Data for Figure 8.26 from Chapter 8 of the Working Group I (WGI) Contribution to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6).

Figure 8.26 shows the rate of change in basin-scale annual mean runoff with increasing global warming levels.

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How to cite this dataset
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When citing this dataset, please include both the data citation below (under 'Citable as') and the following citation for the report component from which the figure originates:
Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, and O. Zolina, 2021: Water Cycle Changes. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1055–1210, doi:10.1017/9781009157896.010.

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Figure subpanels
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There is one single NetCDF file for data for all panels.

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List of data provided
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This dataset contains relative changes (%) in basin-averaged annual mean runoff estimated as multi-model ensemble median from a variable subset of CMIP6 models for each SSP over nine major river basins:

- Mississippi (a),
- Danube (b),
- Lena (c),
- Amazon (d),
- Euphrates (e),
- Yangtze (f),
- Niger (f),
- Indus (g),
- Murray (h).

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Data provided in relation to figure
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The NetCDF file contains a multi-dimensionnal variable 'mrro_mean' which matches the various curves showing in the figure. These are parametric curves, and the parameter is a period index. The file also contains a variable 'tas' for the value of global warming for the period, for each scenario.
 
Dimension 'period' is a period index, which is the parameter for the parametric curves linking variables 'mrro_mean' and 'tas'. Period value 1 stands for 1901-1920, 2 for 1911-1920 ...,

Dimension ssp is the SSP index, for that order : ssp585 ,  ssp245 , ssp126.

Variable 'tas' is the change of globally averaged surface temperature w.r.t. 1850-1900 average, indexed by period.

Variable mrro_mean provide statistics of relative changes (%) of runoff in basin-averaged annual mean runoff. The basin averages have been estimated after a first-order conservative remapping of the model outputs on the 0.5° by 0.5° river network of  (Decharme et al., 2019). It is indexed by  :
            - dimension 'stats' for statistics over a CMIP6 multi-model ensemble, in that order : percentile 5, mean, and percentile 95,
            - dimension 'basin' for this ordered list : Mississippi, Danube, Lena, Amazon, Euphrates, Yangtze, Niger, Indus, Murray

Variable mrro_std is not used in the figure.

CMIP6 is the sixth phase of the Coupled Model Intercomparison Project.
SSP stands for Shared Socioeconomic Pathway.
SSP126 is the Shared Socioeconomic Pathway which represents the lower boundary of radiative forcing and development scenarios, consistent with RCP2.6.
SSP245 is the Shared Socioeconomic Pathway which represents the median of radiative forcing and development scenarios, consistent with RCP4.5.
SSP585 is the Shared Socioeconomic Pathway which represents the upper boundary of radiative forcing and development scenarios, consistent with RCP8.5.

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Notes on reproducing the figure from the provided data
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Curves are parametric curves. The parameter is the period index.

So each curve for a given statistics 'stat', scenario 'ssp' and basin 'basin' is defined by varying period_index in:

x=tas(ssp,period_index),

y=mrro_mean(ssp, basin, stat, period_index)

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Sources of additional information
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The following weblinks are provided in the Related Documents section of this catalogue record:
- Link to the figure on the IPCC AR6 website
- Link to the report component containing the figure (Chapter 8)
- Link to the Supplementary Material for Chapter 8, which contains details on the input data used in Table 8.SM.1
- Link to the code for all figures in Chapter 8, archived on Zenodo.
- Link to the documentation for CAMMAC, the tool used for AR6 analysis.