Climate change likely intensified Pakistan floods, study finds

It says country needs to adapt to a future with more periods of extreme rain, build resilience

Climate change likely increased the intense rainfall that flooded large parts of Pakistan in recent weeks, and the nation needs to adapt to a future with more periods of extreme rain, an analysis by an international team of scientists says.

The study by the World Weather Attribution (WWA) initiative, which investigates to what extent climate change has played a role in a major weather event, found that extreme rainfall in the Pakistan region increased 50 per cent to 75 per cent in recent decades.

"Our evidence suggests that climate change played an important role in the event, although our analysis doesn't allow us to quantify how big the role was," Dr Friederike Otto, WWA co-founder and senior lecturer at the Grantham Institute for Climate Change and the Environment in London, said in a statement.

She said what occurred in Pakistan was exactly what climate projections have been predicting for years.

"The real lesson here is that this (extreme rainfall) will become more likely and probably a lot more likely. So being more resilient to these kinds of events is a very high priority," she told a media briefing.

Pakistan received more than three times its usual rainfall in August, making it the wettest August since 1961. The southern provinces of Sindh and Balochistan recorded their wettest August, receiving seven and eight times their usual monthly totals, respectively.

More than 33 million people were affected by the rain and floods, which destroyed 1.7 million homes and killed around 1,500 people.

WWA's rapid analysis of the disaster involved more than two dozen scientists. They analysed weather data and simulations from 31 computer climate models to compare the climate today, after about 1.2 deg C of global warming since the late 1800s, with past climate conditions, using peer-reviewed methods.

The researchers focused on the 60-day period of heaviest rainfall over the Indus River basin between June and September, and the five-day period of heaviest rainfall in Sindh and Balochistan.

Modern climate models cannot fully simulate monsoon rainfall because the region is at the western edge of the monsoon belt and its rainfall pattern is extremely variable from year to year. This meant there were large uncertainties in climate modelling of the 60-day rainfall period in the Indus basin.

Consequently, the scientists could not quantify the influence of climate change as accurately as has been possible in other studies of extreme weather events.

The results were clearer for the five-day total rainfall. Some computer models suggest that climate change raised rainfall in Sindh and Balochistan by up to 50 per cent.

And this tallies with recent United Nations projections of more intense rain in the region and with weather records showing that these episodes have risen 75 per cent in the past few decades.

Other factors also worsened the floods.

Extremely hot summer temperatures sped up the melting of 7,000 glaciers that feed the Indus River, while the unusually hot spring and summer enhanced storm systems from the Arabian Sea.

In addition, a La Nina event caused warmer ocean waters to pile up in the western Pacific and around South-east Asia, enhancing the monsoon in South Asia.

Pakistan's 220 million people remain extremely vulnerable to weather-related disasters, especially floods. Many of them live near flood plains.

Poverty also limits access to funds to build stronger houses and flood defences, and information on steps to reduce risks. Better early warning systems and river management are life-saving steps.

The researchers said rebuilding provides an opportunity to strengthen resilience.

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A version of this article appeared in the print edition of The Straits Times on September 16, 2022, with the headline Climate change likely intensified Pakistan floods, study finds. Subscribe