Climate change is creating “Urban Heat Islands” - here are the solutions

In the Potomac River region, summer doesn't always receive a warm welcome.

What should be a season of beach vibes and outdoor fun is simply too hot for a lot of us. It's even worse for urban and suburban dwellers, and worse still for those in marginalized, non-white communities. 

What’s more, the climate crisis is intensifying what’s known as the “Urban Heat Island Effect”.

We'll dive further into the future of global heating and rising temperatures in our upcoming Climate Report, but for now let's talk about some solutions to this particular problem plaguing city-dwellers.

So what’s an “Urban Heat Island” anyway?

We know that climate science is often presented as too esoteric or complicated for non-climate-experts to understand. But the science behind the Urban Heat Island is actually simple enough for a anyone to grasp…which means anyone can explain it to our elected leaders and advocate for action!

Here’s the gist:

• The Urban Heat Island effect occurs when natural land covers (soil, forests, grasses, etc.) are replaced by impermeable surfaces (pavement, buildings, metal, etc.).

• As you move from rural to urban areas, natural surfaces are replaced by impermeable surfaces more and more, hence the Urban Heat Island effect.

• While the sun’s rays hits urban, rural, and suburban areas equally, the darkly-colored, impermeable surfaces found in cities absorb and retain heat (think of navigating your local pool’s parking lot on a hot day in bare feet!) far more than natural ground cover.

• Further exacerbating this effect is the fact that cities and suburban areas have fewer plants than rural areas. This means they lack the natural cooling power of plants! Transpiration is how plants act as free A.C. - they take up water from the ground through their roots, store the water in their stems and leaves, and then the liquid water turns into water vapor and is released into the air.

• As the climate crisis heats up our entire planet, the factors creating the urban heat island effect also mean that downtown areas are heating up even faster than the rest of our region.

If you’ve ever been in the DC area on a summer day, we don’t need to tell you to care about this problem getting worse. (And get worse it will - climate models from ATMOS say that the number of days when the heat index tops 95°F in the nation’s capital may double by mid-century and triple by 2080.)

But here’s another reason to care - heatwaves are the deadliest weather-related event worldwide. Heat-related deaths and illnesses especially effect vulnerable populations like the unhoused, elderly, and those with respiratory illnesses. And the urban heat island effect is effecting non-white populations the most…

Why does this problem affect some people more than others?

More on planting trees below. First, let’s talk about racism (which is not entirely unrelated to trees!).

Now that you understand what makes cities hotter than rural areas, you’ve probably already put together that, within cities, certain neighborhoods are hotter than others. A recent study published in Nature Communications confirmed that “the average non-white person lived in a census tract with higher heat island intensity.”

But why? Why are non-white people throughout the U.S. consistently exposed to more intense heat (and therefore suffering more from the health ramifications of heatstroke and air pollution) regardless of income level?

The study found that “that the average person of color is exposed to a higher heat island intensity than the average person living below poverty. This is the case even though only 10 percent of people of color lived below the poverty line in 2017.”

This means that racist housing policies and zoning laws like redlining are to blame. Similar policies are the reasons that communities of color face disproportionate levels of air pollution and water contamination as well.

So, as we work to address the heating effects of climate change and the urban heat island effect, dismantling racist policies must be part of the solution.

How can we keep our cities cool?

No one is suggesting we abandon cities and all move to the country! (That would really not be good for the climate.)

Rather, we need to 🌳 grow 🌳 better cities that use nature-based solutions and smart infrastructure to create cooler, more equitable neighborhoods and communities.

And, yes, planting trees is a huge part of this! Trees provide shade, which blocks the sun’s rays from being absorbed by surfaces like roads, parking lots, and rooftops. They also cool the air by transpiring water. Urban trees can cool a neighborhood by 4°F!

Trees are also economical. A Nature Conservancy study found that investing just US$4 per resident in cities experiencing intense heat island effects could improve the health of millions of people.The localized nature of trees’ cooling effect also means that city planners can use them to target plantings in areas with especially vulnerable populations - like near schools and hospitals.

While trees are an incredibly cost-effective solution (and we’ve got lots up our sleeves to increase tree plantings in the Potomac River region!), they’re just one part of the puzzle.

Basically, anything that trades impermeable surfaces for green space is good for city-dwellers (and clean water). This can look like adding rain gardens in parking spaces, planting “green roofs”, or investing more in public transportation to reduce the need for roads and parking lots.

Want to learn more about how the climate crisis will affect our local communities, what the solutions are,
and how you can take action?

Sign up to receive the release of our upcoming, locally-focused Climate Report!

“Rising to the Challenge: A New Climate Reality in the Potomac River Region”
will break down the effects of the climate crisis into easily-understandable science and propose root-cause solutions that we can enact at the local level.

For each issue addressed in the report, we’ll provide a way for you to take action right away. Whoever you are, we want you to be part of this fight for our climate!

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