Quantifying the climate impacts of industrial fossil fuel producers
My postdoctoral research, conducted as the Hitz Fellow at the Union of Concerned Scientists, is now published in Environmental Research Letters. Additional materials for this work include a press release, fact sheet, and blog summary.
We find that emissions traced to products produced by the world’s largest 122 industrial fossil fuel and cement producers (Carbon Majors) between 1854-2020 contributed:
🌡️37%–58% to present day surface air temperature rise
🌊24%–37% to present day global mean sea level rise
Emissions from their products through 2020 are projected to add an additional 0.26-0.55 m to average global sea level rise through 2300. We find attribution to past emissions is robust regardless of future emissions trajectories.
We construct 3 historical counterfactual scenarios representing different paths that could have been taken:
🏭1854 counterfactual: the earliest time in the Carbon Majors dataset representing a hypothetical world where industrial fossil fuel development was largely avoided.
🏭1950 counterfactual: when some of the Carbon Majors knew of the impacts their products would have on the climate since the 1950s.
🏭1990 counterfactual: At the onset of international efforts to address climate change fossil fuels could have been rapidly phased out.
If the Carbon Majors stopped fossil fuel production in 1854 or 1950 our modeled results show present day surface air temperature rise ~0.39-0.66°C above preindustrial and CO2 concentrations below 350 ppm. The Carbon Majors emissions after these time periods are projected to add an additional 0.26-0.55 m to global mean sea level rise at 2300. If the Carbon Majors stopped production in 1990 we find present day surface air temperature rise would have been 0.65-0.9°C above preindustrial and CO2 concentrations likely below 370 ppm. Their emissions after 1990 are projected to add an additional 0.16-0.35 m to long term sea level rise.
We find that emissions traced to products produced by the world’s largest 122 industrial fossil fuel and cement producers (Carbon Majors) between 1854-2020 contributed:
🌡️37%–58% to present day surface air temperature rise
🌊24%–37% to present day global mean sea level rise
Emissions from their products through 2020 are projected to add an additional 0.26-0.55 m to average global sea level rise through 2300. We find attribution to past emissions is robust regardless of future emissions trajectories.
We construct 3 historical counterfactual scenarios representing different paths that could have been taken:
🏭1854 counterfactual: the earliest time in the Carbon Majors dataset representing a hypothetical world where industrial fossil fuel development was largely avoided.
🏭1950 counterfactual: when some of the Carbon Majors knew of the impacts their products would have on the climate since the 1950s.
🏭1990 counterfactual: At the onset of international efforts to address climate change fossil fuels could have been rapidly phased out.
If the Carbon Majors stopped fossil fuel production in 1854 or 1950 our modeled results show present day surface air temperature rise ~0.39-0.66°C above preindustrial and CO2 concentrations below 350 ppm. The Carbon Majors emissions after these time periods are projected to add an additional 0.26-0.55 m to global mean sea level rise at 2300. If the Carbon Majors stopped production in 1990 we find present day surface air temperature rise would have been 0.65-0.9°C above preindustrial and CO2 concentrations likely below 370 ppm. Their emissions after 1990 are projected to add an additional 0.16-0.35 m to long term sea level rise.
Surface air temperature (left) and sea level rise (right) in the control and each counterfactual scenario. Image via Sadai et al., 2025.
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Long-term sea level rise attributable to past emissions traced to products produced by the Carbon Majors. Image via Sadai et al., 2025.
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For this project I worked closely with my research partner, Meghana Ranganathan, and a team which included Alex Nauels, Zeb Nicholls, Kristina Dahl, Delta Merner, Brenda Ekwurzel, and Rachel Licker. This work was also supported by a huge team of people at UCS. Preliminary results from this work were shared at the American Association of Geographer's conference in 2023 and 2024.
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Coupling Ice Sheet Models and Climate Models
Seeking to advance the work from my first dissertation chapter (described below) assessing Antarctica's impact on global climate I worked from 2019-2022 on developing a method to couple the Community Earth System Model (CESM) 1.2 (Hurrel, 2013) and the Penn State University Ice Sheet model (PSU-3D) (Pollard & DeConto, 2012; Pollard & DeConto, 2015). CESM contains coupled ocean, atmosphere, sea ice, and land models. PSU-3D is a dynamic-thermodynamic ice sheet model with hybrid ice physics and a parameterization at the grounding line (Pollard and DeConto, 2012; Schoof, 2007).
Coupling the two models allows for a better view of how ice sheet mass loss impact climatology and in turn how meltwater-perturbed climatology impacts ice sheet evolution. Initial results can be found at this poster, and further results were shared at AGU 2022, AGU 2023, and the Community Earth System Modeling Workshops. This paper is now under peer review at Nature Communications.
