Warm spells and tropical nights are on the rise in the UK as the climate changes, says a report from the Met Office.
The duration of warm spells, when temperatures are well above average for the time of year, has more than doubled between the periods 1961 -1990 and 2008 to 2017. Scorching summer days are getting hotter, with the hottest day of each year in the most recent decade on average 0.8°C warmer than each year’s hottest days in the period 1961-1990.
The chilliest extremes of the year are not quite as biting as they were in the past, with the lowest temperature of the year 1.7°C milder in the last decade than it was in the three decades up to 1990.
Tropical nights — where minimum temperatures do not fall below 20°C — are still rare in the UK, and are largely confined to southern England. But they included in the report as they are likely to become more common in the future as climate change becomes more pronounced.
The report finds that while the 1976 heatwave is one of the most significant heatwaves for the UK, tropical nights only really start to stand out after 1995. Between 2008 and 2017 a cluster of tropical nights were recorded in the South East, the Midlands and South Wales.
“Minimum overnight temperatures of over 20°C in the UK are rare currently and even during this summer this threshold was only exceeded on a few occasions,” says Mark McCarthy, at the Met Office. “However, with projections in climate suggesting warmer temperatures, it is useful to have this metric in place, so that future changes can be monitored.”
Heavy rainfall is also on the increase, with extremely wet days up 17 per cent in the period 2008-2017, compared to 1961-1990.
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