The regular ‘Atlantic Circulation Collapse’ story

One of the many regular climate scare stories you can rely on is the one about failing currents in the Atlantic Ocean bringing cold climate chaos to Europe. It’s one of the most favourite doomsday speculations, based on computer models pushed to the edge - but who cares, it’s a good shock-horror story and it pops up regularly.

Actually we should care because it’s well known that most people only register the top line of any news story — especially a climate disaster prediction - while they don’t take-in or even read up on the context and the qualifications. That’s when the headline becomes accepted as fact and takes its place as an undisputed example of the looming climate catastrophe.

For example see the tweets by Roger Hallam and John Simpson.

If some of the headlines in recent days are to be believed we are headed for a global climate disaster because of a slowdown in the circulation of the northern Atlantic Ocean predicted by computer models. But are we? No.

I suspect that people are thinking about the wrong thing here. This is not about the North Atlantic Drift - the current that brings warm water to Northern Europe from the Gulf of Mexico. That is a consequence of the Earth’s rotation and the distribution of the continents and it’s not going to change as long as the Earth keeps turning. This story is about another

Michael Le Page in New Scientist says that the Atlantic current shutdown is a real danger, but then backtracks qualifying what he means by “real danger,” when he adds:

The most detailed computer model run so far shows that melting ice sheets could cause the collapse of the major ocean current that warms Europe, but it's still unclear how likely this is to happen.”

So what is unclear is how unlikely it really is, according to one of the scientists concerned René van Westen of Utrecht University in the Netherlands, and whether it’s “indeed possible.” He knows this because his team used six months on the Netherlands’ national supercomputer, called Snellius, that demonstrated that there is that climate catastrophists trump card involved – a tipping point.

The Guardian likes tipping points and makes a lot of the idea; “The circulation of the Atlantic Ocean is heading towards a tipping point that is ‘bad news for the climate system and humanity,’ ” it says reporting that the Atlantic Meridional Overturning Circulation (AMOC) is weakening and has collapsed in the distant past.

It is the case that it has declined 15% since 1950 and is possibly in its “weakest” state in more than a millennium, but no one really knows if whether this is significant. Some studies have suggested the tipping point could happen between next year and 2095. However, the UK Met Office said large, rapid changes in AMOC were “very unlikely” in the 21st century.

Nethertheless, the Guardian forecasts an impending disaster saying this new work provides a “clear answer!” They say it found a slow decline that can lead to a sudden collapse over less than 100 years, with calamitous consequences. “This is bad news for the climate system and humanity as up till now one could think that AMOC tipping was only a theoretical concept and tipping would disappear as soon as the full climate system, with all its additional feedbacks, was considered.” It concludes.

I think you are beginning to see the pattern. Top-load the story with disaster that confirms what many think they already know and add the qualifications (in order to keep the story ‘ballanced’) so far down the story few will get to them.

New Scientist too continues to claim that a slowdown or complete shutdown of the AMOC is linked to episodes of dramatic cooling around Europe during the past 100,000 years or so - when it passes a tipping point at which time changes can make a system flip into a different state.

But, as I have said, when you look a little closer into this research and the media coverage, the dramatic headlines start to dissolve. New Scientist goes on to say that the modelling has proved tricky and the prediction of a shutdown involves adding unrealistically large quantities of fresh water all at once. Also in some recent simulations no shutdown took place suggesting that there is no potential tipping point at all.

New Dutch computer simulations added fresh water gradually, that eventually shut down the overturning circulation, causing temperatures to rise in the southern hemisphere, but plummet in Europe. The researchers say that some of the changes seen in the model ahead of the collapse correspond with changes being seen in the real Atlantic in recent decades.

But then the story flip-flops again. The freshwater added is about 80 times more than is currently entering the ocean as Greenland’s ice sheet melts. “So that is absurd and not very realistic,” van Westen now says! So perhaps the headlines describing this research should have included the words ‘absurd’ and ‘not very realistic’? In addition the simulation didn’t involve any global warming. The team will now rerun the simulation to include it.

The Telegraph was the most realistic and sober-headed leading its coverage saying a climate model predicting a devastating ‘Day After Tomorrow’ collapse of ocean systems has been criticised for relying on ‘entirely unrealistic’ scenarios. Adding, although ice-core data suggests the AMOC can switch off, recent sophisticated computer modelling has not been able to reproduce the effect, leading many scientists to think a collapse is unlikely to happen.

The Telegraph wisely says, “Models are not reality. The real system may be more, or less, prone to collapse than this model suggests.”

So don’t despair at the scientific results, but perhaps at some of the hyped-up journalism.