Met Office heatwave thresholds are to be updated ahead of Summer 2022 as the UK sees impacts due to climate change.
Warming across the country has, however, not been even with
some regions experiencing more rapid change than others. Heatwave thresholds in
8 counties in a band from Surrey to east Yorkshire are now changing.
Dr Mark
McCarthy is the head of the Met Office National Climate
Information Centre, which manages the UK’s climate records. He said: “Climate
statistics over time reveal an undeniable warming trend for the UK. Temperature
rise has been greatest across parts of central and eastern England where they
have increased by more than 1.0°C in some locations, while further north areas
of Scotland and Northern Ireland have seen temperatures rise by closer to
0.7°C.”
The original heatwave
thresholds were based on a reference climate period for
1981-2010. The heatwave definition was intended to be flexible and to be
reviewed and revised in order to follow our changing climate and represent
heatwaves relative to the “current” climate. Therefore the thresholds are
moving to the most recent 1991-2020
climate averaging period introduced in January this year. 6
counties are moving from a 27°C threshold to 28°C, one from 26 to 27°C, and one
from 25 to 26°C.
Counties changing from a 27C to a 28C threshold:
Surrey, Berkshire, Buckinghamshire, Bedfordshire,
Hertfordshire, Cambridgeshire
Counties changing from a 26C to a 27C threshold:
Lincolnshire
Counties changing from a 25C to a 26C threshold:
East Riding of Yorkshire
Dr McCarthy added: “Although heatwaves are extreme weather
events research shows that climate change is making these events more likely. A
scientific study by the Met Office into the Summer 2018 heatwave in the UK
showed that it was 30 times more likely to occur now than in 1750 because of
the higher concentration of carbon dioxide (a greenhouse gas) in the
atmosphere. As greenhouse gas concentrations increase heatwaves of similar
intensity are projected to become even more frequent, perhaps occurring as
regularly as every other year.”
The central map above shows the original thresholds, the
right hand one the updated thresholds and, as an additional demonstration of
our changing climate, the left hand one shows what they would have been if we
had had this definition in place for 1961-1990.
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