“We are not preparing for extreme heat”: The world’s first Global Chief Heat Officer on what cities must do now

Gavin Allen: As the world’s first Global Heat Officer, your remit is, as the science journal Nature put it, to “keep people cool as the planet boils.” What’s that like?

Lenio Myrivili: It's a crazy title and the remit is insane, but the fact it exists raises awareness that this is not a regional issue any more. From Europe to the Tropics, Global North to Global South, this problem is everywhere. People in cities have to really start preparing for extreme heat, because it's only getting worse.

Gavin Allen: You once warned: "We stand at the precipice of losing our city spaces to the rising heat." Are we closer than ever to that precipice?

Lenio Myrivili: More and more cities are facing dangerous temperatures that will affect people's health and reduce productivity across multiple sectors. They’ll have to shovel out incredible amounts of money to deal with the catastrophic results. In the last decade, the number of city residents facing heat dangerous to their health has tripled: close to one-quarter of the Earth’s population, or 1.7 billion people. Because there is no light at the end of the tunnel, we really have to take seriously the need to prepare, and we're not preparing.

Gavin Allen: Why is this “silent killer” – responsible for almost half a million deaths worldwide each year – not taken more seriously?

Dr. Lenio Myrivili, UN Global Chief Heat Officer

Lenio Myrivili: Because it's not visible. We give a lot of priority in our culture to extreme images: cars floating down the street, or roofs flying off buildings.

Heat lacks these extravagant visuals. There's nothing to see. Instead, it's like a ghost that comes into a city, perniciously looks around and hits the weakest – such as poor people in informal housing with very little infrastructure. Women are particularly vulnerable. When we get pregnant, we're in greater danger. Women look after the home, and cooking means spending longer in a hot environment. Women who work in agriculture, where it can be dangerous to go to the bathroom or even leave an area safely, don't drink as much water and dehydrate faster. Old people and workers are vulnerable as well.

Gavin Allen: You’ve noted that better early warning systems can address these issues?

Lenio Myrivili: Early warning systems are the cheapest, most effective thing a city can do, and they would have an enormous impact in saving lives. The challenge is to reach the target populations. What media do they trust? What language do you use? You have to figure out the best ways to alert people. The Red Cross in Athens, for example, set up a heatwave hotline to answer people's questions. They invited the Red Cross from Australia, which had experience with heat hotlines, to make sure the narratives were as effective as possible.

Gavin Allen: What impact can technologies such as digital twins, thermal mapping, smart infrastructure, and AI have in this battle against urban heat?

Lenio Myrivili: They can have a huge impact, but the basic foundation is social resilience. We have to bring communities together, because that's what saves lives. It used to be that people could immediately find out what to do in a crisis through social media. But now, there is so much misinformation that people are increasingly mistrustful.

But yes, technology systems matter. Rio de Janeiro, for instance, has built a data-gathering operations center—a cross-sector partnership spanning major providers, universities, and 50 agencies. The volume and granularity of data are astonishing. It helps the city manage both day-to-day operations and crises better. When combined with AI, this data reveals exactly where interventions are needed. It can show, for example, that three people died from heat in a specific neighborhood on a specific day.

Many cities lack this kind of data, especially because heat rarely appears as a direct cause of death. But it worsens cardiovascular disease, stroke risk, kidney failure, and mental-health conditions, and its effects often emerge days later. That’s why we increasingly rely on excess-death analyses to understand heat’s true impact. In Europe, for example, more than 61,000 excess deaths were recorded during the summer of 2022.

Gavin Allen: Are we at the foothills of that data gathering?

Lenio Myrivili: Yes, and AI – along with research centers and universities – is helping us build that capability. Modelling will enable us to better figure out which neighborhoods are losing the most people and need help the quickest. Heat maps and sensors can identify hotspots and help prioritize the most vulnerable groups.

Gavin Allen: Digital twins can trial-run possible solutions too?

Lenio Myrivili: Absolutely. In Athens, for example, Dr. Keramitsoglou at the National Observatory is developing a digital twin to identify the city’s most vulnerable areas. During heat waves, this would allow emergency services to pre-position ambulances, plan faster routes, and respond more effectively. These tools can also show where new canopy cover is needed and which tree species offer the best cooling benefits. Smart materials are advancing, too—from experimental concrete that lowers surface temperatures, to reflective paints that reduce indoor heat. If demand grows and prices fall, these materials could become invaluable for informal settlements, as well as wealthier cities.

Gavin Allen: At the end of your tenure as Global Chief Heat Officer, what will success look like to you?

Lenio Myrivili: I’d like to see a big global network of cities that have established the governance needed to break through silos and so that people collaborate on heat solutions. I want standardized policies for how we build our cities. That’s building codes, percentages of canopy coverage, transportation modes that shift away from cars. A different city-making logic that prioritizes climate resilience and heat security.

Gavin Allen: You’ve said that heat compounds existing economic, social, and resource challenges, such as water management.

Lenio Myrivili: Absolutely. Cities now face both droughts and flash floods because the global water cycle is so disrupted. Rainfall that once arrived steadily over months can now fall in a matter of hours. Longer heatwaves dry out the soil, and with so much of the urban surface covered in concrete and asphalt, water can’t be absorbed, creating dangerous flooding conditions.

Heat and water are tightly linked: cities need reliable backup water supplies for drinking and for irrigating parks that provide cooling shade. Heat also worsens air pollution, and pollution in turn traps more heat, creating a deadly feedback loop.

Gavin Allen: Solve one problem, and you start to solve others?

Lenio Myrivili: We have to create resilience, which understands these things in a systemic way. It's crazy to attack one issue without considering the co-benefits, to get the best results for your buck.

Gavin Allen: So, a more joined-up approach within a city, but also across cities?

Lenio Myrivili: Yes. There are things that can be standardized and pushed forward on a global level. But the actual work has to happen in cities, because that's where the people are, and where the problem is. Cities are heating up twice as fast as the global average, and soon, 70% of people will be living in them.

Gavin Allen: And if we don’t address the problem?

Lenio Myrivili: Our cities will see rich people retreat into air-conditioned fortresses, while the poor get pounded by heat in the streets, or in their stifling homes. The lucky ones will be in expensive hospitals trying to improve our health, while outdoor laborers work in unbearable conditions. Traditional retail commerce could grind to a halt or be done exclusively online, as our city centers, plazas, cafes, and restaurants empty out. Access to good, fresh food will be harder. Biodiversity loss will make our lives tougher day by day.

Gavin Allen: That’s a bleak picture.

Lenio Myrivili: It's a very bleak picture. We’ll be living in cities where survival will be linked to degrees of temperature. We urgently need to reallocate resources, decision-making, and governance to match the scale of the problem. We are better than this. And cities are beginning to show that they can rise to the challenge.