Water cycle changes: interpretation of IPCC AR6

doi:10.12006/j.issn.1673-1719.2021.160

Abstract

Abstract:

The water cycle plays an important role in global and regional climate changes, and problems such as shortage of freshwater resources, expansion of subtropical drylands, and frequent occurrence of extreme droughts and floods, which are closely related to water cycle changes in the context of global warming, are becoming increasingly prominent and seriously constrain the sustainable development of ecosystems and human society. In the IPCC Sixth Assessment Report (AR6), Working Group I established a separate chapter, namely Chapter 8, for an integrated assessment of global water cycle changes. AR6 suggested that human activity has significantly altered the global water cycle since the mid-20th century, including an overall increase in atmospheric moisture and precipitation intensity, changes in the global drought patterns, and the poleward shift of storm tracks in the Southern Hemisphere. Changes in the water cycle that have occurred were influenced by a variety of anthropogenic forcing including greenhouse gases, aerosol and land use change, while future water cycle changes will gradually be dominated by greenhouse gases.

Key words: IPCC, Water cycle, Assessment, Human activity

JIANG Da-Bang, WANG Na. Water cycle changes: interpretation of IPCC AR6[J]. Climate Change Research, 2021, 17(6): 699-704.

Figures/Tables 1

Fig. 1 Depiction of the water cycle. (In the atmosphere, which accounts for only 0.001% of all water on Earth, water primarily occurs as a gas (water vapor), but it is also present as ice and liquid water within clouds. The ocean is the primary water reservoir on Earth, which is comprised mostly of liquid water across much of the globe, but also includes areas covered by ice in polar regions. Liquid freshwater on land forms surface water (lakes, rivers), soil moisture and groundwater stores, together accounting for 1.8% of global water. Solid terrestrial water that occurs as ice sheets, glaciers, snow and ice on the surface and permafrost currently represents 2.2% of the planet's water. Water that falls as snow in winter provides soil moisture and streamflow after melting, which are essential for human activities and ecosystem functioning. Data derived from references [4,5,6,7,8,9,10,11,12,13,14])

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