Hokkaido U Reveals La Niña to El Niño Transition as Key Factor in 2022-2023 Earth Energy Absorption Surge

Understanding the Surge in Earth's Energy Uptake

Recent observations have pinpointed a remarkable surge in Earth's energy uptake during 2022-2023, setting the stage for record-breaking global surface temperatures and intensified climate extremes in the following year. Researchers from Hokkaido University, in collaboration with the University of Tokyo, have uncovered the primary driver behind this phenomenon: the dramatic shift from a prolonged multi-year La Niña phase to a strong El Niño event. This discovery, detailed in a groundbreaking study published in Nature Geoscience, illuminates how natural climate variability can amplify human-induced warming trends.

The study's lead insights come from Professor Shoshiro Minobe of Hokkaido University's Faculty of Science, Department of Earth and Planetary Sciences, alongside Ko Tsuchida and Associate Professor Yu Kosaka from the University of Tokyo's Research Center for Advanced Science and Technology. Their work leverages satellite observations and advanced climate models to dissect this extreme event, offering critical new understanding for climate scientists worldwide.

What is Earth's Energy Imbalance?

Earth's Energy Imbalance (EEI), also referred to as Earth's energy uptake, represents the difference between the solar energy absorbed by the planet and the thermal infrared radiation it emits back to space. In a balanced state, these fluxes are equal, maintaining stable temperatures. However, due to rising greenhouse gas concentrations from human activities, more energy is trapped, resulting in a positive EEI that fuels global warming.

Typically measured at the top of the atmosphere using NASA's Clouds and the Earth's Radiant Energy System (CERES) satellite data, EEI has averaged around 0.90 ± 0.15 W/m² from 2005 to 2019. The 2022-2023 period saw an extraordinary spike, with the October 2022 to September 2023 average reaching 1.94 W/m²—exceeding the historical mean by more than three standard deviations. This surge trapped additional heat equivalent to vast amounts of energy, accelerating ocean warming and atmospheric changes.

Understanding EEI is vital for climate modeling and prediction. Hokkaido University's research highlights how internal variability, like ocean-atmosphere interactions, modulates this forced imbalance, providing a more nuanced view of short-term extremes atop long-term trends.

Decoding La Niña and El Niño: The ENSO Phenomenon

The El Niño-Southern Oscillation (ENSO) is a recurring climate pattern involving fluctuations in sea surface temperatures (SST) across the equatorial Pacific Ocean. La Niña features cooler-than-average SST in the central and eastern Pacific (Niño 3.4 region), strengthening trade winds and upwelling cold water. This leads to global cooling effects, drier conditions in some regions, and wetter in others. El Niño, conversely, warms these waters, weakening trade winds and redistributing heat eastward, often causing opposite weather patterns worldwide.

The 2020-2023 period marked a rare 'triple-dip' La Niña, the longest since 1955-1957, with three consecutive years of cool phases. This built subsurface ocean heat reservoirs. The abrupt transition to the strong 2023-2024 El Niño released this stored heat, amplifying surface warming. Hokkaido researchers emphasize the multi-year persistence of La Niña as crucial, differentiating it from single-year shifts.

• La Niña (2020-2023): Increased cloud cover over Pacific, reducing shortwave absorption but sequestering heat subsurface.
• Transition (late 2022-early 2023): Subsurface heat upwells, clouds diminish, boosting net energy uptake.
• El Niño (2023-2024): Sustained warm SST, further enhancing EEI.

The Hokkaido University Study: Methodology and Data

To unravel the 2022-2023 EEI surge, the team employed multi-model ensembles from the Coupled Model Intercomparison Project Phase 6 (CMIP6), under Shared Socio-economic Pathway (SSP) scenarios like SSP2-4.5 and SSP5-8.5. These simulations allowed sampling of analogous La Niña-to-El Niño transitions over centuries of model data.

