Post by World Resources Institute

🌳😌🌇The cooling power of trees starts with shade. When surfaces like pavement, rooftops and buildings are exposed to direct sunlight, they absorb and store heat, releasing it back into the air long after the sun goes down. Trees interrupt that process. They shade sidewalks, streets and people, preventing surfaces from heating up in the first place. They also cool the surrounding air through evapotranspiration, the release of water vapor from leaves. A global study of 806 cities found that increases in tree canopy are associated with midday reductions in land surface temperature of around 1.5 degrees C (2.7 degrees F) — demonstrating how shade limits the amount of heat that is absorbed and re-radiated by urban surfaces. A global meta-analysis found that increasing tree cover also cools the air itself, with each 10% increase in canopy lowering ambient air temperatures by about 0.3 degrees C (0.54 degrees F). But ambient and land temperatures aren’t the only factors that determine how hot it feels. The way we experience heat — quantified by “thermal comfort indices,” various measures of how hot an average person feels — is also shaped by factors like humidity, wind and direct solar radiation. Trees make it feel dramatically cooler by blocking direct sunlight. Data from WRI’s Cool Cities Lab shows that trees can improve thermal comfort by 2-8 degrees C (3.6-14.4 degrees F). Together, shade and evapotranspiration allow trees to provide cooling at multiple scales at once — from lowering neighborhood air temperatures to reducing surface heating to easing hyperlocal thermal stress. This all makes outdoor conditions more bearable during the hottest months of the year and reduces heat-induced illness and mortality. Learn more about the cooling potential of urban trees➡️ https://lnkd.in/eDbrmN6q