ASMEEN KHAN AND SIBONGILE MAZIBUKO: Heat mapping plan aims to help keep citizens cool

Picture a summer’s day in Alexandra township, in the north of Johannesburg. Tin roofs swelter in the sun. Heat rises between densely packed buildings and dust swirls on parched, unpaved streets. Trees are few and far between. Even for early risers heading to work, school and daily errands, it’s hard to get respite from the sun’s rays.

Now imagine the scene in the leafy suburbs and cosmopolitan business hub of nearby Sandton. The branches of a jacaranda tree cast generous shade. Breezes circulate along tree-lined boulevards and between widely spaced buildings whose interiors are cool and inviting.

These neighbourhoods are a short drive apart, yet on a hot day they feel like different worlds. The temperature differences, which are partly rooted in apartheid spatial planning, might be dismissed by some as an issue of mere “comfort”.

Unfortunately, average air temperatures have already increased by at least 1°C globally because of climate change, and by even more in fast-growing cities where man-made materials absorb and radiate energy from the sun. The result is that heat in cities is no longer a matter of comfort but of survival.

A recent study by the National Treasury Cities Support Programme and the World Bank found that in Johannesburg and Ekurhuleni, most neighbourhoods experienced about 20 hot nights a year in recent decades. But Soweto, Alexandra and Thembisa experienced night-time temperatures that were 3°C higher than the city average. By 2050 these neighbourhoods could see as many as 120 hot nights per year. 

Temperature increases not only have an effect on the environment but have measurable effects on human health. High night-time temperatures are associated with increased mortality from respiratory, cardiovascular and renal conditions because the human body maintains an internal temperature of 37°C partly through rest and cooling at night. 

Across SA the story in our cities is similar: the climate is getting hotter, and it is poor and marginalised neighbourhoods that suffer most. Historical inequalities such as the legacies of the apartheid era, which left some neighbourhoods lush and green but others dense and bereft of trees — contribute to these temperature differences. These disparities mean climate change is hitting the vulnerable hardest. 

Fortunately, South Africans are mobilising to find solutions to extreme heat. Residents of Tshwane, Cape Town and Buffalo City have taken to the streets in an innovative “citizen science” heat mapping initiative.

The citizen scientists fix heat sensors onto cars and drive pre-planned routes across their cities, collecting thousands of temperature measurements as they go. The resulting heat maps will provide crucial information for municipal authorities, which have partnered in this initiative with the Treasury’s Cities Support Programme, the World Bank’s Global Facility for Disaster Reduction and Recovery, and the Swiss Secretariat for Economic Affairs, to use when developing heat action plans.

Heat action plans save lives. After Ahmadabad, one of India’s hottest cities, experienced 800 excess deaths in one week during the 2010 heatwave, its leaders acted. City authorities now issue yellow, orange or red alerts when temperatures surpass thresholds known to predict illness. The alerts are widely disseminated on television, radio and via social media and are coupled with measures to prevent harm from extreme temperatures in homes, hospitals, streets and workplaces.

Researchers at the University of Washington estimate that the alerts — and accompanying actions such as equipping ambulances with more ice packs, mandating shade and water breaks at building sites and planting fast-growing urban forests — now avert 1,100 hot-season deaths per year.

Encouragingly, cities across SA are developing measures to protect their residents, economies and infrastructure from the ill effects of extreme heat. An example is Cape Town, where the city’s own recently approved heat action plan sets out clear measures to help vulnerable citizens stay safe in hot weather.

Will SA cities continue to swelter in heatwaves? Global climate change means the answer is unfortunately yes. But heatwaves need not be health crises. By understanding the hidden hazard of extreme heat and implementing responses that put the most vulnerable citizens first, SA’s cities can lead the world on climate change adaptation.

By setting aside their time and volunteering in the heat mapping campaign, SA communities are demonstrating their dedication to creating a better life for future generations on a liveable planet.

• Khan is acting SA country director at the World Bank, and Mazibuko programme manager of the National Treasury’s Cities Support Programme.