"Rising temperatures have helped blunt plants' ability to pull carbon from the atmosphere, according to a study published yesterday in Science." Is it a threshold in the warming cycle? Scientific American reports that: "The amount of carbon soaked up by Earth's plants and trees fell by roughly 1 percent, or 550 million metric tons, between 2000 and 2009. Researchers at the University of Montana say that global warming, large-scale droughts and an overall drying trend in the Southern Hemisphere contributed to the drop. Warmer temperatures did lengthen growing seasons in high northern regions, but that wasn't enough to counteract the effect of changes in Earth's water cycle."