Why Scotland is one of the most sensitive places in the world to climate change

Arctic air has meant June has been a little cool so far but last month was the warmest May ever recorded in Scotland in records which go back to 1884. High night-time temperatures pushed the average up so that it was 1.6C warmer than the previous warmest May in 2018 and 3.2C warmer than the long-term average for the month.

That long-term average is calculated from the years between 1991 and 2010. However, compared to the first 20 years of the temperature record, May 2024 was a stunning 4.3C warmer than the 1884-1903 ‘normal’. June 2023 was also the warmest June ever recorded.

So far climate change has mostly been about the world getting warmer and the extra energy in the atmosphere driving increasing flooding and stronger storms. There have also been regional changes, bringing more intense rain in some areas and drought in others.

A vision of Scotland's future? The stretch of water along the coast of Newfoundland and Labrador is known as Iceberg Alley (Picture: Drew Angerer/Getty Images)

Vast Atlantic Ocean currents

Although Scotland has been regularly breaking weather records – 2022 was the warmest year ever and the ten warmest years in the 140-year record have all been since 1996 – we have actually been cushioned from more extreme variations by changes in ocean currents.

People talk about the Gulf Stream feeding warm water to the west of Scotland, but the reality is a bit more complex. Scientists talk about the Atlantic Meridional Overturning Circulation (AMOC) which brings warm surface waters from the Tropics to the north-east Atlantic, which then sink when they meet the cold waters of the Arctic returning to the west and south as a cold, deep-water current. The heat energy contained in this flow is huge – about 50 times more than all the energy that human society uses.

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Scotland is several degrees warmer than it would otherwise be because of this warm water circulation. If it switched off completely, our climate would be more like that of Labrador in Canada, which is at the same latitude as Scotland.

We know that this current has been weakening since the 1930s, with a marked shift in the 1970s. This is why temperatures in Scotland and north-west Europe have not been rising quite as fast as in other parts of the world. We also know from ice core measurements that this current has completely and abruptly switched off for periods in the past.

An incentive to act

A workshop this month looking at the science of abrupt changes to ocean circulation concluded that the risk of these kind of sudden, major changes has been underestimated in the past. A third of the best computer models predict major changes to the AMOC as soon as 2040.

One study shows a complete shutdown of the AMOC could see Scotland get more than 2C colder while most of the world is heading for 3C warmer than pre-industrial times. There would be major knock-on impacts on rainfall patterns around the world, creating droughts and reducing agricultural yields.

The threat of losing this ocean heat source means that Scotland is one of the most sensitive places in the world to climate change, and therefore has one of the greatest incentives to help lead the charge to reduce emissions.

Dr Richard Dixon is an environmental campaigner and consultant