As UK chancellor backs expansion at London’s biggest airport, we assess possible environmental impacts

More climate-heating carbon emissions, more people enduring noisy aircraft over their homes and, most likely, more air pollution – these would be the environmental impacts of building a third runway at Heathrow airport, a plan that has been backed by the chancellor, Rachel Reeves.

Despite many years of lobbying for a third runway, there is no current proposal that can be analysed for its environmental impacts. However, the last proposal was extensively assessed by the Airport Commission (AC) in 2017 and remains relevant.