Hazards: floods, drought and water resources

Future projections of low extremes of river runoff (7-day moving average) at global warming levels (1.5°C, 2.0°, 3.0°, 4.0°). Below, a list of the fields included in the files:

- laea: empty variable containing the projection (Lambert azimuthal equal area) parameters.

- x, y: coordinates in Lambert azimuthal equal area.

- lon, lat: matrices containing the lon-lat coordinates of the pixels.

- baseline_return_level: magnitude of the baseline 15-year event (year 1995).

- return_level_prec_chng_XX: percentage changes in magnitude of the 15-year event, at warming level XX°C.

- baseline_rp_shift_XX: return period at wariming level XX°C, of the event with the same mangitude as the baseline 15-year one. This variable is a proxy for the change in frequency.

- significant_XX: significance of the XX°C projected change. 1: significant, 0: not significant.

Future projections of annual mean river runoff at global warming levels (1.5°C, 2.0°, 3.0°, 4.0°). Below, a list of the fields included in the files:

- laea: empty variable containing the projection (Lambert azimuthal equal area) parameters.

- x, y: coordinates in Lambert azimuthal equal area.

- lon, lat: matrices containing the lon-lat coordinates of the pixels.

- baseline_median: magnitude of the baseline annual mean river runoff (year 1995).

- median_prec_chng_XX: percentage changes in magnitude of the annual mean river runoff, at warming level XX°C.

- significant_XX: significance of the XX°C projected change. 1: significant, 0: not significant.

Future projections of high extremes of river runoff at global warming levels (1.5°C, 2.0°, 3.0°, 4.0°). Below, a list of the fields included in the files:

- laea: empty variable containing the projection (Lambert azimuthal equal area) parameters.

- x, y: coordinates in Lambert azimuthal equal area.

- lon, lat: matrices containing the lon-lat coordinates of the pixels.

- baseline_return_level: magnitude of the baseline 100-year event (year 1995).

- return_level_prec_chng_XX: percentage changes in magnitude of the 100-year event, at warming level XX°C.

- baseline_rp_shift_XX: return period at wariming level XX°C, of the event with the same mangitude as the baseline 100-year one. This variable is a proxy for the change in frequency.

- significant_XX: significance of the XX°C projected change. 1: significant, 0: not significant.

The outcomes of the 2015 Paris Agreement triggered a number of climate impact assessments, such as for floods and droughts, to focus on future time frames corresponding to the years of reaching specific levels of global warming. Yet, the links between the timing of the warming levels and the corresponding greenhouse gas concentration pathways to reach them, remain poorly understood. To address this gap, we compare projected changes of annual mean, extreme high and extreme low river discharges in Europe at 1.5° and 2° under scenarios RCP8.5 and RCP4.5 from an ensemble of Regional Climate Model (RCM) simulations. The statistical significance of the difference between the two scenarios for both warming levels is then evaluated. Results show that in the majority of Europe (>95% for the annual mean discharge, >98% for high and low extremes), the changes projected in the two pathways are statistically indistinguishable. These results suggest that in studies of changes at specific warming levels the projections of the two pathways can be merged into a single ensemble without major loss of information. With regard to the uncertainty of the unified ensemble, findings show that the projected changes of annual mean, extreme high and extreme low river discharge are statistically significant in large portions of Europe.