Climate Change Made Valencia’s 2024 Flood Far Worse, Detailed Study Finds

On October 29, 2024, parts of Valencia experienced rainfall so extreme that it exceeded what the region usually receives in an entire year.

At the Turís weather station, 771.8 millimeters of rain fell in only 16 hours. Even more striking, 184.6 millimeters fell in a single hour. That became a national rainfall record for Spain.

The storm triggered devastating flash floods south of the Valencia metropolitan area. Eleven tornadoes were reported. Large hail fell in some locations. Roads turned into rivers, neighborhoods were submerged, and rescue operations continued for days.

At least 230 people died. Economic losses ran into billions of euros.

For many residents, the question was simple and heavy at the same time. Was this just extreme weather, or was climate change involved?

A new study published in Nature Communications offers a detailed scientific answer.

Replaying the Storm in Two Different Worlds

Extreme storms are complicated. They form because of shifting winds, unstable air, moisture, and local geography. So linking a single event to climate change is not straightforward.

To understand what happened, researchers used the Weather Research and Forecasting model, a powerful computer model widely used to simulate severe weather.

They recreated the Valencia storm twice.

First, they simulated it under today’s climate conditions, including current greenhouse gas levels and warmer sea surface temperatures.

Then they ran the same storm again, but under pre-industrial conditions, meaning before large-scale fossil fuel emissions changed the climate.

This method is called pseudo-global warming. In simple terms, scientists keep the same storm structure but change the background temperature and moisture conditions. It is like asking, “If this exact storm happened in a cooler world, how different would it be?”

That comparison allows researchers to isolate the effect of modern warming.

A Small Temperature Rise With Big Consequences

The difference between the two climate setups was about 1.08 degrees Celsius.

At first glance, that might not seem dramatic. But physics tells us something important. Warmer air can hold more water vapor. Roughly speaking, for every degree Celsius of warming, the atmosphere can hold about 7 percent more moisture.

More moisture means more fuel for heavy rain.

In the simulations, present-day conditions produced a 20 percent per degree Celsius increase in one-hour rainfall intensity. That increase was stronger than the basic physical expectation.

In other words, the rainfall intensified faster than what simple moisture scaling alone would predict.

The warmer Mediterranean Sea played a major role. Higher sea surface temperatures increased evaporation, loading the lower atmosphere with additional water vapor. That extra moisture fed the storm.

Stronger Updrafts Inside the Storm

Storms like the Valencia event depend on rising air currents, known as convection.

One measure scientists use is Convective Available Potential Energy, or CAPE. Higher CAPE means air parcels can rise more forcefully, forming taller and more intense clouds.

Under modern climate conditions, CAPE increased.

Vertical wind speeds inside the storm rose by nearly 12 percent. At the same time, latent heat release increased by almost 30 percent. Latent heat is the energy released when water vapor condenses into liquid droplets. This release of energy strengthens upward motion even further.

So the storm entered a kind of feedback cycle. Warmer air held more moisture. That moisture condensed and released heat. The released heat strengthened updrafts. Stronger updrafts produced heavier rainfall.

The simulations also showed about a 9 percent increase in graupel, soft ice pellets that form inside strong storm clouds. These particles influence how precipitation develops and falls. Even subtle changes in cloud microphysics can alter rainfall intensity.

Cloud layers extended higher into the atmosphere as well, supporting more efficient warm-rain processes. That means clouds converted water vapor into heavy rain more effectively.

All of these processes worked together.

A 55 Percent Expansion of Extreme Rainfall Area

It was not just the intensity that changed.

The area experiencing extreme rainfall expanded by 55.4 percent in the present-day simulation compared with the pre-industrial version.

That is a large spatial increase.

Six-hour rainfall rates were about 21 percent higher. Within the Júcar River basin, total rainfall volume rose by 19 percent.

When heavy rain falls over a larger area, flood risk increases sharply. Water from multiple tributaries combines, rivers rise faster, and urban drainage systems are overwhelmed.

Flash floods are especially sensitive to short bursts of intense rainfall. If rain falls faster than soil and infrastructure can absorb it, runoff accumulates rapidly.

