The world has gotten stormier over the past two decades — and the reason is a mystery, a new study says. In the past 20 years, winds have picked up around 5 percent on average. Extremely strong winds caused by storms have increased even faster, jumping 10 percent over 20 years, according to the new analysis of global satellite data. The study, the first to look at wind speeds across such a large swath of the planet, bolsters some earlier findings, according to study leader Ian Young, of the Swinburne University of Technology in Melbourne, Australia. "Some regional studies had found similar results, so we suspected there may be an increasing trend," Young said.