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Published 24 Jun, 2015 06:58am

Heat VS heat index — understanding the Karachi heatwave

The recent heatwave that has swept across the southern parts of Pakistan has already killed hundreds of people in Karachi in a matter of days. The abnormally high death toll has also left many wondering why temperatures like those which are experienced in many parts of Sindh almost every summer have claimed so many lives in the provincial metropolis. Dawn spoke to a couple of climatic experts and asked them to explain this anomaly.

Dr Mohammad Hanif, director, Pakistan Metrological Department

“This was an extreme weather occurrence which could not be predicted because Karachi does not have a history of fatal heatwaves or extreme low pressure phenomena. The impact of the high temperatures may be understood through the concept of the heat index. This index combines temperature, air pressure, humidity and the speed of wind to determine how the rising temperatures would ‘feel like’ to a person in a particular area. While the temperature in Karachi was around 43 degrees Celsius over the last three days, the heat index was around 49 degrees because of low air pressure, low wind speed and very high humidity. In areas such as Turbat, Sibbi and Sukkur, the temperature was even higher at 47 degrees Celsius, but due to a light breeze, low humidity and normal air pressure, the heat index there was at a mere 41 degrees Celsius. We hope that the heat index in Karachi will drop to around 40 degrees Celsius by Wednesday evening”.

Arshad H Abbasi, Water & Renewable Energy adviser, Sustainable Development Policy Institute

“The extreme heat wave in Karachi is an extension of the deadly conditions experienced in parts of India over the last few weeks. This is fallout from climate change caused by human activities. In India too, carbon emissions from massive coal based power plants was one major contributing factor. These plants are using old technology which emits hazardous gasses into the atmosphere. Disturbances in glaciers are also negatively impacting the climate. I have been expressing concern over the military activity in the Siachin Glacier as it is hazardous for the environment of the entire region. Winters are becoming colder and fog is becoming denser while rain is more erratic and heat waves are more intense. The impact of climate change is now clearly visible. However, it is not too late and the political leadership of South Asia must join hands to tackle manmade disasters”.

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