Climate Change in IAP RAS Global Model Taking Account of Interaction with Methane Cycle under Anthropogenic Scenarios of RCP Family

S. N. Denisov, A. V. Eliseev, and I. I. Mokhov

Carried out are numerical experiments with the IAP RAS global climate model (IAP RAS CM) under new RCP scenarios of anthropogenic impact for the 18th–21st centuries taking account of the response of the methane emission from the soil to the atmosphere and effects of chemical processes in the atmosphere on the climate changes. The model generally simulates the preindustrial and present- day characteristics of the methane cycle. Methane emissions from the soil to the atmosphere (within the range of 150–160 Mt CH4/year for the present-day period) reach 170–230 Mt CH4/year by the late 21st century depending on the scenario of anthropogenic impact. The methane concentration under the most aggressive RCP 8.5 anthropogenic scenario increases up to 3900 ppb by the late 21st century. Under more moderate RCP 4.5 and 6.0 anthropogenic scenarios, it reaches 1850–1980 ppb in the second half of the 21st century and decreases afterwards. Under RCP 2.6 scenario, the methane concentration maximum of 1730 ppb in the atmosphere is reached in the second decade of the 21st century. The taking account of the interaction between the processes in the soils and the climate leads to the additional increase in the methane content in the atmosphere by 10–25% in the 21st century depending on the scenario of anthropogenic impact. The taking account of the methane oxidation in the atmosphere in the case of warming reduces the increase in its concentration by 5–40%. The associated changes in the surface air temperature turn out to be small (less than 0.1 K globally or 4% of the warming expected by the late 21st century).