Johannesburg feeling the heat

If global heating continues unabated, because of climate change, the difference between 1.5 °C and 3 °C of average warming above pre-industrial temperatures will not be academic — it will be life-altering, especially for cities in Africa.

A new report by the World Resources Institute (WRI) paints a stark picture of what South Africa’s largest city, Johannesburg, and its peers could endure, and offers urgent warnings, and opportunities, for preparation and adaptation.

Cities around the planet are already feeling the heat. Under the 1.5 °C warming scenario agreed in the Paris Agreement in 2015, many urban centres imagine relatively limited, but still serious stresses in the form of heatwaves, shifting rainfall patterns, rising demand for cooling and public health challenges.

But if warming reaches 3 °C, the world of large cities becomes far more hazardous, unequal and unpredictable.

The WRI study covers nearly a thousand large cities worldwide, those with over 500,000 inhabitants, including dozens in sub-Saharan Africa.

These are the places that already strain under inequality, aging infrastructure and stretched public services.

The forecast of 3 °C warmer makes clear that without fast and ambitious mitigation and adaptation, many will face multiple severe hazards at once.

Johannesburg is among the South African cities that will see notably sharper increases in heat extremes and energy demand. According to the WRI findings:

• Heatwaves will get much longer and more frequent. Under 1.5 °C, the longest annual heatwave in many cities may last about 16 days, on average. But at 3 °C of warming, this figure may jump to roughly 24-25 days, with more cities facing heatwaves of a month or longer each year.
• Cooling demand will escalate. In Johannesburg, in particular, energy demand for cooling at 3 °C is estimated to be about 69% higher than under 1.5 °C.

These figures matter not just statistically but practically. A good number of Johannesburg’s residents live in informal settlements or inadequate housing, about one in five people.

In those areas, electrical supply is often unreliable, as are water systems.

During recent heat waves, power outages and water shortages have exacerbated suffering. When heat becomes extreme and sustained, without reliable infrastructure, it becomes a public health crisis.

Measures to tackle this

To its credit, Johannesburg has begun taking some steps. WRI notes that local government, working with community volunteers, has started mapping fine-scale spatial variations in temperature and heat vulnerability across the city.

These maps help identify the most exposed neighbourhoods, informing where street trees should be planted, where “white” or reflective roofs might help, and where shade structures and passive cooling interventions are most required.

It would be great if such information was to be made public to enable individuals to plan for their own resilience.

Johannesburg is far from alone in being vulnerable to compounding risks.

Across sub-Saharan Africa, WRI’s data show that low-income cities will bear the brunt of heatwaves, increased mosquito-borne disease risk, particularly arboviruses such as dengue, chikungunya, Zika, and rising demand for cooling.

The sub-continent’s cities rank highest globally for the increase in heat wave frequency and peak arbovirus risk under 3 °C.

Some of the findings that cut across many African cities include:

• Cities in low-income countries could see heat waves rise from an average of about 4.7 per year to approximately 6.9 per year under 3 °C.
• Days suitable for arbovirus transmission increase, meaning disease risk becomes more widespread and lasts longer into the year.
• Energy infrastructure must contend with surging demand in the form of doubling of cooling demand in many cities compared to historic averages. For example, the report notes that globally, tens of millions more people would face this doubled cooling need at 3 °C.

The report makes very clear that 3 °C is not inevitable although policy choices, emissions reductions, adaptation investments and collective action can still tilt the balance. The difference between 1.5 °C and 3 °C is enormous in terms of human suffering, economic cost and public health.

The following would need to be done to mitigate and adapt to the heating crisis:

• Limiting warming toward 1.5 °C can prevent many of the worst heat extremes.
• Infrastructure may need to be redesigned since of the existing infrastructure is  designed for lower levels of heat and may be overwhelmed at 3 °C, leading to cascading failures in power, water, transport, and health services.
• Particular attention would need to be given vulnerable populations, those in informal settlements, the elderly, people without reliable access to cooling, water or medical services because they will suffer disproportionately.
• Equality in adaptation must be central.

Urgent priorities needed

To avoid the worst, every level of government has a role. For Johannesburg and other South African cities, here are some of the urgent priorities:

1. Data-driven planning. The mapping of heat vulnerability already underway in Johannesburg should be expanded. Disaggregated data, by neighbourhood, by socio‐economic status, by service access, can let authorities target cooling measures where they will do the most good.
2. Passive and nature-based cooling. Tree planting, designing public spaces to allow airflow and preserving green space are cost-effective that can be undertaken. Low‐carbon ways to reduce heat exposure, especially for those who cannot afford or rely on mechanical air conditioning is another way.
3. Reliable utility services. Water supply and power must be reliable even, especially under extreme conditions. Rolling blackouts, water shortages, failures in sanitation worsen heat’s risk to health.
4. Health systems readiness. Increased surveillance, mosquito control, public awareness, early warning systems for heat waves, cooling centres for vulnerable people.
5. Climate mitigation aligned with national and international goals. South Africa must continue reducing greenhouse gas emissions, invest in renewable energy, electrification and encourage resilient building design.
6. Funding and collaboration. Adaptation finance is currently far below what is needed globally, something that mostly affects especially for low-income communities. International funds, national budgets and private investment will all have to increase. Partnerships between city government, civil society, academia and communities are essential.

Johannesburg, like many cities across the developing world, is caught in a precarious space: already exposed to heat, inequality, resource constraints and infrastructural limitations.

The WRI findings make it clear that the path we choose toward stronger emissions cuts and serious adaptation, or toward business-as-usual makes a profound difference.

At 1.5 °C, cities are challenged; at 3 °C, many will be overwhelmed.

For the residents of Johannesburg, for those living in informal settlements, for future generations, the message is urgent: ambitious action now can still make immense difference.

And in the face of warming, what we build and prepare today will determine how well we survive and thrive tomorrow.

• Dr. Enock Sithole is the executive director of the South Africa-based Institute for Climate Change Communication.