From Bangkok to Buenos Aires, here's how 12 global cities are tackling extreme heat

Parts of the world have always been hot. But climate-driven heat that has spilled over into the northern hemisphere, and spawned record-breaking temperatures that impact life and work in cities, has emerged as a serious threat in recent years.

In fact, the World Economic Forum’s Global Risks Report 2023 highlights this risk and suggests extreme weather events will be the second-biggest threat facing the world in as short as just two years.

Now a new report, 'Hot Cities, Chilled Economies: Impacts of Extreme Heat on Global Cities', published by the Adrienne Arsht-Rockefeller Foundation Resilience Center, puts the spotlight on the social, economic and health impact of extreme heat on 12 global cities – and outlines some of the policy measures to tackle it.

In July alone, the United States set 350 daily heat records, while Europe grappled with an unprecedented heatwave that claimed 2,700 lives in Spain and Portugal. Europe's wildfires exacerbated an already dire drought situation. Pakistan's scorching heat led to catastrophic floods, and soaring temperatures in southern China disrupted entire sectors and rendered cities uninhabitable.

It’s taking a staggering toll on urban centres – particularly those in the global south. By 2050, nearly 970 cities could experience average summer highs of 35C, impacting 1.6 billion urban residents, according to the report.

It also points out that the phenomenon of urban heat islands disproportionately affects marginalized communities, with Native American and Black populations in the US enduring high heat-related mortality rates, underscoring existing inequalities.

As agricultural failures and wildfires prompt an urban migration surge, the US urban population has surged to 83%, projected to reach 11% by 2050, underscoring the urgency of immediate action.

The Adrienne Arsht-Rockefeller Foundation is a World Economic Forum partner on the The Heat Action Platform, where city officials and financial institutions can find guidance on reducing the human and economic cost of extreme heat on their cities, towns and regions.

Other key findings of the report include:

Here’s how extreme heat affects 12 global cities and how they are dealing with it:

Athens has upped its heat reduction efforts in an effort to safeguard its population from rising temperatures. In Central Athens, heat-related output losses could double to $230 million in 2050 from almost $100 million now. Construction and manufacturing workers face disproportionate impacts due to limited cooling coverage and labour intensity.

Key actions include worker protections during heatwaves (longer breaks during peak heat hours and mandated air-conditioned rest areas with water provided), communication campaigns for vulnerable individuals, and the appointment of a Chief Heat Officer.

Initiatives involve categorizing heatwaves to prompt swift responses. Renovation of historic fountains and creation of cooling “pocket parks” in the dense urban landscape are underway. Preserving street trees, like the iconic mulberry trees, is crucial to prevent new heat islands.

Bangkok faces high and rising temperatures. Heat and humidity cut productivity by 5%, costing $8.6 billion annually. Without action, losses may rise to $15.6 billion by 2050, 6% of output.

In the face of these high numbers, local authorities have upped their efforts to stem heat-related economic losses. Bangkok Metropolitan Administration's climate plans offer an opportunity for impactful regulations and investments targeting extreme heat and its impacts. Thailand's 2016 occupational heat standard uses so-called wet bulb globe temperature (WBGT) to manage heat stress, limiting effort beyond specific thresholds. A 2021 study found compliance protects four out of five workers.

The Bangkok Master Plan on Climate Change emphasizes insulation, thermal barrier coatings and greening roofs and walls. Urban greening, tree planting and mangrove reforestation amplify heat-resilient efforts.

Hot days in Buenos Aires are particularly dangerous in disadvantaged areas where temperatures can be as much as 15C hotter than surrounding rural areas, and current heat occurrence will become twice as common. The city loses $115 million annually in productivity due to heat, expected to triple by 2050.

Buenos Aires aims to expand existing mitigation efforts, prioritizing vulnerable residents against escalating heat. The Buenos Aires Climate Action Plan outlines strategies where private sector resilience will be promoted via a buildings code, mandating solar protection and ventilation in new structures.

Vulnerable communities receive education through programmes like the Adaptation to Extreme Climate Events. National Weather Service heat alerts further inform Argentina.

The city will invest in 20% tree cover increase, biocorridors, green roofs, walls, and vertical gardens. Solar photovoltaic generation for residential rooftops is also going to get a boost.

Dhaka's scorching temperatures and humidity pose risks, as temperatures surpass human tolerance for the year's 10 hottest days.

Dhaka's labour-intensive economy and low cooling capacity lead to 8% productivity loss now, rising to 10% by 2050 due to extreme heat, the highest in the study.

City officials have long employed adaptations but increasing severity necessitates swift actions:

Rising temperatures pose socioeconomic development and adaptation challenges for Freetown.

Freetown faces rising heat-related productivity losses forecast to reach over 6% of output by 2050 from currently 3.5% or $30 million.

A Chief Heat Officer is in charge of adaptation measures such as development plans to improve housing and water availability to enhance heat resilience. Water access combats heat through hydration and evaporative cooling.

