A new study published in Nature Geoscience offers important insights into the long-term shifts occurring in tropical weather patterns, resulting in a rise in severe weather events such as heatwaves and heavy rainfall in the Indo-Pacific region. These shifts may be largely influenced by global warming, among other factors. The research, titled “Indo-Pacific regional extremes aggravated by changes in tropical weather patterns,” adopts a novel approach that analyzes occurrence trends in weather patterns through atmospheric analogues, which relate to the concept of recurrences found in dynamical systems theory.
Unlike past methods that often focused on average climate behavior, this study’s approach effectively identifies occurrence trends for each type of daily weather pattern. This advancement allows for a thorough examination of their connections to extreme weather events, which was previously not feasible. The new methodology enabled researchers to pinpoint the development of fresh, large-scale atmospheric patterns that are intensifying regional weather extremes.
The research was spearheaded by graduate student Chenyu Dong and Assistant Professor Gianmarco Mengaldo from the College of Design and Engineering (CDE) at the National University of Singapore (NUS), in collaboration with a team of international scientists. They utilized advanced reanalysis datasets to explore the evolving weather systems in the tropical Indo-Pacific region. The findings reveal that since the 1990s, unusual weather patterns have become more frequent, while some prominent patterns have nearly faded away. These modifications are related to changes in the Pacific Walker Circulation, a fundamental driver of tropical weather and climate, which maintains uncertain future shifts as per current climate models. Tracking long-term trends in tropical Indo-Pacific weather has historically been difficult, especially on a daily basis due to the overlap of numerous variability modes that mask trend signals. This investigation stands out as one of the first to analyze long-term tropical weather pattern changes and their links to extreme events on a daily scale.
“Significant alterations in tropical weather patterns are remarkably worsening regional extremes, including heatwaves and heavy rainfall, in the tropical Indo-Pacific area. Our research represents one of the initial attempts to disentangle trends from variability in the tropics—a task that has historically been challenging. We demonstrate that the changes we observed cannot solely be attributed to interannual variability, and that anthropogenic global warming might be a contributing factor, although other influences could also play a role. More comprehensive analyses are needed to enhance climate modeling and adaptation strategies, particularly in the tropical Indo-Pacific, where current climate models face challenges in delivering reliable forecasts. It is crucial for Singapore and other Southeast Asian countries to advance climate projection capabilities and deepen understanding of changing tropical dynamics and regional extremes. This study is a crucial step in that direction,” stated Asst Prof Mengaldo from the Department of Mechanical Engineering at CDE, NUS.
Key findings
- Emergence of new weather patterns: Fresh large-scale atmospheric patterns that were uncommon before the 1990s have surfaced, while others that were once significant have nearly vanished. These new patterns are characterized by a stronger Pacific Walker circulation and are linked to wetter and warmer conditions in Southeast Asia, whereas the equatorial Pacific is experiencing dryer weather. These developments cannot be accounted for solely by interannual natural variability modes such as the El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). Instead, they are likely influenced by long-term trends dating from the 1940s to the present, which may be tied to global warming and additional factors. Despite being driven by a combination of different influences (excluding known inter-annual variability modes), these identified emerging patterns carry significant implications for current and near-future climate conditions.
- Marked increase in weather extremes: The emerging weather patterns are closely associated with a rise in regional weather extremes, specifically heatwaves and extreme rainfall events. In certain areas, these extremes can be up to four times more frequent compared to historical climatology. For example, various regions, including parts of Indonesia, Singapore, South India, the Philippines, and the western Pacific, show a significantly higher frequency of heatwaves compared to historical averages. Notably, areas around the South China Sea, such as Vietnam, the Philippines, and the Malay Peninsula, along with Singapore, South India, and part of the Indian Ocean near the Australian coast, are experiencing a considerable rise in extreme rainfall. The occurrence of such extreme weather changes is particularly alarming, as these are tied to long-term climate trends in a region that is highly susceptible to weather extremes.
- Importance of the study: These findings are vital in the climate change discussion, revealing that new and emerging weather patterns are leading to increasingly severe weather in a region inhabited by over a billion people, along with distinct and vulnerable ecosystems. The rise in heatwaves and extreme rainfall can result in severe heat distress and flooding. As extreme weather events create significant socio-economic and environmental challenges, understanding these changes is crucial for enhancing climate models and guiding future adaptation efforts.
This research involved an international team of climate scientists from premier institutions, including NUS, Institut Pierre-Simon Laplace (IPSL), Uppsala University, Stockholm University, the University of Cambridge, Columbia University, the World Meteorological Organization (WMO), and the Centre for Climate Research Singapore (CCRS). The team is dedicated to advancing climate research to better understand the effects of climate change on regional weather patterns and extremes.
“The emergence of new tropical weather patterns signals the impact of human-induced climate change on daily atmospheric dynamics. Our results indicate a significant rise in heatwaves and extreme precipitation in the Indo-Pacific, which may have serious ramifications not only for the region but for global climate patterns as well. This shift in weather patterns challenges our understanding of historical tropical variability and underscores the urgent need to enhance climate predictions and readiness for extreme events in vulnerable areas,” said Dr. Davide Faranda, Research Director at the Laboratoire de Science du Climat et de l’Environnement (LSCE) of the Institut Pierre-Simon Laplace (IPSL), French National Center for Scientific Research (CNRS).
“To mitigate the impacts of heatwaves and extreme rainfall, policymakers must engage in strict planning. More frequent heatwaves could drive up electricity demand, leading to potential outages, escalate heat-related health issues requiring sufficient hospital capacity, and cause crop failures threatening food security. Similarly, increased extreme rainfall may cause floods, posing direct threats to lives, buildings, and infrastructure. Extreme rainfall can also result in agricultural losses, contamination of drinking water, and landslides. Southeast Asia lacks extensive research on extreme weather, necessitating further efforts to effectively prepare policymakers and local communities for climate changes,” Asst Prof Mengaldo remarked.
