Award Announcement: Effects of SAI on Tipping Points & Climate Impacts
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Reflective is excited to announce our grantees for the Effects of Stratospheric Aerosol Injection (SAI) on Tipping Points & Climate Impacts funding opportunity.
We have selected thirteen grantee teams to perform research spanning two questions: how SAI might interact with tipping elements in the earth system, and how it might reshape climate impacts and their underlying processes.
We’d like to acknowledge all the incredible proposals we received, and thank all applicants for taking the time to submit one. Additionally, we’d also like to thank our amazing team of reviewers for providing peer reviews for all proposals, an essential step in our evaluation process.
About the Grant
The IPCC’s Seventh Assessment Report’s analysis of SAI will shape the field for years to come. AR7 will consider literature submitted by the end of March 2027, and its treatment of SAI will set the terms of the conversation for years. We designed this opportunity to expand the evidence base available to the report’s authors on these two vital topics, by supporting projects that can move fast to deliver new assessments and insight within that window.
The grant covers two topics:
Topic 1 — Tipping Points: Abrupt, hard-to-reverse shifts — a weakening of the Atlantic Meridional Overturning Circulation, the loss of major ice sheets, the dieback of large biomes — are among the most serious climate risks. Early evidence suggests sunlight reflection could ease pressure on some of the drivers behind these shifts, but to date there has been very little research on the interaction of SAI with tipping risks. New research is needed because SAI may drive novel responses in tipping points for a variety of reasons, including alteration of global temperatures without changing CO2 levels, changing of meridional temperature gradients and additional regional climate responses, among others.
Topic 2 — Climate Impacts: SAI’s downstream effects on food, health, ecosystems, infrastructure, and economies have had significant research. However, there have been more limited comprehensive assessments and process-level studies of these impacts, a research gap which the grant seeks to address.
We prioritized two kinds of contributions across both topics:
Novel insights into processes which drive the response to SAI
Expansion of the scope of current assessments, for example, to consider scenario dependence, inter-model uncertainty, or under-researched tipping elements/impacts.
About the Grantees
Please read more about the grantees and their projects below.
Map of groups funded with this opportunity Assessing SAI’s Novel Impacts on Extreme Heat Exposure, Human Health, and Economic Implications due to Modification of Diffuse Fraction
Dr. Yangyang Xu & Dr. Xiaohong Liu, Texas A&M University
The project addresses how SAI’s alteration of the direct-to-diffuse radiation ratio affects human heat stress and socio-economic outcomes, which are often overlooked in standard assessments. First, the team will mechanistically quantify how SAI modifies human heat stress across the Western Hemisphere — with a focus on tropical urban centers in Brazil and Mexico — by calculating Universal Thermal Climate Index (UTCI) and Wet Bulb Globe Temperature (WBGT) metrics using daily outputs from ARISE-SAI, UKESM1, G6-1.5K-SAI, and G6-1.5K-HiLLA simulations. Second, they will evaluate the political-economic disparity of these impacts by integrating mortality damage functions and labor productivity frameworks with GDP data to identify “winners” and “losers” under different SAI scenarios.
Can SAI slow or reverse a projected feedback amplification from methane wetland emissions?
Dr. Benjamin Gaubert & Dr. Simone Tilmes, NSF National Center for Atmospheric Research (NSF NCAR)
This project aims to provide an estimate of future methane emissions from wetlands under different climate projections with and without SAI. The team will use the CESM land model (CLM) driven with atmospheric forcings from G6-1.5K-SAI simulations to estimate wetland methane emissions, assessing the range of emissions needed to trigger potential tipping points and the amount of SAI that may prevent, slow, or reverse them. They will then use the Community Atmosphere Model with chemistry (CAM-chem) to quantify changes in methane chemical loss through forward interactive chemistry simulations, allowing assessment of the chemical feedback resulting from these emissions, the direct radiative forcing, and impacts on ozone and air quality.
Drivers, observable benchmarks and teleconnections of Antarctic Ice Sheet mass balance response across SAI simulations
Dr. David P. Schneider, Phare Manchot, LLC (Visiting Scientist at NCAR)
The project seeks to establish an updatable set of physically motivated metrics relevant to Antarctic mass balance which can be systematically applied across multi-model SAI experiments. First, the team will connect SAI strategies with the latest insights on the drivers of ice sheet destabilization — including dynamic ice loss and surface mass balance — by calculating a suite of metrics including basin-level critical temperature thresholds for tipping, surface mass balance, surface melt volume, meridional winds in the Amundsen Sea Embayment, Amundsen Sea Low depth and position, and Southern Hemisphere Westerly Winds. The team will analyze these metrics in the ARISE-SAI, G6-1.5K-SAI, and G6-1.5K-HiLLA experiments. Second, the team will use paleoclimate data assimilation products to develop an observational benchmark for the atmospheric response to major volcanic eruptions over the past two centuries, which can be used to assess model fidelity in representing SAI-like energy balance perturbations.
