The deadly and catastrophic floods in Libya 2:04

(CNN) -- September began with a typhoon that swept through Hong Kong, uprooting trees and flooding the city. It was the first in a series of extreme weather events that have hit ten countries and territories in just 12 days; the most catastrophic was the floods in Libya, which according to the UN left more than 11,000 dead and many thousands missing.

Scientists warn that these types of extreme weather events, affecting countries around the world, may become increasingly frequent as the climate crisis accelerates, putting pressure on governments to prepare.

"Global warming changes the properties of precipitation in terms of frequency, intensity and duration," said Jung-Eun Chu, an atmospheric and climatological scientist at City University of Hong Kong, though she added that this summer's devastation was due to a combination of different factors, including natural climate fluctuations.

People walk past houses destroyed by heavy rains and flooding in Derna, Libya, on September 13, 2023. (Credit: Esam Omran Al-Fetori/Reuters)

The huge toll of flood victims also highlights the urgent need for governments to prepare for this new reality, and how the poorest and most conflict-ridden countries are on the frontlines of climate catastrophes.

Governments "have to be prepared," Chu said. "They have to start thinking about it, because they've never experienced these kinds of extreme events before."

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One of the worst storms in Europe

This month, swaths of the Mediterranean region were hit by Storm Daniel, the result of a very strong low pressure system that became a "medicane," a relatively rare type of storm with characteristics similar to those of hurricanes and typhoons that can cause dangerous rainfall and flooding.

The storm, which formed on Sept. 5, hit Greece first, releasing more rain than is normally seen in an entire year. The streets turned into deadly rivers, submerging entire villages and forcing emergency workers to rescue families from their flooded homes in rubber dinghies.

A man carries a girl and a dog in the flooded village of Palamas, in central Greece, on September 8, 2023. (Credit: Angelos Tzortzinis/AFP/Getty Images)

At least 15 people were killed, according to Greek Prime Minister Kyriakos Mitsotakis, who called it "one of the most powerful storms to hit Europe."

The floods, which followed devastating wildfires in the country, "have the imprints of climate change," Greece's Environment Minister Theodoros Skylakakis told CNN on Tuesday.

"We've had the warmest summer ever recorded. The sea was very warm, which caused this unique weather phenomenon," he said.

A flooded area following Storm Daniel in Megala Kalyvia, Greece, on September 9, 2023. (Credit: Giannis Floulis/Reuters)

Neighboring Turkey also felt the impact, recording at least seven deaths. Residents of forested areas had to wade through knee-deep waters surrounded by fallen trees, while in some areas of Istanbul, the country's largest city, deadly flash floods left at least two people dead.

In Bulgaria, northern Greece, severe flooding was also reported, with at least four confirmed deaths.

In the rest of Europe, another storm – Storm Dana – brought torrential rains to Spain, damaging homes and killing at least three people.

Devastation in Libya

By far the most devastating impact was felt in Libya, as Storm Daniel moved across the Mediterranean, gaining strength thanks to unusually warm sea waters, before dumping torrential rains on the country's northeast.

The catastrophic rainfall caused two dams to collapse, unleashing a 7-meter (23-foot) wave, according to the International Committee of the Red Cross (ICRC). The water rushed toward the coastal city of Derna, where it swept away entire neighborhoods and swept homes into the ocean.

More than 11,000 people have died and at least 10,000 others are still missing, according to the UN, and many are believed to have been washed out to sea or buried under the rubble.

As the country reels and search and rescue operations become desperate, experts say the scale of the catastrophe has been greatly magnified by a combination of factors including crumbling infrastructure, inadequate warnings and the effects of the accelerating climate crisis.

"This is a tragedy where climate and capacity have collided to cause this terrible, terrible tragedy," U.N. aid chief Martin Griffiths said Friday.

• Why have the floods in Libya been so deadly? A mix of factors led to one of Africa's worst tragedies

Libya has been plagued by civil war and political stalemate for nearly a decade, with the nation divided between two rival administrations since 2014, one of which is not recognized by most of the international community and controls the region where Derna is located.

The North African country's fragmented state has made it unprepared for flooding, experts say, and may hamper the delivery of urgently needed humanitarian aid.

