The weather in the UK seems to be going wild: we have just had our warmest April, our driest spring and one of our coldest winters. At the same time, the Arctic has undergone its most dramatic shrinkage of sea ice. Many climate experts believe that this is playing a hand in our dramatic weather.
As the Arctic Ocean warms up it is upsetting the global balance between cold Arctic air and warm tropical air. This is the engine that drives our weather. In recent years Atlantic winds have been blocked by high pressure systems, leaving us exposed to freezing winters and droughts in spring. The Atlantic depressions have returned in summer, bringing buckets of rain.
There were fears that the melting of the Arctic ice would swamp the Meridional Overturning Circulation, plunging northern Europe into colder winters. But a new array of buoys in the Atlantic has revealed only a slight weakening of the MOC. Most experts expect a slowdown of around 25 per cent by 2100, with a small chance of greater change.
There are other suspects playing a hand in the extreme UK weather, such as changing winds in the stratosphere, a quiet phase in the activity of the Sun and even random chaos in the atmosphere. Another concern is the Pacific. Every few years its tropical seas seesaw between a warm El Niño and a cool La Niña. Recent El Niños and La Niñas have set off mayhem. A record-breaking La Niña may have played a part in the cold start to our winter, and a powerful El Niño may have led to record rains in November 2009.
Although these upheavals are becoming more extreme and frequent, it is not certain if climate change is to blame. If it is, our weather could turn even more severe.