Can global warming induce aridification in sub-tropical regions? Insights from geological global warming events

Climate modeling projections suggest that anthropogenic global warming will induce intensified dry conditions in Mediterranean regions. This projected hydroclimate change has potential impacts on water and food security. However, this prediction contrasts with some geological records that indicate wetter conditions in sub-tropical zones due to increased temperatures in the ocean/atmosphere system. Furthermore, model experiments are uncertain about the controls of global warming on the hydrological cycle because they may underestimate the influence of higher temperatures in biogeochemical cycles. These limitations have hindered quantification of hydrological cycle recovery timescales following global warming events–i.e., the time required to reestablish the hydrological cycle to a pre-warming state–which may affect development of climate policy and climate change mitigation strategies.
In our research, we studied the impacts of global warming on the hydrological cycle using the chemical and magnetic properties of a series of late Palaeocene-early Eocene (~52-57 millions of years ago) sedimentary rocks that are located in Italy, but were also part of the proto-Mediterranean continental  regions. 

Study area with its paleogeographic position and its current location in Italy. Modified from Piedrahita et al. (2024), Nature Communications. 

Late Palaeocene-early Eocene climates were characterized by hothouse conditions that may be similar to those projected for extreme scenarios of future anthropogenic climate change. Therefore, rock records of those geological times have been extensively used to identify possible environmental impacts of human-driven climate change. We found that global warming  events, associated with carbon cycle perturbations, intensified dry conditions in proto-Mediterranean continental zones. We also detected that precipitation variability, which was driven by orbital changes (Milankovitch cycles), was disrupted by increased temperatures in the ocean/atmosphere. Recovery timescales of the hydrological cycle following the greatest late Palaeocene-early Eocene global warming events exceeded ~20,000 years. 

Dry/wet index of proto-Mediterranean continental regions showing long-term aridification and rapid transitions to dry conditions during global warming/carbon cycle perturbation events. Hydroclimate recovery timescales following the greatest global warming events are indicated within dashed line boxes. Modified from Piedrahita et al. (2024), Nature Communications. 

Our research supports the notion that Mediterranean zones can experience aridification because of global warming, which remarks the need to limit anthropogenic greenhouse gas emissions to avoid long-term adverse environmental impacts of human-driven climate change.
—————————————————————————