Higher temperatures mean more rain for Scotland

FLASH floods caused by torrential summer rain and nights so hot it’s hard to sleep - most Scots would view the current weather as decidedly unseasonable.

But for the children growing up in Scotland today it is likely to become more usual as global temperatures gradually rise over the next decades.

The west coast of Scotland is the first point of arrival for weather blown in on south-westerly winds from the Atlantic and, as a result, is well-known for its showers.

But arrival of the remains of Hurricane Alex, which unusually has decided to sit off the coast, has drenched the country in 48 hours of bizarrely tropical rain.

The last few days have seen top temperatures of 20C to 23C - above average for Scotland at this time of year even when the sun is shining - combined with rainfall of up to an inch in less than two days.

Hurricanes are born off the west coast of Africa and generally travel west to the Caribbean, where they can run out of steam, or head northwards up the east coast of the United States and then east into the Atlantic.

Normally they dissipate in the ocean but some, like Hurricane Alex, survive sufficiently to have a significant effect on the weather in Britain.

Alex is no longer a hurricane but it is a large depression which has a lot of warm air and a fairly vigorous circulation. Hurricanes rotate anti-clockwise and so, because Alex is sitting to the west of us, we are getting southerly winds from Spain which are not only moist but fairly warm.

What can be said is that the global temperature is rising. As the climate warms, it is thought Britain will tend to get more rain as warm air can hold more moisture.

Depressions like Alex feed on warm air and moisture so it is logical to predict that in future we will see more of this kind of weather in this country.

But anyone expecting El Nio-style storms that will lay waste to the country will have a long wait. Climate systems do not change quickly, it is something that happens over decades rather than from year to year.

There has been a suggestion that Scotland could become dramatically colder because global warming will cause the Gulf Stream - warm water coming from the Caribbean - to switch off. But, if this prediction is correct, it will not happen on the timescale that Hollywood would have us believe.

Again it would take place over decades rather than in two weeks, as I think it was in the film The Day After Tomorrow.

Dr Keith Weston, of Edinburgh University’s School of GeoSciences, is vice-president of the Royal Meteorological Society