Mark C. Serreze is the Director of the National Snow and Ice Data Center (NSIDC), part of the Cooperative Institute for Environmental Sciences (CIRES) at the University of Colorado Boulder. He is also a fellow of CIRES and a Professor in the Department of Geography. His Arctic research interests are wide-ranging, and include atmosphere–sea ice interactions, synoptic climatology, hydro-climatology, boundary layer problems, numerical weather prediction, and climate change. Dr Serreze has conducted fieldwork in the Canadian Arctic on sea ice and ice caps, and on the Alaskan tundra. Roger G. Barry is a Distinguished Professor of Geography Emeritus at the University of Colorado Boulder and the former director of NSIDC. He is currently the Director of the International CLIVAR Project Office at the National Oceanography Centre in Southampton, UK. He has written more than 250 research papers, and his books include Mountain Weather and Climate, 3rd edition (Cambridge University Press, 2008); Atmosphere, Weather and Climate, 9th edition (with Richard Chorley, 2009); Synoptic Climatology: Methods and Applications (with A. H. Perry, 1973); Synoptic and Dynamic Climatology (with Andrew Carleton, 2011); and The Global Cryosphere: Past, Present and Future (with Thian Gan, Cambridge University Press, 2011). In 1999, Dr Barry was elected a Fellow of the American Geophysical Union in recognition of his contributions to research in climatology and cryospheric science. In 2009–10 he spent nine months on a Humboldt Fellowship at the Glaciology Commission in Munich.