More concrete equals more heat. We’ve heard about the urban heat island effect, where replacing vegetation with asphalt leads to greater localised warming, but what impact do urban heat islands have on the countryside around them? A new study, published in Environmental Research Letters, shows that the warming impact of urbanisation extends far beyond the city boundaries.
In Great Britain 5.8% of land area is covered by artificial surfaces, up from 4.3% in 1975. It is one of the most urbanised countries in the world with 83% of the population living on 6% of the land. Using air temperature and wind speed measurements, researchers created a statistical model to estimate the warming impact that Great Britain’s cities have on the surrounding countryside, and investigated how this has changed over time.
They show that Great Britain’s urban areas are responsible for about 0.04C of the warming the country has experienced to date, with the last 40 years of urbanisation pushing warming rates up by 3%. The UK’s fastest urbanising regions are feeling the heat most, with warming rates up to three times faster in the south-east. But the good news is that the urban heat island effect can be diminished, for example by painting roofs white and planting more vegetation.