In Our Backyard No. 3 (bonus): Heat islands are killers, but they don’t have to be

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This is a special third bonus episode to In Our Backyard: Heat is the deadliest aspect of climate change. It’s turning LA’s neediest neighborhoods red hot.

Do you live on a heat island? Edith de Guzman from the Los Angeles Cooling Collaborative overviews the science behind urban heat islands and cutting edge ways we can be more informed about the most deadly consequence of climate change.

Read the full transcript below:

WARREN: Did you want to know a little more about heat islands? Well, you might, for good reason.

Edith: If you are an urban resident, congratulations, you live on an island, a heat island. Now, your experience of that will differ depending on whether your neighborhood has a lot of trees, has very dense development, has large parking lots or not. 

WARREN: That’s Edith de Guzman from our heat islands episode. And, she’s here now in our bonus episode to give you some more technical knowledge about something many of us are facing. But, first how do you even identify a heat island?

Edith: So the urban heat island effect that you've heard of is measured as the temperature difference between an urban area and a close by natural site, undeveloped site that serves as a reference, which sounds like an easy approach, but it's actually quite complicated. And in Los Angeles, where we have such a built out space, it's very challenging to do so. 

WARREN: Now the EPA has reviewed a lot of research studies and data and found that in the United States, the heat island effect results in daytime temperatures increasing in urban areas about 1 to 7 degrees Fahrenheit higher than in rural places. In nighttime temperatures, the increase is about 2 to 5 degrees Fahrenheit.

Edith: And so then the question becomes, what are those alterations that caused the temperatures to be different between that natural site, reference point and the urban area? And those fall into a few categories with our built environment being a major one. So our buildings, our roads, our parking lots, all of these surfaces absorb heat during the day and then they release it during the night. So not only do they bump up temperatures, the daily highs, but they also really markedly increase nighttime temperatures. Another factor is lack of trees and vegetation relative to more natural areas. And those types of surfaces, trees, vegetation, they would otherwise be providing shade and evaporative cooling benefits, which we have less of in the urban area. And finally, we also produce our own heat in the urban space. We have air conditioners, cars, other engines, and machinery that generate heat and increase the temperature. And we can think about the fact that we use more air conditioning when it's hot out. So we contribute to the problem not only by releasing more heat in the air conditioning unit itself, but also by releasing more climate changing emissions into the atmosphere, which creates sort of a nasty feedback loop for us to contend with. 


Edith: We've essentially changed the balance that we have with our relationship with the sun, such that we've created more opportunities for heat to be retained rather than dissipated. And, you know, some researchers and practitioners actually don't like the idea of it being called an island. Some people call it a heat archipelago, which is a group of of small islands. Right. Because in truth, it's not really evenly spread. You can move through different parts of the city, different parts of Los Angeles, for example, and have vastly different experiences of heat during a heat wave day. 

Warren: Is there any way to deal with heat islands short of removing the built infrastructure, which I take it is the main cause? 

Edith: Yes, there are ways to modify our urban environment without chucking people and cities out. We can make modifications that make really significant shifts. 

WARREN: Well, obviously, we can plant more trees. But, as you already know, these are not any silver bullet. That’s due to maintenance and property issues. But, there are other options you might not have thought of before.

Edith: There are also modifications that we can make to the built environment in terms of the solar reflectance of surfaces, which is also called albedo. Roofs, pavements, even walls can be coated or built in such a way that they refract or bounce back much of that solar radiation so that they don't retain it. 

WARREN: And, there’s lots of ways to do this.

Edith: You can certainly invest in proprietary, very fancy materials produced for roofing, but you can also paint commercial roofs white. You know, and that's not a huge investment. And, of course, we can also think about social infrastructure practices -- communications infrastructure -- and how we equip individuals and communities to respond during heat waves. 

WARREN: Here’s what she means.

Edith: The first thing that we can do is to make what is a largely invisible and silent threat more visible and less silent. So one effort that is currently underway that I know Rockefeller Foundation is part of is ranking heat waves, much in the same way that we rank hurricanes. If we were able to give an indication to the public of the severity of the heat wave that is coming, is it a Category three? You know, and what does that mean exactly? What kinds of precautions should you take? What kinds of activities should you not participate in? We have some versions of this in heat warnings and heat alerts, but being able to really categorize things in a way that indicates to people, you know, this heat wave just went from a category three to a category four. You better watch out. Could be a way to make it more visible and more actionable and could also give a trigger to, for example, to different industries that they have to see certain types of activities if they have a workforce that is particularly at risk. So there are small things that we can begin to do at various scales that can really begin to have an impact.

WARREN: Well, thanks, Edith. And, to everybody, stay cool.



Warren Olney


Julie Carli