When the last shimmering autumn leaves drift to the ground, it doesn’t just mark a seasonal change. It’s also a turning point in the global carbon cycle, as forests and other plants start to emit carbon dioxide instead of soaking it up. New research shows that, as the planet warms, deciduous trees in temperate European forests are losing their leaves earlier, and that could reduce the amount of CO2 forests will remove from the atmosphere in the decades ahead. “Against previous expectations, leaves are likely to fall earlier in the autumn,” said Constantin Zohner, a climate biologist with the Crowther Lab at ETH Zürich … For decades, scientists have projected that increasing temperatures and CO2 would cause trees to shed their leaves later in the year and lengthen the overall growing season, which would help slow the rate of global warming. But the new study “reverses our expectations”…