Why so Wet?

“For England and Wales this was one of, if not the most, exceptional periods of winter rainfall in at least 248 years . . . the clustering and persistence of the storms is highly unusual. December and January were exceptionally wet.”

This was England on Valentine’s Day, 14 February 2014. The Met Office and the Centre for Ecology and Hydrology (CEH) responded to our extreme weather in February with a report on “The Recent Storms and Floods in the UK.” Over the last 248 years of record keeping, this most recent spate has been one of the worst periods ever recorded and we aren’t done yet. As other storm systems continue to pass through the country, this year may become the worst on record.

As unbelievable as this year has been, four of the five wettest years since 1910 — when national record keeping began — have occurred since 2000. As our rivers have changed shape due to increased drainage, channeling, and different water management, it is difficult to notice the increase in rainfall because there is no corresponding flooding. However, the graph below shows that while rainfall had remained relatively steady in the beginning of the 20th century, there has been an increasing trend in rainfall levels since the 1970s.

graphrain

The most likely scientific explanation for our miserable weather — weather that has even the hardiest Brit wishing for sun — is the Floppy Jet Stream.

The jet stream should be a tight circle of atmospheric activity, running roughly parallel to the Arctic Circle. Freezing arctic air clashes with humid, warm southern air, generating moisture laden storms. However, a warmer Arctic with its unprecedented sea ice melt has caused this tight band to relax. Satellite records have shown that the arctic sea ice has reached an all-time low of 4 million square kilometers in 2012, roughly half of what it was in the 1980s. The warmer temperatures have brought this ‘meandering’ jet stream to a much lower latitude — right over England — bringing its storms along with it.

graphiceProfessor Richard Harding from CEH data (2012)

Other explanations for this weather exist but they are far from scientific. Last month, David Silvester, Henley town councilor for the UK Independence Party (now expelled), said that permitting gay marriage would bring on divine retribution, with “natural disasters such as storms, pestilence and war.”

In my view, science has the upper hand over divine retribution. And science tells us that as long as the arctic continues to warm, the UK can expect more of this persistent weather. This persistence is at the heart of our increased rainfall: it doesn’t necessarily rain more frequently, but rather it rains longer because an inconsistent jet stream keeps weather systems in place longer. Like the floods in Colorado earlier this year, the increased rainfall in Britain is the result of stationary weather systems. That means next year the story could be sustained droughts rather than rain.

If we are to break the pattern of these storms, we must go beyond understanding their scientific explanations. Science has shown that the deluge is, at least in part, due to the changing climate. How we respond to that information is the realm of politics and public action. Perhaps the sight of flood water — or sustained drought — will motivate that action in a way scientific explanation alone cannot.

Image Credit: Stephen McKay via Wikimedia Commons

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