By increasing both intensity and spatial coverage, modern warming amplified the hydrological impact.

What Did Not Change

Interestingly, not everything was different.

Large-scale wind patterns and overall atmospheric circulation looked similar in both simulations. That suggests climate change did not fundamentally alter the broad weather setup for this event.

Instead, the main difference came from thermodynamics, meaning temperature and moisture.

This distinction matters. Even without changing the wind patterns that trigger storms, a warmer atmosphere can still make them much wetter.

That is an important takeaway.

Matching the Real-World Observations

To ensure the model was realistic, researchers compared their simulation to observations from 256 weather stations across the region.

They also used atmospheric reanalysis data from ERA5, which combines observations and models to reconstruct past weather patterns.

The simulated storm closely matched the timing, structure, and rainfall distribution of the real event.

Because of this agreement, scientists gained confidence that the differences between the modern and pre-industrial runs reflected genuine climate effects, not model errors.

Why Hourly Rainfall Matters

Many climate studies focus on daily rainfall totals. However, flash floods often depend on rainfall that falls within a few hours.

The Valencia disaster was driven by extraordinary one-hour and six-hour rainfall amounts.

Short-duration rainfall extremes are closely linked to convective processes inside storm clouds. These processes can respond strongly to warming.

By analyzing rainfall at sub-daily timescales, the study captured details that would be hidden in daily averages.

That choice revealed that warming intensified rainfall beyond the standard moisture increase rule.

The Mediterranean as a Climate Hotspot

The Western Mediterranean region is already known for intense rainfall events.

According to assessments by the IPCC, heavy precipitation extremes are expected to intensify in many parts of southern Europe, even if total rainfall days decrease.

Warmer Mediterranean waters enhance evaporation. When the right atmospheric setup occurs, that stored moisture can be released in powerful downpours.

The Valencia event shows that these projected changes are not just theoretical. They are already observable under current climate conditions.

Understanding the Study’s Limits

The researchers are careful about what their analysis does and does not claim.

The pseudo-global warming approach keeps the storm’s large-scale pattern fixed. It does not determine whether climate change made the storm more likely to occur in the first place.

Instead, it measures how much stronger the storm became because of warmer background conditions.

The pre-industrial climate was constructed using averages from 15 models in the CMIP6 archive. All models have uncertainties, particularly regarding small-scale cloud processes.

Even so, multiple simulations with different initial conditions produced consistent results. The signal of intensification remained clear.

Broader Implications for Flood Risk

Flash floods are among the deadliest natural hazards in Europe.

Urban expansion increases exposure. Impermeable surfaces such as asphalt and concrete reduce water absorption, increasing runoff speed.

When heavier rain falls over a wider area, the risk multiplies.

The Valencia flood illustrates how even modest global temperature increases can produce disproportionate changes in extreme rainfall.

For infrastructure planning, this means historical rainfall records may no longer fully represent future risk. Drainage systems, flood defenses, and emergency planning may need to account for faster and more spatially extensive downpours.

A Physical Chain of Cause and Effect

What makes this study notable is its focus on physical mechanisms.

It documents how warmer sea surfaces increased evaporation. It shows how higher moisture raised atmospheric instability. It quantifies how latent heat release strengthened updrafts. It measures how rainfall intensity and area expanded.

Each link in the chain is supported by model output and observation comparisons.

The storm itself was still shaped by natural weather variability. But when modern warming was removed from the simulation, the storm weakened.

Rainfall rates declined. The extreme rainfall footprint shrank. Total water volume decreased.

The disaster did not vanish, yet its severity was reduced.

That difference reflects the measurable influence of human-driven warming on an extreme weather event.

Looking Forward

The study does not argue that climate change single-handedly caused the Valencia flood. Extreme weather events are complex and multi-factorial.

However, the findings show that warming amplified the intensity and spatial extent of the rainfall.

As global temperatures continue to rise, similar Mediterranean storms may produce even heavier rainfall.

The Valencia flood of 2024 now serves as a detailed case study. It demonstrates how a warmer atmosphere can intensify storms not only in theory, but in measurable, physical terms.

For communities across southern Europe, that understanding is essential.

The research was published in Nature Communications on February 17, 2026.