Coupling the two models allows for a better view of how ice sheet mass loss impact climatology and in turn how meltwater-perturbed climatology impacts ice sheet evolution. Initial results can be found at this poster, and further results were shared at AGU 2022, AGU 2023, and the Community Earth System Modeling Workshops. This paper is now under peer review at Nature Communications.
Climate impacts of Antarctic Ice Sheet mass loss
The first chapter of my dissertation was published in Science Advances in 2020. We used used the Community Earth System Model (CESM) 1.2 to assess the global climate response to Antarctic Ice Sheet melt provided by the Penn State University Ice Sheet model (PSU-3D) from the publication DeConto & Pollard 2016. Results showed a delay in the increase of projected global mean surface air temperature (GMST) rise under RCP4.5 and 8.5 through 2250, and an increase in 400 m water temperature, particularly in the Ross and Weddell Seas (Sadai et al., 2020). The simulated changes in climatology have implications for ice sheet evolution, and the Paris Agreement. Press coverage of this work can be found here.
A preliminary assessment of the interaction between the competing feedbacks seen in this paper was published in Nature in 2021. In this work we used the meltwater-perturbed climatology from Sadai et al., 2020 to drive the PSU-3D ice sheet model. The net result of the two competing feedbacks- 1) the reduction in surface air temperature delaying surface melt and 2) the increase in 400 m ocean temperature accelerating basal melt was a delay in the pace of ice loss.
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Image: Ensemble simulations of ice sheet response under RCP8.5 show a 5-10 m projected Antarctic contribution to sea level rise by 2300. Forcing for the ensemble used 400 m ocean temperatures provided by CCSM4 (the precursor to CESM1) and atmospheric forcing provided by an RCM. Alternative simulations show the ice sheet response to CESM1 ocean and atmosphere forcing in a control simulation (red) and meltwater perturbed simulation (blue). This image is from DeConto et al. 2021. |
Dr. Yue Dong has led work exploring the mechanisms behind Antarctic meltwater delaying surface air temperature rise in her paper "Antarctic Ice-Sheet Meltwater Reduces Transient Warming and Climate Sensitivity Through the Sea-Surface Temperature Pattern Effect." This work finds that:
- "Accounting for Antarctic meltwater input in a global climate model reduces the global warming rate and produces a warming pattern closer to the observed
- Antarctic meltwater impacts not only the Southern Ocean, but also the tropics via teleconnections
- The reduced global warming rate is driven by changes in both ocean heat uptake efficiency and radiative feedbacks"
Projecting ice sheet contributions to future sea level rise
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Dr. Natalya Gomez led work exploring how coupling ice sheet models and glacial isostatic adjustment models impacts projections of future global sea level finding that under low emissions scenarios the solid Earth can help reduce ice mass loss. My contribution to this paper was to map the global fingerprint of the sea level projections and discuss the spatial variability of these projections, following the methodology I used to project impacts to Alliance of Small Island States member nations in my Earth's Future climate justice paper. Dr. Gomez and I co-wrote an explainer blog for this work which can be found here, and a press release is here.
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Both maps show sea level rise projections at the year 2150 in the simulations where we use the realistic Earth structure. Darker blue means higher sea level rise. On the left is a map of how sea level rise changes in the low emissions scenarios. Take note that in the low emissions scenario, the highest sea level rise is 0.35 m or 1.5 ft. On the right is the high emissions scenario: note that the darkest blue is 3.6 m of sea level rise, or 11.8 ft! Credit: Gomez, et al., 2024; produced by Shaina Sadai. Caption and image are from the explainer blog linked above.
Recorded research talks
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"Investigating Antarctic Ice Sheet-Climate Feedbacks and Climate Justice Implications" was a talk given at the NASA Goddard Sea Level Rise seminar series in April 2023.
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"Investigating Antarctic Ice Sheet-Climate Feedbacks and Climate Justice Implications" was a talk given at the NASA Goddard Sea Level Rise seminar series in August 2021 about my 2020 Science Advances publication.
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"Antarctica and Paris Goals: Risks of Massive Sea Level Rise from Antarctica" was a joint presentation with my PhD advisor, Dr. DeConto which was given at COP26 in Glasgow.
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"Sea Level Rise, Climate Justice, and Antarctica" was a talk on my dissertation work on the UNFCCC, sea level rise, and climate justice given at COP26 in Glasgow (see this page for more on that research). At COP26 I also had the honor of being taught some Inuit dance steps by Piita Taqtu Irniq, which you can see it starting at minute 1:29 of this video.
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