What is the Impact of a Warming Climate on London's Temperatures and UHI?

With a warming climate and the majority of the world's population living in urban areas there is a need to understand how urban temperatures and the urban heat island (UHI) will be affected by a changing climate in order to help with urban planning strategies. Most global and regional climate models do not represent urban processes adequately due to their coarse horizontal scale and UHI's have mostly been studied on a case study basis.

We know that the urban heat island is mainly driven by the difference in the surface energy balance between urban and rural areas with the individual terms of the surface energy balance differing between different climates and city layouts and building use. For instance studies have shown that the major contributing factor for the intensity of the urban heat island in Western European cities such as London is the urban land-use fraction followed by the building morphology and anthropogenic sources (Bohnenstengel et al. 2011 and 2013). However, the UHI has been less well studied from a climate change perspective.

The MetOffice has undertaken high-resolution convection-permitting regional climate simulations for the UK (Kendon et al. 2014). This talk presents results from an RCP8.5 climate scenario covering 13 years of simulations over southern UK to demonstrate how a warming climate might affect urban temperatures in London. We analyse the differences in temperatures simulated for London and the processes leading to differences between the control and the future climate run.

Bohnenstengel, S. I., Evans, S., Clark, P. A. and Belcher, S. E. (2011) Simulations of the London urban heat island. Quarterly Journal of the Royal Meteorological Society, 137 (659). pp. 1625-1640. ISSN 1477-870X doi: 10.1002/qj.855

Bohnenstengel, S. I., Hamilton, I., Davies, M. and Belcher, S. E. (2013) Impact of anthropogenic heat emissions on London's temperatures. Quarterly Journal of the Royal Meteorological Society, 140 (679). pp. 687-698. ISSN 1477-870X doi: 10.1002/qj.2144

Kendon EJ, NM Roberts, HJ Fowler, MJ Roberts, SC Chan and CA Fowler (2014), Heavier summer downpours with climate change revealed by weather forecast resolution model , Nature Climate Change, 4, 570-576 doi: 10.1038/NCLIMATE2258