The Treetown project employs social media, mobile payments and machine learning for community-driven reforestation, offering cooling and employment, especially for marginalized groups. Cooling shades tackle market overheating by providing sun protection. Freetown's approach aims to tackle both heat and socioeconomic advancement.

London, unaccustomed to frequent extreme heat, has developed heat awareness measures but requires sustained investments in buildings and infrastructure as extreme heat events become more frequent.

Losses of $730 million in 2020 make up 0.9% of output; that figure is expected to reach $840 million by 2050 without emissions reduction or adaptation.

A 2015 report outlined policy measures to curb residential overheating. Workplace temperature laws offer minimal protection, lacking specific guidance for hot conditions.

The UK Met Office issues heat-health warnings for temperatures exceeding 30C by day and 15C overnight for two consecutive days. "Cool Spaces" provide heat relief locations, while Transport for London's "Beat the Heat" campaign promotes safety during high temperatures.

Enhancing indoor cooling efficiency and integrating passive cooling in building design mitigates overheating. Tree-planting initiatives combat heat, with over 280,000 trees planted since 2016. Retrofitting transport for heat reduction is ongoing but needs rapid scaling as London's transport lines modernize.

Los Angeles, familiar with warmer temperatures, pursues ongoing adaptations to alleviate its impact on the economy and populace, with a focus on vulnerable groups. Heat and humidity cause LA to lose nearly $5 billion yearly; projected to rise to $11 billion by 2050.

California's Extreme Heat Action Plan and Los Angeles's Green New Deal enhance existing plans. Green New Deal initiatives include cool pavements, transit shading, and "cool neighbourhoods'' for elderly and disabled residents, setting ambitious temperature reduction targets.

The city appointed its first Chief Heat Officer in November 2021, enhancing public awareness and adaptation goals based on the County Climate Vulnerability Assessment.

Los Angeles's Cool Roof ordinance mandates sunlight-reflecting, energy-efficient roofs since 2014. Further plans include a 50% increase in crucial tree canopy by 2028, aiding heat reduction and energy savings.

Miami, with average highs exceeding 28C on the 10 hottest days, requires substantial scaling for effective heat mitigation solutions. Miami loses $10 billion in productivity yearly due to heat, exceeding the county’s annual budget. Without action, losses may double to $20 billion by 2050. The world's first Chief Heat Officer, appointed in May 2021, coordinates the region's actions.

Proposed Florida legislation, backed by the Chief Heat Officer, advocates 10-minute breaks for outdoor workers above 32C. Legal standards for heat-resilient infrastructure and public spaces will enhance private-sector adaptation.

Million Trees Miami aims for 30% tree canopy, reducing urban heat. Cooling stations, street, housing and park heat mitigation, and innovative materials like cool pavements and solar panel shading are also planned.

Monterrey is one of the hottest cities in Mexico. Monterrey suffers $1.8 billion annual labour productivity losses due to heat and humidity, projected to double by 2050. It’s actively pursuing private-sector investments and pilot projects to enhance heat resilience.

With a newly appointed Chief Heat Officer, the city aims to expand existing efforts for urban heat management. Initiatives include awareness campaigns, passive cooling building designs, and nature-based solutions like reforestation.

Lessons from across Mexico, such as Mérida's citizen-involved reforestation project, offer insights for Monterrey to mitigate economic losses and protect its population from escalating heat challenges.

New Delhi faces extreme heat, with average highs surpassing 36.2C on the hottest 10 days. Labour productivity losses cost $3.9 billion in 2020, set to rise to $ 6.1 billion by 2050, or 5% of potential output. Adaptation efforts include adjusted working and schooling hours ending some classes by 11am, and halting outdoor work by noon.

The draft Master Plan for Delhi to 2041 prioritizes heat resilience, including permeable paving, district cooling, green solutions, increased tree cover by 20% and biocorridors. Collaborations include "cool roofs'' and sustainable cooling technologies to manage increased AC demand while mitigating energy strain and pollution.

Santiago's generally mild yet dry climate leaves residents vulnerable to sudden heatwaves. Annual heat- and humidity-linked worker productivity losses surpass $100 million, and this figure is set to double by 2050.

Santiago has introduced a tiered warning system, allowing for potential water rationing. The city's inaugural Regional Climate Action Plan, featuring an extreme heat chapter, is in design.

Green roof pilot projects, starting at Hospital Dr Exequiel Fernandez Cortes, are underway. Tree canopy expansion, urban heat reduction through shading, and alleviating heat-induced water stress are also slated.

Sydney faces extreme heat, exceeding 45C during the worst heatwaves, with increased frequency predicted. Unabated climate change could make scorching days 60% more frequent by 2050, causing significant productivity losses. Current heat exposure already results in $310 million annual losses, projected to double to over $700 million by 2050 without adaptation.

The Western Sydney Regional Organisation of Councils offers guidelines for heat-resilient urban planning. The Resilient Sydney 2018 strategy promotes cool roofs, permeable infrastructure, and green designs. While Greening Sydney 2030 proposes green roofs, walls and tree cover investments for heightened heat resilience.