Autumn weather will be drier and more summer-like due to increasing climate change, according to new Met Office research.
There is an increased risk of drought from the mid-2020s, warned the study due to hot and dry summers followed by warmer autumns. It also projected that longer summers could delay the start of autumn.
The Met Office study found autumns will have less rain on average, but also suggested 'extreme rainfall events' could be strewn between dry spells. The severity of these projections, however, depend on the rate of greenhouse gas emissions that are emitted.
Daniel Cotterill is the lead scientist behind the study, which focusses on the projected likelihood of occurrence of weather patterns, of which there are 30 standard types.
He said: "Using climate models and the UK Climate Projections, our research found that the largely 'summer-like' weather patterns – bringing drier conditions – will begin to extend into the start of autumn. And weather patterns such as those dominated by large low-pressure systems, will tend to occur slightly less in autumn in future.
"Although we don't expect to see this shift in pattern imminently, a key finding from this study is that from the mid-2020s warmer and drier autumns following hotter and drier summers could increase drought risk."
The strength of the shift in weather patterns depends on the rate of greenhouse gas emissions are emitted into the atmosphere, which scientists refer to as emissions' pathways.
Daniel added: "Our research compares a very low-emissions pathway to a very high-emission scenario. What we see is these effects are a lot stronger in the high-emissions scenarios, and this suggests that these changes in weather patterns are due to human influence and the resulting effect of warming on atmospheric circulation."
The study shows that we're likely going to see less rain in autumn on average. But, backing up other studies, it signalled the potential for extreme rainfall events to be interspersed between the drier spells.
Daniel added: "This is a signal we'll start to perhaps see over the next ten years. We're likely to see a 4 to 12% reduction in rainfall in English regions in the future in autumn.
"And this depends very much on the greenhouse gas emission scenarios. One of the things we are already seeing in autumn as average seasonal temperatures rise is an increase in the number of extreme rainfall events. But in future, we're likely to see this drying effect as well.
"UK Climate Projections have shown for some time that we can expect hotter, drier summers and warmer and wetter winters. Our study shows we are likely to see hotter and drier autumns on average too.
Daniel added: "To see how situations might unfold we could consider the autumn of 2020. On 3 October we saw the UK's wettest day on record and the volume of rainfall which fell on the UK that day could have filled Loch Ness.
"However, if you look at the overall rainfall for that autumn, it's actually only 6% above average and that is because of a drier September and November that year."
The paper 'Future extension of the UK summer and its impact on autumn precipitation' is published in the journal Climate Dynamics.
