A recent article in Geophysical Research Letters has called into question the traditional understanding of the relationship between **global warming** and **ocean evaporation**.
Researchers from the Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences have discovered that, despite the increase in **sea surface temperatures**, global ocean evaporation has decreased in the last decade.
The crucial role of oceanic evaporation in the hydrological cycle
Ocean evaporation is fundamental to our planet’s **hydrological cycle**, contributing over 85% of the **water vapor in the atmosphere**. Traditionally, it was expected that the increase in temperatures on the **ocean surface** would also increase evaporation rates.
However, observations since the early 2000s have shown an unexpected slowdown in the growth of **global water vapor**, leading scientists to reassess the response of ocean evaporation to **rising temperatures**.
To explore this phenomenon, researchers analyzed advanced satellite-based **ocean heat flux data**, evaluating long-term trends in global ocean evaporation. Their findings revealed a significant shift in **evaporation trends** in recent decades.
The study showed that while global ocean evaporation exhibited an upward trend between 1988 and 2017, this trend reversed in the late 2000s.
The influence of wind and atmospheric circulation on ocean evaporation
Since then, two-thirds of the world’s oceans have experienced a **reduction in evaporation**, resulting in a slight decrease in global evaporation rates between 2008 and 2017. “This contradicts what we would normally expect in a warming climate,” said Dr. Ma Ning, lead author of the study.
The researchers identified a key factor behind this unexpected trend: a decrease in **wind speed**, a phenomenon known as “wind speed slowdown.” They argue that the wind decrease is likely related to changes in **atmospheric circulation patterns**, especially the North Atlantic Oscillation, which has recently shifted from a positive phase to a negative one.
“Changes in wind speed may be associated with decadal variations in the **Earth’s climate system**,” explained Dr. Ma. “The recent decrease in ocean evaporation should not necessarily be interpreted as evidence of a weakening hydrological cycle, as it could reflect **natural climate oscillations**.”
Although the declining trend in ocean evaporation may seem counterintuitive in the context of global warming, it underscores the complexity of the Earth’s climate system and the intricate feedback mechanisms that govern the planet’s **hydrological processes**.
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