A new study reveals important information about the long-term shifts in tropical weather that are causing a rise in extreme weather events, including heatwaves and heavy rainfall in the Indo-Pacific region. These patterns are likely influenced by global warming, along with other factors.
A new study published in Nature Geoscience sheds light on the long-term transformations in tropical weather patterns that are resulting in a higher frequency of extreme weather events, such as heatwaves and intense rainfall, in the Indo-Pacific. These changes may be driven partially by global warming. The article, titled “Indo-Pacific regional extremes aggravated by changes in tropical weather patterns,” uses a new methodology to analyze trends in weather occurrences through atmospheric analogues, which tie into the concept of recurrence in dynamic systems theory.
This study deviates from earlier techniques that mostly focused on average weather behaviors. Instead, it tracks trends for individual daily weather patterns, allowing researchers to directly connect these patterns to extreme weather events—something that had not been feasible before. This innovative approach has made it possible to identify newly emergent large-scale atmospheric patterns that are worsening local weather extremes.
The research, led 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 partnership with an international team of scientists, utilizes advanced reanalysis datasets to study how tropical weather systems in the Indo-Pacific are changing. Their findings indicate that since the 1990s, weather patterns that were once uncommon have begun to occur more frequently, while some previously common patterns have nearly vanished. These transformations are associated with alterations in the Pacific Walker Circulation, a crucial factor influencing tropical weather and climate, though future changes in this circulation remain uncertain in current climate forecasts. Detecting long-term trends in this region has historically been challenging, particularly on a daily scale, due to overlapping variability influences that can obscure these signals. This study is among the pioneers in examining the long-term shifts in tropical weather patterns and their link to daily extreme events.
“Significant shifts in tropical weather patterns are greatly intensifying regional extremes, especially heatwaves and heavy rainfall, in the tropical Indo-Pacific. Our investigation is one of the first to untangle trends from variability in the tropics, a task that has been notably difficult. We demonstrate that the changes we observed cannot be entirely attributed to interannual variability factors, with anthropogenic global warming being a potential contributor, along with other influences. More thorough analyses are needed to enhance climate models and adaptation strategies, particularly in the tropical Indo-Pacific, where existing models struggle to deliver trustworthy predictions. For Singapore and other Southeast Asian nations, strengthening climate projection capabilities and understanding evolving tropical dynamics and regional extremes is critically important. This study marks a step towards achieving these goals,” stated Assistant Professor Mengaldo from the Department of Mechanical Engineering at CDE, NUS.
Key findings
- New weather patterns emerging: Large-scale atmospheric changes that were rare before the 1990s are now appearing, while other weather patterns that were previously dominant have vanished. These new patterns correspond with a stronger Pacific Walker circulation and are associated with increased rainfall and warmer conditions in Southeast Asia, as well as drier conditions in the equatorial Pacific. The pattern changes cannot be completely explained by natural interannual variability shifts like the El Niño Southern Oscillation (ENSO) or Indian Ocean Dipole (IOD). Instead, they are likely driven by enduring trends from the 1940s up to now, possibly influenced by global warming and other factors. Despite being possibly driven by a combination of various influences, excluding known interannual waves, the implications for current and near-future climates are significant.
- Marked rise in extreme weather events: The newly identified weather patterns are closely linked to a rise in regional extremes, particularly heatwaves and heavy rainfall. In certain areas, these extremes are up to four times more common in relation to historical norms when associated with emerging patterns. For instance, regions such as Indonesia, Singapore, South India, the Philippines, and parts of the western Pacific are witnessing a substantial increase in heatwaves compared to average conditions. Areas like the South China Sea and its neighboring regions, including Vietnam and the Philippines, as well as the Malay Peninsula and parts of South India, are seeing a notable increase in extreme rainfall. This rise in severe weather is particularly noteworthy, given the long-term climate trends in a region already vulnerable to such extremes.
- Importance of this research: These findings are crucial in the climate change context as they indicate that new weather patterns are contributing to increasingly severe weather conditions in a region inhabited by over a billion people and diverse vulnerable ecosystems. The growing occurrence of heatwaves and extreme rainfall can lead to significant health risks and flooding impacts. Understanding these changes is essential for enhancing climate models and guiding future adaptation plans in response to severe weather challenges.
This research was undertaken by a global team of climate scientists from prominent institutions, including NUS, Institut Pierre-Simon Laplace (IPSL), Uppsala University, Stockholm University, University of Cambridge, Columbia University, World Meteorological Organization (WMO), and the Centre for Climate Research Singapore (CCRS). The team aims to advance climate research to enhance our understanding of the effects of a changing climate on local weather patterns and extremes.
“The introduction of new tropical weather patterns signifies how human-induced climate change is transforming atmospheric dynamics daily. Our research highlights a notable increase in heatwaves and heavy precipitation in the Indo-Pacific, which could have serious implications, not just for the region but for the global climate as well. These changes challenge our existing knowledge of tropical variability and emphasize the urgent need for better climate predictions and readiness for extreme weather in vulnerable areas,” remarked Dr. Davide Faranda, Research Director at the Laboratoire de Science du Climat et de l’Environnement (LSCE) of IPSL and the French National Center for Scientific Research (CNRS).
“Heatwaves and heavy rainfall are two types of extreme weather that need careful planning from policymakers to minimize their impact. For example, an increase in heatwave frequency could drive up electricity demand, potentially leading to power outages, a rise in heat-related health issues requiring hospitalizations, and threats to food security from crop failures. More frequent heavy rainfall could result in flooding, posing risks to life, property, and infrastructure, along with causing crop failures and water contamination. Southeast Asia is a relatively understudied region concerning extreme weather, indicating the need for further efforts to prepare policymakers and local communities for changing climate conditions,” added Assistant Professor Mengaldo.
