Officials have said London’s flood defence walls will need to be half a metre higher in the future to protect against climate change. The announcement came as they marked the 40th anniversary of the Thames Barrier, which defends the capital against flooding. Though initially intended to protect London until 2030, the moveable barrier and the city’s wider flood defences will function until 2070, the UK’s Environment Agency expects. But sea levels are projected to rise by around a metre by 2100 and storms are becoming increasingly intense due to climate change. This, officials have said, means g…