REVIEW OF 2011 AND 2012

Scientists are more less agreed that the variability in rainfall that we are starting to see across the UK is due to a change in the behaviour of the jet stream. The fast current of air in the upper atmosphere is what drives the weather across the UK, insomuch that it determines the course of mid latitude depressions – the source of much of our rainfall. Normally, the jet stream follows a meandering path which is constantly moving and changing its position in relation to the UK. However, in recent years the jet stream appears to be becoming more static such that we are finding ourselves for long periods either to the south of the jet stream, causing dry years like 2011, or north of the jet stream favouring the developing of frequent depressions such we have seen for much of 2012.

The path of the jet stream during the summer of 2012 – a more usual path for summer is to the north

However, there is every indication that not only is the timing of rainfall changing, but also the nature of rainfall itself. When it does rain, it is tending to rain harder and for longer. Again, this may be the result of an increase in number of depression ‘trains’ tracking across the UK – a product of the static position of the jet stream,  but it may also be the result of more energy in the atmosphere which points to global warming as an ultimate cause. In Northampton, an analysis of temperature data in 2010, suggests the county has seen an overall increase in average temperatures of 0.1C since 1931.

Although the precise cause of the change in nature of the jet stream is uncertain, it is likely that climate change is implicated somewhere. The jet stream is after all the result of thermal differences between polar and tropical regions. Current research is very much focused on understanding what controls the wavy nature of these air currents and why they may get locked into position. So the future climate for the UK and Northampton in particular is likely to be a continuation of extremes: from very dry months to very wet months, and from very dry years to very wet years. This is the pattern already emerging in China and India and there is no reason why we cannot expect to see the same emerging here.

The impact of these changes is profound and will affect us all. There is a very real need for more effective means of storing water and redistributing it from parts of Britain that have more than their fair share, a so-called national water grid, so that we can cope better with the water shortages through the dry spells such as we saw during 2011. Such as a strategy has so far been dismissed on account of the huge cost involved, but we may be faced with a far greater costs if we are to do nothing. To offset the effects of flooding when it does rain, there needs to be more investment made in effective flood defence strategies including more sustainable strategies which link the need store water such as rainwater harvesting. High rainfall and drought also impact on farmers and reduced yields which ultimate translates into reduced income and higher prices for consumers in shops. Again, farmers may need to adjust by considering crops that can tolerate standing in waterlogged fields for weeks on as well as being drought resistant. The solution may lie with genetically modified crops, something which the public may have to come to accept or swallow the higher cost of importing foodstuffs from abroad.

These changes will all require significant investment by both government and private companies, and there may be some reluctance initially to commit to major projects such as a national water grid. The British have come to accept their changeable weather, indeed their conversation is much dependent on it. However, the next few years are likely to present a major challenge to our way of thinking and how we deal with the weather

M Lewis
Manager, Pitsford Hall weather station