A recent study led by The Hong Kong University of Science and Technology (HKUST) warns that under high-emission scenarios, the Northern Hemisphere summer monsoon region will experience extreme weather events starting in 2064. The research indicates that Asia and broader tropical regions will be particularly vulnerable to frequent “subseasonal whiplash” events, which are characterized by alternating periods of intense rainfall and dry spells occurring every 30 to 90 days. These shifts pose significant risks to food production, water management, and clean energy systems.
The findings, published in the journal Science Advances under the title “Increased Global Subseasonal Whiplash by Future BSISO Behavior,” were co-led by Prof. LU Mengqian, Director of the Otto Poon Center for Climate Resilience and Sustainability at HKUST, and Dr. CHENG Tat-Fan, a postdoctoral fellow in the Department of Civil and Environmental Engineering at HKUST. The study benefits from collaboration with researchers from the University of Hawaiʻi at Mānoa, Sun Yat-Sen University, and Nanjing University of Information Science and Technology.
Understanding the Climate Dynamics
To project future climate patterns, the team utilized up to 28 coupled general circulation models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). This research specifically examined the Boreal Summer Intraseasonal Oscillation (BSISO), the primary driver of summertime tropical intraseasonal variability. The study identified three distinct BSISO propagation patterns: the canonical northeastward propagating mode, the northward dipole (ND) mode, and the eastward expansion (EE) mode.
The results indicate that both the canonical northeastward and ND modes will become more intense, leading to increased extreme rainfall and drought in South and East Asia. Notably, the study highlights that the EE mode is expected to double its propagation speed by the end of the century under high-emission scenarios. Dr. Cheng stated, “The eastward-moving rain-bearing wave will expand eastward by approximately 30 degrees of longitude.”
Wider Implications and Urgent Needs
Beyond Asia, the research points to increased risks in other regions. For instance, atmospheric teleconnections may intensify rainfall variability in Greenland and northern Russia. In addition, rising whiplash events in central and northern Africa could affect Saharan dust emissions, potentially impacting tropical cyclone formation over the Atlantic Ocean.
Prof. Lu emphasized the serious implications of these subseasonal shifts for global food production, stating, “The risk of global rice yield loss is 43% higher from sudden shifts from drought to flood than from wet-to-dry swings.” The anticipated increase in dry-to-wet events across arable regions in Asia and Africa could severely threaten future food security.
The authors advocate for urgent investment in subseasonal-to-seasonal (S2S) forecasting models to better prepare for these challenges. Prof. Lu added, “Strengthening urban infrastructure against climate impacts, ensuring sustainability within the water-energy-food-economy nexus, and enhancing our predictive abilities for climate-sensitive diseases are critical for informed long-term planning and policy development.”
This study is part of the “Seamless Prediction and Services for Sustainable Natural and Built Environments” (SEPRESS) program, a global initiative led by HKUST. Recently endorsed by the United Nations Educational, Scientific and Cultural Organization (UNESCO), this program aims to facilitate the transition from research to practical applications in response to climate change challenges.
The findings from this research underscore the critical need for immediate action to mitigate climate change effects and protect vulnerable regions from impending environmental shifts.
