Carbon dioxide uptake by terrestrial ecosystems is critical for moderating climate change but the processes involved are challenging to observe, quantify and model. To provide an independent, ground-based assessment of the contribution of forests to terrestrial uptake, we synthesized the best available in situ forest data from boreal, temperate and tropical biomes spanning three decades. This data publication includes regional and country-level estimates of forest areas, carbon stocks and carbon sinks from 1990 to 2020. Data are based on ground measurements of trees from different forests worldwide and specifically include forest areas, forest carbon stocks, forest carbon stock changes of all global forest biomes (including components of living biomass, deadwood, litter, soil and harvested wood product) and formulas used for synthesizing and calculating the data which can be used for reproducing analysis results and graphics. This data publication also provides raw forest inventory data for Sweden, Norway and Finland from 1960 to 2020 which includes total area, increment, growing stock, harvested, harvested residues, and total decrement for all forest land and productive forest lands. Information for all data sources is also included.