Laserfiche WebLink
PART I: WHAT ARE CLIMATE RESEARCHERS SAYING <br />ABOUT WESTERN WATER? A GUIDE FOR NON - SCIENTISTS <br />CLIMATE SCIENCE AND RESEARCH: THE BASICS <br />AVERAGES AND EXTREMES <br />A wide variety of scientists and other researchers investigate the relationship between climate and <br />water resources. Some of this science is focused on the possibility of long -term climate change, <br />while other investigations focus on climate variability — particularly, extreme events such as <br />droughts and floods. In the language of statistics —the foundation of most climate research the <br />former is the study of fundamental movements in averages (means), while the latter is focused on <br />event - specific deviations from average (e.g., standard deviations). Both parameters have always <br />been important to water managers. Average climatic conditions establish the basic contours of long- <br />term water availability and system yields, while extreme events shape the design of spillways, <br />reservoir curves, safe yield calculations, and many related facets of water management. Both <br />subjects are independently worthy of study; for example, even in the absence of climate change, <br />increased variability could be highly problematic for water managers. Yet it is the combined impact <br />of changing averages and extremes that is perhaps most relevant to improved resource planning and <br />management. <br />Historic records of water data are routinely used to estimate both averages and variability, and are <br />the foundation of many current water planning and management decisions. With an adequate history <br />of streamflow monitoring data, for example, it is a simple matter to calculate the average discharge <br />of a river, and to generally describe what a 100 -year drought might look like. Often, this history of <br />monitoring data can be greatly extended by paleoclimate reconstructions —i.e., the use of data such <br />as tree -rings to provide estimates of prehistoric climate regimes. However, a detailed knowledge of <br />past climatic conditions is useful for managers only as long as one overriding assumption is valid: <br />that the climate of the fixture will look like the climate of the past. Unfortunately, that assumption <br />seems increasingly tenuous. In just the past century, the average annual US temperature has risen by <br />almost 1°F (0.6 °C), and precipitation has increased by 5 to 10 percent — mostly due to big storms. <br />Changes in the past decade have been the most dramatic, leading some researchers to believe that the <br />1990s were the hottest decade of the millennium. The trends observed in the 1990s have also <br />sparked interest in the subject of abrupt climate change, as opposed to more gradual (linear) <br />movements in means and variability. Evidence of several large- scale, abrupt climate changes can be <br />found in the geologic record. <br />CLIMATE CHANGE PROJECTIONS <br />The research community is increasingly asked to provide projections of future climatic conditions <br />and, more specifically, what this might mean for water availability in specific regions such as the <br />western United States. This is an exceedingly complex task usually involving several linked stages, <br />each aided by different models and, in the latter stages, the involvement of an increasingly diverse <br />4 <br />