1. Introduction

More frequent and intensified extreme weather events driven by global warming pose significant challenges worldwide. In this context, El Niño–Southern Oscillation (ENSO)—first identified in Peru—plays a critical role in shaping global atmospheric and oceanic patterns and remains a vital source of climate predictability. In the Asia–Pacific region, the additional influence of ENSO amplifies these impacts, contributing to heightened uncertainty in climate prediction. The recent climate symposium held in Peru to discuss ENSO underscored its importance in understanding and addressing the far-reaching implications of this phenomenon. The Asia–Pacific Economic Cooperation (APEC) Climate Symposium 2024—an official annual APEC climate-related event co-hosted by the APEC Climate Center (APCC) and the APEC host country—focused on integrating advanced climate science into policymaking to improve preparedness and resilience against ENSO, the most representative climate driver, and its associated impacts. With the theme of “toward a sustainable and resilient society through enhanced ENSO responses and preparedness,” the event showcased best practices, several case studies, and lessons learned to address the multifaceted impacts of ENSO on society (apcc21.org/board/BBSMSTR_000000000031?lang=en). The symposium, held over two and a half days, was organized in collaboration with the Meteorological and Hydrological Service of Peru (SENAMHI) and APEC Peru. It is particularly meaningful that this event took place in Peru, widely known as the home of ENSO.

2. ENSO and its global influence in a warming climate

ENSO is a coupled ocean–atmosphere phenomenon, with El Niño characterized by warm sea surface temperatures (SSTs) in the equatorial Pacific. Keynote speaker Professor Shang-Ping Xie from the University of California, San Diego, emphasized the global impacts of ENSO, highlighting its role in modulating extreme weather events and explaining how El Niño affects atmospheric circulation. Advanced prediction models now provide more accurate ENSO forecasts by analyzing key climate factors such as SST anomalies and circulation patterns over the equatorial Pacific. However, predicting ENSO’s future behavior in a warming climate still remains a challenge, with some models predicting increased intensity and others suggesting a decrease. He stressed that the rising global temperatures have intensified El Niño–induced effects, such as more frequent storm activity and heavy rainfall. On the other hand, he mentioned that the long-term warming trends might eventually moderate ENSO’s intensity, underscoring the importance of understanding the role of ENSO in climate variability. The interaction between SST patterns in the tropical Atlantic, Indian Ocean, and subtropical Pacific was also highlighted as a significant source of predictability, both directly and indirectly, through its modulation of ENSO. Finally, he concluded the need for better observation data, improved climate models, and a deeper understanding of ocean–atmosphere dynamics to enhance the prediction of ENSO and its global impacts.

3. Advanced science and technology in ENSO monitoring and forecasting

Ms. Michelle L’Heureux introduced advancements in ENSO forecasting, including a relative SST index of the National Oceanic and Atmospheric Administration (NOAA) which addresses limitations of traditional indices like Niño-3.4 (170°–120°W, 5°S–5°N) which depends on periodic climatological updates, causing inconsistencies over time due to shifting baselines. The new and alternative index, i.e., the tropical mean SST index, adjusts Niño-3.4 by subtracting an area-averaged SST across the tropical region (20°S–20°N), consequently producing a more stable indicator of ENSO conditions. Real-time monitoring of both indices was recommended to assess relative SST’s implications in a changing climate and to improve predictable resilience for ENSO events. Emerging technologies such as artificial intelligence (AI) and regional ocean–atmosphere models have been utilized and developed, which in turn could contribute to enhancing forecasting accuracy. For instance, the International Research Institute for Climate and Society (IRI) has made efforts to incorporate AI models into its ENSO plume forecasts, which provide probabilistic information, aggregating several dynamical and statistical models to extend current lead times for longer-range ENSO predictions. Dr. Andrew Robertson from IRI explained that subseasonal forecasts complement the gap between weather forecasts and seasonal predictions by offering temporal specificity and more sharpness at shorter lead times with the potential to capture ENSO-related features, enabling proactive climate risk management and decision-making. The diverse El Niño events, including eastern Pacific and central Pacific types, were highlighted by Dr. Ken Takahashi from the Geophysical Institute of Peru (GIP), focusing on their distinct impacts on the Peruvian climate. While recognizing the challenges for global models in predicting coastal El Niño events due to limited climate data and climate model biases, GIP is leveraging regional ocean–atmosphere models and AI to improve forecasts of coastal El Niño events whose frequency is expected to be increased due to climate change, amplifying local impacts on health, agriculture, and climate in Peru.

