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

Background

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 allow 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 carbon dioxide (CO₂) concentration was comparable to present (~400 ppm). Studies indicate that the during the mid-Pliocene global temperatures were up to 5^oC 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.

The Project

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.

Objectives

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 0.87^o) 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).

The student will have the option (depending upon technical progress and interest) to run a high-resolution regional atmosphere model (0.44^o and 0.22^o resolution). In such high-resolution models, the structure of weather events and their variability and extremes are more likely to be simulated accurately for the Pliocene.

Potential for high profile outcomes and publications

Using observational data sets alone it is often difficult to discern reliable trends in climate extremes. This project will provide a new perspective by analysing extreme climate extremes that characterise an equilibrium climate state warmer than the pre-industrial era. Comparison to newly published geological data provides the opportunity to ground truth model outcomes in novel ways.

An excellent training and research environment

The student will learn how to:

Implement geological reconstructions of past topography, bathymetry, and vegetation distribution within Earth system models (ESMs) and run models to test hypothesis.

Process earth system model output and interpret climate system dynamics and ground-truth against geological evidence.

Review and interpret Pliocene environmental records such as charcoal, working alongside members of the rich and diverse PlioMIP international project research team.

Student Profile

Candidates should have an undergraduate degree (2.1 or better) in Climate Science, Environmental Science, Mathematics, Chemistry, Physics, Computing, Earth Sciences or similar. A keen interest in climate modelling is required, although previous experience is not required as our training will equip the student with the necessary skills. A high-level of IT aptitude is essential. Experience in programming (e.g., Python or Matlab) is an advantage but not essential.