“In order to detect a weakening of the AMOC, you have to measure the ocean for long enough to be able to characterise all that natural variability. We've only been measuring the AMOC for 20 years. We expect it to be at least another 10 years or 20 years before we can really detect whether there's a climate change signal over the natural variability.”
The Climate Question · Climate & Energy · November 2026
Context
The host pointed to the thousands of instruments used to monitor the Atlantic overturning circulation and asked whether they'd give warning of a weakening. The answer: yes, but the record is still too short to separate a climate signal from natural swings.
Transcript
…or not being completely knowledgeable about the physics of the AMOC, we can't get that to be reproduced in the climate models. So, there's work to be done to improve how the AMOC is represented in climate models so that we can reduce that envelope of uncertainty that we have at the moment.
…nearly 500 kilometres of wiring to just measure what you're talking about and 3,000 pieces of equipment out there monitoring. So, it's not through lack of trying. I guess all of that equipment and all of that wiring, will it give us a warning if weakening is happening? Will we get time to prepare?
It will do. I'm absolutely sure of that. One thing to understand, I think, is that the ocean does vary, it does change, it has fluctuations on lots of time scales. So, you're all familiar with the idea that there's tides, okay? So, we have a 12-hour fluctuation in sea level based on tides. We also have storm surges and we have different processes that happen on quite short time scales. And there are similar cycles of changes in the ocean over long time scales, too. It varies according to the season, it varies on time scales of one year to another, 10 years to another, 10 years. And in order to detect a weakening of the AMOC, you have to measure the ocean for long enough to be able to characterise all that natural variability and look to see whether you can detect a long-term climate change signal in it. We've only been measuring the AMOC for 20 years. We expect it to be at least another 10 years or 20 years before we can really detect whether there's a climate change signal over the natural variability that the AMOC also contains. Based on the science we have available now, before the next decade of data that we might get, what's…
I've got a bit of a weird question to end on with, Penny, if that's okay. What's your favourite bit of the ocean?
My favourite bit of the ocean is probably the subpolar North Atlantic. So that's the area between Canada, Greenland, Iceland, and the UK. It's cold and it's stormy, but it's incredibly beautiful. I've spent a lot of time out on ships there. The wildlife is spectacular.
Polar bears?
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