Hysteretic Response of the Global Carbon Cycle to Anthropogenic CO₂ Emissions into the Atmosphere

Idealized numerical experiments have been performed with the earth system model developed at the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS ESM), under anthropogenic CO₂ emissions into the atmosphere, which increase initially and decrease afterwards. These numerical experiments revealed the inertia of various components of the earth system, leading to a delay in the response of various components of the carbon cycle relative to the anthropogenic emissions by several decades. The inertia of the carbon cycle components leads to a hysteretic response of its characteristics to anthropogenic CO₂ emissions into the atmosphere that are nonmonotonic in time and, noticeable, in particular, for the gross primary production and respiration of plants and soil. In turn, the hysteretic response of the characteristics of the global carbon cycle indicates the irreversibility of its changes on the scale of (at least) several decades. The latter should be taken into account when planning for adapting and/or mitigating climate change.