Zeng et al. (2025) Different Climate Responses to Northern, Tropical, and Southern Volcanic Eruptions in CMIP6 Models

Identification

• Journal: Climate
• Year: 2025
• Date: 2025-12-28
• Authors: Qinghong Zeng, Shengbo chen
• DOI: 10.3390/cli14010008

Research Groups

• College of Geo-Exploration Science and Technology, Jilin University, Changchun 130026, China

Short Summary

This study investigates how the spatial distribution of volcanic aerosols from Northern Hemisphere (NH), Tropical (TR), and Southern Hemisphere (SH) eruptions modulates climate responses using CMIP6 models. It finds that hemispheric aerosol distribution strongly controls radiative forcing, surface air temperature, and hydrological responses, leading to distinct ITCZ displacements and ENSO-like patterns (El Niño-like for TR/NH, La Niña-like for SH).

Objective

• To examine how the spatial distribution of volcanic aerosols from Northern Hemisphere (NH), Tropical (TR), and Southern Hemisphere (SH) eruptions modulates climate responses.
• To elucidate the mechanisms driving these responses by analyzing the spatial and temporal characteristics of climate anomalies.
• To contribute to a more comprehensive understanding of the climatic impacts of volcanic eruptions and inform improvements in the representation of volcanic forcing in climate models.

Study Configuration

• Spatial Scale: Global, Northern Hemisphere, Southern Hemisphere, Tropical (20°N–20°S for tropical mean SST), equatorial Pacific, Intertropical Convergence Zone (ITCZ). Model outputs bilinearly interpolated onto a uniform 2.5° × 2.5° grid.
• Temporal Scale: Historical simulations covering 1850–2014. Decadal Climate Prediction Project (DCPP) simulations covering 1960–2018. Superposed Epoch Analysis (SEA) applied over a compositing window from 4 years prior to the eruption to 7 years after, with a focus on monthly and annual post-eruption responses.

Methodology and Data

• Models used:
  • Coupled Model Intercomparison Project Phase 6 (CMIP6) historical simulations (multi-model ensemble, minimum 10 ensemble members per model): ACCESS-CM2, ACCESS-ESM1-5, CanESM5, CESM2, CNRM-CM6-1, GISS-E2-1-G, GISS-E2-1-H, INM-CM5-0, IPSL-CM6A-LR, MIROC-ES2L, MIROC6, MPI-ESM 1-2-HR, MPI-ESM 1-2-LR, MRI-ESM 2-0, NorCPM1, UKESM1-0-LL.
  • CMIP6 Decadal Climate Prediction Project (DCPP) protocols A (with volcanic forcing) and C (without volcanic forcing): EC-Earth3, CESM1-1-CAM5-CMIP5, CMCC-CM2-SR5, CanESM5, HadGEM3-GC31.
• Data sources:
  • Observational datasets: HadCRUT5 for near-surface temperature, Global Precipitation Climatology Centre’s (GPCC) Full Data Reanalysis Version 6 for precipitation.
  • Volcanic forcing: CMIP6 standard dataset for stratospheric aerosol optical properties (referenced at 550 nm wavelength, following Thomason et al. [32]). Latest volcanic aerosol reconstruction dataset [42] for eruption classification.
  • Variables analyzed: Monthly mean surface air temperature (SAT), sea surface temperature (SST), precipitation, and 850 hPa wind components (zonal and meridional winds).
  • Statistical method: Superposed Epoch Analysis (SEA) with Monte Carlo testing for 95% confidence level. Volcanic events (VEI ≥ 4) classified into NH, TR, and SH based on the ratio of aerosol loading between hemispheres.

Main Results

• The CMIP6 multi-model ensemble reasonably reproduces observed climatological patterns of surface air temperature and precipitation, with the multi-model ensemble mean (MME) showing improved performance.
• Radiative Forcing and Surface Air Temperature (SAT):
  • Tropical (TR) eruptions cause nearly symmetric global cooling, but SAT responses show clear hemispheric differences due to unequal land/ocean distribution.
  • Northern Hemisphere (NH) eruptions lead to stronger radiative forcing and SAT response in the NH, amplified by the larger land fraction.
  • Southern Hemisphere (SH) eruptions exhibit stronger radiative forcing and SAT response in the SH.
  • Global mean SAT cooling typically peaks around 1 year after eruption, persisting for 2 to 3 years and recovering in approximately 5 years.
• Precipitation and ITCZ:
  • TR eruptions result in a broad reduction in tropical precipitation and slight increases in subtropical regions.
  • NH and SH eruptions induce a pronounced displacement of the ITCZ away from the perturbed hemisphere, leading to significant precipitation suppression in the forced hemisphere and increases in the opposite hemisphere.
• ENSO-like Response:
  • TR and NH eruptions favor El Niño-like warming in the central and eastern Pacific (positive relative SST anomalies) in the year following the eruption, associated with westerly wind anomalies and Bjerknes feedback.
  • SH eruptions induce La Niña-like cooling (negative relative SST anomalies) in the eastern Pacific, associated with enhanced upwelling and Bjerknes feedback.
• Vertical Temperature Structure: All eruption types show characteristic stratospheric warming and tropospheric cooling. TR eruptions exhibit a largely symmetric vertical structure, while NH and SH eruptions produce pronounced asymmetric anomalies with stronger lower-stratospheric warming in the erupting hemisphere, enhancing cross-equatorial energy transport and Hadley circulation shifts.
• Contribution of Internal Variability: DCPP experiments confirm that the identified post-eruption cooling and circulation responses are primarily driven by volcanic forcing, effectively isolating them from internal climate variability.

Contributions

• Provides the first comprehensive multi-model ensemble assessment using CMIP6 historical and DCPP simulations to differentiate climate responses to Northern, Tropical, and Southern Hemisphere volcanic eruptions.
• Demonstrates the robustness of asymmetric cooling, ITCZ shifts, and distinct ENSO-like responses across a wide range of state-of-the-art climate models.
• Elucidates the critical role of aerosol asymmetry and the vertical temperature structure in shaping post-eruption climate patterns, including cross-equatorial energy transport and Hadley circulation shifts.
• Confirms that the observed post-eruption climate signals are primarily attributable to volcanic forcing rather than internal climate variability, leveraging the DCPP experiments.
• Advances the understanding of volcanic–climate interactions, offering insights for improving the representation of volcanic forcing and its impacts in future climate models and predictions.

Funding

• National Key Research and Development Program of China (2020YFA0714103)
• Department of Emergency Management of Jilin Province (JLSZC202002826-1)

Citation

@article{Zeng2025Different,
  author = {Zeng, Qinghong and chen, Shengbo},
  title = {Different Climate Responses to Northern, Tropical, and Southern Volcanic Eruptions in CMIP6 Models},
  journal = {Climate},
  year = {2025},
  doi = {10.3390/cli14010008},
  url = {https://doi.org/10.3390/cli14010008}
}