Satellite imagery to identify cities’ hottest neighbourhoods

The climate crisis will play out (is playing out) in various ways, two of them are more frequent and more extreme weather events, and another is temperatures rising unevenly. Some countries, and especially some cities, are already being hit hard.

We already know cities to be hotter than surrounding areas, and we are getting better at going to a more granular level to identify which neighbourhoods are warmer still since some “get dangerously warmer than others just a few miles away.” As with virtually every aspect of the climate crisis, poorer and more disenfranchised people bear the brunt of the consequences. That’s true between countries, but also within cities.

Among the many things we’ve been able to track with increasingly detailed satellite data is that the hottest neighborhoods are typically low-income and often have predominantly Black or Hispanic residents.

Scientists are now using satellites to zoom in on cities’ hottest neighbourhoods to better identify different zones and help combat the urban heat island effect. There are actually two types of effects, urban heat island and surface urban heat island. The atmospheric urban heat island is simply warmer air in urban areas, relative to the cooler air in outlying locations. The surface urban heat island is the additional effect of heat-absorbing materials, such as asphalt, concrete and metal. Heat enhancing materials, deforestation and the removal of vegetation, in general, all compound to make heat waves even worse in relation to how each area has been built up.

The July 1995 Chicago heat wave was blamed for over 739 deaths in a five-day period. Most victims were poor and elderly people who lacked air conditioning or feared opening windows because of crime.

Satellite imagery can help to identify those communities and of course use that information to better prepare, and better support harder hit communities quicker.

My research has found that on warm summer days, low-income communities of color can experience extreme heat conditions that are often more than 10 degrees Fahrenheit (5.5 C) warmer than surrounding areas. Other research has found similar differences among neighborhoods and stark racial and economic disparities when it comes to heat exposure.

Indianapolis has been using this information to “guide outreach to the most vulnerable people both before and during periods of elevated temperatures.” New York now runs the “Cool Neighborhoods NYC” program which helps to strategically plant trees and vegetation to “increase shade and evapotranspiration, which cools the surrounding area.”

A good example where technology can help gather useful information, and better organization on the ground, with simple solutions like more trees and more intelligently built neighbourhoods, can come together for better safety and, yes, better liveability.