Extreme heat is deadly, but inequality is deadlier

As we enter the hottest months of the year, Cynthia Wang discusses the impact of extreme heat on vulnerable populations in urban spaces in the United States, focusing on the significance of inequality in climate change. Cynthia is an Imperial MSc Climate Change, Management, and Finance postgraduate student. Most recently, she has been conducting research on equity, diversity and inclusion at the Grantham Institute.

Each year in the United States, more Americans die from extreme heat than from hurricanes, tornados, or floods. Since 2006, the United States has experienced its top five warmest years in history, and the rate of annual heat waves in cities has tripled over the last six decades. Seven US states (California, Arizona, New Mexico, Utah, Colorado, Wyoming and Montana) faced record-breaking temperatures this past June, with Phoenix, Arizona, topping the list at 46.1°C for six consecutive days. With high confidence, climate models predict increasing frequency and intensity of extreme temperature change around the world. As we settle in for a future of more frequent and intense extreme heatwaves, hundreds of millions more will be exposed globally. Fortunately, as far as climate risks go, extreme heat deaths are readily avoidable. The true complication is inequality.

Extreme heat preys on the most vulnerable. Reported victims are commonly homeless, neglected and/or elderly, low-income, minority groups, or individuals suffering from mental illnesses. They are connected by a shared inability to afford or access cooling, shelter, hydration, or help in times of need. Extreme heat kills by overwhelming the body’s ability to sweat and regulate internal temperature, causing heat stress. Once the body tops 39.4°C, sweating stops, heart rate and breathing escalates, and people lose consciousness, which is sometimes followed by multiple-organ failure. Extreme heat is a threat multiplier because it amplifies pre-existing health conditions such as diabetes, mental health, and heart, lung and kidney disorders. Thus, society’s most underserved are also the most vulnerable to this climate impact.

In the US, deaths from extreme heat are primarily recorded in urban areas. The urban heat island effect amplifies the impacts of high temperatures. High-density urban infrastructures like pavement, buildings, highways and roads replace natural land coverage and decrease albedo (the proportion of solar radiation reflected by surface areas), making cities hotter by trapping heat at the ground level. Adaptation efforts that attempt to combat this effect include installing more green spaces and water features to provide shade and increase cooling effects. However, it is doubtful that infrastructure installations will be enough to combat extreme heat death. Centralised urban planning has historically neglected to provide green and blue spaces to the most vulnerable communities.

In fact, research implies that it is not extreme heat that kills, but weak social safety systems and inequality. In the US, numerous studies have documented the effect of systemic racial segregation on urban environmental health inequalities. Racially discriminatory housing policies, known as ‘redlining’, have long denied African-American communities the most basic of public services. Recent research on 108 urban areas in the US proved that historically redlined neighbourhoods were consistently hotter by 2.6°C than their non-redlined counterparts. Exclusionary urban planning practices pushed redlined communities into urban areas dominated by factories, roads, and large and dense housing developments that capture more heat. These areas are also provided fewer environmental amenities, such as tree coverage, to cool and clean the air. Due to historical disenfranchisement, residents in redlined neighbourhoods also experience lower incomes, higher energy costs, and more frequent medical bills. These financial burdens further exacerbate their climate vulnerability.

As the world attempts to recover from the COVID-19 pandemic, the Biden-Harris administration has the opportunity to build back better with a greater emphasis on environmental health and equity. Increasing funding for the Centers for Disease Control and Prevention (CDC)’s climate health program could help it provide more research on the most impacted populations and build capacity in communities that need it the most. Clear federal guidance and a targeted, equitable climate health strategy could help states avoid hundreds of climate-related extreme heat deaths each year. Some physical climate impacts, like extreme heat, are now out of our control, but who we let slip through the cracks of our climate safety net is our decision alone to bear.