Spatial–temporal changes in runoff and terrestrial ecosystem water retention under 1.5 and 2 °C warming scenarios across China

Abstract

<p><strong>Abstract.</strong> The Paris Agreement set a long-term temperature goal of holding the global average temperature increase to below 2.0<span class="thinspace"></span><span class="inline-formula">^∘C</span> above pre-industrial levels, pursuing efforts to limit this to 1.5<span class="thinspace"></span><span class="inline-formula">^∘C</span>; it is therefore important to understand the impacts of climate change under 1.5 and 2.0<span class="thinspace"></span><span class="inline-formula">^∘C</span> warming scenarios for climate adaptation and mitigation. Here, climate scenarios from four global circulation models (GCMs) for the baseline (2006–2015), 1.5, and 2.0<span class="thinspace"></span><span class="inline-formula">^∘C</span> warming scenarios (2106–2115) were used to drive the validated Variable Infiltration Capacity (VIC) hydrological model to investigate the impacts of global warming on runoff and terrestrial ecosystem water retention (TEWR) across China at a spatial resolution of 0.5<span class="inline-formula">^∘</span>. This study applied ensemble projections from multiple GCMs to provide more comprehensive and robust results. The trends in annual mean temperature, precipitation, runoff, and TEWR were analyzed at the grid and basin scale. Results showed that median change in runoff ranged from 3.61 to 13.86<span class="thinspace"></span>%, 4.20 to 17.89<span class="thinspace"></span>%, and median change in TEWR ranged from <span class="inline-formula">−</span>0.45 to 6.71 and <span class="inline-formula">−</span>3.48 to 4.40<span class="thinspace"></span>% in the 10 main basins in China under 1.5 and 2.0<span class="thinspace"></span><span class="inline-formula">^∘C</span> warming scenarios, respectively, across all four GCMs. The interannual variability of runoff increased notably in areas where it was projected to increase, and the interannual variability increased notably from the 1.5 to the 2.0<span class="thinspace"></span><span class="inline-formula">^∘C</span> warming scenario. In contrast, TEWR would remain relatively stable, the median change in standard deviation (SD) of TEWR ranged from <span class="inline-formula">−</span>10 to 10<span class="thinspace"></span>% in about 90<span class="thinspace"></span>% grids under 1.5 and 2.0<span class="thinspace"></span><span class="inline-formula">^∘C</span> warming scenarios, across all four GCMs. Both low and high runoff would increase under the two warming scenarios in most areas across China, with high runoff increasing more. The risks of low and high runoff events would be higher under the 2.0 than under the 1.5<span class="thinspace"></span><span class="inline-formula">^∘C</span> warming scenario in terms of both extent and intensity. Runoff was significantly positively correlated to precipitation, while increase in maximum temperature would generally cause runoff to decrease through increasing evapotranspiration. Likewise, precipitation also played a dominant role in affecting TEWR. Our results were supported by previous studies. However, there existed large uncertainties in climate scenarios from different GCMs, which led to large uncertainties in impact assessment. The differences among the four GCMs were larger than differences between the two warming scenarios. Our findings on the spatiotemporal patterns of climate impacts and their shifts from the 1.5 to the 2.0<span class="thinspace"></span><span class="inline-formula">^∘C</span> warming scenario are useful for water resource management under different warming scenarios.</p>