A large city’s built-up environment can make it nearly 3 C warmer than the surrounding countryside during the day and up to 11 C warmer at night.
In Dallas, where a persistent heat dome in the 2018 summer has sent temperatures soaring past 40 C, volunteers have fanned out around the low-income neighborhood of Oak Cliff, working with residents to plant 1,000 new trees around schools and homes.
Trees don’t just provide much-needed shade for a sweaty city. The water evaporating from their leaves can cool a neighborhood by a few degrees during the hottest periods. Tree leaves also absorb and filter local air pollution — a crucial benefit, since heat waves can worsen urban smog, sending people to the hospital with asthma and other illnesses.
Other cities have their own ideas for promoting urban vegetation: Seattle now encourages developers to add rooftop gardens or even walls covered by vegetation to new building projects. London recently conducted an audit of its central business districts and identified over 10 million square feet of space that could be converted to rain gardens, green roofs and green walls.
In the industrial city of Stuttgart, Germany, refreshing breezes are both scarce and valuable. The city sits in a river valley basin, surrounded by steep hills that can trap both heat and polluted air over the region. It’s a potentially lethal combination during the hotter months.
In response, Stuttgart has created a number of ventilation corridors throughout the city: wide, tree-flanked arterial roads that help clean air flow down from the hills at night to cool the city. Officials have also restricted new buildings from going up on certain hillsides in order to keep the air moving.
Some experts are skeptical that this strategy will work for every city because a lot depends on local weather patterns and geography. But China is becoming interested. Beijing and Xian are looking to create their own ventilation corridors, studying local wind patterns and strategically placing parks or lakes instead of buildings along key pathways so that the cooler breezes can flow freely.
In Dallas, where a persistent heat dome in the 2018 summer has sent temperatures soaring past 40 C, volunteers have fanned out around the low-income neighborhood of Oak Cliff, working with residents to plant 1,000 new trees around schools and homes.
Trees don’t just provide much-needed shade for a sweaty city. The water evaporating from their leaves can cool a neighborhood by a few degrees during the hottest periods. Tree leaves also absorb and filter local air pollution — a crucial benefit, since heat waves can worsen urban smog, sending people to the hospital with asthma and other illnesses.
Other cities have their own ideas for promoting urban vegetation: Seattle now encourages developers to add rooftop gardens or even walls covered by vegetation to new building projects. London recently conducted an audit of its central business districts and identified over 10 million square feet of space that could be converted to rain gardens, green roofs and green walls.
In the industrial city of Stuttgart, Germany, refreshing breezes are both scarce and valuable. The city sits in a river valley basin, surrounded by steep hills that can trap both heat and polluted air over the region. It’s a potentially lethal combination during the hotter months.
In response, Stuttgart has created a number of ventilation corridors throughout the city: wide, tree-flanked arterial roads that help clean air flow down from the hills at night to cool the city. Officials have also restricted new buildings from going up on certain hillsides in order to keep the air moving.
Some experts are skeptical that this strategy will work for every city because a lot depends on local weather patterns and geography. But China is becoming interested. Beijing and Xian are looking to create their own ventilation corridors, studying local wind patterns and strategically placing parks or lakes instead of buildings along key pathways so that the cooler breezes can flow freely.
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