A new report by the Met Office which reveals further details about changes in the UK’s climate since the 1960 shows that heatwaves in the UK are lasting twice as long as they did 50 years ago.

The report, State of the UK Climate 2017: Supplementary report on Climate Extremes, is the first study of climate extremes in the UK by the Met Office.

The latest State of the UK Climate report published in July shows that nine of the 10 warmest years for the UK have occurred since 2002 and that seven of the 10 wettest years for the UK have occurred since 1998.

By documenting temperature and rainfall climate extremes, including periods of warmth, cold and spells of wet or dry weather, the report reveals changes in some types of extreme weather.

By comparing different meteorological reference periods, a number of interesting trends can be observed. For example, the hottest day of each year over the most recent decade (2008-2017) in the UK has been on average 0.8 °C warmer than the hottest day of each year over the period 1961-1990.

The lowest temperature of the year has shown an even greater increase, becoming 1.7 °C milder between the two periods in the UK.

The warm spell period of 13.2 days in the most recent decade 2008-2017, is more than double that of 5.3 days during 1961-1990. South east England has seen some of the most significant changes, with warm spell duration increasing from 6.1 days in the 1961-1990 average to 18.3 days per year on average for the most recent decade.

The study uses a set of measures agreed around the globe by the World Meteorological Organization and World Climate Research Programme, and are widely used in global climate change research.

These metrics include at least one measure – Tropical Nights – which is currently not a common feature of the UK climate, but it could become more widespread in future. Tropical nights are defined as 24-hour periods when the minimum temperature doesn’t fall below 20.0 °C.

Dr Mark McCarthy is the head of the Met Office’s National Climate Information Centre, the team which produced the report. He said:

“Monthly, seasonal and annual climate data provide a valuable record of the changing climate in the UK. However, these average figures have a tendency to mask extreme weather and climate events. So in our latest report we have focussed on those measures which record weather extremes – complementing our recently published State of the UK Climate 2017."

Commenting on the tropical nights measure, Dr McCarthy added:

“Minimum overnight temperatures of over 20.0 °C in the UK are rare currently and even during this summer this threshold was only exceeded on a few occasions. However, with projections in climate suggesting warmer temperatures, it is useful to have this metric in place, so that future changes can be monitored.”

The report summarises a set of core indices, which can be obtained from temperature and rainfall data. It also shows climate shifts for UK countries and regions, along with maps showing the data across four time periods: 1961-1990; 1981-2010; 2008-2017; and 2017.

According to the report, warm spells have more than doubled in duration between 1961-1990 and 2008-2017 while overall, the longest dry spells have decreased by 2.5 days, on average.

However, total rainfall from extremely wet days has increased by about 17%.

The Met Office’s 4th annual State of the UK Climate report published in July confirmed that 2017 was the 5th warmest year in a record dating back to 1910. The report also flagged up the fact that mean sea level around the UK has risen at a rate of approximately 1.4 mm per year since the start of the 20th Century, equivalent to a rise of about 16 cm.

Click here to download State of the UK Climate 2017: Supplementary report on Climate Extremes

Click here to download State of the UK Climate 2017