Human-caused climate change likely doubled the likelihood of the 1-in-100-year floods that have devastated Pakistan this year, per CNN. That's according to researchers in a fast-growing field known as attribution science, which seeks to determine how climate change contributes to extreme weather events, per the New York Times. Such events have occurred throughout human history but are becoming more intense and frequent as more greenhouse gases land in the atmosphere. Natural variability in Pakistan's monsoon season meant researchers had difficulty in determining the exact role climate change played in the floods, which killed 1,500 people and covered 10% of the country in water. Still, "the fingerprints of global warming are evident," says lead study author Friederike Otto, a climate scientist at Imperial College London, per the BBC.
Some computer models based on the maximum five-day rainfall each year over the southern provinces of Sindh and Baluchistan indicated climate change may have increased the intensity of rainfall by up to 50%, per CNN. The provinces each experienced the wettest August on record, with "about seven to eight times as much rain as usual," per the Guardian. "We can say with high confidence that [the rainfall] would have been less likely to occur without climate change," says Otto, whose research was published Thursday by the World Weather Attribution initiative. A WWA study published earlier this year found climate change made pre-monsoonal heat waves in Pakistan some 30 times more likely.
Researchers also blamed "existing vulnerabilities" for the flooding and its effects. They noted changes to the environment, including the cutting down of forests, likely had an impact on natural flood patterns, while poor infrastructure put people at risk. But "a lot of these vulnerabilities are from colonialism," Otto says, referring to the fact that Pakistan's territory includes part of the former British colony of India. "So there is a ... very huge responsibility for the Global North to finally do something real." "The kind of assistance that's coming in right now is a pittance," adds study author Ayesha Siddiqi, per CNN. The United Nations estimates the cost of recovery at $30 billion—or the same value as Pakistan's annual exports. (Read more climate change stories.)