Temperature extremes and records in the UK most affected by human induced climate change

New analysis of observations shows that extremes of temperature in the UK are most affected by human induced climate change. This means the UK is seeing, on average, more frequent periods of hot weather, bringing challenges for infrastructure, health and wellbeing. The observations also suggest an increase in rainfall extremes.

The new analysis features in this year’s annual publication of the ‘State of the UK Climate’ report. Published in the Royal Meteorological Society’s ‘International Journal of Climatology’, the report is a comprehensive review of the UK climate and significant weather events through 2023. This report is based on observations from the UK’s network of weather stations, using data extending back to the 19th Century to provide long term context.

Using an example of 28°C, the frequency of days reaching this threshold has increased nearly everywhere across the UK. Where in the 1961-1990 averaging period only London and Hampshire recorded six or more days over 28°C, by the latest decade (2014-2023) this has spread across much of England and Wales, with frequencies in the south east increasing to over 12 days each year in many counties.

Furthermore, the proportional increase across all counties over time is much more pronounced as the temperature threshold gets higher. The number of ‘pleasant’ days (daily maximum 20°C) has increased by 41% for the most recent decade (2014-2023) compared to 1961-1990. The number of ‘warm’ days (25°C) has increased by 63%, ‘hot’ days (28°C) have more than doubled and ‘very hot’ days (30°C) have more than trebled over the same period.

The most recent decade has had around 20% more days of exceptional rainfall compared to the 1961-1990 averaging period. While there is no significant signal for this change being more pronounced in a specific area of the UK, overall, this analysis clearly shows an increase in the number of very wet days in the UK’s climate in recent years compared to what was observed just a few decades ago.

Lead author and Met Office climate scientist, Mike Kendon, said: “What we are showing here is the notable change in frequencies of extreme weather that can have a real impact on people’s lives.

“2023 was another year of interesting and at times significant weather. From the UK’s record warmest June by a wide margin, to a significant September heatwave and the most active start to the storm naming season culminating in serious flooding problems in the autumn, it was another year of typically varied weather. But underlying this natural variability is a continuing and increasing influence of climate change which is influencing the weather we experience.”

Attribution studies were conducted on the record breaking June monthly temperature, the joint warmest September on record and the year as a whole being the second warmest on record for the UK. All of these studies found that human induced climate change had made them much more likely to happen than they would have been in a natural climate.

Professor Liz Bentley, Chief Executive of the Royal Meteorological Society, said: “This report is the authoritative annual summary of the UK climate published as a special supplement in our International Journal of Climatology. It not only helps to highlight the latest knowledge on our changing climate but also enables us to understand the trends, risks and impacts to help inform how we will need to adapt, now and in the future.

Significant weather events through 2023 include the record warm June, coinciding with a significant marine heatwave. 30°C was recorded in September in the UK on seven consecutive days for the first time on record, and unusually, the hottest day of the year was recorded in September (33.5°C on 10 September).

Scotland had its wettest 2-day period on record on 6 to 7 October in a daily series from 1891, 65.9mm, 39% of the 1991-2020 October whole-month average.

The 2023-2024 storm season had its most active start with respect to the number of named storms since storm naming was introduced in 2015, with seven named storms from September to December. Storm Babet brought widespread prolonged and heavy rainfall and was the UK’s most impactful weather event of the year. Eastern Scotland – where a red warning for rain was issued – was particularly badly affected due to an unusual south-easterly flow with increased rainfall across high ground. Winds from storm Ciarán on 2 November had the potential to be as severe as from the ‘Great Storm’ of 16 October 1987, but the strongest winds missed the UK to the south.

The UK recorded its wettest September to December period since 2000 due to persistently wet and unsettled weather, including the sequence of named storms from Agnes to Gerrit.

Find out more here.