Abstract <p>Correct assessments of greenhouse gas fluxes and the global carbon cycle require well-provided data on greenhouse gas sources and sinks in the surface–air system at different natural sites. This work summarizes the results of shipboard measurements of carbon dioxide concentration in surface water throughout the water area of Lake Baikal in eight spring campaigns of Limnological Institute, Siberian Branch, Russian Academy of Sciences. Spring period is of particular interest for research, since due to the large geographical extent of the lake from south to north, after the ice breakup, the water gradually warms up. This makes it possible to take measurements in relatively different “seasons” during a time-limited expedition. Against the background of interannual variability of the spatial distribution of CO₂ concentration in the Baikal surface water in spring, its decrease from the Southern to the Northern basins of the lake is pronounced. While moving away from the coastal zone to the central part of the water area (to depths of more than 200 m), the concentration of dissolved carbon dioxide increases. The results of the study are of interest to specialists in climate issues and biologists, since carbon dioxide is one of the integral components of the carbon cycle during photosynthesis of aquatic plankton in the Baikal water.</p>