Water vapor feedback

An early decision in producing MERRA was to release data to the science community before the completion of the full time series, in the hopes that early analysis would provide insight to the data in a timely manner. In this months Journal of Climate, Dessler and Wong evaluate the water vapor feedback in the climate system using AR5 models, ERA40 and MERRA. The models and reanalyses all show consistent positive feedback (see the excerpt figure below). MERRA (point L in the figure) does show a bit more variability than the climate models (points A-J). A contributing factor to that variability may be a smaller number of years considered for MERRA, as the data was analyzed early in the production. Even so, the inclusion of MERRA in this research does help characterize the system and contribute to the understanding of its capabilities for climate research. At present, 1979 through Feb 2008 are approved for release at the MDISC data site.