Article

Comments on “Evidence for global runoff increase related to climate warming” by Labat et al.

Center for Climatic Research, University of Delaware, Newark, DE 19716-2541, USA; U.S. Geological Survey, Reston, VA 20192-0002, USA; U.S. Geological Survey, Denver, CO 80225-0046, USA
Advances in Water Resources (Impact Factor: 2.41). 01/2005; DOI:10.1016/j.advwatres.2005.04.006

ABSTRACT We have examined the evidence presented by Labat et al. and found that (1) their claims for a 4% increase in global runoff arising from a 1 °C increase in air temperature and (2) that their article provides the “first experimental data-based evidence demonstrating the link between the global warming and the intensification of the global hydrological cycle” are not supported by the data presented. Our conclusions are based on the facts that (1) their discharge records exhibit non-climatic influences and trends, (2) their work cannot refute previous studies finding no relation between air temperature and runoff, (3) their conclusions cannot explain relations before 1925, and (4) the statistical significance of their results hinges on a single data point that exerts undue influence on the slope of the regression line. We argue that Labat et al. have not provided sufficient evidence to support their claim for having detected increases in global runoff resulting from climate warming.

0 0
 · 
0 Bookmarks
 · 
89 Views
  • [show abstract] [hide abstract]
    ABSTRACT: Increased atmospheric CO2 concentration and climate change may significantly impact the hydrological and meteorological processes of a watershed system. Quantifying and understanding hydrological responses to elevated ambient CO2 and climate change is, therefore, critical for formulating adaptive strategies for an appropriate management of water resources. In this study, the Soil and Water Assessment Tool (SWAT) model was applied to assess the effects of increased CO2 concentration and climate change in the Upper Mississippi River Basin (UMRB). The standard SWAT model was modified to represent more mechanistic vegetation type specific responses of stomatal conductance reduction and leaf area increase to elevated CO2 based on physiological studies. For estimating the historical impacts of increased CO2 in the recent past decades, the incremental (i.e., dynamic) rises of CO2 concentration at a monthly time-scale were also introduced into the model. Our study results indicated that about 1–4% of the streamflow in the UMRB during 1986 through 2008 could be attributed to the elevated CO2 concentration. In addition to evaluating a range of future climate sensitivity scenarios, the climate projections by four General Circulation Models (GCMs) under different greenhouse gas emission scenarios were used to predict the hydrological effects in the late twenty-first century (2071–2100). Our simulations demonstrated that the water yield would increase in spring and substantially decrease in summer, while soil moisture would rise in spring and decline in summer. Such an uneven distribution of water with higher variability compared to the baseline level (1961–1990) may cause an increased risk of both flooding and drought events in the basin.
    Climatic Change 01/2012; 110(3):977-1003. · 3.63 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Graphical abstract Figure optionsView in workspace Highlights ► The influences of temperature rise on the trend of water yield were suppressed by precipitation. ► The long-term mean water yield by climatic zone had similar pattern as precipitation. ► The volumetric water yield for each land cover was highly dependent on its area within one zone. ► The mean water yield decreased from low to high latitude with the rates of changes varied. ► The sensitivity of water yield to T and P changes increased from northern to southern latitude.
    Journal of Hydrology 02/2013; 481:96–105. · 2.96 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Emissions of greenhouse gases and aerosols from human activities continue to alter the climate and likely will have significant impacts on the terrestrial hydrological cycle and water quality, especially in arid and semiarid regions. We applied an improved Soil and Water Assessment Tool (SWAT) to evaluate impacts of increased atmospheric CO(2) concentration and potential climate change on the water cycle and nitrogen loads in the semiarid James River Basin (JRB) in the Midwestern United States. We assessed responses of water yield, soil water content, groundwater recharge, and nitrate nitrogen (NO(3)-N) load under hypothetical climate-sensitivity scenarios in terms of CO(2), precipitation, and air temperature. We extended our predictions of the dynamics of these hydrological variables into the mid-21st century with downscaled climate projections integrated across output from six General Circulation Models. Our simulation results compared against the baseline period 1980 to 2009 suggest the JRB hydrological system is highly responsive to rising levels of CO(2) concentration and potential climate change. Under our scenarios, substantial decrease in precipitation and increase in air temperature by the mid-21st century could result in significant reduction in water yield, soil water content, and groundwater recharge. Our model also estimated decreased NO(3)-N load to streams, which could be beneficial, but a concomitant increase in NO(3)-N concentration due to a decrease in streamflow likely would degrade stream water and threaten aquatic ecosystems. These results highlight possible risks of drought, water supply shortage, and water quality degradation in this basin.
    Science of The Total Environment 05/2012; 430:150-60. · 3.26 Impact Factor

Full-text (2 Sources)

View
22 Downloads
Available from
Mar 19, 2013