Researchers from Tsinghua University have identified a connection between the increasingly early arrival of powerful tropical cyclones and global warming driven by human emissions. The study, published in Nature, highlights how rising temperatures in the world’s oceans may be advancing the onset of these extreme storms and altering their behavior over time.
Tropical cyclones with sustained winds above 110 knots (about 126 mph or 56.5 m/s) are categorized as strong or intense storms. These systems rank among the most destructive weather events on the planet, capable of devastating coastlines, spreading dangerous storm surge, and dumping extreme rainfall. While scientists have long tracked changes in the frequency, strength, and duration of intense tropical cyclones, understanding how their seasonal timing may be shifting has proven more elusive. This new work sheds light on how the timing of storm formation is evolving alongside shifts in climate.
To investigate these questions, the researchers analyzed satellite observations spanning from 1981 to 2017. The data reveal a clear pattern: the first appearances of intense tropical cyclones occurred earlier in the year as the study period progressed. On average, the emergence date shifted by roughly three days each decade, a noticeable acceleration in season timing that aligns with broader climate trends.
The study suggests that the earlier onset of storms is linked to warmer sea surface temperatures and higher ocean heat content. These oceanic changes are primarily driven by elevated greenhouse gas concentrations in the atmosphere, which trap heat and transfer it into the upper layers of the ocean. As the surface warms, the atmospheric and oceanic conditions become more favorable for the formation and intensification of cyclones earlier in the season, extending the window during which these powerful storms can develop.
Beyond shifting timing, the researchers found that earlier storm emergence correlates with increases in heavy rainfall and the overall duration of rainfall associated with cyclones. When intense storms arrive sooner, their rainfall tends to last longer within affected regions, contributing to greater flood risk and complicating disaster preparation and response efforts for communities and authorities in North America and other storm-prone regions.
These findings add to a growing body of evidence showing how climate change affects mid-latitude weather patterns, ocean heat uptake, and the behavior of tropical systems. They highlight the need for updated risk assessments, improved forecasting that accounts for changing seasonal timing, and stronger adaptation measures in vulnerable coastal areas across Canada and the United States. The study also reinforces the importance of reducing greenhouse gas emissions to limit future warming and its consequences for tropical cyclone activity and associated rainfall patterns [Attribution: Nature study, 2024].