Water forecasts | Nature Climate Change

The effect of climate change on precipitation and flooding is of global concern. The strength of water movement through the hydrological cycle is influenced by climate change. Warming of the

atmosphere increases its water-holding capacity — by approximately 7% per degree — which can increase the intensity of precipitation. This impact is expected to be seen predominantly in the

tropics and high-latitude regions. Overall precipitation is also expected to increase in the tropics, and it is assumed that wet regions will get wetter and dry areas will get drier. In a

web focus this month on precipitation trends and extremes, we have a collection of articles that looks at the hydrological cycle, climate change and the impacts on society and ecology. The

hydrological cycle has not responded as strongly to climate change as has been predicted. The increase in greenhouse gas concentrations and the warming atmosphere were expected to strengthen

the cycle. However, particles in the atmosphere, known as aerosols, are shown by Peili Wu and collaborators to have counteracted the effect of the increased emissions (page 807). From the

1950s higher aerosol concentrations relative to greenhouse gases lead to a suppression of the hydrological cycle. Since the 1980s aerosols have been reduced in the atmosphere, whereas

greenhouse gas emissions have continued to increase, resulting in a recovery of the strength of the hydrological cycle. If the current trend continues, the cycle can be expected to

intensify. Changes in total precipitation, as well as in the frequency, intensity, timing and duration will impact human population and infrastructure, as well as ecosystems. Global

projections of flooding are made using river discharge and the extent of the area that would be inundated. Yukiko Hirabayashi _et al_. forecast an increase in flooding in southeast Asia,

peninsular India, eastern Africa and the northern Andes, whereas decreased flooding is predicted in some other areas (page 816). The costs associated with flooding are expected to increase

as the frequency and extent of these events rises. In a Letter by Stephane Hallegatte and colleagues, they report the current costs and estimates future costs of coastal flooding (page 802),

categorized as those owing to socio-economic change, climate change and land subsidence. In this study they focused on flooding caused by sea-level rise and storms, but the lessons are

applicable to other areas where flood protection methods are needed. The impact of changing precipitation intensity on plant growth is investigated by Andrew Kulmatiski and Karen Beard (page

833). Higher-intensity rainfall will push water deeper into the soil, benefiting plants that have the ability to increase root depth, such as trees and other woody plants. The supply of

water is essential to maintain life, but it is a fine balance as excessive amounts and flooding are dangerous. Better understanding of the hydrological cycle and its changes will help us to

adapt to give a healthier future. RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Water forecasts. _Nature Clim Change_ 3, 765 (2013).

https://doi.org/10.1038/nclimate2005 Download citation * Published: 28 August 2013 * Issue Date: September 2013 * DOI: https://doi.org/10.1038/nclimate2005 SHARE THIS ARTICLE Anyone you

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