01:47 - Source: CNN
1-in-1,000-year weather events are increasing. Here's why
Hong Kong CNN  — 

September started with a typhoon that ripped through Hong Kong, uprooting trees and flooding the city. It was the first of a slew of extreme weather events that have hit ten countries and territories in just 12 days – the most catastrophic being the floods in Libya, which have killed more than 11,000 people according to the UN and left many thousands missing.

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

“Global warming actually changes the properties of precipitation in terms of frequency, intensity and duration,” said Jung-Eun Chu, an atmospheric and climate scientist at the 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.

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

The huge toll of the floods also highlights the urgent need for governments to prepare for this new reality, and the ways conflict-ridden and poorer countries sit on the front lines of climate disasters.

Governments “have to be ready,” said Chu. “They have to start thinking about it, because they’ve never experienced these kinds of extreme events before.”

One of the worst storms in Europe

This month, swaths of the Mediterranean region have been lashed by Storm Daniel, the result of a very strong low-pressure system that became a “medicane” – a relatively rare type of storm with similar characteristics to hurricanes and typhoons which can bring dangerous rainfall and flooding.

The storm, which formed on September 5, affected Greece first, releasing more rain than is normally seen in an entire year. Streets turned into deadly rivers, submerging whole villages and forcing emergency workers on inflatable boats to rescue families from their flooded homes.

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

At least 15 people died, according to the Greek Prime Minister Kyriakos Mitsotakis, who called it “one of the most powerful storms to ever hit Europe.”

The floods, which followed devastating wildfires in the country, “have the fingerprints of climate change,” Greek environment minister Theodoros Skylakakis told CNN on Tuesday.

“We have had the warmest summer on record. The sea was very warm, which lead to this unique meteorological event,” he said.

00:42 - Source: CNN
See people try to save belongings in Greece's rushing floodwaters

Neighboring Turkey felt the impact too, recording at least seven deaths. Residents in wooded areas had to wade through knee-high water, surrounded by fallen trees – while parts of Istanbul, the country’s biggest city, saw deadly flash floods which killed at least two people.

Severe flooding also struck Bulgaria, north of Greece, with at least four deaths confirmed.

Elsewhere in Europe, a separate storm – Storm Dana – saw torrential rain across 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 from the sea’s unusually warm waters, before dumping torrential rain on the northeast of the country.

02:44 - Source: CNN
Pulling bodies with 'a rope tied around his waist.' How Libyans deal with lack of international help

The catastrophic rainfall caused the collapse of two dams, 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, wiping out entire neighborhoods and sweeping homes into the ocean.

More than 11,000 people are dead and at least another 10,000 still missing, according to the UN, with many believed to have been swept out to sea or buried beneath rubble.

As the nation reels, and as search and rescue operations grow desperate, experts say the scale of the disaster has been greatly magnified by a combination of factors including crumbling infrastructure, inadequate warnings and the impacts of the accelerating climate crisis.

“This is a tragedy in which climate and capacity has collided to cause this terrible, terrible tragedy,” said UN aid chief Martin Griffiths on Friday.

Libya has been wracked by a civil war and a political standoff for almost a decade, with the nation split between two rival administrations since 2014 – one of which isn’t recognized by most of the international community, and which controls the region where Derna is located.

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

“The situation in Libya has been steadily deteriorating due to years of conflict and instability, compounded by the impacts of climate change,” said Ciaran Donnelly, senior vice president for 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 harder for communities to cope and rebuild, especially in conflict-affected regions,” he added.

