Climate projections for heat in UK cities

With the recent COP26 focussing heavily on the chances of keeping global temperature rise below 1.5°C, it might be easy to forget that we are still committed to further climate change and a resulting increase in the frequency and intensity of heatwaves.

The impact of this will be felt increasingly in cities, where the majority of the world’s population now live, where much of our businesses, industry and infrastructure are concentrated, and where extreme temperatures are exacerbated by the urban heat island effect.

With many cities across the UK declaring climate emergencies, city councils and other decision-makers are asking how they can use increasingly refined and detailed climate projections to better understand the impact of extreme heat on urban communities.

The Met Office’s high-resolution projections from UKCP provide some of the most accurate climate modelling of heat in urban areas available. Dr Will Keat is a Met Office climate scientist who has studied these new projections. He said: “Our most detailed climate projections over the UK also contain a much more realistic representation of cities and other urban areas than used previously. We have found that these projections provide a marked improvement when investigating how extreme temperatures will change in UK cities when compared to less detailed models.”

The high resolution projections are being used by scientists working with local authorities to understand the effect these changes will have on their cities.

Dr Tyrone Dunbar is the Met Office Scientific Manager for urban climate services. He said: “The concept of urban heat islands – where urban locations retain more heat than surrounding areas – has long been understood. By combining our higher resolution projections with detailed information about where vulnerable people and buildings are in cities, we are helping local authorities and planners gain a far more detailed picture of the impacts their residents and visitors will increasingly face in future.

“The Met Office has been working with a number of local authorities to help inform their heat resilience strategies and planning. When they combine this information with their own mapping they gain a far more clear picture of where the areas of greatest risk are across the city, such as areas of densely populated older housing or if a care home is situated in particularly hot area. This ability to know where to focus effort is extremely important.”

Local authorities are keen to consider how they can make cities more resilient to extreme heat. Different actions can be carried out, such as retrofitting buildings to shade their windows or by increasing green spaces which can provide cool oases within the city. Councils are also making contingency plans to protect residents whenever heatwaves occur.

Victoria Ramsey is a Met Office climate services scientist working with local authorities. She said: “When it comes to emergency planning, we find that a lot of the local authorities we speak to have lots of plans for cold events and flooding events. But increasingly with climate change they are being forced to think more about how heat-related impacts will affect local communities.”

“We can see the impact extreme heat can have on communities from the heatwaves experienced by a number of our UK cities in recent years. For example, in June 2018 the greater Belfast area experienced high temperatures resulting in severe transport disruption to the rail network and schools having to send children outside when classroom temperatures got above 30C. This year saw the first ever amber heat warning over Northern Ireland and the high temperature record was broken three days in a row.”

The Met Office Urban Climate Services team have developed a set of factsheets about climate change for cities around the UK called the City Packs as part of the UK Climate Resilience programme, funded by the Strategic Priorities Fund. The team are currently developing an updated version of this product and are happy to hear from any cities that would like to be added to the shortlist to receive a City Pack – for info please contact urbanclimateservices@metoffice.gov.uk

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