Methane cycle in the INM RAS climate model

Abstract

The atmosphere-ocean general circulation model with the carbon cycle is coupled to a model of methane evolution, in which methane sources in the soil of wetlands and methane evolution in the atmosphere are calculated. A numerical experiment on the simulation of climate and methane-cycle changes in 1860–2100 has been conducted with the model forced by methane emissions prescribed from scenario A1B. The distribution of the sources of methane from soil agrees with the available estimates and amounts to about 240 Mt/year in the 20th century. The methane flux from soil increases to 340 Mt/year by the end of the 21st century. The model adequately reproduces an increase in the atmospheric methane concentration from 800 ppb in 1860 to about 1800 ppb in 2000, but does not produce the observed stabilization of methane concentration in the early 21st century. By 2060, the methane concentration in the model attains 2700 ppb. The increase in atmospheric methane concentration is due mainly to anthropogenic emissions. A similar numerical experiment with fixed sources of methane from soil at the 1860–1900 level suggests that the maximum methane concentration in the model in this case could amount to 2400 ppb. A temperature increase at the end of the 21st century relative to the 19th century is 3.5° for a simulated change in the methane flux from soil and 0.25° less for a fixed methane flux.