During my interview for my undergraduate Engineering course at St John’s, I talked about how the photograph ‘Earthrise’, taken during the Apollo 8 mission in 1968, sparked my interest in engineering. At school I became captivated by the ambition and marvels of the space race of the 1950s and 60s. Learning about the monumental challenges that landing humans on the moon had entailed and how they had been overcome in such a short time inspired me to study engineering. I wanted to know more about the technology behind the camera that took ‘Earthrise’, and during each year at St John’s I had a copy of the photograph on display in my room.
Although I therefore came to St John’s with the ambition of specialising in aerospace engineering, during my first two years I came to realise that the world is facing a challenge far greater in scale and severity than putting a human on the moon ever was. A challenge that, if not overcome, will lead to catastrophe for the world, endanger all life and subject future generations to a world of turmoil: climate change. I was in a privileged position and felt that I had a duty – and a real opportunity – to contribute to the drive behind tackling climate change. As a result, I switched my focus and specialised in topics related to renewable energy and sustainability.
I learnt the disturbing reality of the situation: that we are not on track to keep warming of our planet below the target of 1.5°C by 2100, as set out in the 2015 Paris Agreement. In fact 2023 was, on average, 1.48°C warmer than pre-industrial temperatures. It just so happens that 1.5°C represents an acute tipping point for many of the world’s most vulnerable and vital ecosystems, including ice shelves, tropical reefs, boreal permafrost and the Arctic. Even if we were to halt global emissions right this instant, global temperatures would still rise and exceed the 1.5°C target way before the end of the century.
As we make tentative steps towards decarbonising, the disruption and destruction of ecosystems around the world will continue as a result of the changing climate. We are at a real risk of this damage being irreversible and losing these ecosystems entirely. It seems we need additional time to make the transition to a net-zero emissions world achievable, during which we need to protect and restore the most fragile and at-risk ecosystems to prevent their complete collapse. One potential saving grace could be solar radiation management strategies, such as marine cloud brightening – which is a topic I worked on during my undergraduate and Master’s degrees and am now doing a PhD on with the Centre for Climate Repair, funded by the Refreeze the Arctic Foundation.
Marine cloud brightening involves spraying tiny salt crystals into the atmosphere over oceans in an attempt to nucleate smaller droplets within oceanic clouds. This mimics the naturally occurring process of salt crystals from sea spray acting as cloud condensation nuclei (the particles required for cloud droplets to form). It is imperative that this injection of salt particles into already existing clouds reduces the average cloud droplet size as this increases the albedo of the cloud and brightens it; it is the opposite effect as to why rain clouds, with large cloud droplets, appear dark. The increased reflectivity of the cloud should then provide a cooling effect within the atmosphere. Marine cloud brightening is therefore being looked to as a way of providing either a localised cooling (for example targeting the Arctic or the Great Barrier Reef) or a larger scale global cooling to counter the global increasing average temperature.
To be clear, marine cloud brightening is not a solution for climate change. It is not a long-term strategy either, but it could provide vital additional time for countries to make the transitions required to meet their net-zero targets and to protect and repair environments being lost to rising temperatures. It also has the potential to reduce the severity of hurricanes, a weather event that will only become more frequent and severe as climate change worsens.
When I started learning about marine cloud brightening, I was surprised at how little research on it there was even though, if it were to work without any unintended consequences, it could be a lifesaver for this planet. I became increasingly fascinated by the topic as it aligned with my ambition of working in a field dedicated to combating climate change.
Unfortunately we are at a point where reducing emissions alone is no longer enough to avoid serious ecological damage…
For marine cloud brightening to be operational, however, there are significant engineering challenges related to generating the submicron salt crystals necessary for brightening clouds. My research focuses on novel techniques that could be used to generate these salt crystals from spraying and evaporating submicron droplets of seawater. The techniques I’m developing have the potential to be highly energy efficient droplet generation methods, which are crucial for achieving feasible and scalable deployment of marine cloud brightening. My work is aimed at evaluating the suitability of these droplet generation methods for cloud brightening through building and testing prototype sprayers.
The work so far has not been plain sailing, but I have found it immensely rewarding being part of a community dedicated to helping this planet. It is too early to know for sure whether marine cloud brightening will be feasible at the scale we need it or will work as well as we hope, but we have recently had encouraging results from our preliminary experiments with our prototypes and are looking to conduct field tests soon.
Unfortunately we are at a point where reducing emissions alone is no longer enough to avoid serious ecological damage, and the Arctic is predicted to have ice-free summers by 2030–40, which would be a catastrophe. We’ve entered a new stage where we must consider climate repair schemes such as marine cloud brightening, alongside rapid emissions reduction, if we want to ensure a safe planet for all.
Although the work is tough and there are many challenges left to overcome, I am driven by the fact that there is a chance, no matter how small, that this research could lead to a development that helps save critical ecosystems such as the Arctic, minimises catastrophic changes to the climate and keeps the 1.5°C target alive.
I decided to stay on at St John’s for my PHD because the College environment and community was wonderful throughout my undergraduate and Master’s degrees and I felt honoured to be part of that community. The College has been very supportive both financially and pastorally, and I have greatly enjoyed the last four years here – in no small part due to the Studentship bursary, which provided me with financial security and countless opportunities to enrich my studies and enhance my time in Cambridge.
The image ‘Earthrise’ will always be very special to me; however, I realise now that I have been viewing it wrong. What is truly captivating and empowering about that image is the beauty and fragility of the Earth.
