With rivers bursting their banks, flash floods and glaciers calving, Pakistan is experiencing the worst flooding of this century. At least a third of the country is under water. Scientists say several factors have contributed to the extreme event, which has displaced some 33 million people and killed more than 1,200.
The researchers say the catastrophe probably started with the exaggerated heat waves. In April and May, temperatures exceeded 40°C for extended periods in many places. On a sweltering day in May, the city of Jacobabad exceeded 51 °C.
“These were not normal heat waves, they were the worst in the world. We had the hottest place on Earth in Pakistan,” says Malik Amin Aslam, the country’s former climate change minister, who is based in Islamabad.
Warmer air can hold more moisture. So meteorologists warned earlier this year that extreme temperatures would likely result in “above normal” levels of rainfall during the country’s monsoon season, from July to September, says Zia Hashmi, a water resources engineer at the Center for Global Change Impact Studies in Islamabad.
melting of glaciers
The intense heat has also melted glaciers in mountainous regions to the north, increasing the amount of water flowing into tributaries that eventually reach the Indus River, says Athar Hussain, a climate scientist at COMSATS University of Islamabad. The Indus is Pakistan’s largest river and runs the length of the country from north to south, feeding towns, cities and vast tracts of agricultural land along the way.
It’s unclear exactly how much excess glacial melt has flowed into rivers this year, but Hashmi visited some high-altitude glacial regions in July and noted high flows and cloudy water in the Hunza River, which empties into the Indus. He says the mud suggests there has been rapid melting, because fast-moving water picks up sediment as it moves downstream.
The heat waves also coincided with another extraordinary event: a depression, or intensely low air pressure system, in the Arabian Sea, which brought heavy rain to Pakistan’s coastal provinces as early as June. “Rarely do we have large-scale depression systems that get there,” says Hussain.
These unusual features were compounded by the early arrival of the monsoon on June 30, which “was generally wetter over a larger region for a very long period of time,” says Andrew King, a climate scientist at the University of Melbourne, Australia. .
The effect is that Pakistan has received nearly twice its average annual rainfall. The southern provinces of Sindh and Baluchistan have received more than five times that average. “The flood is over,” says Hashmi.
Once on land, much of that water has nowhere to go. More than 1.2 million houses, 5,000 kilometers of roads and 240 bridges have been destroyed. In Sindh, an elongated lake, tens of kilometers wide, has formed, and more water will continue to pour into it, says Aslam. “The worst is not over.”
Other factors
Some weather agencies have also forecast that the ongoing La Niña weather event, a phenomenon usually associated with stronger monsoon conditions in India and Pakistan, will continue through the end of the year, King says. “It’s not a super strong link, but it’s probably playing a role in enhancing precipitation.”
Human-induced global warming could also be intensifying downpours. Climate models suggest that a warmer world will contribute to more frequent and intense precipitation, says Hussain. Between 1952 and 2009, temperatures in Pakistan increased by 0.3°C per decade, more than the global average.
Researchers and public officials also say other factors have likely added to the devastation, including an ineffective early warning system for floods, poor disaster management, political instability and unregulated urban development.
Also implicated are the lack of drainage and storage infrastructure, as well as the large number of people living in floodplains. “These are governance issues, but they are miniscule relative to the level of tragedy we are seeing,” Aslam explained.
