How Does Climate Change Compare to Natural Variability for Managing Energy Infrastructure in the North?

Several geographic characteristics of Southeast Alaska (SEAK) make assessing the regional impacts of climate change on hydroelectric power infrastructure particularly complex: one is the steep, heterogeneous topography surrounded by ocean; second is the strong influence of interannual and decadal-scale climate variability, a third is the presence of glaciers in many of the reservoir watersheds. Climate models project annual warming of 3–4 degrees C over the 21st century for Southeast Alaska and a 5–8% increase in annual precipitation, with a significant shift from snow to rain. Increases in runoff are expected to exceed increases in precipitation in basins with glaciers, as those glaciers melt, but not after they have receded entirely. Analysis of historical data show that approximately half of the observed warming in SEAK since 1920 is attributable to the variability of the Pacific Decadal Oscillation, a naturally occurring mode. This pattern of climate variability drives persistence of temperature and precipitation anomalies in such a way that utilities managers in SEAK should anticipate the possibility of "non-normal" inflows for an entire decade or longer, as part of natural variability. On top of this decadal persistence are the long-term trends associated with global climate change: warming and wetting. New scoping projects should analyze long-term (multi-decadal) climate and hydrology datasets where possible, as well as look at downscaled climate projections, while recognizing the limitations of these data and models. Managers of existing utilities should be aware of the availability of seasonal prediction tools from NOAA's Climate Prediction Center and other resources.