Challenges in quantifying changes in the global water cycle

Understanding observed changes to the global water cycle is key to predicting future climate changes and their impacts. While many datasets document crucial variables such as precipitation, ocean salinity, runoff, and humidity, most are uncertain for determining long-term changes. In situ networks provide long time series over land, but are sparse in many regions, particularly the tropics. Satellite and reanalysis datasets provide global coverage, but their long-term stability is lacking. However, comparisons of changes among related variables can give insights into the robustness of observed changes. For example, ocean salinity, interpreted with an understanding of ocean processes, can help cross-validate precipitation. Observational evidence for human influences on the water cycle is emerging, but uncertainties resulting from internal variability and observational errors are too large to determine whether the observed and simulated changes are consistent. Improvements to the in situ and satellite observing networks that monitor the changing water cycle are required, yet continued data coverage is threatened by funding reductions. Uncertainty both in the role of anthropogenic aerosols and because of the large climate variability presently limits confidence in attribution of observed changes.

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Author Hegerl, Gabriele
Black, Emily
Allan, Richard
Ingram, William
Polson, Debbie
Trenberth, Kevin
Chadwic, Robin
Arkin, Phillip
Sarojini, Beena
Becker, Andreas
Dai, Aiguo
Durack, Paul
Easterling, David
Fowler, Hayley
Kendon, Elizabeth
Huffman, George
Liu, Chunlei
Marsh, Robert
New, Mark
Osborn, Timothy
Skliris, Nikolaos
Stott, Peter
Vidale, Pier-Luigi
Wijffels, Susan
Wilcox, Laura
Willett, Kate
Zhang, Xuebin
Publisher UCAR/NCAR - Library
Publication Date 2015-07-01T00:00:00
Digital Object Identifier (DOI) Not Assigned
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Resource Version N/A
Topic Category geoscientificInformation
Progress N/A
Metadata Date 2023-08-18T19:04:59.213456
Metadata Record Identifier edu.ucar.opensky::articles:16875
Metadata Language eng; USA
Suggested Citation Hegerl, Gabriele, Black, Emily, Allan, Richard, Ingram, William, Polson, Debbie, Trenberth, Kevin, Chadwic, Robin, Arkin, Phillip, Sarojini, Beena, Becker, Andreas, Dai, Aiguo, Durack, Paul, Easterling, David, Fowler, Hayley, Kendon, Elizabeth, Huffman, George, Liu, Chunlei, Marsh, Robert, New, Mark, Osborn, Timothy, Skliris, Nikolaos, Stott, Peter, Vidale, Pier-Luigi, Wijffels, Susan, Wilcox, Laura, Willett, Kate, Zhang, Xuebin. (2015). Challenges in quantifying changes in the global water cycle. UCAR/NCAR - Library. http://n2t.net/ark:/85065/d7542psd. Accessed 24 June 2025.

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