Do forests cool the planet or warm it? It’s a deceptively simple question with no clear answer. The catch is that the same forest can push climate in opposite directions at once. Forests are widely viewed as climate change mitigators—and planting trees as a partial climate solution—because they absorb carbon dioxide. Yet that framing is incomplete. Trees also release reactive gases called biogenic volatile organic compounds (BVOCs) that can influence cloud formation, contribute to air pollution, and extend the atmospheric lifetime of methane, a greenhouse gas that can trap about 80 times as much heat as carbon dioxide. …Whether forests cool or warm the planet depends on how BVOCs behave once they leave the foliage. From there, the normal steps of plant metabolism synthesize and release BVOCs. …The Model of Emissions of Gases and Aerosols from Nature estimates BVOC emissions by combining information about terrestrial vegetation with data on environmental conditions that influence emissions.