UK’s future climate to deliver hotter summers

The heatwave, which peaked in August 2003, is thought to have caused the deaths of 20,000 people and was the hottest spell in Europe for more than 500 years.

The report examines the drivers and impacts of seasonal weather extremes in the UK, to see how much they can be attributed to climate change.

It has been published ahead of the latest Intergovernmental Panel on Climate Change assessment due next week.

As well as extreme heat, extreme cold, rainfall and dryness (drought) are examined, with a large variation in confidence about what will happen with each in a future climate.

Although the confidence level is rated as four out of five (high) for hotter summers, confidence in future rainfall is much lower at two out of five. This is because UK rainfall shows large year to year variability, making trends hard to detect.

Despite long-term averages pointing to an increase in the frequency of wetter winters and drier summers, natural variability will still give wetter summers – 2012 being a recent example, when the UK had its wettest summer in 100 years.

Confidence in seasonal rainfall is low due to a natural cycle of the climate system called the Atlantic Multi-decadal Oscillation. These 10-year cycles of warming and cooling sea surface temperatures significantly influence patterns of rainfall, with more rainfall occurring when the sea is warmer.

While confidence in seasonal rainfall is low, it is noted that daily rainfall events are becoming more intense – a pattern likely to be linked to climate change and the fact that a warmer atmosphere in the future will be able to hold more moisture.

In terms of rainfall intensity, what would have been a one-in-125 day event in the 1960s or 1970s is now a one-in-85 day event.

Other recent cases of extreme weather, such as spring 2013 (coldest for 50 years) and the dry spell of 2010-12 (led to water restrictions), are more likely to be caused by natural variability, rather than climate change.

Aside from the warming trend for temperatures, given the relatively low confidence in other aspects of our future climate, the report acknowledges that a lot more work needs to be done in order to attribute changes to anthropogenic global warming.

It says that the solution to this problem lies in further research, as well as the climate models of higher resolution – tools that are now becoming available.

The effect of climate change on the UK will extend well beyond our borders. Yields of foods from the tropics, such as rice and maize are likely to suffer in the future, meaning that prices will inevitably rise.