Kim et al. (2025) Hysteresis response of Northern Hemisphere winter temperature variability under different CO₂ removal pathways

Identification

• Journal: npj Climate and Atmospheric Science
• Year: 2025
• Date: 2025-12-01
• Authors: S.-J. Kim, Seung‐Ki Min, Soon-Il An, Maeng‐Ki Kim, Hyo‐Seok Park, Jong‐Yeon Park, Doo‐Sun R. Park, Hyun Min Sung, Young‐Hwa Byun, Kyung-On Boo
• DOI: 10.1038/s41612-025-01277-5

Research Groups

• Division of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang, South Korea
• Institute for Convergence Research and Education in Advanced Technology, Yonsei University, Seoul, South Korea
• Department of Atmospheric Sciences, Yonsei University, Seoul, South Korea
• Department of Atmospheric Sciences, Kongju National University, Gongju, South Korea
• Department of Marine Science and Convergence Engineering, Hanyang University, Ansan, South Korea
• Department of Earth and Environmental Sciences, Jeonbuk National University, Jeonju, South Korea
• Department of Earth Science Education, Kyungpook National University, Daegu, South Korea
• Climate Change Research Team, National Institute of Meteorological Sciences, Jeju, South Korea

Short Summary

This study investigates the hysteresis and reversibility of Northern Hemisphere winter daily temperature variability (Tstd) under different CO₂ removal pathways, finding that Tstd partially recovers but exhibits regional hysteresis and irreversibility, particularly in high-concentration scenarios, driven by changes in local temperature gradients.

Objective

• To investigate the hysteresis and reversibility of Northern Hemisphere winter daily temperature variability (Tstd) under various CO₂ removal pathways.
• To evaluate the influence of peak CO₂ concentration and CO₂ removal rates on the recovery of temperature variability.
• To identify regional factors contributing to irreversibility if complete recovery is not observed.

Study Configuration

• Spatial Scale: Northern Hemisphere (mid-latitudes 45°–65°N), Arctic (60°–90°N), eastern Canada (45°–65°N, 270°–300°E), northwestern Eurasia (45°–65°N, 0°–60°E), Barents Sea, Hudson Bay, North Atlantic Ocean.
• Temporal Scale: Northern Hemisphere winter (December–February, DJF). Simulations include ramp-up (140 years), ramp-down (140 years), and stabilization (150 years) periods. Key analysis periods are peak (±15 years from maximum CO₂), early stabilization (31 years post ramp-down), and late stabilization (last 31 years of stabilization).

Methodology and Data

• Models used: UKESM1-0-LL (atmosphere: N96 resolution, 85 vertical levels; ocean: 1° resolution, 75 vertical levels), Community Earth System Model version 1 (CESM1) (atmosphere: CAM5, 0.94° × 1.25° horizontal resolution, 30 vertical layers; ocean: POP2; land: CLM4; sea ice: CICE4).
• Data sources: Climate model simulations.

Main Results

• Increased CO₂ concentrations lead to pronounced Arctic warming and a substantial reduction in mid- and high-latitude daily temperature variability (Tstd).
• Tstd partially recovers following CO₂ removal, but the magnitude of recovery is regionally dependent and strongly influenced by the peak CO₂ concentration.
• In low- and middle-concentration experiments (L1%, M1%), Tstd nearly returns to pre-industrial levels during the stabilization phase.
• In high-concentration experiments (H1%, H2%), Tstd exhibits hysteresis and irreversibility, with persistent anomalies in eastern Canada and northwestern Eurasia even after 150 years of stabilization (e.g., H1% shows approximately +2 K in mean temperature and -0.4 to -0.2 K in Tstd anomalies).
• The degree of hysteresis, quantified by the hysteresis area, increases with peak CO₂ concentration (e.g., from 50 K·ppm for L1% to 309 K·ppm for H1%) but is less sensitive to the CO₂ removal rate.
• Regional differences in Tstd hysteresis are primarily driven by changes in local temperature gradients:
  • In eastern Canada, the dominant factor is the meridional temperature gradient (dT/dy), linked to persistent sea surface temperature (SST) anomalies in Hudson Bay (correlation with Tstd: -0.96).
  • In northwestern Eurasia, the dominant factor is the zonal temperature gradient (dT/dx) related to land-sea thermal contrast, influenced by incomplete cooling of the Barents Sea and weakened Atlantic Meridional Overturning Circulation (AMOC) (correlation with Tstd: -0.99 to -0.98).
• Variance budget analysis confirms that mean temperature gradient terms provide the most coherent explanation for regional hysteresis and partial irreversibility of Tstd, while diabatic and eddy heat flux convergence terms exert secondary or inconsistent influences.
• CESM1 simulations qualitatively confirm the UKESM1-0-LL findings, demonstrating robust Tstd hysteresis and spatially heterogeneous recovery, including in western Canada.

Contributions

• Provides the first systematic investigation into the hysteresis and reversibility of Northern Hemisphere winter daily temperature variability (Tstd) under various CO₂ removal pathways.
• Quantifies the dependence of Tstd recovery on peak CO₂ concentration and removal rates, highlighting the critical role of peak forcing.
• Identifies and elucidates distinct regional mechanisms (meridional versus zonal temperature gradients) driving Tstd hysteresis and irreversibility in key mid-latitude regions (eastern Canada and northwestern Eurasia).
• Utilizes a variance budget analysis to demonstrate that large-scale mean temperature gradients are the dominant control on Tstd hysteresis, rather than diabatic or eddy processes.
• Reinforces the robustness of Tstd hysteresis through multi-model evidence from both UKESM1-0-LL and CESM1, enhancing confidence in the findings.

Funding

• National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (NRF2021R1A2C3007366)
• Korea Meteorological Administration Research and Development Program under Grant RS-2024-00403386
• Human Resource Program for Sustainable Environment in the 4th Industrial Revolution Society
• Model simulation and data transfer supported by the National Center for Meteorological Supercomputer of the Korea Meteorological Administration (KMA)

Citation

@article{Kim2025Hysteresis,
  author = {Kim, S.-J. and Min, Seung‐Ki and An, Soon-Il and Kim, Maeng‐Ki and Park, Hyo‐Seok and Park, Jong‐Yeon and Park, Doo‐Sun R. and Sung, Hyun Min and Byun, Young‐Hwa and Boo, Kyung-On},
  title = {Hysteresis response of Northern Hemisphere winter temperature variability under different CO₂ removal pathways},
  journal = {npj Climate and Atmospheric Science},
  year = {2025},
  doi = {10.1038/s41612-025-01277-5},
  url = {https://doi.org/10.1038/s41612-025-01277-5}
}