Plants Decrease Efficiency As Global Air Conditioner

GreenTracker| Rising levels of carbon dioxide in the atmosphere are turning down the global air conditioner effect that trees and other plants provide for the planet, says Ken Caldeira of Carnegie’s Department of Global Ecology.

According to a new study by researchers at the Carnegie Institution for Science, in some regions more than a quarter of the warming from increased carbon dioxide is due to its direct impact on vegetation.

Caldeira says that existing climate models (what we call silo-issue thinking among researchers) do not factor this effect into their forecasts.

Plants give off water through tiny pores in their leaves, a process called evapotranspiration that cools the plant, just as perspiration cools our bodies. On a hot day, a tree can release tens of gallons of water into the air, acting as a natural air conditioner for its surroundings. The plants absorb carbon dioxide for photosynthesis through the same pores (called stomata). But when carbon dioxide levels are high, the leaf pores shrink. This causes less water to be released, diminishing the tree’s cooling power. Read on at Science Daily