Carbon dioxide levels in the atmosphere are increasing much faster and will be harder to control than scientists have predicted, a study has found. An international team of researchers has found that, since 2000, the rate at which CO2 has been pumped into the atmosphere is 35 percent greater than most climate-change models have allowed for. The conclusions have serious implications for forecasts of how much and how quickly the world's temperature will rise and mean that global warming will be harder and more expensive to control than feared.