Natural Sinks and Sources of CO2 and CH4 in the Atmosphere of Russian Regions and Their Contribution to Climate Change in the 21st Century Evaluated with the CMIP6 Model Ensemble

Abstract

The natural fluxes of CO₂ and CH₄ into the atmosphere from the territory of Russia in the 21st century have been analyzed using the results of simulations with the ensemble of global climate models of the international CMIP6 project. Estimates of natural CO₂ fluxes in Russian regions differ greatly for different models. Their values for the beginning of the 21st century range from –1 to 1 GtC/year. In the 21st century, the differences in model estimates of fluxes are growing, and, at the end of the 21st century, in the scenario with the largest anthropogenic impacts, SSP5-8.5 range from –2.5 to 2.5 GtC/year. Estimates of natural methane emissions to the atmosphere from the territory of Russia also differ greatly for different models. Modern methane emissions are estimated in the range from 10 to 35 MtCH₄/year, with an increase in the 21st century of up to 300%. Ensemble model simulations show general trends for changes in natural greenhouse gas fluxes. Most CMIP6 models are characterized by a maximum of CO₂ uptake by terrestrial ecosystems and its further reduction by the end of the 21st century, while natural methane emissions to the atmosphere for all models and scenarios of anthropogenic impacts grow throughout the 21st century. The cumulative temperature potential of natural CO₂ fluxes on the territory of Russia in the 21st century is estimated, depending on the scenario of anthropogenic impacts, to be from –0.3 to 0.1 K, and the accelerating warming impact of natural CH₄ emissions is estimated in the range of 0.03–0.09 K.