- Climate change is ‘supercharging’ storm systems, leading to more rainfall that creates worse flooding, says hydrologist Hannah Cloke

- Climate change ‘may also make storms slower moving, increasing rainfall accumulation and flooding,’ says John Marsham, a professor of atmospheric science

- ‘Rain will be more concentrated in events such as flash floods in autumn. Extreme weather events will become more intense and more frequent,’ says scientist Marilena Oltmanns

ISTANBUL 

Spain’s recent devastating flash floods killed more than 200 people, sweeping through homes, destroying cars, bridges and all sorts of essential infrastructure.

The ferocity of the floods was astounding, capturing global attention, particularly as the destruction played out in a developed European nation, and leading to another round of urgent warnings from climate scientists and researchers around the world.

According to estimates from the National State Meteorological Agency (AEMET), some areas in southern and eastern Spain received a year’s worth of rainfall in a span of just eight hours, going up to a staggering 491 liters per square meter in the Chica area of Valencia.

Adding to the shock is the fact that all of this happened in late October, in the thick of the fall season, one not usually associated with such climate disasters.

That raises the obvious question of where all this water came from and just how common an occurrence this could be in the future.

The answer, according to several experts of the field, is rooted in the biggest threat facing humanity as a whole: climate change.

It is a result of rising temperatures and unprecedented heat in water bodies such as the Mediterranean Sea accelerating hydrological cycles, making them much more erratic and dangerous.

“The high sea surface temperatures of the Mediterranean are a critical factor contributing to the flash floods. The Mediterranean has warmed more than twice as fast as the global sea surface over the last 30 years,” Marilena Oltmanns, a senior scientist in marine physics and ocean climate at the National Oceanography Center in the UK, told Anadolu.

“The increased heat means that the air can hold more moisture. It also leads to a stronger temperature contrast with the cold winds from the European continent, which makes these flash floods more intense.”

John Marsham, a professor of atmospheric science, further broke down the way man-made climate change is exacerbating the crisis: “While warmer air can hold more water, leading to heavier rainfall, more water vapor can also mean more energy available to storms, again intensifying rainfall.”

Another effect of climate change is that “may also make storms slower moving, increasing rainfall accumulation and flooding,” Marsham, the Met Office Joint Chair at the University of Leeds, told Anadolu.

“Finally, climate change has been increasing droughts in the Mediterranean area, leading to hard sunbaked soils, so when it rains more water runs off, rather than entering the soils, increasing flooding.”

A ‘virtually certain’ warmer future

Given the crucial link between warming temperatures and increasingly frequent flood disasters, a new report released Thursday by the EU’s Copernicus Climate Change Service paints a picture of a grim future.

The report said 2024 is now “virtually certain” to be the warmest year on record and will also be the first year when the planet is over 1.5 degrees Celsius warmer than the 1850-1900 pre-industrial period.

For the Mediterranean, according to Oltmanns, all indicators point to the region “becoming hotter and drier” over the coming years.

“Rain will be more concentrated in events such as flash floods in autumn. Extreme weather events will become more intense and more frequent, also in other parts of Europe and globally,” she said.

Carola Koenig, a reader at the Center for Flood Risk and Resilience at Brunel University, reiterated that “climate change is a key contributing factor” in these worsening scenarios for the future.

“We are seeing the number of more extreme weather events, whether it’s on the heat side or on the rain and storminess side, definitely being fueled by climate change,” she told Anadolu.

“If you’re going back centuries, we had extreme weather events as well, but not at this frequency and not with those extreme levels.”

For floods specifically, she said if a full statistical evaluation were to be done, it would clearly illustrate a global increase in their frequency.

“I’ve seen animations in terms of the increase in the air temperature over the years, going back for about 100 years, and the extreme temperatures kept rising and rising, and the frequency of those rises has also been increasing enormously,” she said.

“I’m sure if you do the statistical evaluation, you see that on the rain side as well.”

Expectations for fall and winters

Hannah Cloke, a British hydrologist, pointed out that along with land surfaces, ocean temperatures have also been shattering all previous records, while climate change is “kind of supercharging these types of storm systems.”

“The warmer atmosphere, the warmer ocean means we’re getting more water picked up ... and that means that these supercharged storms create more rainfall that creates worse flooding,” Cloke, a natural hazards researcher and climate scientist at the University of Reading told Anadolu.

“So we’ve got bad floods being made worse by climate change.”

For the fall and winter seasons, Koenig explained that as the atmosphere starts to cool, the increased moisture it contains starts to come down as precipitation in the form of very heavy rains.

“This is why we are seeing, over the last few years, increased amounts of rain in the winter months than before,” she said.

She said environmental watchdogs and met offices are expecting many more alerts during winter months compared to the summer.

Koenig also spoke about another effect of warmer winters, specifically decreasing snowfall across Europe.

“In the wintertime, you hardly see any snow anymore … I think we will see an increased phenomenon of rain, while snow will become increasingly rare,” she said.

This is already being seen in areas like the Alps and others dependent on winter tourism, who are increasingly using snow guns to be make up for the thinning natural snow cover, she added.

Protective and preventive measures

Cloke explained that floods do not always necessarily have to be a destructive force.

“Slow floods that gently cover the landscape … that’s really handy because we can store that water within the landscape, and use it later on when there is no rain,” she said.

But in the case of flash floods, they happen really suddenly and are incredibly destructive, as they rip out the soil from the landscape, she added.

On the question of possible protective measures, Cloke stressed the need for better and improved warning systems.

“We can use the technology that we have, which forecasts when and where rain will fall, and translate that into action on the ground so people know what to do and they have enough warning to evacuate if they need to,” she said.

Another step could be building structures that can store water temporarily when there is heavy rainfall, she added.

Koenig built on her point with the example of Tokyo, where a large underground cavern was built a few years ago to keep the Japanese capital from flooding.

“These are obviously very costly infrastructure projects and not every city and nation will have the funds,” she said.

“But I think individuals, house owners, communities, and policymakers can take small steps and measures with the same outcome.”

She stressed that people in vulnerable regions need to be informed in a timely manner about flooding risks, as well as safe areas on higher ground.

Hospitals and care homes need to have plans and trainings for staff to help people with mobility issues, she added.

“The fact that we have seen, both in the European floods of 2021 as well as with the Spanish floods, that people are being trapped in their cellars and drowning is really dreadful,” said Koenig.

Measures like green roofs and drainage ponds can significantly slow down floodwaters, so these must be pursued on an increased scale, she continued.

“We need to do an awful lot in order to become more resilient with a changing climate. It’s not going to go away,” she said.