Smokestack Pollution (image) University of Colorado at Boulder Caption Earth's carbon sinks have doubled their uptake in past 50 years, lessening the warming impacts on Earth's climate even as CO2 emissions have quadrupled. It's unclear how long this trend can continue, say scientists involved in study led by CU-Boulder. Credit Global Campaign for Climate Action, Alfred Palmer Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.