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The authors emphasize the importance of land-cover change in forecasting future freshwater …


Biology Articles » Bioclimatology » Changes in climate and land use have a larger direct impact than rising CO2 on global river runoff trends » Figures

Figures
- Changes in climate and land use have a larger direct impact than rising CO2 on global river runoff trends

mcith_zpq0370776120001.jpg Figure 1  Change in global runoff anomalies from 1901 to 1999. (A) Comparison of global runoff change between that reconstucted by Labat et al. (2) and that modeled in simulation E3, including climate, atmospheric CO2, and land-use change. (B) Interannual variation and trend in modeled global runoff resulting from the effects of increased atmospheric CO2 (simulation E1), climate change (simulations E2–E1), land-use change (simulations E3–E2), and a decrease in stomatal conductance associated with rising atmospheric CO2 (simulation E4), respectively. The ORCHIDEE-simulated global runoff in simulation E3 shows a significant increasing trend with a rate of 0.17 mm/year2 during the last century, which is close to the estimation of 0.18 mm/year2 by Labat et al. (2). The global runoff trend derived from simulation E4 is estimated to be ≈0.16 mm/year2 for the period from 1960 to 1999, which is close to the study of Gedney et al. (1), who estimated a trend of ≈0.2 mm/year2 in response to the reduced leaf-level stomatal conductance because of rising atmospheric CO2 since 1960.

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mcith_zpq0370776120002.jpg Figure 2  Change in the runoff anomalies during the 20th century in the different continental regions. All continents show that the runoff derived from simulation E3 is significantly correlated with that estimated by Labat et al. (2) (P < 0.02). Because of the small number (seven) of observing stations that were available in Africa since 1983, the trend in Africa runoff is calculated based on the period from 1901 to 1982. Trend_ob, runoff trend reconstructed by Labat et al. (2); Trend_climate, the modeled runoff trend because of climate change (simulations E2–E1); Trend_CO2, the modeled runoff trend because of increasing atmospheric CO2 (allowing LAI changes) (simulation E1); Trend_land, the modeled runoff trend because of land use change (simulations E3–E2). The sum of Trend_climate, Trend_CO2, and Trend_land reflects the runoff trend derived from simulation E3 that consider all factors change.

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mcith_zpq0370776120003.jpg Figure 3  Spatial distribution of the trend in modeled runoff (A–D), precipitation (E), and fraction of agriculture area (F) over the last century. (A–D) Runoff trend because of the combined effects of climate, land use, and atmospheric CO2 (simulation E3) (A); increase in atmospheric CO2 (allowing LAI changes) (simulation E1) (B); climate change (simulations E2–E1) (C); and land use change (simulation E3-E2) (D).

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