4. Impacts of ENSO on water, health, and agriculture and collaborative efforts

ENSO is not just a local phenomenon in the Pacific but has wide-ranging impacts on global climate, hydrological cycles, and socioeconomic conditions. Changes in ENSO can lead to extreme weather events affecting agriculture, public health, water management, and human society. In this regard, experts discussed the impacts of ENSO, focusing on water management, public health, and agriculture and how these are currently being mitigated through research and collaboration. In terms of water management, Dr. Jing-Shan Hong from the Central Weather Administration (CWA) of Taiwan shared insights on the “triple dip” La Niña event that occurred from 2020 to 2022. Taiwan, whose climate is influenced by the major climate drivers of the Pacific–East Asian regions, experienced a severe mega drought during this period due to significantly reduced rainfall and the absence of typhoons, which are vital for replenishing water resources. Concerning this, CWA closely collaborated with their water agencies to manage droughts using high-resolution precipitation forecasts created by advanced forecasting techniques, including machine learning algorithms. From the public health perspective, Ms. Patricia del Pilar Rivera Giron from SENAMHI presented a study on dengue incidence in Peru, identifying specific climate thresholds and temporal lags associated with outbreaks. She noted a rising trend in dengue cases over the past 20 years (2001–22) in Peru, and the study found that the dengue incidence is positively associated with climate variables such as temperature, precipitation, and humidity. With these findings, she reiterated that understanding these thresholds which are significantly influenced by ENSO is vital for effective dengue outbreak management. Agriculture in Peru is closely linked to ENSO events, with El Niño often bringing heavy rains and floods that disrupt crops, while La Niña can lead to droughts. These events significantly affect food production and livelihoods. In fact, ENSO-induced heat stress impaired crop growth and increased water demand, further reducing crop productivity in 2023. In this context, Ms. Greys Otiniano Mego from SENAMHI shared their experience with participatory approaches, highlighting how engaging farmers in climate change adaptation fosters collaboration between technical specialists and the agricultural sector through shared knowledge and resources.

In order for local and regional communities to better respond to and sustainably manage ENSO events and their impacts, further understanding of ENSO and its climate teleconnections, such as extreme events, is necessary. Professor Sang-Wook Yeh from Hanyang University discussed the significant impacts of ENSO including altered hydrological cycles, extreme weather events, and their consequences on ecosystems and human society. He explained that the changes in the characteristics of ENSO and the ocean mean state in the tropical Pacific and elsewhere around the globe since the 1990s have altered ENSO atmospheric teleconnections in terms of precipitation and temperature. While changes in ENSO teleconnection patterns have contributed to the predictability and statistics of extreme events, the statistically valid significance of changes in precipitation, temperature, and extreme events linked to ENSO teleconnections is limited in many regions. Thus, understanding ENSO teleconnections under global warming requires more accurate simulation of the tropical Pacific Ocean’s mean state and ENSO properties, such as its spatial pattern and amplitude, for improving predictability and resilience. Case studies from Ecuador highlighted community-driven early warning systems, which effectively mitigated flood risks during the 2024 El Niño event. A comprehensive approach was taken to understand hazards and vulnerabilities using open-source software, enabling effective communication across municipal departments. This project involved collaboration between the municipality, researchers, and the community to design and implement the early warning system and resilience strategies of the region, underscoring the importance of collaboration among multilevel stakeholders.

5. Managing ENSO impacts through collaboration

The panel discussion featured a diverse group of experts representing public, academic, private, and international sectors in order to promote mutual understanding among stakeholders in the scene. Panelists shared insights as to collaboration efforts to enhance response and preparedness against ENSO and climate change in the Asia–Pacific region. Some key recommendations were made as follows:

First, it is important to implement comprehensive early warning systems focused on modeling, monitoring, and acting, with a strong emphasis on proactive measures to prevent climate-induced disasters. In addition to developing and standardizing early warning systems based on accurate and timely forecasts, it is vital to outline specific actions for volunteers, community members, and local authorities before, during, and after extreme climate events to save lives and protect livelihoods. A focus should be given to local-level protocols tailored to extreme conditions and prioritize actions based on lead times and forecast accuracy. Moreover, many participants emphasized that it is important for early warning systems for extreme events including ENSO to be imbedded within national climate action plans, targeting key areas like water, agriculture, and public health.

Second, promoting mutual understanding and coordination between climate information providers and users is essential for transitioning to a climate-resilient society. While the climate science community should make the climate information more accessible to users, the private sector, including financial institutions is encouraged to consolidate and translate technical climate data into more general terms so that companies can incorporate them into their decision-making. As global standards on the understanding and utilizing climate information evolve, institutions should align with those international climate frameworks to minimize climate-induced risks, utilizing the most reliable climate information available. Stronger coordination between private entities and government authorities was also emphasized to optimize resource deployment and prevent redundancy.

Third, it is necessary to increase efforts to bridge the communication gap between technical authorities and the public so that communities can fully understand risks and respond appropriately. Local authorities need to be well informed and capable of responding to forthcoming ENSO events to improve regional and local preparedness. At the same time, governments and academia are encouraged to partner with media outlets to timely and effectively communicate ENSO forecast and their impacts to the public.

These recommendations underline the critical need for practical, community-level solutions and cross-sectoral collaboration to enhance early warning systems and build resilience against ENSO-related risks. The APEC Climate Symposium 2024 reinforced the critical importance of innovation and collaboration across central and local governments, academia, and local communities in addressing ENSO-related risks. By integrating scientific advancements, emerging technologies, and cross-sectoral partnerships, the symposium charted a pathway toward a more sustainable and resilient future for the Asia–Pacific region.