The effect of global warming and global cooling on the distribution of the latest Permian climate zones

The end-Permian biotic crisis is commonly associated with rapid and severe climatic changes. These climatic changes are commonly suggested to have originated from solid Earth carbon degassing (leading to global warming), but aerosol- and ash-induced cooling induced by lava degassing has been suggested as well. The application of an Earth System Model of Intermediate Complexity has enabled a visualisation of the major climatic shifts on the supercontinent Pangaea caused by rapid temperature changes due to changed radiative properties from greenhouse gases. The reconstructed reference climate was validated by latest Permian climate indicative sediments to investigate the possible climatic shifts. From a set of 22 reconstructions which varied with temperature a minimum global annual mean temperature of 18.2 °C for the late Permian climate prior to the climatic perturbation event was determined. Starting from this pre-event setup, global warming and global cooling scenarios were simulated. The response of the end Permian climate system to temperature increase and decrease show marked differences. While global cooling is followed by major climatic changes in the high latitudes and replacement of boreal biomes by tundra and polar frost, the changes during global warming are less pronounced with only locally increasing aridity compensated by humidisation in other regions. The different behaviour of the climatic belts under warm and cold conditions is accompanied by different climate sensitivities caused by different strength of the snow cover–albedo feedback. Thus, changes in the energy balance of the latest Permian surface–troposphere system have a 30% higher perturbation potential during cold climate conditions than during warmhouse conditions. Therefore substantial global cooling resulting in coldhouse climate conditions and an annual global mean temperature below 18 °C is more efficient in perturbing the Earth palaeoclimate during the end-Permian warmhouse. The results suggest that global cooling mechanisms as injection of sulphur aerosols and ash particles from the Siberian Traps Large Igneous Province into the Late Permian palaeoatmosphere have a higher climate perturbation potential than a warming due to carbon greenhouse gases with a similar magnitude of radiative forcing.