ActiveClimate, Earth & EnvironmentChemistry

VOLCANIC CLASSIC: VOLCANIC eruptions and CLimAte response - Stratospheric Sulfate isotopes in Ice Cores, data assimilation, and climate sensitivity

FunderUKRI
Recipient organisationUniversity of St Andrews
Funding£2.6M
PeriodDec 2024 — Nov 2029

In plain English

AI plain-English summary

Volcanic eruptions have jolted the climate 233 times in the last 2,000 years, and a new project will use those natural experiments to pin down how sensitive the planet really is to atmospheric changes. Climate models disagree sharply on how much the Earth warms when carbon dioxide doubles, a gap that makes future projections unreliable. One reason is that models also disagree on how the climate responds to volcanic sulfate aerosols, which cool the planet for one to five years after an eruption. The problem has been uncertainty in both the volcanic forcing—how much sunlight the aerosols actually block—and the global temperature response. This project attacks both unknowns at once. By measuring sulfur isotopes in ice cores with new technology, the team will determine the precise amount of stratospheric sulfate from each eruption, along with its latitude and season. They will then compare that to improved reconstructions of past climate, built by feeding new paleoclimate records into data-assimilation models. If successful, the work will produce robust observational constraints on volcanic climate sensitivity, which can be used to test and refine the leading climate models. Because model responses to volcanoes and to CO₂ are linked, narrowing the volcanic uncertainty will directly tighten the range of plausible future warming. The results will also inform the debate on solar geoengineering, which deliberately mimics volcanic cooling. This is fundamental science with no immediate practical application, but it addresses a core question that has resisted resolution for decades.

View original technical description
How does Earth's climate respond to perturbation? Despite decades of work, this fundamental question remains difficult to answer, with a wide range of climate sensitivities to external forcing persisting in state-of-the-art models. To improve understanding of the climate system and narrow the range of uncertainties in future climate projections, innovative new approaches are required. Here I propose a novel strategy that will provide unique new tests of climate models and emergent constraints on climate sensitivity, by harnessing the record of major volcanic eruptions. Volcanic eruptions exert an enormous influence on climate, as their sulfate aerosols reflect incoming sunlight, driving abrupt cooling on timescales of 1-5 years. However our ability to read this record is currently limited by uncertainties in volcanic forcing (the impact of eruptions on incoming radiation - primarily a function of stratospheric sulfate) and global climate response. By using cutting edge new technology to measure sulfur isotopes in ice cores, I will uniquely constrain stratospheric sulfate and eruption latitude and season, transforming knowledge of past volcanic forcing. I will compare this to new and improved reconstructions of global climate response, achieved by incorporating new, globally-distributed paleoclimate records into model-data assimilation products. By examining the climate response to each of the 233 major eruptions of the last 2000 years, I will provide robust observational constraints on volcanic climate sensitivity. I will use these to test sensitivity and feedbacks in state-of-the-art climate models. These tests will inform both understanding of the wide range of sensitivity to aerosols in current models and the debate on controversial geoengineering schemes. As model response to volcanoes and CO2 are linked, this work will ultimately be used to refine the range of sensitivity to CO2 rise and improve projections of future climate.

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Researchers

Andrea Burke (Principal Investigator)

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