Extreme heat can harm human health, but so can extreme temperature swings. Large daily temperature variation (DTV) has been associated with elevated mortality in studies around the world. Trees and other vegetation can lower DTV, as trees reduce temperature through transpiration during the day and also trap long-wave radiation in the atmosphere under the canopy at night, increasing temperature. Extreme heat can harm human health, but so can extreme temperature swings. Large daily temperature variation (DTV) has been associated with elevated mortality in studies around the world. Trees and other vegetation can lower DTV, as trees reduce temperature through transpiration during the day and also trap long-wave radiation in the atmosphere under the canopy at night, increasing temperature. Environment Phys.org – latest science and technology news stories