From Permian To Post-Modern: Changing Climate And Hab-Itability In A Warming World

The climate on planet Earth is a forever-changing, dynamic system. From the tiniest microorganismsto the largest planetary-scale processes, countless factors drive changes across timescales ranging frommilliseconds to millions of years. While many of these drivers act slowly and subtly over geologicalepochs, others can trigger rapid and far-reaching transformations. In modern times, climate change islargely attributed to anthropogenic emissions from fossil fuel use, with rising atmospheric CO2 levelsas a central driver. The socioeconomic pathways SSP370 and SSP585 project that CO2 concentrationscould reach 710 to 900 ppm respectively in Post-Modern Earth (PM) by the year 2080 — roughly threetimes higher than in the Pre-Industrial (PI) era of the 1850s — without involvement from large-scaleplanetary processes. Similar atmospheric conditions have existed in Earth’s distant past. One suchepoch is the Pre–End Permian (PEP), which occurred approximately 250 million years ago. Duringthis period, atmospheric CO2 levels are likewise estimated to have reached between 710 to 900 ppm.However, the planetary conditions were drastically different, as nearly all landmasses were clustered intoa single supercontinent known as Pangaea, the days were 2 hours shorter than today and Earth received2% less solar radiation.In this paper we present a comparative study between three distinct periods — Pre-End Permian (PEP),Pre-Industrial (PI), and Post-Modern (PM) — to explore the influence of planetary-scale changes andanthropogenic CO2 emissions on Earth’s climate and inhabitability. By focusing on the magnitude ofchange rather than timescale, we isolate the effects of these climate drivers using K¨oppen-Geiger cli-mate classification and Wet-Bulb Temperature as key indicators. Computed climate simulations usingROCKE-3D for each scenario are used to evaluate shifts in land area fractions of climate zones andinhabitable regions. Our findings show that increasing CO2 concentrations from PI to PM scenarioscorrelate with global warming and expanding the areas of uninhabitability from the equator toward thepoles. A transition toward more arid climates with the reduction in ice-covered and tundra zones is alsoshown. When comparing PEP and PM using 710 and 900 ppm CO2 our findings show that planetary-scale changes give rise to larger and more uneven changes of the K¨oppen-Geiger climate classificationsthan anthropogenic CO2 emissions. The extent of arid- and cold climate decreases while the extent oftropical, temperate and polar regions increases from PEP to PM for both 710 and 900 ppm. These find-ings suggest that the overall magnitude of climate change is more strongly influenced by planetary-scaledrivers than by anthropogenic emissions alone. To further evaluate spatial and temporal patterns in thesimulated data, we applied a modified Mann-Kendall trend test. This non-parametric method, adaptedfor gridded climate data, was used to detect significant monotonic trends in both spatial distributionand mean climate variables. The results confirm that planetary-scale changes generally cause more pro-nounced shifts in both climate trends and mean values compared to those driven by rising atmosphericCO2 levels. Finally, we simulate Earth’s climate with transmission spectra to see if any changes in cli-mate can be seen through the eye of spectroscopy. No discernible spectral differences are found betweenthe epochs, suggesting that changes in Earths climate remain undetectable with this method.