"The situation in Libya has continued to deteriorate due to years of conflict and instability, exacerbated by the effects of climate change," said Ciaran Donnelly, Senior Vice President, Crisis Response, Recovery and Development at the International Rescue Committee.

"Globally, climate change has made these extreme weather events more frequent and intense, making it even more difficult for communities to cope and rebuild, especially in conflict-affected regions," he added.

Drone shows devastation in Libya after floods 0:48

Typhoon duel in Asia

While the scale of devastation and loss of life was smaller in Asia, it has also seen deadly and unprecedented storms.

Two typhoons — Saola and Haikui — tore through the region within days of each other during the first week of September, causing widespread damage to Taiwan's autonomous island, Hong Kong city and other parts of southern China, including Shenzhen.

Although Typhoon Saola closed Hong Kong's schools and businesses for two days, the real damage came a week later, when the city was hit by a flash storm, with flash floods submerging subway stations and stranded on roads.

According to Hong Kong authorities, the storm caused the highest rainfall per hour since records began in 1884.

This was the passage of Typhoon Doksuri through China 1:58

In Taiwan, Typhoon Haikui left tens of thousands of homes without power and more than 7,000 residents were evacuated.

The two typhoons were an "exceptional case" that created the conditions for an unusually severe storm the following week, Chu said. The typhoons brought two slow-moving air masses, both laden with moisture and traveling in different directions, which collided and dumped the water over Hong Kong.

"If there was only one typhoon, there wouldn't be such heavy rainfall," he explained. He added that while the event is not explicitly linked to climate change — converging typhoons occurred "by chance" — man-made global warming is helping fuel stronger storms.

"If the climate warms, if the surface (of the ocean) warms, the atmosphere can retain more moisture," he explained. "If the temperature rises one degree, the atmosphere can retain 7% more moisture."

Chu pointed to the history of hourly rainfall records in Hong Kong. In the past, decades used to elapse between record rainfalls, but the differences are rapidly narrowing. As the world warms, once-in-a-lifetime extreme weather events are becoming more frequent.

Torrential rains in America

Some parts of America were also flooded. Brazil recorded more than 30 deaths last week following heavy rains and flooding in Rio Grande do Sul state, the worst natural disaster to hit the state in 40 years, according to CNN regional affiliate CNN Brazil.

Brazilian meteorologist Maria Clara Sassaki told CNN Brazil that, in less than a week, the state had received the average amount of rainfall expected for the entire month of September.

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Meanwhile, in the United States, the Burning Man festival topped the international stage after a heavy downpour lashed the area and forced tens of thousands of attendees to conserve food and water while stranded in the Nevada desert.

In just 24 hours, the remote area was hit by rainfall of up to 0.8 inches, about twice the September average.

On the opposite end of the country, flooding in Massachusetts damaged hundreds of homes, businesses and infrastructure, including bridges, dams and railroads. Rainfall in parts of Massachusetts and New Hampshire exceeded normal volumes by more than 300 percent over the past two weeks, according to weather service data.

Drivers attempted to cross a flooded street Monday in Leominster, Massachusetts, on Sept. 11, 2023. (Credit: Rick Cinclair/Worcester Telegram & Gazette/AP)

Experts say record ocean temperatures have fueled a hyperactive Atlantic hurricane season that shows no signs of slowing down.

More than 90% of global warming over the past 50 years has occurred in the oceans, according to the National Oceanic and Atmospheric Administration.

Phil Klotzbach, a research scientist in Colorado State University's Department of Atmospheric Sciences, explained to CNN that this means more storms may form than would be possible in a typical El Niño year. Even storms that weaken due to changes in wind can stay alive and gain strength again once they find better conditions.

CNN's Taylor Ward, Sana Noor Haq, Celine Alkhaldi, Eyad Kourdi, Hamdi Alkhshali, Mostafa Salem, Kareem El Damanhoury, Nadeen Ebrahim, Laura Paddison, Chris Liakos, Christian Edwards, Louise McLoughlin, Brandon Miller, Elizabeth Wolfe and Mary Gilbert contributed to this report.

Floods