Leo Pena With Microscope (IMAGE) Columbia Climate School Caption In this image, Leo Pena (above) and colleagues analyzed fossil plankton shells to reconstruct ocean circulation over the last 1.2 million years. Credit Kim Martineau 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.