Can the hottest city in the US be saved by cooling technologies?

Climate crisis and rapid urban expansion have turned Phoenix, Arizona, into a heat island with dwindling water supplies and inadequate shade

People watch the sunset at a park in Phoenix, Arizona. AP

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Phoenix, Arizona, a city in the south-western US known for its scorching temperatures, is experiencing such rapid warming that its long-term sustainability is being called into question.

The surge in the city's population – now topping 1.6 million, making it the fifth largest in the country – has prompted significant expansion in infrastructure, leaving few green spaces.

This expansion has given rise to heat islands, which are urban areas that become dangerously hot as they absorb and release the sun's heat more effectively than natural landscapes.

Over the summer, temperatures soared to an astonishing 47°C, and the city shattered its previous record for the most consecutive days with temperatures above 43.3°C.

The climate crisis and decades of rapid urban expansion have scorched this desert city, which is also facing dwindling water supplies.

When questioned about how they cope with the hot summers in the Valley of the Sun, many residents told The National: “We stay indoors.”

In response to escalating temperatures, Phoenix in 2021 launched the country’s first dedicated unit to combat the increasing urban heat hazard.

Phoenix has an ambitious vision to emerge as the most environmentally sustainable desert city worldwide. Over the years, efforts have been focused on discovering solutions for alleviating the heat.

Among the simplest methods identified is the strategic planting of trees to shade 25 per cent of the city by 2030.

Phoenix is about one million trees away from achieving a Tree Equity Score of 100.

Tree Equity is dedicated to ensuring people benefit from trees, from the shade they provide to their air-filtering processes.

“If we can figure out the best way to plant and care for trees in desert conditions amid a changing climate in Phoenix, we can create a viable model for other hot cities,” said Jake Simon, senior manage of Urban Forestry Southwest at American Forests.

“Our goal is to preserve and grow urban forests in the most heat-vulnerable neighbourhoods by creating ‘cool corridors’ for walking and well-canopied city parks that enhance recreational opportunities and mitigate heat islands.”

Mr Simon told The National that extreme heat is a problem for most metropolitan areas in the US.

“This is an urgent, life-and-death crisis for many people living in America’s fifth largest city,” he added.

In 2021, Phoenix hired David Hondula as its first director of the Office of Heat Response and Mitigation, the first local government-funded heat team in North America.

Mr Hondula oversees Phoenix's immediate actions and long-term plans aimed at improving comfort and cooling measures.

He told The National they are using a “very broad approach” to mitigate heat by installing cool and green roofs, electrifying buildings and ensuring housing infrastructure has cooling systems.

They are also actively engaged in transitioning the city's vehicle fleet to alternative fuels.

Phoenix’s proactive approach in addressing excessive heat has also led to the “cool pavement” initiative aimed at enabling surfaces to deflect solar radiation rather than absorbing it as heat.

Characterised by extensive pavement and buildings, Phoenix is classified as an “urban heat island”, with the abundant concrete and asphalt surfaces absorbing and trapping substantial heat.

This results in elevated daytime temperatures and reduced night-time cooling and is where the concept of cool pavement becomes significant.

Cool pavement is a water-based asphalt treatment that is applied on top of the existing asphalt. It produces an average surface temperature that was up to 12°C cooler than traditional asphalt at noon and in the afternoons.

By introducing cooling technologies as well as planting trees, Mr Hondula said, the city in the future could be significantly cooler than it is now.