1229. Permanent Changes in the Global Water Cycle

Understanding the relationship between atmospheric carbon levels and global temperature dates back to 1895, when Swedish scientist Svante Arrhenius argued that variations in carbon dioxide concentrations could affect global warming. How global warming will affect the global water cycle (the continuous movement of water between the Earth and the atmosphere) is also an important issue for water resource management and weather forecasting. Although local and regional changes in the water cycle have been observed, conclusive evidence of global change is still lacking. Answering this question requires decades of global mean sea level data and advanced climate and hydrological modeling.

A paper published in Science provides evidence of a permanent decline in land water storage under current climate change by integrating multiple global geophysical datasets. The paper finds that the world's land water storage has been steadily declining, with a significant decline of about 1.6 gigatonnes in the early 21st century. Regions such as East Asia, Central Asia, Central Africa, and the Americas have experienced significant declines in soil moisture. It also found that the lost land moisture has not recovered to previous levels. This persistent decline suggests that the decline in soil moisture may be irreversible due to prolonged drought conditions and reduced precipitation in certain regions.

Meanwhile, experts said that to better understand the global water cycle under climate change, it is necessary to consider various factors that affect precipitation and evapotranspiration (the movement of water from land to the atmosphere through evaporation and transpiration), and that developing advanced land surface and hydrological models capable of accurately capturing these factors under the influence of a changing climate will be essential.

(References)
Ki-Weon Seo et al, Abrupt sea level rise and Earth's gradual pole shift reveal permanent hydrological regime changes in the 21st century, Science (2025). https://www.science.org/doi/10.1126/science.adq6529
Luis Samaniego, Permanent shifts in the global water cycle. Decades of terrestrial water-storage changes reveal an irreversible decline in soil moisture. Science (2025) https://www.science.org/doi/10.1126/science.adw5851

Contributor: IIYAMA Miyuki, Information Program