Heat wave definition in Peterborough changes due to climate change

While unlikely to have an impact this week, when snow and wintry showers could hit the city, the definition is changing across much of the south and east of the country.

Previously in Peterborough - and the rest of Cambridgeshire, a heat wave was defined as being a period of at least three consecutive days where the temperature reaches at least 27C. That will now change to 28C.

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 Met Office said original heat wave thresholds were based on a reference climate period for 1981-2010. However, the heat wave definition was intended to be flexible and to be reviewed and revised to take into account climate change and represent heat waves relative to the “current” climate.

Therefore the thresholds are moving to the most recent 1991-2020 climate averaging period introduced in January this year. A total of six counties are moving from a 27°C threshold to 28°C, one from 26 to 27°C, and one from 25 to 26°C.

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.”