Blogs from our Scientific Researchers

Ah, summertime! In Pittsburgh, after months of cold, grey days, the warm temperatures and sunshine bring a collective sigh of relief. Plants are roaring back, coloring the world green. Animals are out and about singing and foraging; people are picnicking, barbequing, gardening. Life feels abundant. But summer can quickly become oppressive, even deadly, if it gets too hot. Extreme heat is among the deadliest weather-related phenomena in the US, and cities are most at risk for this hazard.

The concentration of impervious surfaces and low-rise buildings in cities raises temperatures significantly, creating what is termed the urban heat island effect. Temperatures in a single urban area can vary as much as 18 F depending on the density of the grey stuff (buildings, sidewalks, roadways, and parking lots) relative to the green stuff (trees, parks). The urban heat island effect also interacts with global climate change. Rising temperatures due to emissions of heat-trapping gases from the extraction and burning of fossil fuels is making urban communities increasingly vulnerable to extreme heat. And like so many other pressing issues in the early summer of 2020, namely the coronavirus pandemic and police violence, extreme heat is experienced inequitably.

In the US, communities of color and resource limited communities are both disproportionately exposed and sensitive to extreme heat. One recent study explores this climate inequity and its relationship to the historic racially discriminating housing policy, called ‘redlining’. In an analysis published in the journal Climate in January 2020, Jeremy Hoffman, Chief Scientist at the Science Museum in Virginia, and colleagues ask: “do historical policies of redlining help to explain current patterns of exposure to intra-urban heat in US cities? and how do these patterns vary by geographic location of cities?” As the study describes, in the 1930s, redlining distinguished neighborhoods that were considered “best” (outlined in green) and “hazardous” (outlined in red) for investment by the Home Owner’s Loan Corporation, a federally funded program. Categorization on a scale from A (best) to D (hazardous) was based largely on racial makeup. The program prioritized white neighborhoods for economic investment and access to credit. While the practice ended in 1968 with passage of the Fair Housing Act, its legacy has persisted in structuring the social-economic and ecological landscape of US cities today. The study examines the pattern of land surface temperatures in cities today in relation to historic housing policy.

The results for 108 urban areas in the United States can be explored in an open access article, and also shared through an explorable map. Overall, Hoffman and colleagues found that yes, for 94% of US cities, historical policies of redlining track surface land temperatures. Historically redlined neighborhoods are about 5 degrees F warmer on average today than historically greenlined neighborhoods. While temperature patterns within a city are complex and influenced by microclimates and other factors, the authors argue that the heat burden in redlined neighborhoods has been aggravated by housing policy. Redlined neighborhoods have significantly fewer trees, and an abundance of public highway projects and large building projects that create especially high asphalt to vegetation ratios.

Examining the map of the analysis in Pittsburgh, shows a complex relationship between redlining and land surface temperature, part of which I would guess reflects our extremely variable topography and a complex history of shifting neighborhood demographics associated with the boom and bust of the steel industry. I encourage you to investigate the results yourself.

Hoffman’s research demonstrates how structural inequities and institutional racism in the US affects people’s differential experience with the Anthropocene. Anthropocene challenges, like global warming and global pandemics, reveal the coupled dynamics among human social-economic-political systems and ecological-climate systems. They reveal the way that discriminatory race-based policies from the past animate the present. The experience of the pandemic, the experience of summer heat, the experience of poor air quality, the experience of police violence, the list goes on, are not evenly felt across communities. In the US, research shows time and time again that low resource communities and communities of color are disproportionately suffering. In the processes of doing sustainability and adaptation to address the Anthropocene, the work of undoing injustice is essential. In the case of increasing urban heat, as cities adapt, an important research and practice will involve work to ensure greening policies undo racial discriminatory neighborhood investing practices, while also ensuring protection from gentrification and displacement.

Putting research into practice, Hoffman in his role at the Science Museum of Virginia, is collaborating with youth community organization, Groundwork RVA, to build solutions to urban heat that are both low-cost and high impact. At CMNH’s Center for Anthropocene Studies we are inspired and motivated by the role that museums are playing in empowering communities to understand global change and build social equity and resilience.

Nicole Heller is Curator of Anthropocene Studies at the Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences working at the museum.