Original title: Did recent sea surface temperature warming reinforce the extreme East Asian summer monsoon precipitation in 2020?
Taeho Mun, Haerin Park, Dong-Hyun Cha, Chang-Keun Song +2 · September 2026
Scientists wanted to know if warmer oceans caused the extreme summer rains in East Asia during 2020. To test this, they used a regional climate model to compare real, observed ocean temperatures against cooler ocean conditions that had a 22-year warming trend removed. Warmer ocean waters change how air and moisture move through the atmosphere. The simulations revealed that warmer seas actually boost rainfall near the equator while reducing rainfall in the East Asian monsoon region. This pattern directly contradicts what happened in 2020. The warmer water slowed key winds and altered large air circulation loops, keeping moisture from traveling north. Therefore, recent ocean warming was not the driver of the extraordinary 2020 monsoon rains. Instead, shifts in wind patterns overpowered moisture increases to suppress rainfall.
Imagine you are watering a garden with a hose. You expect that turning up the water flow will give more water to the flower bed. But the sprinkler system is designed so that when pressure increases, it redirects water away from the bed and onto the lawn. So the flowers actually get less water. In this paper, the warming ocean is like turning up the hose, but the atmospheric circulation acts like the sprinkler system, diverting moisture away from the monsoon region, so the expected increase in rain does not happen.
For millions of people in East Asia, understanding why the 2020 monsoon brought record floods is critical for preparing for future extremes. This study shows that warming oceans alone cannot explain the event, meaning other factors—like atmospheric patterns or internal variability—must be at play. That shifts how scientists attribute and predict such disasters.
The abstract does not discuss limitations explicitly, but the study only examines the effect of SST warming on the 2020 event using one regional climate model. Other potential drivers—such as internal atmospheric variability, land surface changes, or aerosols—are not considered. The results may be model-dependent and do not rule out SST warming's role in other years.
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Did recent sea surface temperature warming reinforce the extreme East Asian summer monsoon precipitation in 2020? — Taeho Mun, Haerin Park, Dong-Hyun Cha et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.