The effect of changes in cloudiness parameterization on the equilibrium climate sensitivity (ECS) of the climate model INM-CM4-8 is investigated. The reasonable changes in parameterization of cloudiness amount only lead to variability of ECS in INM-CM4-8 in the interval of 1.8 - 4.1 K, that is more than a half of the interval for CMIP6 models. Two mechanisms are mainly responsible to increase of ECS. The first one is increase of cloudiness dissipation in warmer climate because of increased water vapor deficit in non-cloud fraction of a cell. The second one is decrease atmospheric boundary layer cloudiness generation in warmer climate. The amplitude of natural climate variability change with respect to ECS change was studied. Increase of ECS doesn’t lead to increase of the value of natural climate variability at most time and spatial scales.