In June, Beninese oceanographer Dr Casimir Y. Da-Allada was lead author on the first SRM modelling paper to come from a Least Developed Country. We recently had a chance to catch up with him.
Casimir grew up in rural Benin and first became interested in climate change when he was a teenager. In the 2000s, rumours began to spread in his town that the world would come to an end due to “global warming”, but no one was able to explain the science behind the rumours. He wanted to find out more and chose to focus on science at high school and then physics and oceanography through his career.
Now, Casimir is part of one of the eight research teams funded by the DECIMALS fund. The Benin team’s first paper was published in June in Earth’s Future, and it explores how SRM could affect the West African summer monsoon. We recently had a chance to discuss the paper with Casimir, and to learn more about the pathways that brought him from rural Benin to leading the world’s first LDC study on SRM.
What are the main climate threats to Benin and its region?
Rising temperatures and floods are two major threats. Right now, it is flood season here, and many houses are being flooded while some people are no longer able to move around properly due to the impracticability of some roads. The climate is already changing, and changes to monsoon rains or rising sea levels will increasingly affect coastal towns like Cotonou. All these changes will have important socio-economic consequences, as they impact agriculture, water resources, health and energy production. We must therefore find effective adaptation and mitigation strategies—with or without SRM—and to do this, we must do more research.
Why is the West African summer monsoon important for people living there?
The West African monsoon is a wind system that blows over West Africa every year, usually from May to August. As the African continent warms up, it draws in moisture-laden air from the Gulf of Guinea, leading to the heavy monsoon rains. West Africa is highly dependent on rainfall, particularly because agricultural production is virtually rain-fed. But other economic sectors depend on it too, such as hydroelectric power generation. Monsoon rains are therefore crucial for the region’s economy.
Tell us about your research: what did you study, and what did you discover?
As I mentioned, the monsoon plays an important role in West Africa. However, the timing of the monsoon as well as the amount of rainfall associated to it vary considerably from one year to another. Some studies have shown that these changes will become even more pronounced due to climate change: some areas with high rainfall will receive even more rain, and other areas with low rainfall will receive even less of it.
Since it has been suggested that solar geoengineering could help slow or stop the rise in temperature that is causing these disruptions, our research team asked itself two questions: what would be the impact of solar geoengineering on West African monsoon precipitation, and what mechanisms would cause that impact? To understand this, we designed a study drawing from two simulations carried out under the RCP8.5 scenario—the most pessimistic in terms of greenhouse gas emissions. In the first simulation, SRM was used, while in the second it wasn’t. This allowed us to conclude that, relative to the present-day climate, SRM should globally reduce the excess of monsoon rains caused by climate change. But these reductions would not be uniform. In the southern and northern regions of the Sahel, SRM would reduce the excess of monsoon rains caused by global warming by an equivalent amount. But in the coastal regions of the Gulf of Guinea, the reduction caused by SRM would be much more significant. We were also able to determine that SRM would produce these effects largely through changes to monsoonal circulation.
What are the implications of these findings?
In our scenario, although SRM would work better for some areas than others, I find it reassuring that it seems to work well in the northern and southern Sahel, because these areas get their rains almost exclusively through the monsoon. This is indeed the only time of the year when rainfall gets this far north; if the SRM were to reduce rainfall there too much, it would be very problematic. But according to our models, this is not the case, and so much the better! On the other hand, we found that if we used SRM to mitigate the increase in temperatures by only one-third instead of trying to eliminate it altogether, then we would reach a compromise where SRM would lower temperatures a little but would not create a rain deficit in the coastal regions of the Gulf of Guinea. Adjusting the intensity of SRM could therefore lead to a more comfortable situation for these countries.
When I talk to people, a frequent confusion about our results is to think: “There were already water problems. Luckily, we would have a little bit more rain because of climate change, and now you want to take it all away?” So, I explain to them that this is not the case: our models indicate that we would keep a moderate increase in rainfall compared to the present-day climate, which would be beneficial for the region while reducing the risks associated with rising temperatures. This means that people would even get a little bit more rain than before for their crops.
Why are these results significant?
Firstly, this is the first time that a comprehensive study has been done on the subject in the region. Secondly, our study looks at both the effects of SRM on our region and the mechanisms involved. This is crucial: understanding the underlying causes of reduced rainfall in West Africa will enable us to help improve or even initiate new strategies for injecting sulphur into the stratosphere so as to alleviate undesirable effects in regions such as those in the Gulf of Guinea. Having said that, we must remain cautious: these first results come from models and we must continue to work until they are confirmed by more studies.
Your team had to overcome some challenges, especially in order to get the data needed for your study despite limited internet access. How did you deal with these hurdles?
Getting hold of the data that we needed was very challenging indeed because we had to deal with limited internet access and huge data sets. Fortunately, the first DECIMALS meeting was at TWAS in Italy and that allowed us to download some of the data we needed to hard drives. Then SRMGI helped by sending us hard disks loaded with data, and also providing hard disks to our colleagues when they were travelling. But research is a dynamic process, so you can’t anticipate everything. We can very well think that this or that data will be sufficient, retrieve it, and then realise in the middle of our study that we would have to do further tests, but that this would require additional data that we don’t have, and which is perhaps too heavy to download from Benin. It’s sometimes frustrating, because I have ideas that I’d like to test, but I don’t even know if the data I think I need is really going to be useful. And so, I’d have to ask people to retrieve that data, mail it to me, and sometimes find out that I didn’t use it, because I would have needed more data. So, you have to get creative and do mental gymnastics to make the most out of the data you have.
