ABSTRACT
The sensitivity of river discharge to climate-system warming is highly uncertain, and the processes that govern river discharge are poorly understood, which impedes climate-change adaptation. A prominent exemplar is the Colorado River, where meteorological drought and warming are shrinking a water resource that supports more than 1 trillion dollars of economic activity per year. A Monte Carlo simulation with a radiation-aware hydrologic model resolves the longstanding, wide disparity in sensitivity estimates and reveals the controlling physical processes. We estimate that annual mean discharge has been decreasing by 9.3% per degree Celsius of warming because of increased evapotranspiration, mainly driven by snow loss and a consequent decrease in reflection of solar radiation. Projected precipitation increases likely will not suffice to fully counter the robust, thermodynamically induced drying. Thus, an increasing risk of severe water shortages is expected.
ABSTRACT
Water availability on the continents is important for human health, economic activity, ecosystem function and geophysical processes. Because the saturation vapour pressure of water in air is highly sensitive to temperature, perturbations in the global water cycle are expected to accompany climate warming. Regional patterns of warming-induced changes in surface hydroclimate are complex and less certain than those in temperature, however, with both regional increases and decreases expected in precipitation and runoff. Here we show that an ensemble of 12 climate models exhibits qualitative and statistically significant skill in simulating observed regional patterns of twentieth-century multidecadal changes in streamflow. These models project 10-40% increases in runoff in eastern equatorial Africa, the La Plata basin and high-latitude North America and Eurasia, and 10-30% decreases in runoff in southern Africa, southern Europe, the Middle East and mid-latitude western North America by the year 2050. Such changes in sustainable water availability would have considerable regional-scale consequences for economies as well as ecosystems.
Subject(s)
Greenhouse Effect , Rivers , Water Movements , Water Supply , Africa , Asia , Ecosystem , Europe , History, 20th Century , Humans , Models, Theoretical , North America , Rain , Time Factors , Water Supply/historyABSTRACT
Radiative effects of anthropogenic changes in atmospheric composition are expected to cause climate changes, in particular an intensification of the global water cycle with a consequent increase in flood risk. But the detection of anthropogenically forced changes in flooding is difficult because of the substantial natural variability; the dependence of streamflow trends on flow regime further complicates the issue. Here we investigate the changes in risk of great floods--that is, floods with discharges exceeding 100-year levels from basins larger than 200,000 km(2)--using both streamflow measurements and numerical simulations of the anthropogenic climate change associated with greenhouse gases and direct radiative effects of sulphate aerosols. We find that the frequency of great floods increased substantially during the twentieth century. The recent emergence of a statistically significant positive trend in risk of great floods is consistent with results from the climate model, and the model suggests that the trend will continue.
ABSTRACT
OBJECTIVE: To investigate the thrombin inhibitory capacity of antithrombin III in the inflamed human joint. METHODS: Thrombin inhibitory capacity was measured, using a kinetic spectophotometric method, in matched plasma and synovial fluid samples of patients with rheumatoid arthritis (n = 22) and osteoarthritis (n = 16), together with normal control plasma samples (n = 13). In the same samples, the concentration of antithrombin III was also determined by the method of radial immunodiffusion. The combination of these measurements allowed the calculation of the specific thrombin inhibitory capacity of these samples. RESULTS: An increased concentration of antithrombin III in rheumatoid compared with osteoarthritic synovial fluid was noted (p < 0.05). However, there was a significant depression in the specific activity of antithrombin III in rheumatoid synovial fluid when compared with matched plasma samples (p < 0.001) or with osteoarthritic synovial fluid (p < 0.05). CONCLUSION: In rheumatoid synovial fluid the thrombin inhibitory capacity of antithrombin III is disproportionately depressed relative to the concentration of antithrombin III, indicating the inactivation of antithrombin III in the rheumatoid joint.
