A new study reveals increasing extreme weather events in the Indo-Pacific region, driven by changes in tropical weather patterns.

A recent study published in Natural geosciences provides groundbreaking insights into long-term changes in tropical weather patterns that are leading to increased frequency of extreme weather events such as heat waves and heavy precipitation in the Indo-Pacific. These changes may be due, among other factors, to global warming.

The paper, titled “Indo-Pacific regional extremes worsened by changes in tropical weather patterns,” uses a recently proposed methodology that characterizes trends in weather pattern occurrence using atmospheric analogues, related to the concept of recurrences in dynamic systems theory.

Unlike previous approaches, which often focused on changes in average behavior, the method used in the study can identify trends in the occurrence of each daily weather pattern, allowing direct study of their association with extreme events, which which was previously unachievable.

Using this methodology, it was possible to identify the emergence of new large-scale atmospheric patterns, which exacerbate regional weather extremes.

The study, led by doctoral student Chenyu Dong and Assistant Professor Gianmarco Mengaldo from the College of Design and Engineering (CDE) at the National University of Singapore (NUS), and a collaborative team of international scientists, uses sets of Advanced reanalysis data to analyze tropical conditions. The evolution of weather systems in the Indo-Pacific region.

Researchers have found that since the 1990s, previously rare weather conditions have become more common, while others that were once important have almost disappeared. These changes are linked to changes in the Pacific Walker Circulation, a key driver of tropical weather and climate, whose future changes remain highly uncertain in current climate models.

Detecting long-term trends in the tropical Indo-Pacific has always been challenging, particularly at the daily scale, due to the confluence of multiple modes of variability that tend to overshadow trend signals. This study is one of the first to investigate long-term changes in tropical weather patterns and their relationship to extreme events on a daily time scale.

“Critical changes in tropical weather patterns are significantly worsening regional extremes, namely heat waves and extreme precipitation, in the tropical Indo-Pacific region. Our study is one of the first to disentangle the trend versus the variability in the tropics, an aspect that has been historically difficult.

“We show that the identified changes cannot be fully explained by interannual modes of variability, and that one possible culprit is anthropogenic global warming, although the influence of other factors may play a role.

“More in-depth analyzes are needed to better inform climate modeling and climate adaptation strategies, particularly in the tropical Indo-Pacific region, where climate models still struggle to provide reliable projections.

“For Singapore and other Southeast Asian countries, improving climate projection capabilities and better understanding changing tropical dynamics and regional extremes is of vital importance. This study is a step in this direction,” said Assistant Professor Mengaldo of the Department of Mechanics. Engineering at CDE, NUS.

The study shows that new large-scale atmospheric configurations (or weather patterns), rare before the 1990s, have appeared, while other, more important ones have disappeared. These emerging weather conditions manifest as a stronger Pacific Walker circulation (or Walker cell) and are associated with wetter and warmer conditions in Southeast Asia and drier conditions in the equatorial Pacific.

The emerging trends cannot be explained by interannual modes of natural variability, such as the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), the Pacific Decadal Oscillation (PDO), and the Atlantic Multidecadal Oscillation (AMO), but are likely driven by long-term trends from the 1940s to the present.

These large-scale trends and changes in atmospheric dynamics in the tropical Indo-Pacific may be caused by global warming and other factors. Although these identified emerging trends may be driven by the combined effect of different factors (excluding known modes of interannual variability), the implications for current and near future climate are crucial.

Emerging weather phenomena are also strongly linked to increasing regional weather phenomena, namely heat waves and extreme precipitation. In some regions, these extremes are up to four times more common than climatology when associated with emerging weather conditions.

For example, several regions, including parts of Indonesia, Singapore, South India, the Philippines, and the Western Pacific, exhibit significantly increased heatwave frequency relative to climatology. The South China Sea and surrounding areas, including Vietnam and the Philippines, the Malay Peninsula, Singapore, the southern tip of India, and part of the Indian Ocean off the coast of Australia, show significantly increased frequency of extreme precipitation.

This increase in extreme weather events is notable, as these changes are associated with long-term climate trends in a region highly vulnerable to extreme weather events.

These findings are important in the context of climate change because they reveal that new and emerging weather patterns are contributing to increasingly extreme weather conditions in a region home to more than a billion people, as well as unique ecosystems and vulnerable.

Increased frequency of heatwaves and extreme precipitation can lead to acute thermal distress and flooding, respectively. With extreme weather events posing serious socio-economic and environmental challenges, understanding these changes is essential to improve climate models and inform future climate adaptation strategies.

This study was carried out by an international team of climate scientists from leading institutions including NUS, Institut Pierre-Simon Laplace (IPSL), Uppsala University, Stockholm University, of Cambridge, Columbia University, the World Meteorological Organization (WMO) and the Center. for Climate Research Singapore (CCRS). The team is committed to advancing climate research to better understand the impacts of climate change on regional weather patterns and extremes.

“The emergence of new tropical weather patterns is a key signal of how anthropogenic climate change is altering atmospheric dynamics on daily scales. Our results show a significant increase in heat waves and extreme precipitation in Indo- Pacific, which could have profound consequences not only for the region, but also for the global climate.

“This shift in weather patterns challenges our previous understanding of tropical variability and highlights the urgency of improving climate projections and preparedness for extreme events in vulnerable regions,” said research director Dr. Davide Faranda at the Climate and Environmental Science Laboratory (LSCE) of the Pierre-Simon Laplace Institute (IPSL), National Center for Scientific Research (CNRS).

“Heatwaves and extreme precipitation are two extreme weather events that require careful and advance planning by policymakers to mitigate their effects. For example, more frequent heat waves can lead to high peaks in electricity demand with possible power outages, many heat-related illnesses that need enough hospital beds, and crop failures that could threaten food security.

“More frequent extreme rainfall can lead to flooding, which in turn poses a direct threat to human life, buildings and infrastructure. Extreme rainfall can also lead to crop failure, contamination of drinking water and landslides.

“Southeast Asia is a relatively research-poor region in terms of extreme weather, and more efforts are needed to better prepare policymakers and local communities for climate change,” said Assistant Professor Mengaldo.