Earth's Atmosphere (IMAGE) Duke University Caption The Earth's thin atmosphere as viewed from space. A new study from NASA and Duke finds natural cycles alone aren't sufficient to explain warming trends observed over the last century. Credit Credit: NASA Usage Restrictions None License Licensed content 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.