Climate change and our recent extreme weather

East Lyng flooding 2014

The rainfall and flooding experienced across Somerset and other parts of the UK in recent weeks has been extraordinary. It has been hard on those who have been flooded or found themselves cut off as they have been surrounded by water, with local roads turned into rivers. Unfortunately, the Somerset flooding may not subside for weeks and that may be just the start of a long process for some to get their lives back to normal, amid on-going concern that it could happen all over again in the future. We must hope solutions will be found to protect more homes and businesses from flooding and severe weather in future.

Met Office Recent Storms BriefingInevitably, the question arises whether the rain and storms we have experienced are related to climate change. Last week, the Met Office addressed this question with a report, which documents the record-breaking weather and flooding, considers the potential drivers and discusses whether climate change contributed to the severity of the weather and its impacts.

Their conclusions (with my added emphasis) include (on pages 25-26):

There is an increasing body of evidence that shows that extreme daily rainfall rates are becoming more intense, and that the rate of increase is consistent with what is expected from fundamental physics. Although formal attribution is still challenging, it is possible to identify a contribution from climate change for some major flooding events … . It is worth emphasizing that there is no evidence to counter the basic premise that a warmer world will lead to more intense daily and hourly heavy rain events.

“In terms of the impacts of changing weather and climate patterns, the cluster of drought and flood events through the early years of the 21st century and the recent runoff and recharge patterns, are near to the extreme range of historical variability. They therefore also raise the question that they may reflect anthropogenic [caused by human activity] climate change. ….

“Enhanced groundwater flood risk may be expected if average winter rainfall in the UK increases. Flash flooding, which can be exacerbated by land management and land use practices (particularly the extension of impermeable areas), may also increase if the recent intensification in rainfall translates into an enduring trend.

In terms of the storms and floods of winter 2013/2014, it is not possible, yet, to give a definitive answer on whether climate change has been a contributor or not. The climatological context … was unusual, with the Atlantic jet stream being more intense and reaching further back into the tropical East Pacific than normal. Those factors in themselves would allow warmer and moister air to enter the storm systems. It is also the case that the sub-tropical Atlantic is now warmer than it was several decades ago and that too would act to enhance the moisture content of the storms.

“More research is urgently needed to deliver robust detection of changes in storminess and daily/hourly rain rates. The attribution of these changes to anthropogenic global warming requires climate models of sufficient resolution to capture storms and their associated rainfall. Such models are now becoming available and should be deployed as soon as possible to provide a solid evidence base for future investments in flood and coastal defences.”

Dave M

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One thought on “Climate change and our recent extreme weather

  1. The BBC has reported on research by the American Association for the Advancement of Science, which like the Met Office report, found that changes to the path taken by the jet stream in the atmosphere is behind recent stormy weather over the UK and bitter winter weather in the US Mid-West. The American research suggests this has been caused by high levels of warming at the Arctic which will lead to more frequent meandering of the jet stream, so leading to weather patterns becoming stuck over areas for weeks on end and also driving cold weather further south and warm weather further north. See: http://www.bbc.co.uk/news/science-environment-26023166

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