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Climate change row as British scientists claim ‘Day After Tomorrow’ modelling is wrong - by Sarah Knapton for The Telegraph - 09.02.24

Prediction by Dutch team that vital Atlantic system could reach a tipping point and trigger new ice age has been ‘forced’, say experts


A climate model predicting a devastating ‘Day After Tomorrow’ collapse of ocean systems has been criticised for relying on ‘entirely unrealistic’ scenarios.


A Dutch team from Utrecht University published work in the journal of Science Advances this week suggesting that the Atlantic Meridional Overturning Circulation (AMOC) could reach a tipping point, triggering a new ice age.


The AMOC transports heat and salt throughout the world’s oceans and helps regulate the global climate, driving the Gulf Stream that keeps Britain warmer than it should be for its northerly latitude.


In the apocalyptic science fiction film The Day After Tomorrow, the ocean system is disrupted by climate change, plunging the northern hemisphere into a permanent winter.


Although ice-core data suggests the AMOC can switch off, recent sophisticated modelling has not been able to reproduce the effect, leading many scientists to think a collapse is unlikely to happen.


The new study claims to have shown that AMOC is “on route to tipping”, a prospect that the authors say is “bad news for the climate system and humanity”.


However British scientists warned that the outcome had been “forced” by using unlikely variables, such as assuming large influxes of freshwater into the Atlantic.


Prof Jonathan Bamber, director of the Bristol Glaciology Centre at Bristol University, said: “They did this by imposing a huge freshwater forcing to the North Atlantic that is entirely unrealistic for even the most extreme warming scenario over the next century.


“Their freshwater forcing applied to the North Atlantic is equivalent to six cm/year of sea level rise by the end of the experiment, which is more than seen during the collapse of the ice sheet that covered North America during the last glaciation.”


The UN’s Intergovernmental Panel on Climate Change has said that the AMOC is unlikely to collapse this century, and many scientists do not believe it will fail even if the climate continues to warm.


Observational data for the ocean system only goes back to 2004, making it difficult to predict, and because it spans the globe, most models cannot account for all the nuances and influences.


Commenting on the new research, Prof Andrew Watson, of Exeter University, said “They say it suggests that ‘the present day AMOC is on route to tipping’.


‘Push it quite hard’


“This sounds alarming, but it’s important to note that this is not the same as saying collapse is going to happen imminently. They have to run their model for a long time (1,700 years) and push it quite hard to make the collapse happen.


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


The authors said that the collapse of the AMOC would result in the “very strong and rapid cooling of Europe” by about 3C per decade, which they said ‘no realistic adaptation measures’ would be able to mitigate.


They said their study had picked up an early warning signal that the collapse was just 25 years away, when the movement of freshwater flowing through the southern Atlantic slows to a minimum.


Other experts said the research was a reminder of the possible unexpected impacts of uncontrollable global warming, which could actually plunge the world into a new ice age.

Prof Jeffrey Kargel, senior scientist at the Planetary Science Institute in Arizona, said: “A shut down of the AMOC would be felt globally, according to the model, from Europe to Antarctica.


 ‘Sea ice has diminished drastically’


Sea ice in the Arctic, which has diminished drastically in recent decades, would expand in winter to the latitudes of Ireland, the UK and Denmark.


“The projected changes in climate in Scandinavia and parts of Greenland and the United Kingdom and elsewhere may threaten those countries’ humanly habitability if glacier and ice sheet growth extends from the mountains and hill terrains to lowlands.”


Last year a paper published in the journal Nature suggested the AMOC was likely to collapse by 2057, and possibly as early as 2025.


But the study was criticised as “far too simplistic” by the Met Office, which warned readers not to despair.



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Sarah Knapton, Science Editor



 

 

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