Considerations of Earth climate sensitivity based on peculiarities of planetary heat capacity using system identification method: Runaway greenhouse effect scenario is still possible

Abstract: System identification method (SIM) was used to evaluate the Earth equilibrium climate sensitivity. According to our simulations, the equilibrium climate sensitivity was found to be between 2 deg C and 7 deg C. Analysis of the changes in heat inventory of oceans, atmosphere, land, and cryosphere was based on the experimental data of IPCC6. The equation derived for Earth's global surface temperature (GST) shows that the sum of the dimensionless feedback coefficients from water vapor, methane, and Earth albedo could be less than 1. However, due to the positive feedback from carbon dioxide (the combined greenhouse catastrophe) and the revised equilibrium climate sensitivity estimate based on an increase in equilibrium climate sensitivity, the probability of the runaway greenhouse effect increases significantly. It is still less than the critical number when not considering the feedback associated with carbon dioxide, water vapor, and methane buildup in Earth's atmosphere. The analysis considers the thermal dynamics of the oceans and other factors, including the exponential growth of the Earth's global temperature based on IPCC6 data.