Atmospheric CO₂ response to volcanic eruptions: The role of ENSO, season, and variability

Frölicher, Thomas; Joos, Fortunat; Raible, Christoph; Sarmiento, Jorge Louis (2013). Atmospheric CO₂ response to volcanic eruptions: The role of ENSO, season, and variability. Global Biogeochemical Cycles, 27(1), pp. 239-251. American Geophysical Union 10.1002/gbc.20028

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Tropical explosive volcanism is one of the most important natural factors that significantly impact the climate system and the carbon cycle on annual to multi-decadal time scales. The three largest explosive eruptions in the last 50 years—Agung, El Chichón, and Pinatubo—occurred in spring/summer in conjunction with El Niño events and left distinct negative signals in the observational temperature and CO2 records. However, confounding factors such as seasonal variability and El Niño-Southern Oscillation (ENSO) may obscure the forcing-response relationship. We determine for the first time the extent to which initial conditions, i.e., season and phase of the ENSO, and internal variability influence the coupled climate and carbon cycle response to volcanic forcing and how this affects estimates of the terrestrial and oceanic carbon sinks. Ensemble simulations with the Earth System Model (Climate System Model 1.4-carbon) predict that the atmospheric CO2 response is ˜60% larger when a volcanic eruption occurs during El Niño and in winter than during La Niña conditions. Our simulations suggest that the Pinatubo eruption contributed 11 ± 6% to the 25 Pg terrestrial carbon sink inferred over the decade 1990–1999 and −2 ± 1% to the 22 Pg oceanic carbon sink. In contrast to recent claims, trends in the airborne fraction of anthropogenic carbon cannot be detected when accounting for the decadal-scale influence of explosive volcanism and related uncertainties. Our results highlight the importance of considering the role of natural variability in the carbon cycle for interpretation of observations and for data-model intercomparison.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Physics Institute

UniBE Contributor:

Frölicher, Thomas; Joos, Fortunat and Raible, Christoph

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

0886-6236

Publisher:

American Geophysical Union

Language:

English

Submitter:

Doris Rätz

Date Deposited:

15 Sep 2014 11:25

Last Modified:

15 Nov 2016 15:28

Publisher DOI:

10.1002/gbc.20028

BORIS DOI:

10.7892/boris.47699

URI:

https://boris.unibe.ch/id/eprint/47699

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