Could SRM help Cape Town avoid ‘Day Zero’ droughts?

Beninese climatologist Dr Romaric Odoulami is the lead author of a major new study that assesses how sunlight reflection might affect the chances of so-called ‘Day Zero’ droughts in Cape Town and its region.

When Romaric moved to South Africa in 2017, his first lesson on global warming was more visceral than he had anticipated. Within a few months, his new home of Cape Town nearly became the world’s first major city to run out of water, when a three-year drought dramatically reduced water levels in the reservoirs of the region. Climate change is expected to make these ‘Day Zero’ events much more frequent by the end of the century, both in Cape Town and other cities around the world. Here he tells us about his paper, his team’s work, and his journey as a researcher working at the intersection of climate science and agronomy.

How is climate change projected to impact South Africa and the Western Cape province?

Overall, Southern Africa is projected to become warmer and drier. In particular, the weather systems responsible for winter rainfall in the Western Cape province are expected to shift towards the south, exposing the region to more frequent and severe droughts which would have significant implications for water security, land degradation and agricultural production.

Tell us about your research: what did you study, what did you discover, and why is it significant?

Our latest paper—just published in Environmental Research Letters—assesses the potential local impacts of SRM on droughts and water availability in Southern Africa. More specifically, it uses climate modelling and the science of attribution to assess how SRM could influence the likelihood of future droughts as severe as Cape Town’s 2015-2017 ‘Day Zero’ drought.

Our study is noteworthy for a couple of reasons. First, it draws inspiration from an iconic event to analyse the potential impacts of SRM at a local scale. Previous studies remained at regional to global scales. Second, its findings are groundbreaking. Indeed, our study found that an event as infrequent as Cape Town’s ‘Day Zero’ drought—one in a hundred years—could become as frequent as one in six years under high-emissions global warming, and 95% of that increase would be due to human activities. Equally important, it also finds that using SRM to keep global temperatures at their 2020 level would bring this likelihood down to one in 75 years by the end of the 21st century—neutralising 90% of the increase in likelihood caused by global warming.

There are a few caveats however. First, this study focused on a specific type of event that occurred in the Western Cape from 2015 to 2017. While we could use this experimental design to study other regions, nothing indicates that the results would be the same. Second, these results are based on climate modelling: using a different model or a different scenario might yield different results. It is therefore crucial to keep these findings in the context of the study and avoid any generalisation.

Photo: Cape Town’s metropolitan area is home to more than 3.7 million people. In 2018, it almost ran out of water after a three-year drought. Credit: Marcelo Novais
Could this study be replicated for other regions that have been exposed to similar droughts?

This study could indeed be replicated for other regions of the world, for example Australia, Brazil, California or Spain that have also experienced extreme events such as long and severe droughts. As my area of interest is really the African continent, I would not want to lead such work. But I am happy to collaborate with anyone interested in doing a similar study elsewhere.

Can you explain the science of attribution—one of the innovative tools behind these findings?

The science of attribution is a young and fast-growing field which aims at quantifying the contribution of human-induced climate change to the occurrence of extreme weather or climate events. In the case of the severe drought that occurred in Cape Town in 2015-2017, we can use the science of attribution to assess how human-induced climate change contributed to the occurrence of the drought.

We do this by calculating and comparing the probabilities of occurrence of the drought in two different simulated worlds called “factual” and “counterfactual”. The “factual” world represents the actual world in which the drought occurred, while the “counterfactual” one is an idealised world in which there has been no human influence on the climate. Comparing the likelihood of the drought under these two situations allows to determine whether human-induced climate change has increased the likelihood of the drought and if so by how much. We applied the same approach to assess how likely SRM could influence the occurrence of ‘Day Zero’ level droughts in Cape Town in a future with and without SRM.

How did you come to work on climate research?

This is actually the result of a happy accident. My background is initially in agronomy, which was a heartfelt choice. My family has a farm in Benin and I used to spend my holidays helping there. This allowed me to develop a strong connection with farming and the rural world. But after completing my degree in agricultural engineering, I took a year off to travel and learn English. I then saw a call for application for a PhD programme in climate science advertised by the West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL). I applied and was selected. This is how I started working on climate science, initially in Nigeria at the Federal University of Technology, Akure and then here in South Africa at the University of Cape Town.

