Climate change-induced sea-level rise and heavy downpour behind this unprecendented calamity, say experts
Heavy downpour resulting in floods in the second week of August have wreaked havoc in Pakistan, especially its Sindh and Balochistan provinces.
In Sindh, more than 1.6 million people have been affected (updated August 23, 2022), according to the Provincial Disaster Management Authority (PDMA). In the about 1,000-kilometre long coastal belt of Thatta district, Sindh, around 15,500 people lost everything and were displaced.
I have no hope of returning to my ancestral village, said Hussain Mallah, 65, standing with his wife and five children on a road surrounded by water, waiting to be rescued.
Floods from the sea washed away their home in Lakho Mallah near Keti Bandar, a town in Thatta.
“I have lost my entire life’s savings — gathered after years of sweat and blood — meant to get my children educated in the city,” Mallah said, pointing to his home submerged in muddy water.
“This is the first time that heavy rainfall has compelled us to displace, washed away our houses,” Mallah said, tears filling his eyes.
Extreme weather events driven by climate change are the reason behind the recent floods across Pakistan, said Waqar Ahmed, environment professor, Karachi University. “Some floods come from inland areas due to heavy downpours but others occur from the seaside due to sea-level rise, leading to destruction in coastal areas.
This time we are facing both types of floods. Mostly coastal areas are facing heavy floods due to high tides in the sea. This is connected with climate change because the global temperature is increasing day by day.
The floods are caused by two main reasons: Sea-level rise due to melting of glaciers and Arctic sea ice, which expand the surface of seawater, and rising ocean temperatures which cause cyclones and heavy rainfall, the expert added.
A significant sea-level rise of 1 millimetre along coastal Sindh observed over hundreds of years has resulted in seawater intrusion inland, according to a research paper by Falak Shad Memon, assistant professor at the Institute of Business Management. Intruding sea water has a strong impact on communities in coastal areas, where economic activities are concentrated.
Recurrent cyclones both in increased frequency and intensity in the Arabian Sea over the past 50 years due to climate change have economic repercussions in urban communities like Karachi, Badin and Thatta, experts have pointed out.
The main reasons behind sea intrusion are thermal expansion, freshwater inputs, physical forces, monsoon variability and ocean current variation, noted Memon in his report.
When seawater becomes warmer, the top layers of the ocean release some heat to the atmosphere but the layers below retain this heat for a longer duration and in larger quantities, he observed. This leads to the temperature rise in seawater on a longer run, in a process called thermal expansion.
Freshwater input from melting glacial layers, ice-sheets and sea ice cause sea-level rise, according to the study. Hydrogen cycle due to heating up of oceans and surfaces also increases the freshwater input.
Tectonic activities like extraction for oil, gas and water create the scenario of subsidence and lifting also affect sea-level without changing the volume of ocean water, Memon wrote in the report.
Climate change has a direct link with monsoon rainfall variability, noted the scholar. Pakistan has witnessed frequent excessive monsoon rainfall and flooding in recent years.
Regional ocean currents, which moves a large amount of water from one location to the other, does not change the volume but affects the sea-level at a different location.
In Sindh, as many as 0.5 million people in the province are homeless, standing crops over 1.4 million acres have been destroyed, more than 386,039 houses were submerged and 231 people (updated August 23, 2022) lost their lives due to the recent floods.
Chief Minister of Sindh Sayed Murad Ali Shah has declared 22 districts of the province as ‘Calamity Affected Areas’.
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