Replanting forests can help cool the planet even more than some scientists once believed, especially in the tropics. But even if every tree lost since the mid-19^th century is replanted, the total effect won’t cancel out human-generated warming. …In a new study published in Communications Earth & Environment, researchers at the University of California, Riverside, showed that restoring forests to their preindustrial extent could lower global average temperatures by 0.34 degrees Celsius. That is roughly one-quarter of the warming the Earth has already experienced. The study is based on an increase in tree area of about 12 million square kilometers, which is 135% of the area of the US. …It is believed the planet has lost nearly half of its trees since the onset of industrialized society.  “Reforestation is not a silver bullet,” said Bob Allen, at UC Riverside and the lead author. “It’s a powerful strategy, but it has to be paired with serious emissions reductions.”