Cooling the hottest cities needs momentum

A pedestrian walks on a heat-absorbing asphalt road in Bangkok. A typical asphalt road absorbs up to 95% of the sunlight that falls on it. (Photo: Patipat Janthong)

Extreme heat has its moment in the sun. This year’s headlines have been as relentless as the temperatures: “Spain suffers record-breaking heatwave,” “South Asia heatwave devastating,” “Texas breaks heat record,” “Can- Do you still call deadly heat “extreme”? »

This global coverage has drawn attention to a colossal challenge that will only grow in scale and severity. Nowhere are cooling measures more urgent than in our cities, where streets, buildings, industries and vehicles could catastrophically raise temperatures by 4° Celsius by the end of the century, putting people the world’s poorest in danger.

The search for solutions is already underway, but it must be stepped up. At last year’s UN Climate Change Conference, the Cool Coalition, a partnership of 120 organizations led by the UN Environment Program and including RMI, released a comprehensive guide to district cooling sustainable.

And in Davos last month, the Cool Coalition and the Adrienne Arsht-Rockefeller Foundation Resilience Center launched an online heat action platform that makes it easy for policymakers and planners to identify the most relevant to them.

To stay ahead of the problem, city leaders will need to adopt many measures, including smarter urban design. To draw fresh air into a city, city planners and developers can orient streets and building heights to prevailing winds and develop more strategically placed green and blue spaces. They can also create more shaded suburban corridors for pedestrians and cyclists and plan more diverse mixed-use developments that lend themselves to efficient district cooling systems.

Planting more trees in concrete jungles could also make a significant difference. Urban forests and parks can be 7C cooler than treeless neighborhoods, and a tree-lined street can be 3C cooler than a treeless street. Cities from Freetown and Athens to Melbourne and Milan are already reaping the benefits of using urban nature as a cooling mechanism – one that also improves stormwater management, sequesters carbon, increases biodiversity and provides recreation.

Another common sense measure is to resurface our cities so that they reject heat rather than absorb it. The typical asphalt road absorbs up to 95% of the sunlight that falls on it, and concrete roads and sidewalks absorb up to 75%. These hot surfaces disproportionately harm outside workers, those without personal vehicles, and the poor who live in neighborhoods dominated by these materials. By using lighter colored building materials that increase the reflectivity of these surfaces by just 10%, we can reduce their temperatures by up to 5°C, a potentially life-saving difference.

Better buildings are also essential. Cooling a poorly designed building with air conditioning is like running a faucet through a leaky bucket. In contrast, good building design can completely minimize the need for AC power. For example, light-colored reflective “cold roofs” are inexpensive and can reject 90% of the thermal energy that lands on them, making a huge difference even where other measures are not viable, such as in informal housing.

Passive building efficiency measures such as orientation, insulation, reflection, shading and ventilation are not new. But we need to enact more ambitious building codes and performance standards, and invest in the institutional capacity to enforce them.

In addition, alternating current, where it is used, can be made more climate-friendly. As it stands, it is both a key enabler of productivity and a major source of urban heat and emissions. By 2050, air conditioners could consume as much energy as the combined economies of the United States, Germany and Japan consume today. The most common refrigerant they use is nearly 2,000 times more potent than carbon dioxide as a global warming agent. Accordingly, regulators must set standards that exclude the worst-performing units from the market; and the public and private sectors must work together on marketing campaigns, financing solutions and incentives to steer buyers towards climate-friendly products.

City planners and developers should also consider district cooling systems, which serve many buildings with a single cooling installation. Since these systems can offer economies of scale without heating city air as much as individual air conditioning units, they should be the default technology choice in large new commercial and mixed-use developments, townships and the campuses.

Finally, policymakers in some cities should consider various last-resort options to protect the most vulnerable. In India, people joke that the reason Bollywood movies are so long is because the filmmakers want to give people the chance to spend hours in an air-conditioned room. But, as this spring’s devastating heat wave showed, the value of cool space is no longer a joke.

Cities in areas prone to extreme heat will need to invest in a range of common spaces that are accessible to the most vulnerable when heat and humidity exceed survival thresholds. These can be cinemas, shopping malls, schools, places of worship, swimming pools, parks, transit centers or dedicated cooling centers. Emergency power generation, potable water, medical supplies, heat and health education materials, and trained personnel would make these spaces even more useful in an emergency.

Extreme heat is arguably the biggest climate justice issue we face. Of the 1.7 billion city dwellers now exposed to extreme heat, most live in fast-growing cities in poor countries and most lack access to the air-conditioned buildings and cars that people in advanced economies hold acquired. Addressing these inequalities should be a top global priority. The Cool Coalition is kicking off in India, where the government has already developed the world’s first National Cooling Action Plan and where state and city leaders are deeply committed to addressing the threat of extreme heat.

But there is still a lot to do. The launch of the $10 billion (353 billion baht) Global Energy Alliance for People and Planet has shown that the international community is still able to rally behind major efforts to mitigate and adapt to climate change. The deployment of renewable energies and the improvement of access to clean energy remain essential objectives. But building thermal resilience and implementing sustainable cooling solutions have also become pressing priorities. We need to take action now to help our hottest cities cool down.©2022 Syndicate Project