Top international climate scientists and disaster experts meeting in Africa had a sharp message Friday for the world’s political leaders: Get ready for more dangerous and “unprecedented extreme weather” caused by global warming.

Making preparations, they say, will save lives and money.

These experts fear that without preparedness, crazy weather extremes may overwhelm some locations, making some places unlivable.

The Nobel Prize-winning Intergovernmental Panel on Climate Change issued a new special report on global warming and extreme weather after meeting in Kampala, Uganda. This is the first time the group of scientists has focused on the dangers of extreme weather events such as heat waves, floods, droughts and storms. Those are more dangerous than gradual increases in the world’s average temperature.

“We need to be worried,” said one of the study’s lead authors, Maarten van Aalst, director of the International Red Cross/Red Crescent Climate Centre in the Netherlands. “And our response needs to anticipate disasters and reduce risk before they happen rather than wait until after they happen and clean up afterward. … Risk has already increased dramatically.”

The report said “a changing climate leads to changes in the frequency, intensity, spatial extent, duration, and timing of extreme weather and climate events, and can result in unprecedented extreme weather and climate events.” And it said that some — but not all — of these extreme events are caused by the increase of man-made greenhouse gases in the atmosphere.