Josh's Water Jobs – 2025-L17 ‘The Road Not Taken’: Impact of past and future climate policy on freshwater availability

Project highlights

This project will explain how past, present, and (potential) future climate related policies effect the hydrological cycle, the resulting impact on global freshwater distributions and the implications for food and water security. Particular focus will be on our current understanding of atmospheric moisture transport pathways and how new satellite measurements could be utilised to improve our understanding of the potential impacts.
You will design and conduct experiments using the UK Met Office HadGEM3 climate model with enabled water tracers. This new feature in the model will allow you to characterise the sensitivity of moisture transport to different emission scenarios. Climate quality and other high-performance datasets will be leveraged to assess your results, providing new insights into our ability to predict future global freshwater distributions.
You will collaborate with scientists from the British Antarctic Survey (BAS) and National Centre for Earth Observation (NCEO) with the opportunity to work on site through placements. Furthermore, this project provides you the opportunity to join the international activities within the Global Energy and Water Exchanges (GEWEX) community and the European Space Agency Water Vapour Climate Change Initiative

Overview

How will freshwater availability be affected by a warming climate? The world is already seeing extreme weather events, likely driven by current warming levels resulting from the industrial and legislative decisions already made, and are expected to increase in frequency and severity as the climate warms. Under potential future emission scenarios, we anticipate a global average temperature increase of 1.5°C to 4°C. The actual rise will depend on the choices and actions global we take to mitigate the impacts of this warming now and in the coming decade.

The hydrological cycle is a critical component of the Earth climate system, constituting the largest movement of any substance on Earth. Water vapour, while only accounting for 0.001% of all water mass, is an essential natural greenhouse gas influencing the radiative balance of the Earth as well as surface and soil moisture fluxes. The time moisture spends in the atmosphere (i.e. the time between evaporation and precipitation) is referred to as the Water Vapour Residency Time (WVRT) and is related to the rate of energy transformations and water mass turnover (sources and sinks) as well as providing essential insight into the time lags and linkages between processes (e.g. precipitation event and contributing evaporation sources).

Studies of past climates have provided us insights into the connections between large-scale atmospheric systems (e.g., extratropical storm tracks, tropical rain belts) and their response to different forcings (e.g., Ortega et al. 2015). However, when it comes to capturing small-scale processes responsible for the changes we would see throughout the day, or the distribution of cloud cover and rainfall can be challenging for climate models as they happen at smaller spatial scales than those resolved by the model. It is these processes which then strongly affect the rate at which the lower atmosphere warms, which is one way small scale processes impact large-scale circulation.

Therefore, advancing our knowledge of atmospheric moisture pathways, and thus improving our understanding of WVRT is a key challenge for understanding changes to global freshwater availability over the next 75 years.

(e.g., Marsham et al. 2013).

A three panel figure showing changes to global rainfall patterns under different global average temperatures under different climate change scenarios.

Figure 1: Adaptation of figure SPM.5 from the recent IPCC AR6 Summary for policy Makers (IPCC, 2021). Within possible warmer futures the rate of heating will drive changes in global precipitation patterns by modifying the time moisture resides in the atmosphere. The resulting changes to atmospheric moisture pathways redistribute moisture as it will potentially be transported further from where it was evaporated. It is important to note in dry areas (deserts or polar regions), large relative changes might only correspond to small absolute changes but have significant impacts.

Host

University of Leicester

Theme

Climate and Environmental Sustainability

Supervisors

Project investigator

Dr Tim Trent, University of Leicester, t.trent@le.ac.uk

Co-investigators

Dr Adam Povey, University of Leicester, adam.povey@leicester.ac.uk
Dr Louise Sime, British Antarctic Survey, lsim@bas.ac.uk
Dr Alison McLaren, British Antarctic Survey, aliren@bas.ac.uk

How to apply

Each host has a slightly different application process.
Find out how to apply for this studentship.
All applications must include the CENTA application form.
Choose your application route

Methodology

In this project, the student will learn to design and run experiments using UK Met Office HadGEM3 climate model and how to use observational datasets from satellites, reanalysis, and in situ measurements to evaluate their results. The project will begin by focusing on model runs within the current satellite era to investigate how well we understand how current natural and anthropogenic forcings can modify moisture transport. These experiments will aid in developing our understanding in how to use new satellite measurements of water vapour isotopologues can provide valuable new insights that could aid in model development or weather forecast accuracy. Finally, in line with upcoming model intercomparison efforts within the Coupled Model Intercomparison Project (CMIP), experimental runs that capture possible policy impacts on greenhouse gas emissions will be run and analysed at global and regional scales.

Training and skills

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.

NCEO will provide access to its Researcher Forum, staff conferences/workshops and national-level training. This has included machine learning and data assimilation courses in the past and is regularly updated.

University of Leicester (UoL) will provide training on using the energy balance model and data processing on the ALICE (Leicester) and JASMIN (NERC) HPC facilities.

There will be the opportunity to receive training at the British Antarctic Survey to work with a state-of-the-art water tracer enabled climate model.

The student will have the opportunity to take the UG Climate Physics and MSc Satellite Data Analysis in Python courses at UoL and other modules deemed suitable.

Partners and collaboration

This project has been developed in collaboration with the British Antarctic Survey who will co-supervise the project and provide training and access to the HadGEM3 model. In addition, a variety of other collaborations include:

European Space Agency – Climate Change Initiative (via Dr Trent, Dr Povey ESA Water Vapour and Cloud projects)
NCEO collaborators working on projects related to global energy and water cycles.
Global Energy and Water Exchanges (GEWEX) – (via Dr Trent, initially through the GEWEX Water Vapor Assessment)

Further details

We strongly encourage anyone considering an application to contact us in advance for an informal chat about the project at an early stage of any application..

Please get in touch with Dr Tim Trent (University of Leicester) at t.trent@le.ac.uk with any questions regarding this project.

To apply to this project: 

You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2025. 
You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities. 
Please submit your application and complete the host institution application process via: CENTA PhD Studentships | Postgraduate research | University of Leicester.  Please scroll to the bottom of the page and click on the “Apply Now” button.  The “How to apply” tab at the bottom of the page gives instructions on how to submit your completed CENTA Studentship Application Form 2025, your CV and your other supporting documents to your University of Leicester application. Please quote CENTA 2025-L17 when completing the application form.

Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025. 

Possible timeline

Year 1

Throughout the entirety of this project the student will spend some time at BAS each project year, the duration of each visit to be discussed and decided upon once the project is underway to ensure appropriate support.

Year 1: Review of existing literature, refinement of research plan & objectives, and training. Initial training will focus on computing skills needed for the project, including (but not restricted to) coding, HPC usage, executing model runs, and attendance at 1-2 suitable meetings/workshops. Analysis of model output from existing default setup with climate quality in situ and satellite products will allow the student to refine the research plan and objectives. The final objective for the year would be for the student to present their work as a poster at an appropriate national/international conference.

Year 2

Year 2: Design, run and analyse current era experiment(s) with the objective to publish the results in a peer-reviewed journal. The student would also look to present at one international meeting/conference and one national conference during this year.

Year 3

Year 3: Design, run and analyse future scenario experiment(s) with the objective to publish the results in a peer-reviewed journal. The student will also collect or create any new data required to run or validate the experiments. The exact nature of this work would be reviewed before starting the third year of the project. The student would also look to present at one international meeting/conference and one national conference during this year.

2025-L17 ‘The Road Not Taken’: Impact of past and future climate policy on freshwater availability - PhD