Alva Review-Courier -

WASHINGTON (AP) — The most effective way to fight global warming is to plant lots of trees, a study says. A trillion of them, maybe more.

And there's enough room, Swiss scientists say. Even with existing cities and farmland, there's enough space for new trees to cover 3.5 million square miles (9 million square kilometers), they reported in Thursday's journal Science . That area is roughly the size of the United States.

The study calculated that over the decades, those new trees could suck up nearly 830 billion tons (750 billion metric tons) of heat-trapping carbon dioxide from the atmosphere....