Worldwide, the proportion of hurricanes reaching categories 4 or 5 – with wind speeds above 56 metres per second – has risen from 20% in the 1970s to 35% in the 1990s.
在世界范围内，达到四级或五级的飓风——表示风速大于每秒56米——的比例从1970年代的20%上升到1990年代的35%。