Understanding London’s Heat Island

As London’s first prolonged heatwave in seven years – including a temperature of 33.5C at Heathrow and the Met Office issuing a level 3 heatwave alert – was brought to a dramatic close with a crash of thunder, it seems an opportune moment to take stock of the recent events.

After the coldest spring in the UK for 50 years most of us welcomed a chance to get out and about, however it is worth noting the adverse effects of sustained periods of hot weather. Reports about the impacts on London have included:

6 July – South West Trains were disrupted between Waterloo and Clapham Junction as the rail tracks rose to almost 50C
15 July – Thousands of passengers were stranded at Waterloo Station as some of the train track buckled at the height of rush hour
18 July – Heatwave caused calls to the London Ambulance Service to rise, with callouts categorised as “life threatening” increasing by 20%
18 July – Temperatures soared on London Underground throughout the week

For most Londoners hot weather can throw up minor inconveniences, but for many thousands, high temperatures have the potential to be dangerous or fatal – a London School of Hygiene and Tropical Medicine study in 2011 looked at the impact of previous hot weather events and highlighted that when temperatures rise above 24 degrees Celsius, mortality rises by 3.8% per degree.

London Climate Change Partnership works to identify how we can better understand and manage extreme weather and climatic events – in doing so we can ensure that London is a resilient and thriving city. In the Heat Thresholds for London report, LCCP has started to map out London’s current limitations in the heat, to understand what actions we need to take to prepare for the future.

Last week LCCP released its latest report Observing London: Weather data needed for London to thrive – which makes the case that with better co-ordinated and more accessible data we can improve our understanding of London’s microclimate.

We can all find out a temperature for London in about two clicks on the internet – but what is the temperature in the street where you live or where you work? If you search the crowd sourced data on the Met Office’s Weather Observations Website you will see that the recordings vary a great deal and on top of this, it is surprisingly difficult to find weather data for Central London. A new academic study released yesterday also shows the potential of mobile phones to gather data which may also help fill the gap.

Better information will highlight how temperatures vary across the capital and how the city’s land cover (buildings, roads and green spaces) exacerbates or help reduce the impact of hot weather – the city’s ‘Urban heat island’. Armed with this information we can take a more strategic approach and plan for heat waves – and other extreme weather events – minimising disruption in the city and the impacts on peoples’ health and wellbeing.

Climate projections suggest that hot weather will become more frequent and intense in the future, and we all need to raise awareness of the severity of the impacts so that Londoner’s have the capacity to act, our emergency plans are up to scratch and that new developments are designed for the climate they will experience throughout their existence.

Changes in the weather are expected and can be prepared for. The recent heatwave highlights the need for us to work more closely together and ensure we help London to be one of the best cities in the world to live and work.

Further information about heatwaves

Heatwave Plan for England – Public Health England launched the earlier this year and this outlines how we can prepare and respond to heatwaves.

Hot Weather Alert Service – Met Office

Beat the Heat Plan, Summer 2013 – Transport for London

London Climate Change Partnership publications:
Observing London: Weather data needed for London to thrive
Overheating Thresholds Report
Your social housing in changing climate
Your home in a changing climate
A checklist for development
London’s Warming

One response to “Understanding London’s Heat Island”

  1. Richard Dawson says:

    Thanks for the post Matthew. The following analysis of satellite data and London’s heat island may also be of interest. If you can’t read the full article, I can email you a copy:

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