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Extreme Heat and Disasters: The Climate Emergency Is Impacting Big U.S. Cities

July 1, 2024

Bar graph showing more heat waves per year in select US cities comparing 1960s to 2020s

Above: A bar graph depicts more heat waves per year in select U.S. cities, comparing the 1960s to the 2020s.

Already this summer, much of the U.S. has been under a heat health emergency due to dangerous record-breaking temperatures. The bar-graph above shows that across big cities in the U.S., heat waves have increased 3-fold compared to decades ago. Heat waves – which can be defined as unusually hot weather for at least two consecutive nights – are well-known to cause morbidity and death, particularly among seniors, residents with chronic diseases and those in lower-income housing.

These data are an example of new climate metrics posted on the Big Cities Health Coalition (BCHC) data platform. The platform is maintained by the Drexel Urban Health Collaborative (UHC) in partnership with BCHC and provides health metrics for the 35 large U.S. cities that comprise the BCHC.

As heat waves become more frequent, the summer hot season is also getting longer. Metrics on the data platform indicate the season average is currently 30 days longer than it was decades ago. These conditions are already having profound wide-ranging impacts on our ecosystem and health; for example, longer pollen/allergen season, increased exposure to mosquito- and tick-borne diseases, and longer drought/wildfire season.

Climate-fueled disasters can be humanitarian emergencies, destroying essential city infrastructure needed to maintain safe drinking-water, sanitation and safety, and with long-term negative effects on health and wellbeing. A new metric on our data platform shows that climate-fueled disasters are already occurring every two years in BCHC cities and last for approximately 30 days. Disasters will become more frequent and devastating as warming oceans fuel extreme weather events. Hurricane season (June-November) 2024 is forecasted by NOAA National Weather Service to bring a record-number of severe storms and experts urge advance preparation to mitigate community impacts.

In recent years, air quality degradation due to massive drought-fueled wildfire disasters have exposed millions of people to hazardous fine particles which can cause lung dysfunction and lead to severe illness and premature death. The health effects of air pollution are most acute for young children, older adults, and those living with asthma and other respiratory and cardiovascular diseases. Metrics on our data platform indicate air pollution already significantly degrades air quality in BCHC cities for approximately 40% of days in the year. As global temperatures increase, air pollution will likely worsen as hot and sunny skies increase ground-level ozone and wildfires become more common.

All cities have been impacted by the climate crisis, but the crisis has been particularly intense in cities that are already the hottest in the U.S. In BCHC cities in the southern and southwestern U.S. (primarily in Texas and Arizona), scorching temperatures last most of the summer: upwards of ninety days per year of daily maximum heat index ≥ 95 °F. Relative to other BCHC cities, the hottest cities have already experienced a disproportionate number of heat waves, climate-related disasters, and worse air quality. Additionally, metrics on our data platform indicate mortality rates are already higher in the hottest cities compared to other cities.

The climate emergency we are experiencing is a human-made crisis that disproportionately impacts low-wealth communities. In the U.S., urban emissions are predominantly due to fossil fuel burning within the transport and building sectors (mainly cars/trucks/aircraft and building electricity and heating consumption). Low-wealth individuals consume far less fossil fuel than high-wealth individuals, nevertheless, their health and safety will be disproportionately affected by global warming. Long-standing structural inequities – including federal and local policies – systematically excluded people living in poverty and communities of color from attaining financial security and quality housing that could have protected them from climate-fueled heat and disasters. While BCHC cities include high-wealth cities, on average BCHC cities have much higher poverty rates and are much more racially and ethnically diverse than the U.S. as a whole. A new metric on our data platform shows that on average, nearly 40% of city neighborhoods have high social vulnerability to climate disasters (compared to 25% for the U.S.) which places them at much higher risk of climate-related morbidity and mortality.

Urgent investment in transformational change is needed to reduce health impacts from global heating by transitioning to a non-fossil fuel economy in ways that are socially equitable. Federal and local health officials are already partners in multi-sector climate action plans that aim to move cities toward this transition. At their best, these plans: prioritize decarbonization of the built environment while enhancing adaptation and preparedness systems in order to mitigate direct threats to health; include robust engagement of historically marginalized communities; and address upstream drivers of health such as equitable access to safe affordable housing and green jobs.

Big Cities Health Coalition recently hosted a webinar to announce the new climate metrics and data updates on the Big Cities Health Inventory. The platform now includes more than 150,000 data points for over 120 metrics of public health importance and available data spanning years 2010 – 2022.

Participants at the webinar shared that city climate metrics will be useful for enhancing their communications materials for stakeholders; and will be useful when justifying increased investment and renewed focus in heat preparedness, disaster planning, and surveillance of climate-related health effects.

Watch a recording of the recent webinar: The Big Cities Health Inventory Data Platform

Visit the Big Cities Health Inventory

Learn about the new Climate Change and Urban Health Research Center at the Urban Health Collaborative.

To stay up-to-date on the Big Cities Health Inventory please follow both the Drexel Urban Health Collaborative (@DrexelUHC) and BCHC (@BigCitiesHealth) on Twitter or subscribe to our newsletter.

The Big Cities Health Inventory data platform is primarily funded by the U.S. Centers for Disease Control and Prevention through a cooperative agreement with the National Association of County and City Health Officials. The views expressed in this article and on the data platform do not necessarily represent the views of the funders.

Suggested citation: Amy Auchincloss and Saima Niamatullah. (2024) Extreme heat and disasters: the climate emergency is impacting big U.S. cities. Drexel University, Urban Health Collaborative. Philadelphia, PA.