Evaluating stratospheric aerosol injections to stabilize free-atmosphere precursors of mountain cryosphere tipping points and impacts
Dr. Alfonso Fernández & Dr. Limbert Torrez, Universidad de Concepción
The project aims to evaluate how energy fluxes at the free-atmosphere freezing level height (FLHFA) respond to several climate scenarios — including SAI — across all major mountain regions hosting glaciers and/or permafrost. The team will pursue three specific goals: (a) compare annual and seasonal FLHFA trajectories globally across SSP and SAI scenarios; (b) quantify energy fluxes at the FLHFA to determine whether free-atmosphere conditions shift toward persistent melting conditions; and (c) statistically assess how the FLHFA energy budget scales with global warming levels using a bootstrapping-based sensitivity analysis. By leveraging the nearly direct impact of free-atmosphere climate forcing on the mountain cryosphere, the project will provide a thorough evaluation of whether glaciers and permafrost can be stabilized via SSP trajectories or SAI.
From Climate to Development: a full uncertainty-auditing of Stratospheric Aerosol Injection strategies
Dr. Pietro Andreoni & Prof. Massimo Tavoni, Politecnico di Milano
The project addresses the uncertainty gap in SAI emulators by developing a coupled, fully probabilistic climate–impacts emulator for climate futures with and without SAI, designed to make uncertainty explicit and policy-relevant. The team will build a modular spatial emulator extended with an SAI forcing term, trained on recent Earth System Model SAI simulations (such as G6-1.5K-SAI) and counterfactuals, while leveraging multiple ensemble members to quantify uncertainty in local responses. To determine which climatic variables ultimately matter for human systems, they will link climate anomalies and extremes to Human Development Indicators (HDI) using recent subnational empirical estimates — moving beyond GDP while transparently propagating socioeconomic and impact uncertainty. The project will then conduct global sensitivity auditing to attribute outcome uncertainty to climate response, SAI strategy, socioeconomic pathways, and impact estimation. The aim is to identify — if it exists — a robust deployment space where SAI benefits are statistically distinguishable from possible harms.
Global Assessment of Heatwave Extremes and Population Exposure under Diverse Stratospheric Aerosol Injection Strategies
Assoc. Prof. Gs. Dr. Mou Leong Tan & Mr. Feng Zeqian, Universiti Sains Malaysia
This project provides a comprehensive global assessment of how different SAI strategies may mitigate or alter the characteristics of extreme heatwaves and associated population exposure. Using CESM2-WACCM outputs, the team will quantify five heatwave metrics: frequency (HWN), maximum duration (HWD), total frequency (HWF), peak intensity (HWA), and average magnitude (HWM). Scenario and strategy dependence will be evaluated by comparing G6-1.5K-SAI, G6solar, and G6sulfur against conventional emission pathways (SSP2-4.5 and SSP5-8.5), with the 2020–2099 projection period divided into four 20-year periods. A key goal is to integrate these climate outputs with NCAR SSP2 and SSP5 population projections to estimate the “People-Day” exposure index. This enables an assessment of the potential role of SAI as a supplementary strategy for reducing heat-related risks, particularly in vulnerable tropical regions.
Here be dragons: Mapping terrestrial carbon cycle tipping points under joint SAI and carbon emissions
Dr. Cristian Proistosescu and Dr. Hannah Horowitz, University of Illinois Urbana-Champaign
The team will build two models to explore this. The first is a conceptual global model designed to yield clear analytical insight into what controls the tipping point. This model will be built by taking the Finite Amplitude Impulse Response (FAIR) model - the state-of-the art global model the IPCC uses to explore future warming scenarios - and implementing a physically based carbon model that allows for tipping point behavior. The second model adds latitude-by-latitude detail to capture how uneven warming patterns (like stronger warming in the Arctic) affect different carbon pools. The project has two main goals: (a) to understand how the land carbon tipping point behaves under the wide range of CO2 and temperature combinations that SAI makes possible (because SAI can cool the planet without lowering CO2); and (b) to understand how the specific north-to-south patterns of warming under different SAI strategies affect vulnerable carbon stores, particularly carbon locked in boreal soils.
Pyro SAI: Predicting Global Wildfire Risk under Stratospheric Aerosol Injection
Dr. Keren Mezuman, Columbia University
This project provides a comprehensive assessment of SAI-induced fire risk by linking atmospheric drivers to physical fire responses. Using high-fidelity G6-1.5K-SAI and G6-1.5K-HiLLA simulations, the team will first quantify the shift in vapor pressure deficit (VPD) and extreme fire weather (P95), then integrate these drivers into the pyrE interactive fire model to project changes in fire frequency, burned area, and smoke emissions. This dual approach will determine whether SAI-induced cooling effectively offsets the fire risk posed by altered precipitation patterns across diverse biomes, including Boreal North and tropical regions. Beyond spatial mapping, the project will evaluate shifting seasonalities by analyzing changes in the onset and duration of peak fire activity and smoke-exposure windows. Deliverables include an interactive Global Fire Atlas, regional time series projections of shifting fire seasonality, a peer-reviewed open-access publication, and a “Living Data Product” hosted on the Reflective Cloud for the continuous integration of future GeoMIP ensemble members.
