Extreme weather patterns are still a mystery

Summer has finally arrived, and not before time. One of the coldest springs on record has made this winter appear to be interminable; we are finally enjoying the heat and sunshine of a summer that seemed to be destined to fizzle out like so many before it.

The weather, especially for a set of islands stuck at this latitude, is notoriously fickle and what we have experienced over the past few summers and winters reminds us of the inherent unpredictability of a fundamentally chaotic system.

The Met Office recently held a workshop of 25 experts to find out if there is a cogent reason why Europe has experienced such an unusual run of unseasonal weather. There is as yet no simple answer, it seems.

Something may be “loading the dice” in favour of weather extremes, but what this is remains something of a mystery. It could be long-term natural cycles in the North Atlantic which operate over decades, or it could be something more directly connected with global warming and climate change.

If the latter proves to be the case, then it is likely to have something to do with what is happening in the Arctic, where the loss of sea ice is perhaps the single most visible outcome of rapidly rising temperatures – the region has experienced a rate of warming that is some two or three times greater than elsewhere in the world.

There is mounting evidence that the jet stream is more liable to change course as a result of rising Arctic temperatures, increasing the chances of it becoming locked in one position, bringing the same kind of weather for days or weeks on end.

Five out of the six last summers in Britain have brought above average rainfall, possibly influenced by shifts in the jet stream. Now this ribbon of air has cleared away to the north – welcome to summer.