The catastrophic flooding that has killed thousands of people in Libya was made up to 50 times more likely because of climate change, with 50% more rain, scientists have calculated.
Around 4,000 people have been confirmed dead so far in Derna after torrential downpours led to two dams bursting and flooding the city, with 10,000 more still missing.
In combination with Libya’s armed conflict, the city having been built on floodplains, and poor maintenance of the dam, climate change has exacerbated the disaster by making such an extreme event happen more frequently.
Named Storm Daniel, it has been the deadliest and costliest storm ever recorded in the Mediterranean, having swept over Greece, Bulgaria and Turkey and caused flooding and death in those countries too.
The global average temperature has risen by around 1.2C since the late 1800s due to human beings emitting greenhouse gases and, because warmer air holds more water, rainstorms are more intense when clouds do burst.
Despite the influence of climate change, the extreme rain in Libya was still a once-in-300-years to once-in-600-years event, World Weather Attribution said.
The group of scientists from Greece, the US, the Netherlands, Germany and the UK used peer-reviewed methods to rapidly assess the role of climate change in Libya’s disaster, as well as the flooding in the Eastern Mediterranean, which spanned a 10-day period.
They estimate it made the heavy rain up to 10 times more likely in Greece, Bulgaria and Turkey, and 40% more intense.
Spain also saw downpours but only within 24 hours, making it much more difficult to analyse, the scientists said, although they estimate this is now a once-in-40-years event.
Flooding killed four people in Bulgaria, five in Spain, seven in Turkey and 17 in Greece.
The scientists said there are “mathematical uncertainties” in their estimates because the rain happened over specific areas and because, unlike heatwaves, extremity of heavy rain does not necessarily correspond with higher temperatures.
However they said there was no evidence of any factors making such events less likely and, because weather stations are recording more intense rainfall as atmospheric temperatures rise, it must be influenced by climate change.
Dr Kostas Lagouvardos, of the National Observatory of Athens, Greece, said extreme rainfall is now a “worldwide phenomenon” that is becoming increasingly dangerous as a lot of the current infrastructure was built to withstand conditions that existed decades ago.
He said Storm Daniel was probably not a “medicane” – a term used by scientists to refer to a hurricane-like storm over the Mediterranean.
It formed in a low-pressure system that became “stagnant”, exacerbating the destruction caused by floods, while northern Europe saw clear, hot and dry conditions with six days above 30C in the UK.
In central Greece, weather forecasts allowed 5,000 people to escape the worst of the flooding, preventing more lives being lost, said Maja Vahlberg, of the Red Cross Red Crescent Climate Centre.
She added: “In Libya, there was also a forecast with a three-day lead time on the track of Storm Daniel but the impact of that potential rainfall on infrastructure and people was not clearly understood in advance.
“Further, it is not clear to what extent forecasts and warnings were communicated and received by the general public or relevant emergency responders in conjunction with improved emergency management capacity.”
The Mediterranean is considered a climate “hotspot” that is warming 20% faster than the global average.
Drought is becoming more frequent and intense and, while the total amount of rain has not changed, it is falling in more intense bursts, increasing the risk of flooding.
Dr Friederike Otto, of Imperial College London, said: “Many of the things you need to do in order to be better able to deal with droughts actually also helps to be better able to deal with floods.
“Deforestation and urbanisation and building on floodplains means that when it’s raining very heavily then water can’t get into the ground but is flooding everything and then immediately going into rivers and into the ocean, which also means then the water is gone and not there to be held in the ground in times of drought.
“So reforestation, renaturalisation of rivers and the desealing of grounds is a really important adaptation measure to adapt to more drought, but also to more floods.”