Pakistan should brace itself for a sweltering summer
SUMMER is finally here, though seems a long way in coming. The past spring was unusually cold in Pakistan, with winter-like temperatures persisting into March. Despite this, the summer ahead is predicted to be hot. May is already sweltering and now there are warnings of severe heat-waves in June. Both months are usually Pakistan’s hottest time of the year, because they take place during increasing intensity of sunshine but before arrival of monsoon rains in July and August which cools the country.
What gives us special cause for concern is that 2023 marks the end of La Nina. La Nina is a climate phase that generally cools the planet down, but only by taking heat out of the atmosphere and storing it in the ocean, specifically the western Pacific. When La Nina ends, the ocean releases that heat. The La Nina that meteorologists say ended this spring was in place since 2020, an unusually long span. That means that, for three years, the western Pacific kept absorbing the accumulating heat of our warming planet and is now releasing it at once. To make matters worse, meteorologists predict an El Nino will begin later this year and last into 2024. El Nino does the opposite of La Nina, releasing more heat from the western Pacific than usual.
So if the forecast is right, the floodgates are about to be opened on three years’ worth of heat, which are likely to make 2023 and 2024 the hottest years ever experienced. Along with that comes the chance of an extremely hot summer in Pakistan this year and next. Note that it is not just high temperature which poses a direct threat to human beings, whether of the air, ground, or direct solar radiation, but also humidity. People are usually able to cope with severe heat by sweating (in which case, only water shortage puts them in trouble), because evaporating water absorbs a large amount of heat. But evaporation slows if the air is already nearing saturation with water vapor, meaning relative humidity is high. As a result, the combination of heat and humid weather is often extremely dangerous, and Pakistan is a country where such conditions are exceptionally common.
Combined heat and humidity is measured by what is called the wet-bulb temperature, generally taken with a thermometer wrapped in a wet fabric. The closer the wet-bulb thermometer’s reading is to that of a dry thermometer, the more saturated the air is, since the moistened thermometer is cooling down less. Very dangerous wet-bulb temperatures are actually uncommon. Scientists believe a sustained wet-bulb temperature of 35 Celsius (95 Fahrenheit) is the point at which people likely overheat and die. This threshold has been recorded a few times in only a few places in the world, around the Red Sea, Persian Gulf, and Indus Valley in Pakistan. The city of Jacobabad in Sindh commonly experiences the world’s highest wet-bulb temperatures.
The reason why extreme sustained wet-bulb temperatures are thankfully rare is that, in most climates around the world, if the air becomes very hot and very humid, it ascends through the atmosphere and produces clouds, rain, and thunderstorms which cool everything down. In order for heat and humidity to keep rising without dissipating, there must be a source of stability, preventing the atmosphere from mixing vertically. A source able to withstand the push from heat and humidity is what is rare. However, atmospheric stability is abundant in the arid subtropics, where the Persian Gulf, Red Sea, and Indus Valley are located. Plus, the Red Sea and Persian Gulf, being very warm, produce high evaporation that humidifies nearby land. The Indus Valley does the same, with flood irrigation probably contributing (Jacobabad is in a canal zone).
Though humanity is currently well-protected from lethal heat-humidity combos, this unfortunately may change along with the climate. Scientists say the 35°C wet-bulb threshold will become more common around the world, and areas already the hottest are most at risk. As the (dry) mercury keeps rising in Pakistan, we need to watch out for the relative humidity in coming weeks, which could be supercharged by moisture lingering from last year’s mega-flood. Whether now or in 2024, we may experience a wave of heat and humidity worse than we ever had before.
Coping with this will be difficult. The people usually most vulnerable to heat-waves are those living in poverty-ridden, water-stressed environments, which Pakistan is, now more so due to the current economic decline and the likelihood of El Nino weakening monsoon rainfall. To protect communities from the heat, a variety of measures and a comprehensive course of action is needed. But here is one broad piece of advice. In life, every endeavour ends up being guided by a leader. Being a literal hotspot, Jacobabad is well-placed to lead the way nationally and globally in adapting to a hotter and more humid future. The city was built from scratch in colonial times. At the time, it was one of the imperial frontier’s most prosperous settlements. Jacobabad was conceived as a place of opportunity and innovation, where a challenging environment is meant to be mastered, like the Dutch mastered flood management.
With the right mindset, we can make Jacobabad a renowned master in heat management.
—The writer is Director at Pakistan’s People Led Disaster Management.
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