PLOS Climate PhD interview: Mitchell Dickau

In the latest in our series of interviews with PhD students in climate research, PLOS Climate speaks to Mitchell Dickau, who recently completed a PhD at Concordia University, Canada.

What did you study before your PhD, and why did you decide to go on to do a PhD?

My journey into climate science wasn’t exactly linear. I began my undergraduate studies at Concordia University in Montreal, Quebec, majoring in English literature and history. However, after a couple of years, I found myself increasingly drawn to the physical sciences. This curiosity led me to pivot my major to physical geography, where I discovered the power of using data to bridge the gap between global climate change and local impacts.

For my undergraduate honours thesis, I wanted to take the abstract concept of global mean temperature change and translate it into something culturally significant and relatable. I used CMIP5 climate model projections to estimate the future length of Montreal’s outdoor skating season under various emissions scenarios. In a city with over 200 rinks, skating is more than a pastime – it’s a cultural mainstay. Seeing how our future emissions would dictate the longevity of this local tradition sparked an interest in understanding Earth system responses.

That project was the definitive turning point for me. The study was published and received attention in the media. Seeing the tangible connection between global climate change and local impacts showed me the power of climate science to inform real-world outcomes. This motivated me to better understand the nuances of how the Earth system responds to anthropogenic emissions and to continue studying at Concordia University and begin a PhD in climate science.

Could you tell us about your project? What are the key questions you’re hoping to address, and what methods/approaches are you using?

My PhD research consisted of three questions related to key uncertainties in the climate system response to emissions that are relevant to climate mitigation policy. The first of these addresses the commitment made in the Paris Agreement to limit warming to well-below 2.0°C and to pursue efforts toward limiting warming to 1.5°C. In my research, I review estimates of how much more CO₂ we can emit before reaching these temperature thresholds – a measure known as the remaining carbon budget – and I explore how uncertainty in remaining carbon budget estimates might implicate policy decisions. This study can be found here.

The second area of my research focuses on the pathway to these temperature targets. Given that global CO₂ emissions and the current policy landscape suggest that we are likely to exceed the Paris Agreement thresholds, there is an increasing likelihood that we will overshoot these thresholds before returning to them using net-negative emissions. Driven by this likelihood, I studied how climate outcomes differ if we reach temperature targets only after a temperature overshoot, as opposed to a scenario where temperature never surpasses a given threshold. A preprint of this study can be found here.

Finally, I examined the role of nature-based carbon storage, which is featured heavily in mitigation strategies. While nature-based carbon storage has the potential to play a critical role in climate mitigation, it is also vulnerable to climate-driven threats like wildfires or human-driven threats like deforestation, which can lead to nature-based carbon storage only providing temporary storage. This vulnerability exposes a fundamental mismatch between the cooling impact of nature-based carbon storage and the centuries-long warming impact of fossil fuel emissions. Motivated by the potential that nature-based carbon storage may only provide temporary storage, I wanted to quantify the climate benefits of temporary carbon storage in idealized scenarios where carbon stored in the first half of the 21^st century is rereleased to the atmosphere in the second half of the century. A preprint of this study can be found here.

The primary tool I used in my research was an intermediate complexity Earth system climate model – the University of Victoria Earth System Climate Model (UVic-ESCM). Using the UVic-ESCM, I simulated both positive and negative CO₂ emissions pathways to investigate the Earth system response. This involved running large ensembles of paired scenarios, comparing baseline trajectories with overshoot scenarios or temporary carbon storage scenarios to identify how climate variables are affected by overshoot and temporary carbon storage.

What excites you most about your project, and about the wider field?

What excites me most about my work is the potential to inform practical, real-world decisions. For instance, my research on temporary carbon storage indicates that it provides only a small climate benefit, and that this small benefit largely disappears if temporary storage isn’t also paired with ambitious mitigation policies. Currently, some carbon markets allow fossil fuel emissions to be offset by nature-based storage that may only be temporary. My work has the potential to push these markets to recognize the inherent physical differences between nature-based storage that may only be temporary in nature and fossil emissions, which have a centuries long warming impact, hopefully paving the way for more scientifically robust and transparent carbon accounting.

Beyond my own projects, I am encouraged by the progress the wider climate science field has made over the last ~15 years. We have reached a consensus that halting warming requires emissions to reach net-zero, and we have begun to deeply explore the uncertainties associated with large-scale net-negative emissions. This exploration has, in my view, replaced previous overconfidence in our ability to reverse climate change with a more realistic understanding of the uncertainties associated with removing carbon from the atmosphere. Additionally, the development of methods to robustly attribute extreme weather events to climate change represents a giant step forward in how we understand and communicate the immediate impacts of a changing climate.

Where you would like to take your career next?

As I move into the next chapter of my career, I am focused on the practical application of climate modeling to the dual challenges of the net-zero transition and climate adaptation. I am particularly drawn to two areas: the evolving carbon dioxide removal space – where scientific transparency is essential for robust carbon accounting – and the climate adaptation sector, where my experience translating global models into local metrics can help inform resilient planning for the future. Ultimately, I see my future career as a bridge between the technical nuances of the Earth system and the high-stakes decisions facing policymakers and industry leaders today, whether that be in academia, industry, or government.

What are your thoughts on the future of climate research? 

I believe climate research is at a critical inflection point. We have reached a stage where all signs point to the same fundamental conclusion: our climate is changing in ways that create immense threats and costs, and avoiding the worst of this reality requires a drastic reduction in global emissions. While there is certainly nuance to be explored – such as resolving uncertainties in the Earth system’s response to future emissions and exploring tipping points – I don’t believe this overarching conclusion will change.

My hope is that as this reality increasingly pushes nations to reduce their emissions, the center of gravity in climate science will shift more toward adaptation and exploring the possibility of reducing global temperature. The next frontier of research isn’t just about predicting warming, but about the high-resolution, local-level climate projections needed to protect communities and ecosystems. We are moving from a phase of proving the problem to a phase of engineering and social cooperation, and I believe the most impactful future research will be that which directly bridges the gap between models and practical needs.