Satellite observations from CERES-EBAF provided EEI estimates, complemented by ERA5 reanalysis for circulation and GISTEMPv4 for global surface air temperature (GSAT). Key analysis involved compositing extreme EEI events, isolating forced responses via trend removal, and attributing contributions from ENSO sequences. Python codes and data are openly available on Zenodo, promoting reproducibility.

This rigorous approach confirmed that samples with multi-year La Niña precursors followed by El Niño replicated observed radiation anomalies, particularly shortwave increases over the Pacific.

Key Findings: Quantifying the ENSO Impact

The study quantifies the La Niña-El Niño transition's role at approximately 75% of the observed EEI extreme, atop the anthropogenic forced baseline. During La Niña, enhanced Pacific stratus clouds reflected more sunlight, but subsurface heat accumulated. The shift reduced cloudiness, allowing greater solar absorption while releasing ocean heat— a 'perfect storm' for energy uptake.

Model composites showed shortwave radiation anomalies dominating net EEI, with patterns matching CERES data: positive over the equatorial Pacific and mid-latitudes. Multi-year La Niña amplified this by 20-30% compared to single-year cases, due to deeper heat storage. Between 2022-2023, EEI heating exceeded prior El Niño onsets (e.g., 2015-2016) by over 75%.

• Observed EEI 2022/23: 1.94 W/m² (vs. historical mean +3σ).
• ENSO contribution: ~75% of anomaly.
• Forced response: Steady increase from GHGs/aerosols.

Links to 2023-2024 Climate Extremes

This EEI surge underpinned 2023's record heat, marine heatwaves, and events like Canada's wildfires and Europe's floods. Ocean heat content (OHC) hit new highs, with the upper 2000m absorbing ~68 ZJ extra during La Niña. The subsequent El Niño propelled GSAT anomalies to +1.5°C above pre-industrial, per related Hokkaido work.

Regionally, Northwestern Pacific SST records stemmed from EEI plus weak winds; similar dynamics in the Atlantic. These insights aid attribution science, distinguishing natural variability from trends.

Hokkaido University's Leadership in Climate Science

Hokkaido University, located in Sapporo, Japan, boasts a storied tradition in Earth sciences. The Faculty of Science's Earth and Planetary Sciences Department excels in paleoclimatology, oceanography, and atmospheric dynamics. Professor Minobe's group focuses on ENSO teleconnections and energy budget variability, building on prior works like regional extreme drivers.

Japan's investment in climate research, via MEXT and JSPS, supports such endeavors. For aspiring researchers, opportunities abound in higher ed research positions or Japan university jobs at institutions like Hokkaido U. Explore academic CV tips to advance in this field.

Japan's Contributions to Global Climate Research

Japanese universities lead in satellite tech (Himawari-8/9) and modeling. Collaborations with NASA/JAXA enhance CERES-like data. Hokkaido U's findings align with national efforts like the Green Transformation (GX) strategy, emphasizing adaptation. This study exemplifies how regional expertise informs global challenges.

Stakeholders, from policymakers to educators, benefit. Professors like Minobe mentor next-gen scientists; check faculty jobs or postdoc opportunities in Japan.

Challenges and Future Projections

Challenges include EEI observation uncertainties (~0.15 W/m²) and model biases in ENSO persistence. Warming may intensify multi-year La Niña frequency, per CMIP6, amplifying future surges. Projections under SSP5-8.5 show rising EEI baselines, with ENSO adding volatility.

• Risks: More frequent extremes (heatwaves, storms).
• Solutions: Enhanced monitoring, decarbonization.
• Outlook: Continuous CERES/JAXA data crucial.

Actionable: Support climate research scholarships; pursue career advice.

Photo by Rick Wallace on Unsplash

Conclusion: Implications for Science and Society

Hokkaido University's pioneering work reframes EEI surges as ENSO-amplified events, urging refined models and policies. As climate volatility rises, such research is indispensable. Stay informed via Rate My Professor, seek higher ed jobs, or explore career advice. Engage with university communities for deeper insights.