Zohra Bensemra/Reuters
People gather for a demonstration outside the Al-Sahaba mosque in Derna, Libya, on Monday, September 18. The protesters are trying to hold leaders accountable for the bursting of dams that some feel could have been avoided. This sign reads: "The sad city of Derna demands its rights."
Karim Sahib/AFP/Getty Images
A building is damaged in Derna on September 18. Experts say the storm's impact was greatly exacerbated by a lethal confluence of factors, including aging, crumbling infrastructure; inadequate warnings; and the effects of the accelerating climate crisis.
Esam Omran Al-Fetori/Reuters
Hassan Kassar, who lost his daughters, two of his sons and his granddaughter, sits inside his damaged house in Derna on Sunday, September 17.
Esam Omran Al-fetori/Reuters
People walk through rubble and debris in Derna on September 17.
Zohra Bensemra/Reuters
A woman who lost family members reacts as she walks past destroyed houses in Derna on September 17.
Amr Alfiky/Reuters
A rescuer from the United Arab Emirates uses a dog to look for human remains in Derna on Saturday, September 16.
Zohra Bensemra/Reuters
Debris is piled up in Derna on September 16.
Ayman Al-sahili/Reuters
This aerial view shows the destruction in Derna on September 16.
Zohra Bensemra/Reuters
Volunteers carry a body to a truck in Derna on September 16.
Zohra Bensemra/Reuters
An overturned car is inside a shop in Derna on September 16.
Yousef Murad/AP
A man walks by the graves of flood victims in Derna on Friday, September 15.
Esam Omran Al-Fetori/Reuters
People line up to receive food aid in Derna on September 15.
Muhammad J. Elalwany/Anadolu Agency/Getty Images
Devastation is seen in Derna on September 15.
Abdullah Doma/AFP/Getty Images
A mosque stands amid damaged buildings in Derna on Thursday, September 14.
Abdullah Doma/AFP/Getty Images
A man carries a child on his shoulder as he walks past a flood-damaged area in Derna on September 14.
Yousef Murad/AP
Toys are scattered outside a damaged house on September 14.
Esam Omran Al-Fetori/Reuters
People look at damaged areas of Derna on September 14.
Abdullah Doma/AFP/Getty Images
People carry some of their belongings as they walk along a muddy street on September 14.
Muhammad J. Elalwany/AP
An overhead view of the flood damage in Derna on Wednesday, September 13.
Mohamed Abd El Ghany/Reuters
Hassan El Salheen weeps in the Egyptian village of Al Sharief on September 13 after burying the repatriated body of his son, Aly, who died along with his three cousins in Libya.
Ahmed Elumami/Reuters
A body is carried away in Derna on September 13.
Yousef Murad/AP
People search for survivors in Derna on September 13.
Esam Omran Al-Fetori/Reuters
A search-and-rescue team from the Egyptian army looks at damaged cars in Derna on September 13.
Yousef Murad/AP
Workers bury the bodies of flood victims in Derna on September 13.
Jamal Alkomaty/AP
An aerial view of Derna on September 12.
Esam Omran Al-Fetori/Reuters
A man sits amid flood debris in Derna on September 12.
Abdullah Mohammed Bonja/Anadolu Agency/Getty Images
A damaged vehicle is partially buried in Derna on September 12.
Abdullah Mohammed Bonja/Anadolu Agency/Getty Images
People cover the body of a victim in Derna on September 12.
Jamal Alkomaty/AP
A road is collapsed in Derna on September 12.
AFP/Getty Images
People make their way through a damaged area of Derna on September 11.
AFP/Getty Images
Toys are strewn across the ground at a damaged store in Derna on September 11.
Ali Al-Saadi/Reuters
Floodwaters cover Shahhat, Libya, on September 11.
AFP/Getty Images
Overturned cars are piled in a street in Derna on September 11.
AFP/Getty Images
The body of a flood victim lies in the back of a pickup truck in Derna on September 11.
Omar Jarhman/Reuters
People stand on a damaged road in Shahhat on September 11.

Asia’s dueling typhoons

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

Two typhoons – Saola and Haikui – passed through the region within days of each other during the first week of September, causing widespread damage in the self-governing island of Taiwan, the city Hong Kong and other parts of southern China including Shenzhen.

Though Typhoon Saola shut down Hong Kong schools and businesses for two days, the real damage came a week later when the city was lashed by a sudden storm, with flash flooding submerging metro stations and trapping ivers on roads.

The storm brought the highest hourly rainfall since records began in 1884, according to Hong Kong authorities.

01:50 - Source: CNN
Video shows heavy rainfall turning Hong Kong streets into rivers

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

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

“If there were only one typhoon, it would not make this kind of severe precipitation,” she said. She added that while the event isn’t explicitly linked to climate change – the converging typhoons happened “by chance” – human-caused global warming is helping fuel stronger storms.

“If the climate warms, if the (ocean) surface becomes warmer, the atmosphere can hold more moisture,” she said. “If temperatures increase by one degree (Celsius), the atmosphere can hold 7% more moisture.”

She pointed to the history of hourly rainfall records in Hong Kong. In the past, there used to be decades between record-breaking rainfall events, Chu said, but gaps between records are narrowing rapidly. As our world warms, extreme weather that used to happen once in a lifetime are becoming more frequent occurrences.

Heavy rain in the Americas

Parts of the Americas have been inundated too. Brazil recorded more than 30 deaths last week after heavy rains and floods in the state of Rio Grande do Sul – the worst natural disaster to hit the state in 40 years, according to CNN’s regional affiliate CNN Brasil.

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

Meanwhile in the United States, the Burning Man festival made international headlines after a heavy rainstorm pummeled the area, with tens of thousands of attendees told to conserve food and water while stranded in the Nevada desert.

The remote area was hit with up to 0.8 inches – about twice the average September rainfall – in just 24 hours.

01:08 - Source: CNN
"A mucky, muddy, environment." This is what Burning Man looks like

On the opposite side of the country, flooding in Massachusetts has damaged hundreds of homes, businesses and infrastructure including bridges, dams and railways. Rainfall in parts of Massachusetts and New Hampshire has been more than 300% above normal volumes over the past two weeks, according to weather service data.

Rick Cinclair/Worcester Telegram & Gazette/AP
Drivers tried to cross a flooded street Monday in Leominster, Massachusetts, on September 11, 2023.

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

More than 90% of warming around the globe over the past 50 years has taken place in the oceans, according to the National Oceanic and Atmospheric Administration.

It means more storms are able to form than would otherwise be possible in a typical El Niño year, Phil Klotzbach, a research scientist in the Department of Atmospheric Science at Colorado State University, told CNN. 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 reporting.