Consequently, careful analyses of longest-term records from many stations across the country and addressing multiple potential explanations are required and are cornerstones of the evidentiary studies described above.Įfforts are underway to continually improve the stability, placement, and numbers of weather observations needed to document trends scientists also regularly search for other previously unanalyzed data sources for use in testing these findings. Observed trends: Precipitation trends are generally embedded amidst large year-to-year natural variations and thus trends may be difficult to detect, may differ from site to site, and may be reflections of multi-decadal variations rather than external (human) forcings. Important new evidence (cited above) confirmed many of the findings from the 2009 National Climate Assessment. New information and remaining uncertainties 20: Southwest) are the basis for the reported projections. Ensembles of climate models 13, 19(see also Ch. ![]() The broad observed trends of precipitation and river-flow increases have been identified by many long-term National Weather Service (NWS)/National Climatic Data Center (NCDC) weather monitoring networks, USGS streamflow monitoring networks, and analyses of records therefrom (Ch. Projected precipitation responses (such as changing extremes) to increasing greenhouse gases are robust in a wide variety of models and depictions of climate. 2013 14) indicate small projected changes in total average annual precipitation in many areas, while heavy precipitation 15, 16 and the length of dry spells are projected to increase across the entire country. 9, 10, 11, 12 As discussed in Chapter 2, the majority of projections available from climate models (for example, Orlowsky and Seneviratne 2012 13 Kharin et al. 2: Our Changing Climate) 3, 4, 5, 6, 7, 8 and river-flow trends. Numerous peer-reviewed publications describe precipitation trends (Ch. 20: Southwest, other technical input reports, 2 and over 500 technical inputs on a wide range of topics that were received as part of the Federal Register Notice solicitation for public input. The key message and supporting chapter text summarizes extensive evidence documented in the inter-agency prepared foundational document, 1 Ch. However, climate change is altering the water cycle in multiple ways over different time scales and geographic areas, presenting unfamiliar risks and opportunities. The water cycle is dynamic and naturally variable, and societies and ecosystems are accustomed to functioning within this variability. Water cycles constantly from the atmosphere to the land and the oceans (through precipitation and runoff) and back to the atmosphere (through evaporation and the release of water from plant leaves), setting the stage for all life to exist. This chapter contains three main sections: climate change impacts on the water cycle, climate change impacts on water resources use and management, and adaptation and institutional responses.Ĭlimate Change Impacts on the Water Cycle ![]() The cycle of life is intricately joined with the cycle of water. University Corporation for Atmospheric Research Introduction National Aeronautics and Space Administration
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