Research Paper (RP)
The Columbia River basin is in a transition climate zone between predominating maritime to the west, arctic to the north, and continental to the east. Consequently, it is difficult to characterize through means and averages. Therefore, many of the current stochastic methods for developing climate-change scenarios cannot directly apply to the basin. To circumvent this problem, a composite approach was taken to generate a climate scenario that considers knowledge of current regional climate controls, available output from general circulation and regional climate models, and observed changes in climate.
The resulting climate-change scenario suggests that precipitation could increase substantially during winter (+20 to +50 percent) and moderately during spring and autumn (+5 to +35 percent). A slight decrease (0 to -5 percent) in summer precipitation is possible, except for the southeastern portions of the basin that may experience an increase in convective precipitation (+5 percent).
Low-elevation (<1 kilometer) temperatures throughout the year may increase 1 to 3 °C, with greatest increases during winter. This amount of temperature change is possible because of an expected loss of low-elevation snow cover. At high elevations, increased cloud cover could cause average temperatures to decrease during winter but be synchronized with possible warming at low elevations during summer. The diurnal range of temperature could decrease, especially in summer and autumn.