Now my dream would be to make my research as relevant as possible to African communities by addressing climate-related issues that are of interest to them, and then provide policy-makers with robust scientific evidence that can influence policy and practices over the continent. This new paper is a step in that direction which will be followed by others as part of our DECIMALS project since we are also planning to assess the implication of SRM for agricultural production—a key sector in Africa.

Photo: South Africa’s agricultural sector is one of the most diverse in the world, but it faces many risks due to climate change. Credit: Wynand Uys
Where did you get this taste for science?

I grew up in a French-speaking educative system—in Benin—and as in most of Francophone Africa, the scientific background is already strong starting from elementary and secondary school. So I was exposed to science early on and later completed a baccalaureate in mathematics and natural sciences. I then moved to the University of Abomey Calavi in Benin where I completed a degree in agricultural engineering. Throughout the years, I’ve always been in love with science and have always done my best to keep the flame alive.

How did you first hear about SRM?

My first encounter with geoengineering took place in 2013 at the Federal University of Technology. Prof. Babatunde Abiodun gave an outstanding presentation on the topic and his work modelling the climate impacts of large-scale afforestation in Africa. That day, I heard the word “geoengineering” for the first time. I loved the idea of being able to perform such research using powerful tools like climate models, and after discussing with him, he was keen to supervise my PhD research on assessing the impacts of large-scale afforestation on climate extremes over West Africa.

It’s only a few years later that I heard of SRM for the first time, as a postdoctoral research fellow at the African Climate and Development Initiative at the University of Cape Town. It was early 2018 and the SRM Governance Initiative had just issued a call for proposals on SRM research in developing countries. My mentor, Prof. Mark New, recommended that I lead a research proposal which we could submit and that’s what we did.

What did you think about it at the time?

Like most geoengineering approaches, SRM is very controversial. I find the concept interesting but also extreme—the kind of crazy idea that seems to come straight out of a science fiction movie! I hope the world never has to implement such a thing. Although SRM research is important to improve our understanding of its potential impacts, we should not consider SRM as an alternative to cutting our emissions.

What is the state of knowledge about SRM in South Africa?

Generally, knowledge of SRM in South Africa and the wider Southern African region seems relatively low. We were expecting to hold an outreach workshop earlier this year, which could have helped us assess the effective state of knowledge about SRM in the region. Unfortunately, the COVID pandemic forced us to put these plans on hold for now.

What would you like to see happening next with SRM research and engagement in Africa?

The DECIMALS Fund is a good initiative in support of SRM research in Africa. This publication is the third SRM research paper on Africa and from Africa, all of which came out in 2020 thanks to the fund; that’s a good start! We need to keep it up by producing more research that will help increase our understanding of the potential impacts of SRM on our climate, society, and the lives of people in Africa. We need to improve knowledge on the topic, and that calls for more research, meaning that more funding is required—especially in Africa.

But first and foremost, I believe such research shall serve a purpose, which is to inform society and policy-makers about SRM—what it is, how it could work, and what it could do. This is very important as policy-makers are the ones designing climate policies in our respective countries. The more they know, the more they can contribute to the global conversation around SRM and the more likely they will be to make the right decisions. Africa needs to have its voice and opinions heard when it comes to SRM, and I hope our research will contribute to that.

How is this search for policy-relevance shaping your research?

This question is very important. I want my research to serve a purpose that goes beyond informing the scientific community. As a researcher, my goal is to influence policies and practices which I think is the best way forward, especially in the context of developing countries which need research to support their development—one that is more responsible for humans and the environment. This is what I’ve tried to achieve with my team through this new research.

What would you like to study next when it comes to SRM?

There is still a fair amount of work going on in my team, including a study on assessing how SRM might influence projected changes in climate extremes in South Africa. We are also planning to work on the potential impacts of SRM on the agricultural sector in Africa. Much to look forward to!


Photo at the top: Dr Romaric C. Odoulami, lead author of this major new study on SRM (personal collection).

Interview written by François Pougel