How did you come to work on climate research?
In high school, I was lucky to have good teachers in maths and physics who believed in me and pushed me beyond my limits. As I was good at maths and physics, people started to ask me for help. It made me want to learn more and got me to love the subjects even more. By helping others, you also help yourself!
I then became interested in climate science as a teenager, when people in my town grew concerned that it could be a threat to humanity, but people couldn’t explain the science to me. I went to study physics and chemistry at Abomey-Calavi University in Cotonou—the only place that was offering these subjects in Benin. When I went there, I felt a bit sad because I wanted to do mathematics and physics but had to choose between them. I liked physics more, and I was advised: “The physicist is first and foremost a mathematician.” That convinced me, and I earned a master’s degree in physics and then taught it to high-school students for a few years.
Four years on, a new master’s degree in physical oceanography was launched at the International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair) of Abomey-Calavi University. I did not hesitate! After obtaining this Master’s degree, fortune smiled again and I was awarded a PhD scholarship co-financed by the French Institut de Recherche pour le Développement (IRD) and the French Embassy in Benin. I was thus able to complete a PhD in physical oceanography between Toulouse III University in France and ICMPA-UNESCO Chair in Benin. I then continued as a post-doctoral researcher in Brest in France before returning to Benin four years ago, this time as Associate-Researcher at the National University of Sciences, Technologies, Engineering and Mathematics of Abomey (UNSTIM) where I got a permanent position.
How did you first hear about SRM, and what did you think about it at the time?
It was through the DECIMALS call for proposals that I first heard about SRM in early 2018. The President of the National Academy of Benin—Professor Mahouton Norbert Hounkonnou, who had been my thesis director—forwarded it to me. Otherwise, I would probably have missed it!
What did I think about it? To be honest, I had not understood anything about SRM. Not a thing. I couldn’t understand how anyone in their right mind could consider artificially altering the climate when we are already experiencing problems. But being curious, I wanted to know more, so I spent a whole night reading about it on the internet. I then understood the idea much better, and how much debate there was about it! It piqued my curiosity and I thought that if there was a debate, then it would be nice to be able to take part in it. And to do that, you’d have to know something about it first.
So, I talked with another researcher on assignment at IRD in Benin, who also found the topic interesting and encouraged me to submit a project proposal. That’s how the idea came about, and one thing leading to another, we put together a team under Professor Ezinvi Baloïtcha’s lead and applied for a DECIMALS grants.
What is the state of knowledge about SRM in Benin and in West Africa? Have local people shown interest in your research so far?
This is something that is starting to attract people’s interest, mainly within the scientific community. Thanks to the workshop we organised jointly with SRMGI in Cotonou in August 2019, and thanks to the discussions we are having with our colleagues on the topic, a number of Beninese researchers are starting to gain a better understanding of what SRM is. Some are asking us questions, while others are even considering working on it. Sometimes the debate can be a bit heated at the beginning because it is such a controversial subject, but with pedagogy we manage to explain what we are doing and why, and a healthy dialogue starts.
So, we are still in the early stages, but we are no longer at square one. For example, we have offered internship subjects on SRM to our Master’s students, and last year two of our students defended their Master’s thesis at the TACCOVAR (Tropical Atlantic Climate and Coastal Variability) conference, which brings together every year in Benin nearly 70 researchers from all over Africa. On this occasion, we managed to make the subject and our work known to researchers from several African countries, which sparked genuine interest.
I have also been approached to give presentations, for example in Senegal (postponed due to COVID-19). Another conference is due to take place in October in Lomé, Togo, and I am also thinking of attending it to present our work. This outreach endeavour is important if we want to work with other colleagues from the region.
Your study is the first SRM research to come from West Africa, and the first from an LDC. What would you like to see happen next with SRM research?
At the moment, we are the only team in Benin studying the subject. So, I would like to see new research teams in Benin taking an interest in the subject in order to study more of its dimensions. Today, Benin and Côte d’Ivoire have the first two teams studying SRM in West Africa. With more teams in more countries, we could exchange further, compare our results, and cover more ground. I would very much like to see the emergence of a network of African researchers working on SRM and developing strong expertise, so that they will be able to advise our leaders the day they are, perhaps, led to take important decisions on this subject. Much more research has been done on SRM in the North than in the South. So today we need to step in and take a leading role so that we do not let other countries decide for us when the time comes for decisions to be made.
What would you like to study next in terms of SRM?
In a future study, we would like to look at the ocean dimension, because it plays such a key role in our climate. For example, we saw that SRM would overall induce a decrease in monsoon rains, a decrease that would in turn have repercussions on the ocean, for example on sea surface salinity which is influenced by rainfall. Similarly, what would be the effects of SRM on sea surface temperature, and what would be the implications? Finding out is always a joy for us researchers. Personally, I became a researcher in physical oceanography because oceans have a tremendous impact on the climate. So, I’m thinking of heading my future research in that direction.
Interview written by François Pougel