Climate Extremes in a Warmer World: What the Pliocene tell us?

Weather and climate extremes, accompanied by adverse socio-economic impacts, are of great interest to the public and decision-makers. The prevalence of these events has intensified. Boreal wildfires have increased in frequency (e.g., Alaska and Siberia). Heat extremes have become more common in Southeast Asia and Europe, and droughts more common in East Africa and South America.

This project will facilitate a novel perspective on hydrological and heat extremes (e.g., wildfire, heat waves, droughts) through the study of a warm climate state in Earth history. The mid-Pliocene Warm Period (~3 million years ago) was the last time atmospheric CO2 was comparable to present (~400 ppm). Studies indicate that the during the mid-Pliocene global temperatures were up to 5oC warmer than the pre-industrial era. The Arctic Ocean was seasonally ice-free, boreal forests reached the Arctic coastline and sea level was metres higher than it is today. Given a rich body of geological evidence, and climate model data the Pliocene is a key focus for international palaeoclimate modelling efforts.

This project will investigate climate extremes during the mid-Pliocene using a spectrum of numerical climate models, that range in spatial resolution and complexity. These outcomes will be compared to both observational trends in climate extremes and simulations of plausible climate extremes of the near future under different greenhouse gas emission/stabilisation scenarios.

The project has three main objectives using historical observations to provide the necessary baseline for comparison:

- Analyse the geographical distribution, duration, and frequency of temperature extremes during the mid-Pliocene and compare these results to future climate scenarios.
- Analyse the geographical distribution, duration, and frequency of hydrological extremes (e.g., droughts, high intensity rainfall events) during the mid-Pliocene and compare these results to future climate scenarios.
- Elucidate the relationship between temperature/hydrological extremes and the geographical occurrence/likelihood of wildfires during the Pliocene. This will include reference to new geological data sets documenting wildfire occurrence through charcoal layers preserved in multiple terrestrial deposits.

Methods
The project will combine existing datasets of terrestrial Pliocene data with new records of fossil charcoal occurrence. It will use climate model outputs produced at Leeds and provided via members of the international Pliocene Model Intercomparison Project (PlioMIP), to investigate high-level granular climate data (e.g., statistical analysis of daily-monthly data). The student will examine climate data (3-hrly) from a set of high-resolution Atmosphere-only model (HadAM3H 1.25 x 0.87o) simulations as well as some of the worlds very latest climate and Earth System Model contributing to PlioMIP (e.g., NCAR - CESM2 & UK Met Office - HadGEM3-AO).