyor belt, carrying warm surface water northward and cold, deep water back south.

So there are warm water flowing from the southern tip of Africa all the way to Greenland near the surface.

As that surface water moves north, two important things happen.

First, some of it evaporates, leaving salt behind and increasing its salinity or saltiness.

Second, it releases heat to the atmosphere and cools.

Both of these processes increase its density.

Once that cool, salty, dense water reaches the North Atlantic, it sinks into the deep ocean and flows back south.

That's the overturning part of the name.

And that sinking is crucial to keeping this whole system moving.

And this massive system transport like tremendous amounts of heat all the way from Southern Hemisphere to the Northern Hemisphere.

So what does that creepy cold patch in the North Atlantic have to do with all of this?

Rene says it may be a warning sign.

If now the AMOC is, for example, slowing down, you are first of all transporting less salinity and less heat northwest, and therefore this cold blob arises.

So this cold anomaly might be an indication that the AMOC is grinding to a halt.

It is like a fingerprint of a weaker AMOC.

But why does moving all of that heat matter so much in the first place?

Well, let's start with Europe.

Without the heat the AMOC brings north, much of the continent would be far colder and far less hospitable.

It's our radiator and therefore we can live relatively far north compared to other locations at the same latitude.

We're skewed in a good way because therefore we can use a lot of crops, harvest, have like a very nice way of living because we have a relatively mild climate over here.

And if the AMOC shut down -.

We have built our entire society with a strong AMOC, and that may shift quite abruptly over a time span of decades up to a century.

And of course, that is very hard to adapt to.

After the recent record-breaking European heat waves, a drop in temperature might sound nice, but only as long as it doesn't drop too far.

So some regions see about five degrees in annual mean temperatures, but if you go to specific seasons, sometimes it can up to like 10 to 15 degrees Celsius.

There's about 20 degrees Fahrenheit.

A huge difference, especially in the winter months.

That's a massive shift in climate, and Europe wouldn't be the only place to feel the impacts.

What makes an AMOC collapse so terrifying is that the consequences would be sudden and global.

Also accelerated sea level rise near the coastal areas for Europe, but also along the North American coastline.

And across the tropics, simulations show the rain belts shifting to the south.

And a lot of regions are quite dependent on the monsoon system.

More than half of the world's population lives in monsoon regions.

Disrupting those rains could threaten food and water supplies for literally billions of people.

And as if that wasn't bad enough, there's all the other critical earth systems the AMOC is connected to.

The Green ice sheets and Western Antarctic ice sheets, the Subpolar Gyre, the Amazon rainforest, the AMOC is a very large-scale system.

And brand new research shows another very surprising effect.

This study found that the AMOC acts like a giant heat release valve, helping the planet shed heat into space.

But when it weakens, less heat escapes overall.

So even as Europe cools, the planet as a whole warms.

So it completely shifts the entire climate.

But what are the odds that this actually comes to pass?

Well, the AMOC is part of an incredibly complex climate system.

So that question is actually subject to some pretty heated debate among experts.

But here's what we do know.

First, we know for a fact that the AMOC can change abruptly.

During the last ice age, it shifted in strength many times, and those shifts have been linked to dramatic changes in climate.

But that doesn't tell us what's happening to the AMOC now.

For that, scientists have been directly measuring its flows since 2004 using the RAPID array, a network of buoys stretching across the Atlantic.

Based on these kind of observations, we already see like a slight weakening of the AMOC.

However, the time series is too short, therefore we cannot say whether this is now a significant trend, yes or no.

So the direct observations raise concern, but they can't settle the question on their own.

But there is a lot of indirect evidence now, like the creepy cold blob that tells us that less heat is arriving in the North Atlantic.

And what may be our strongest evidence yet, increasingly powerful climate models and the physics supporting them.

So these water masses due to global warming are getting lighter and therefore they just stay afloat and prohibit this sinking process.

Warmer surface water doesn't sink as easily.

So as the climate warms, that can weaken the circulation.

A weaker AMOC carries less heat north, which could help explain that cold patch.

And if the AMOC will continue to slow down, this cold patch is becoming larger and larger.

So we have good reason to expect weakening, but what determines whether that weakening becomes a collapse?

In many cases, scientists can answer this question with a global warming tipping point.

For coral reefs, that's around one and a half degrees Celsius.

For the Amazon rainforest, it may be closer to two.

And for the AMOC?

So in the, the big global tipping report, they assess that the AMOC is very likely to collapse at about plus four degree warming.

And in the study in August 2025, we actually recalculated that critical level and we actually said, "Well, probably it is lower at plus 2.5 degrees warming.".

But Rene's latest research says something completely different.

We are actually saying like there is no temperature level, so s- sorry for that.

<Laugh> So wait, then what does determine whether it tips?

Um, so there is no temperature level, but actually the warming rate, that actually controls whether the AMOC is tipping yes or no.

In Rene's model, speed was what mattered.

So we did like a few experiments in which we just imposed like present day warming rates and then eventually the AMOC does collapse.

But if we done it like at a factor of 10 slower compared to present day rates, the AMOC remains stable up to like crazy amount of warming levels.

So that really shows a rate increased tipping.

If the globe warms at a too rapid speed, the AMOC can't keep up and therefore it shuts down.

Okay.

Let's break that down because there's some very bad, but also some kind of good news in there.

Bad news first.

Rene's model suggests that not only could the AMOC's critical threshold be radically different than we believe, but also that we may already be in the danger zone.

But why would the rate of warming matter more than the actual temperature of the water?

So if you are warming your Atlantic ocean, the warming will first happen near the surface and eventually penetrates down towards the interior of the ocean.

If you do it at the very slow pace, like 10 times slower at present day, this whole warming can gradually penetrate your entire ocean and therefore like all the different density gradients remain somewhat coherent.

But if you now do it at a very fast pace, that is currently ongoing, you are only heating up the upper part, but the interior still lacks behind.

So basically, rapid warming leads to a larger contrast between the different density gradients and the sinking or overturning can't take place anymore.

We know when the AMOC becomes critically unstable in those climate model simulations, and it is about 0.3 degrees warming per decade.

And we're currently at that specific level or even beyond that.

For most climate models, the AMOC eventually shuts down if you continue at this pace.

Okay.

The word eventually is carrying a lot of weight in that sentence.

What exactly is the timeline for this?

That's a very good question and that is also our follow-up question.

Now here's the good news.

Renee's research suggests we may not need to stop or even reverse global warming to keep the AMOC stable.

What was the most surprising actually is that the AMOC is actually getting more stable under slow climate change.

With slower warming, the surface and the deep ocean have time to adjust together, keeping the circulation moving.

And that's why this finding gives me both more hope and a greater sense of urgency.

Policy makers say like with future technologies, it's a responsibility for future generations.

For the AMOC, the present day warming rate matters, so therefore the responsibility is now and not in the future.

Slowing warming could help protect the AMOC, but we don't know how long we can keep warming this fast before that opportunity is lost.

I don't think that we're already at the tipping point yet, so I think we still have time to move away from this iceberg, uh, to speak in titanic terms, but we need to act now.

So did this episode change how you think about climate tipping points and does it leave you feeling more hopeful, more concerned, or both?

Let us know in the comments.

As always, thanks for tuning in and we will see you next time on Weathered.