The devastating floods that have swept across parts of southern Africa in recent weeks were caused by a powerful combination of climate change and the natural La Niña weather cycle, according to a report by World Weather Attribution.

The report showed that the intensity of such extreme rainfall events has increased by 40 percent 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 have exacerbated the situation.

Severe flooding since December has wreaked havoc across Mozambique, South Africa, Zimbabwe, and Eswatini, with some areas receiving over a year's worth of rain in just a few days, the study said. Burst rivers forced the closure of South Africa's Kruger National Park, with repairs expected to cost millions of dollars.

"Data confirms a clear trend toward more violent downpours," WWA said. "This effect was compounded by the current La Niña, which naturally brings wetter conditions to this part of the world, but is now operating within a more moisture-rich atmosphere."

La Niña involves the temporary cooling of sea surface temperatures in the central and eastern Pacific Ocean.

The World Meteorological Organization has predicted a weak La Niña in this cycle but warned that warmer-than-normal sea temperatures linked to climate change are increasing the likelihood of both floods and droughts.