Cop26 failure could mean mass migration and food shortages, says Boris Johnson

Ahead of G20 meeting, PM warns of difficult geopolitical events' echoing those that ended Roman empire

A failure by world leaders to commit to tackling the climate emergency at the Cop26 summit in Glasgow could prompt very difficult geopolitical events" including mass migration and global competition for food and water, Boris Johnson has said.

Speaking before the start of a gathering of leaders from the G20 industrialised nations in Rome, where he will push for countries to arrive in Glasgow with fixed plans to cut emissions, Johnson said the chances of success hung in the balance.