Hydrogen: the fuel of the future? Modelling its environmental impacts.

**Please click on the 'Institution website' link to read more details and apply**

Hydrogen is being strongly promoted as a future fuel by governments across the world. It is generally viewed as a clean fuel with few (or no) environmental impacts. However, several studies have shown that hydrogen gas accumulation in the atmosphere has potentially important impacts on climate, ozone depletion, and air quality. It is crucial that these impacts are better understood, so that any side-effects of a future hydrogen economy are known in advance. This project aims to model the global atmospheric chemistry and physics of hydrogen and explore and quantify the mechanisms through which hydrogen leakage leads to impacts.

Hydrogen’s present-day atmospheric budget is currently poorly constrained; we have limited knowledge of its sources and sinks. Its largest source is from the photo-oxidation of methane and other volatile organic compounds, with additional emissions from geological sources, biomass burning, fossil fuels, and nitrogen fixation. Hydrogen is removed from the atmosphere by soil and vegetation uptake, and oxidation by the hydroxyl radical (OH). Hydrogen’s atmospheric lifetime is ~1-2 years, sufficiently long for it to be transported between the Northern and Southern Hemispheres. Although more hydrogen is emitted in the industrialised North, its atmospheric concentrations are larger in the Southern Hemisphere, because of the larger land fraction, and hence sink, in the NH.

Atmospheric hydrogen levels have increased from 350 ppb in the pre-industrial era to 550 ppb currently. It is unclear if this is mainly due to an increase in sources or a decrease in sinks. Hydrogen is not a direct greenhouse gas, however higher levels of hydrogen reduce OH, and hence lengthen the residence time of methane (methane's main sink is reaction with OH), increasing the levels of this key greenhouse gas (GHG). Higher levels of methane lead to more tropospheric ozone, another important GHG and air pollutant. Hydrogen also perturbs water levels in the stratosphere, leading to impacts on stratospheric ozone. 

This project will develop and use state-of-the-art atmospheric models to explore these processes and quantify the associated impacts for a variety of future hydrogen leakage scenarios. The PhD studentship is part of a wider international project funded by the Norwegian Research Council and several industrial partners, and will involve collaboration with several world-leading modelling groups in Norway, France, the USA and the UK.

Research questions

1. How well do we understand the present-day atmospheric budget of hydrogen, and the changes since the pre-industrial?
2. What are the impacts of the likely range of future hydrogen leakage on the environment?
3. What is the net effect on climate of replacing fossil fuels with hydrogen fuels?

Methodology

Year 1. 

You will explore the important mechanisms that control the hydrogen content of the atmosphere, in particular estimates of emissions, and the chemical and soil sinks of hydrogen, and how these are represented in state of the art atmospheric chemistry and Earth System models. Model integrations using prescribed hydrogen and methane concentrations will be used to update hydrogen’s GWP (Global Warming Potential). Emissions-driven models will be evaluated against available observations of hydrogen concentrations.

Year 2.

You will explore scenarios of future hydrogen emissions and consider the range of environmental impacts that these lead to. The focus will be on the most uncertain linkages, for example between hydrogen levels and impacts on OH, and how these translate into changes in methane and ozone.

Year 3.

With a detailed background understanding of hydrogen's atmospheric budget and effects, the full impacts of the range of possible future scenarios for hydrogen will be able to be put into context, including both the benefits from avoided fossil fuel emissions, but also any negative impacts from elevated levels of hydrogen. This research is expected to be of high impact and generate several key publications, which will be important milestones throughout the three years.  

Requirements

A quantitative science background (e.g., physics, chemistry, maths, computing, engineering), with an enthusiasm for atmospheric science. You should be prepared to analyse very large datasets and run complex Earth System models.

**Please click on the 'Institution website' link to read more details and apply**