The urban heat island effect means that city temperatures can be several degrees higher than nearby rural regions. That’s because materials like concrete and asphalt absorb and radiate heat. Vehicles and air-conditioning units expel heat, and towering buildings block wind flow.
Officials across the globe are trying to cool cities down. In Chicago, which has a history of fatal heatwaves, more than 500 rooftops have been covered with vegetation, which releases cooling water vapor and acts as natural insulation for the building. Los Angeles, which has a vast network of freeways, has painted some of its roads with a solar-reflective material.
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Planting trees is also a good idea. Shade does help. But then you must deal with leaves. And you need enough water to keep them alive. Not for desert cities.
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That. And since many want to go solar, turn roof tops and parking lots into solar farms instead of actual farmland.
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Particularly in the mid-latitudes. (In the far north the darker trees reduce albedo.) I was a bit surprised when looking at a recent greenhouse gas report for Australia. It seems over the last 20 years all of the reduction in emissions has been from land use changes and agriculture.
Here’s a graph of total emissions for the country:
Of the 179 Mt drop, 164 Mt came from land use changes and 7 Mt from the agriculture sector.
DB2
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