Annual Runoff and Climate Characteristics in large River Basins of Northern Eurasia under Global Warming

The runoff and climatic characteristics averaged over the basins of major rivers of the East European Plain (Northern Dvina, Pechora, Volga, Don, and Dnieper) and Siberia (Ob, Yenisei, and Lena) under global warming were analyzed. This analysis was based on both observational data and estimates obtained from global climate models (GCMs) under a baseline period (1930s–1980), contemporary global warming conditions (1981–2010), and scenario-based anthropogenic global warming projections into the mid-21st century (2040–2069). The main results suggest that long-term averaged annual runoff estimates derived from an ensemble of 18 CMIP6 GCMs do not accurately reproduce the observed runoff during either the contemporary global warming or baseline periods. Nevertheless, these models generally capture the direction of runoff changes between these two periods, though they tend to underestimate the magnitude of these changes. Consequently, multi-model mean projections are useful in estimating the relative changes in runoff under different global warming scenarios. A key finding of this study is that selecting GCMs that can best reproduce the most reliably observed river runoff and climatic characteristics of river basins under contemporary global warming can improve ensemble model estimates of runoff. In addition, it was found that basin-averaged observed and modeled annual atmospheric precipitation over the Northern Dvina basin, obtained from the RIHMI-WDC archive (after applying all relevant corrections) and multi-model mean data, respectively, were closely aligned. This was in contrast to data of reanalysis and data that only included wetting corrections from the CRU archive.