What makes Sidmouth the perfect place to live?

Snowing and sunshine. David Chaplin

What shapes the weather in East Devon? - Credit: David Chaplin

"The UK’s weather and climate are fundamentally controlled by the Atlantic Meridional Overturning Circulation (AMOC)": An extract from the UK independent Committee for Climate Change Risk Assessment (CCRA3), 2021, author Dame Julia Slingo, Sidmouth (https://www.ukclimaterisk.org/wp-content/uploads/2021/06/CCRA3-Chapter-1-FINAL.pdf).

The AMOC and the Gulf stream warm winter temperatures, reduce midsummer extremes and make Sidmouth/East Devon the perfect place to live. 

The Gulf Stream is a relatively fast flowing river of warm water moving across the North Atlantic from the Gulf of Mexico to Western Europe, driven by mid-latitude westerly winds.

The AMOC, a planetary ocean circulation, is a complex problem to describe. It circulates water from deep in the South Atlantic, rises slowly, before sinking around Greenland, then flows back to the South Atlantic. 

The combination of salinity and temperature is important in this process. Other overturning circulations occur in the Indian and Pacific Oceans. 

The combination of the AMOC and the Gulf Stream keep Northern Europe warm in winter.

Oceanographers continue to study this problem, since the AMOC strength has reduced by 15% over the last 20 years and concerns meteorologists. 

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Why? Any sudden halt to the Northern Hemisphere AMOC would significantly reduce warm water flow into the northern North Atlantic. This happened 12,000 years ago, the Younger-Dryas event. 

Arguably melting Arctic and Greenland Ice sheets could block the AMOC flow, just as when the North American Ice sheets melted, causing the Younger-Dryas event. Future temperatures in Northern Europe, including Scotland, might fall by 5C (compensating for global warming?).

The warm waters of the Gulf Stream and AMOC off the US Eastern sea-board are the spawning grounds for mid-latitude cyclones which track across the Atlantic. 

However, the steeper North South Sea Surface temperature gradient would intensify these mid-latitude storms. Storm tracks could move Southwards towards our latitudes, causing more intense storms. 

The UK growing season would shorten and sea levels would rise ½ metre. The good news for the UK is that more heat waves are predicted in the summer (see CCRA3 report). The cold waters off Greenland absorb much carbon dioxide, effectively slowing down global warming, and this would continue.

So, what is the likelihood of this happening? Is it indeed small? 

None of the latest CMIP6 (Coupled Model Intercomparison Project) computer runs produced for the IPPC Working Group (WG1) report (July 2021) predicted a collapse of the AMOC in the 21st century.

The IPCC6 WG1 states: "There is no observational evidence of a trend in the Atlantic Meridional Overturning Circulation (AMOC) ... While there is low confidence in 20th century AMOC change, it is very likely that AMOC will decline over the 21st century ... There is medium confidence that the decline will not involve an abrupt collapse before 2100."

The WG1 assessment downplays some of the latest research and dismisses the larger sensitivity of newer higher resolution climate models. As mentioned previously, WG1 is a consensus publication which requires the agreement of gas and oil producing nations, such as Russia and Saudi Arabia.

The CCRA3 report, however, suggests the AMOC collapse is plausible. A reduction of the strength of AMOC, up to 45% by 2100, could well occur. Recent research papers are discussed in CCRA3 indicating that there could be a reduction in UK food production. 

Winter storminess in the UK, especially to the North, would increase. UK winter rainfall in the West could increase but with more droughts in Eastern UK.

Reassuringly, the Office of Nuclear Regulation, has included this possibility in its design guidelines for the new Nuclear Build at Hinkley Point, 37 miles as the crow flies, North-East of Sidmouth. (https://www.onr.org.uk/consultations/2021/external-hazards/ns-tast-gd-013-annex-2.pdf).

EDDC/Sidmouth planners take note. Think ahead positively, as in the Netherlands, who have positive flood precaution plans and build retention ponds, or as in China, which constructs sponge basins.