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[ISLAMABAD] Rising average temperatures and increase in the number of heat wave events will adversely impact human health and crop yields across Pakistan, say researchers who participated in what they described as the first country-specific heat wave trajectory study. 
 
A team of international researchers, who published the results of the study this month (June) in Atmospheric Research, found that Pakistan was hit by 126 heat waves of varying durations over the 1997—2015 period for an average of seven heat waves per year. 

“Extreme weather events will become more frequent, prolonged and intense”

Wajid Nasim, COMSATS Institute of Information Technology

“Having studied the past upward trends of the heat waves and annual temperatures, we concluded that extreme weather events will become more frequent, prolonged and intense,” Wajid Nasim, lead author and associate professor at the department of environmental sciences, COMSATS Institute of Information Technology, tells SciDev.Net.
 
According to Nasim, the study suggests a 75 per cent increase in heat waves by 2030, a 189 per cent by 2060 and a 277 per cent increase by 2090. “This means the country will experience around 12 heat wave events annually by 2030, 20 such events by 2060 and 26 events by 2090.”
 
Nasim’s team relied on historical datasets of heat wave events and daily maximum temperature variations for the study period drawn from the Pakistan Meteorological Department (PMD) through 29 weather stations in the provinces of Punjab, Sindh and Baluchistan.
 
Heat waves are defined as spikes in temperature beyond 45 degrees Celsius in the plains areas and beyond 40 degrees Celsius in the hilly areas. Average maximum temperatures of 42 degrees Celsius with a 5—6 degrees rise lasting eight days or more are also considered as heat waves.
 
Researchers warn in the study that the soaring heat wave trends may exacerbate impacts on human health, crop yields, push up irrigation needs of summer crops, increase droughts and contribute to groundwater depletion in the country.
 
Rising average temperatures during pre-monsoon months (March, April and May), during which most of the heat waves are expected to occur in the coming decades, could lead to early maturity of winter crops including wheat, maize, potato and lentils, and consequent decline in crop yields.
 
Higher temperatures during these months will also increase irrigation needs for various summer crops, including rice, cotton, sugarcane and mango, particularly because of rapid decline in soil moisture and higher levels of surface water evaporation.
 
Ghulam Rasul, director-general of the PMD, says the findings demand an adaptation response from the government with focus on early heat wave warning systems.
 
Rasul observes that March and April used to be cool to mild months, which helped the soil to retain moisture.

“It is startling to observe March becoming warmer every year. The high temperatures we used to record in the peak summer months (June and July) about eight years ago are now being recorded in March,” he tells SciDev.Net. Heat waves can result in mass deaths. In June 2015, more than 1,200 people died of heat-related illnesses in the southern port city of Karachi when temperatures soared to 49 degrees Celsius.  In May 2010, the city of Mohenjo Daro, also in southern Pakistan recorded 53.5 degrees Celsius, the highest ever recorded in Asia.
 
Nasim says various adaptation measures such as capacity building of individuals and communities to respond to heat stress during heat waves and raising heat-health awareness campaigns are imperative.  
 
This piece was produced by SciDev.Net’s Asia & Pacific desk.