D.C. heat island effect among worst in U.S.
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D.C. is getting hotter faster, and city programs are underway to combat rising temperatures.
Why it matters: D.C. suffers from the urban heat island effect — where cities experience higher temperatures than outlying areas and suburbs — and localized solutions are needed to protect the most vulnerable residents especially.
- See: this week, when we're breaking heat records, topping 101°F for three consecutive days. It's the first time since the 1930s Dust Bowl.
The big picture: Urban heat islands (UHI) are caused by heat being trapped by impervious surfaces (e.g. roads, sidewalks, roofs), a lack of green space, and additional heat emitted by cars, industrial zones, and the like.
- The heat islands are boosting temperatures within 65 major U.S. cities, according to an analysis by Climate Central.
Zoom in: D.C. ranks sixth among the cities where UHI effects can hike temperatures the most, with an average increase here of 8.5°F. New York is first (+9.6°F).
- Half of D.C.'s population lives in areas where temperatures feel at least 8°F higher, according to Climate Central. Another 35% live in areas where it's 9°F hotter.
The intrigue: There's an archipelago of heat islands within D.C. — certain neighborhoods can feel almost 17°F hotter than others.
Threat level: The city's heat exposure is significantly higher east of Rock Creek Park, according to the D.C. Policy Center.
- The highest heat scores are concentrated in three wards. Ward 1, which includes Columbia Heights, Adams Morgan, U Street, and Shaw.
- Ward 4 (Brightwood and Brightwood Park, particularly), and Ward 6 (Downtown, Penn Quarter, Chinatown).
Among the coolest neighborhoods: Barnaby Woods (adjacent to Rock Creek Park) and the Palisades (along the Potomac River).
State of play: The city has a heat strategy initiative to work on making neighborhoods — especially those with lower-income and more vulnerable residents — more heat resilient.
- Its climate projections include how many heat emergencies (days with a heat index above 95°F) the city can expect annually — and the forecasts are grim.
- New preliminary data for a study that'll be released later this year predicts between 44 to 47 days above 95°F by the 2030s, and up to 65 days by the 2050s.
What they're saying: "By the late century, the entire summer could be a heat emergency day," says Erin Garnaas-Holmes, a climate program analyst for the city's Department of Energy and Environment. "If you think of the heat and humidity over the last two weeks, it's almost unimaginable — but that's what we're projecting."
- One success story: D.C. pioneered a green roof program over a decade ago and leads other cities with over 6 million square feet of green roof coverage.
What's next: D.C. is striving for a 40% tree canopy goal by 2032. Nonprofits will receive over $34 million from federal funds to promote "tree equity" in lower-income neighborhoods.
- And DOEE is pursuing funding to pilot new cool-pavement technology.