HIPPO Logo (IMAGE) U.S. National Science Foundation Caption HIPPO, or HIAPER Pole-to-Pole Observations, scientists study Earth's carbon dioxide levels. Credit UCAR 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.