One of the most important aspects of global climate is precipitation, and variations in its timing or amount can have an enormous impact on human resources and activities. A pair of papers illustrate two different aspects of this type of variability. El Niño and La Niña events have dramatic effects on patterns of precipitation all across the globe and are often cited as the cause of large economic losses, because these events are associated with extremes of weather. However, Goddard and Dilley find that climate anomalies during these events are not greater than those that occur in the intervening periods. Moreover, because climate forecasts during El Niño and La Niña events are more accurate than those in the intervening periods, greater preparedness should actually lead to a diminished economic impact.
Jain et al. focus on regional hydrologic change in western North America during the late 20th century. They find a trend toward increasing year-to-year variance of stream flow in the major river basins, which coincides with an increase in the synchrony of stream flow changes across basins. These trends are closely related to the atmospheric circulation regimes of the late 20th century. They discuss the implications of this regional hydrologic change on the vulnerability of water resources and raise concerns about the adequacy of water resource planning and operations in this region. -- HJS
J. Clim. 18, 651; 613 (2005).
