If you live in the UK, you may have noticed something a little unfamiliar out your window in the past couple of days. For most of the country, the bleak, wet weather that has plagued our so-called summer has finally disappeared and our skies are once again blue. Though you might be busy digging out last year’s shorts and firing up the barbeque, the Scots are still battling the rain up north, and wondering why they haven’t yet seen the week or so of Summer that they normally do.
So why has the weather been so bad? Normally this is the question dreaded by meteorologists – the weather system is chaotic, and so pinpointing why there was a thunderstorm here or a patch of rain there could, quite literally, be down to the beat of a butterfly’s wing. This time, however, there is a pretty definite answer. The jet stream is an incredibly important component of the earth’s weather system. It is a current of fast moving air in the upper layers of the earth’s atmosphere, arising when cold arctic air meets warm tropical air. Normally, the stream passes north of the UK, directing low pressure, and hence bad weather, further north. This year, it is cutting straight across the top of Europe, directing the bad weather towards us.
As the UK is such a small island that relatively small changes in the position of the jet stream can lead to massive changes in our weather. However, this year, temperatures in the US have been soaring due to the same effect – that gives an idea of how great this phenomenon is.
The question scientists are struggling with now is exactly why the jet stream is behaving this way. It is an incredibly complicated mechanism, and although it was first discovered over 80 years ago, scientists know very little about it. Several theories have been put forward as to why the weather is so different, and of course climate change has been considered. Whilst scientists are careful to avoid blaming any specific weather event on global warming, it could be the answer to this situation. Since the 1970s, moisture in the atmosphere has risen by 4%, which could lead to the heavy rains we have experienced.
The main question on everyone’s minds now is whether or not the wet summer has ended for good. The answer, in true meteorologist fashion, is that it probably has. The jet stream does seem to be moving north again, leading to the nicer weather that most of the country has already seen. Hopefully this means that the 2012 Olympics won’t be a washout after all. Unfortunately for some, this movement of the jet stream is expected to push wet and windy weather towards the North-West of Scotland for the foreseeable future. Maybe don’t put the wellies away just yet.