Forest Clues (IMAGE) Columbia Climate School Caption Scientists calculated past rainfall and river discharges by measuring the rings of ancient trees within or near the Brahmaputra watershed. Here, researcher Dorji Dukpa of Bhutan's Department of Forest and Park Services extracts a core from a Himalayan hemlock. Credit Paul Krusic/University of Cambridge Usage Restrictions Credit must be given. 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.