JOHANNESBURG, Jan 29 - A "perfect storm" of climate change and cyclical La Niña weather patterns fuelled catastrophic flooding across southern Africa over the past month, killing 200 people and affecting hundreds of thousands of others, a study showed on Thursday.

The report by World Weather Attribution showed that the intensity of such extreme rainfall events has increased by 40% since preindustrial times - a clear sign that warmer ocean temperatures linked to greenhouse gas emissions are partly to blame - and that current La Niña conditions had worsened things.