Climate change fueled deadly rainstorms in Iberia, Morocco

Human-driven climate change intensified torrential downpours that killed dozens and forced thousands of people from their homes across Spain, Portugal and Morocco earlier this year, a network of climate scientists said Thursday.

Precipitation during the region's wettest days now entail around one-third more rainfall compared with the pre-industrial climate, which was 1.3C cooler, according to a report by the World Weather Attribution (WWA), whose scientists study the link between extreme weather events and climate change.

Nine storms unleashed torrential rain and hurricane-force winds across the three countries from 16 January to 17 February, killing more than 50 people and forcing over 200,000 to flee their homes, mostly in Morocco.

Grazalema, one of the hardest-hit municipalities in southern Spain, saw more than a full year's expected rainfall in just a few days, according to the WWA.

Videos on social media showed residents breaking through the walls of their homes to drain water and prevent further flooding damage.

The volume of rainfall in places like Grazalema is "staggering", said David Garcia-Garcia, a climate scientist at the University of Alicante and study co-author, calling it a "massive shock" to infrastructure and soil.

The WWA estimates that rainfall intensity is now about 11 percent higher in northern Portugal and northwestern Spain than in pre-industrial times.

The researchers were unable to quantify the exact impact of climate change on rainfall in southern Iberia and northern Morocco, as the available data show regional variations.

"This is exactly what climate change looks like: weather patterns that used to be more manageable are now turning into more dangerous disasters," said Friederike Otto, a climate scientist at Imperial College London who also worked on the study.

A "blocked" high-pressure system over Scandinavia and Greenland channeled "storm after storm" towards western Europe, resulting in wetter-than-usual conditions, according to the study.

Abnormally warm Atlantic waters west of the Iberian Peninsula "supercharged" the storms with moisture, it added.

The WWA is a pioneer in attribution science, which uses peer-reviewed methods to quickly assess the possible influence of climate change on extreme weather events.

This allows a comparison of a drought or flood today against simulations that consider the climate before the industrial revolution of the 1800s and the mass fuel burning that came with it.

The study looked at weather data -- in this case the most extreme one-day rainfall events in the three nations -- and extrapolated trends back to the pre-industrial era to see how this type of event has changed over time.