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Global 'precipitation whiplashes' between droughts and floods could intensify by 2028, study warns

A recent study by The Hong Kong University of Science and Technology (HKUST) reveals a looming climate crisis: the world could face heightened risks of "precipitation whiplashes"—violent swings between extreme droughts and floods—as early as 2028.

This research, led by Prof. Lu Mengqian and Dr. Cheng Tat-Fan of HKUST's Department of Civil and Environmental Engineering, attributes the escalating risk to climate-driven intensification of Madden-Julian Oscillation (MJO) events. This large-scale pattern of tropical intraseasonal climate variability is now propagating faster due to global warming.

The findings, in the journal Nature Communications, pave the way for improved subseasonal forecasts, i.e., two to six weeks in advance, enabling timely decision-making in disaster preparedness and management, and helping to enhance food and water security, energy management, and infrastructure resilience.

Understanding the Madden-Julian Oscillation (MJO)

The MJO is a planetary-scale atmospheric disturbance that moves eastward, dominating tropical intraseasonal variability over 30–90-day periods during boreal winter. Regarded as one of the most important sources of subseasonal predictability, it has far-flung impacts on global rainfall patterns, extreme weather conditions, tropical cyclone genesis, monsoons, and mid-latitude circulation patterns.

While existing literature generally concluded that anthropogenic greenhouse gas emissions can accelerate MJO propagation, the mechanism underlying such a relationship remains controversial, with various theories giving different estimates of the propagation speed.

To resolve this puzzle, the HKUST-led research team conducted an analysis based on 28 coupled general circulation models (CGCMs) participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). These models are the most advanced tools currently available for simulating the effects of rising greenhouse gas concentrations.

The team projected an alarming 40% increase in fast-propagating MJO events by the late 21st century compared to historical data (1979–2014).

More imminently, the study warns that an increased frequency of fast and "jumping" MJO events—where convection shifts abruptly—will become more frequent in the near-future (as early as 2028–2063). "Jumping" refers to a strong, westward-propagating equatorial Rossby wave that hinders MJO eastward propagation but initiates subsequent convection over the western Pacific Ocean.

Implications for global weather extremes

"Global precipitation whiplashes have become a growing concern, with a recent report revealing a 31–66% increase in their occurrence since the mid-20th century." Dr. Cheng Tat-Fan, the first author of this work and a postdoctoral fellow at HKUST, explained the implications of the findings.

"A notable example is the severe drought and wildfire that hit California in 2022, followed by record-breaking rainfall that resulted in floods and landslides. The acceleration of the MJO events will significantly shorten response times against compound hazards, catching societies off guard unless adaptation measures are in place."

He further pointed out that as the climate warms, the increase in fast MJO events will heighten the risk of precipitation whiplashes. Such a trend will become apparent from as early as 2028 onwards, if the reality follows a business-as-usual scenario.

The supervisor of Dr. Cheng—Prof. Lu Mengqian, Director of HKUST's Otto Poon Center for Climate Resilience and Sustainability and Associate Professor at HKUST Department of Civil and Environmental Engineering, emphasized the study's role in advancing seamless weather-to-climate predictions for sustainable natural and built environments.

"Future numerical models that accurately simulate diverse propagation behaviors of the MJO will enhance our ability to improve the forecast of extreme compound weather events 4–5 weeks in advance, which will significantly reduce casualties and damage to ecosystems and human societies," she stated.

The research was conducted in collaboration with meteorologists and climate experts, Prof. Bin Wang (University of Hawaiʻi at Mānoa), Prof. Fei Liu (Sun Yat-Sen University), and Prof. Guosen Chen (Nanjing University of Information Science and Technology).

The present study contributed to meteoNEX, an award-winning prediction system that offers seamless weather-to-climate prediction services. This system has been acclaimed with a Gold Award at the 50th International Exhibition of Inventions Geneva. It also supports a HKUST-led, global transdisciplinary "research-to-operation" (R2O) initiative, the decade-long "Seamless Prediction and Services for Sustainable Natural and Built Environments" (SEPRESS) program, recently endorsed by the United Nations Educational, Scientific and Cultural Organization (UNESCO) as part of its International Decade of Sciences for Sustainable Development (IDSSD).

"Our ongoing efforts are focused on bolstering trust in science through reliable weather and subseasonal climate forecast while collaborating with global partners under the SEPRESS program to develop practical strategies against the imminent increase in precipitation whiplashes," Prof. Lu added. "Our goal is to bridge scientific innovation with societal needs through equitable and transparent R2O strategies."