Dr Rebekah Horner celebrates PhD success on air pollution and climate research

Bex’s thesis, ‘Advancing the understanding of global tropospheric nitrogen oxides (NOx) and ozone: insights from the GEOS-Chem model and satellite-derived datasets of lightning NOx production rates and vertically resolved NOx and ozone abundances’, reflects the scale and ambition of her work.

Her research combined satellite data, in situ measurements, and atmospheric models to explore two major air pollutants: nitrogen oxides (NOx) and ozone (O₃). These gases have wide-ranging impacts on air quality, human health, and climate.

“I focused on how these pollutants are distributed vertically in the atmosphere because their altitude matters just as much as their quantity,” she explained. “A key part of my work involved a technique called cloud-slicing, which helps us figure out the concentration of pollutants at different altitudes using satellite data. This kind of insight is important for improving atmospheric models used by policymakers.”

Reflecting on the highlights of her PhD, Bex said: “I’ve always been drawn to Earth observation and atmospheric science. I wanted to apply my background in geophysics to real-world environmental issues. A highlight was publishing my first first-author paper and presenting at international conferences, where I could share my work with the wider scientific community.”

On the viva itself, Bex described the experience as “surprisingly enjoyable! It was a thoughtful and engaging discussion with examiners who were genuinely interested in my work. It felt like a fitting end to the PhD.”

Bex is now continuing her career in atmospheric science research. She has joined Ember as a Coal Mine Methane Data Analyst, tackling the often-overlooked climate challenge of coal mine methane emissions. “My work focuses on using satellite data and in situ data to monitor pollution and support evidence-based policy,” she said.

Asked what advice she would give to prospective PhD students, Bex encouraged: “Go for it. UCL Geography pushes you intellectually, but the support is there too. Be organised, embrace the collaborative nature of research, and don’t be afraid to ask questions (even the ones you think are too basic!).”