Shipping faces turbulent ride on carbon-cutting quest

What’s a natural resource that is free, produces zero carbon emissions and has been used to power ships since time immemorial? The answer is of course the wind. The graceful sailing ships that sent the likes of Christopher Columbus and Vasco da Gama to the Americas and India are long gone, though, replaced by vast iron vessels loaded with crude oil, minerals and neat stacks of shipping containers to feed the voracious global economy.