Radiative Controls on Polar Tipping and Extremes in GeoMIP simulations
Dr. Louise Sime, British Antarctic Survey
This project will deliver a mechanistic, multi-model assessment of how SAI modifies proximity to stability thresholds and tipping drivers in the North Atlantic–Polar system, with particular focus on the Subpolar Gyre–Atlantic Meridional Overturning Circulation (SPG–AMOC) system. The team will quantify how SAI modifies key SPG–AMOC stability controls and tipping drivers — including sea-ice extent and export, freshwater and buoyancy surface fluxes, wind-driven heat and salt transport, upper-ocean stratification, and AMOC strength — and assess injection-strategy dependence alongside model structural uncertainty using ARISE-SAI ensembles, G6-1.5K-SAI, and G6-1.5K-HiLLA. They will also link shifts in background climate state to changes in polar temperature, ice-sheet mass balance, and weather extremes using established metrics and compound-event analysis. By determining whether SAI reduces, delays, or inadvertently exacerbates tipping risk, the project aims to provide a rigorous evidence base for assessing polar tipping dynamics under SAI scenarios.
Stratospheric Aerosol Injection and Ocean Carbon Uptake through 2100
Dr. Holly Olivarez, Climate Confluence, LLC (currently NOAA)
This project aims to elucidate the mechanisms driving ocean carbon uptake under SAI through the year 2100. Despite advancements in understanding ocean carbon uptake responses to natural and anthropogenic CO2, no published research exists on how SAI might impact ocean carbon uptake through 2100 or using dynamical responses rather than prescribed carbon concentrations. The project will leverage five new “ARISE-like” ensemble member simulations conducted with CESM2 paired with CAM5 — which incorporate actual CO2 emissions rather than prescribed concentrations, enabling novel insight into accurate carbon cycle coupling and feedback capture. The team’s goals are to: (1) investigate the response of ocean carbon uptake on global and regional scales through 2100, (2) explore the drivers of this response, and (3) compare the new simulations with the standard ARISE-SAI-1.5 simulations.
Stratospheric Aerosol Injection Impacts on the West African Monsoon System: A Mechanistic Understanding from Volcanic Analogs to Climate Intervention Scenarios
Dr. Amadou Thierno Gaye & Dr. Abdou Lahat Dieng, Cheikh Anta Diop University
The project will provide a focused, process-based assessment of how and why SAI may alter the West African Monsoon (WAM) behavior, moving beyond simple rainfall projections to identify the key dynamical mechanisms involved. The research pursues three interconnected objectives. First, the team will establish a high-resolution baseline climatology of the WAM (1981–2010) using observational and reanalysis datasets (CHIRPS, IMERG, ERA5) to characterize its mean state, variability, monsoon onset and cessation, and extreme rainfall indices. Second, they will use the 1982 El Chichón and 1991 Mt. Pinatubo eruptions as natural analogs for SAI to examine how stratospheric aerosol perturbations influenced monsoon dynamics, including the African Easterly Jet, low-level westerlies, and moisture transport. Third, they will extend this mechanistic framework to future projections (2035–2085) by comparing the G6-1.5K-SAI experiment against a no-SAI scenario (SSP2-4.5) to quantify SAI-induced changes in monsoon seasonality and intensity.
The Effect of Stratospheric Aerosol Injection on North Atlantic Subpolar Gyre Tipping
Dr. Matthew Henry, University of Exeter
This project will use existing Earth System Model simulations to investigate the effect of SAI on the North Atlantic Subpolar Gyre (SPG), a wind- and density-driven ocean circulation that has been identified as a possible tipping element. The research will combine expertise on SPG dynamics and SAI modeling to rigorously analyze if and how SAI would reduce SPG tipping risk. The team will address two main research questions: (1) how deep convection in the Labrador, Irminger, and Nordic regions reacts to global warming and SAI — depending on injection location, intensity, and starting point — through a broad scan of existing state-of-the-art scenario simulations including ARISE-SAI-1.5, G6-1.5K-SAI, and G6-1.5K-HiLLA; and (2) which processes and feedback loops determine SAI’s ability to reduce SPG tipping risk, addressed by analyzing a unique set of high-resolution CESM1 simulations at 0.1° ocean and 0.5° atmosphere resolution that explicitly resolve ocean eddies.
The impact of SAI on primary productivity and global food supply
Dr. Nicole Lovenduski, University of Colorado Boulder & Dr. Lili Xia, Rutgers University
The project will quantify and diagnose the response of ocean and terrestrial primary productivity to SAI and the UV radiation changes it would produce. The team will first analyze existing output from the recent G6-1.5K-SAI GeoMIP simulations to assess regional and time-evolving responses of ocean, terrestrial, and crop net primary production (NPP), and diagnose their drivers. They will then use this output to drive the FishErIes Size and functional TYpe (FEISTY) offline fisheries model to produce estimates of global and regional fish biomass under SAI. Additionally, using CESM2-UV — a new UV-capable version of the Community Earth System Model — the team will conduct novel simulations to quantify the impact of SAI-induced UV radiation changes on photosynthetic productivity. The project will shed light on how and why food supply might change at a global scale under SAI.
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