FIGURE 1.1 Estimated, observed, and projected global sea-level rise from 1800 to 2100. The pre-1900 record is based on geological evidence, and the observed record is from tide gages (red line) and satellite altimetry (blue line). Example projections of sea-level rise to 2100 are from IPCC (2007) global climate models (pink shaded area) and semi-empirical methods (gray shaded area; Rahmstorf, 2007). SOURCES: Adapted from Shum et al. (2008), Willis et al. (2010), and Shum and Kuo (2011).
order was a request that the National Research Council (NRC) establish a committee to assess sea-level rise in California to inform state planning and development efforts. Prior to release of the NRC report, the state agencies were instructed to incorporate sea-level-rise projections into their planning process. The range of projections adopted by California as interim values are 13–21 cm for 2030, 26–43 cm for 2050, and 78–176 cm for 2100 (CO-CAT, 2010).
Following the California executive order, the states of Oregon and Washington, the U.S. Army Corps of Engineers, the National Oceanic and Atmospheric Administration, and the U.S. Geological Survey joined California in sponsoring this NRC study. These agencies need sea-level information for a variety of purposes, including assessing coastal hazard vulnerability, risks, and impacts; informing adaptation strategies; and improving coastal hazard forecasts and decision support tools.
This report provides an assessment of current knowledge about changes in sea level expected in California, Oregon, and Washington for 2030, 2050, and 2100 (see Box 1.1 for the committee charge). The years for the assessment represent planning horizons: 2030 is a typical planning horizon for many local managers; 2050 is the latest date for which conventional population projections are available; and 2100 is the limit beyond which uncertainties become too high for planning.2 The report primarily focuses on how much sea level is likely to rise globally (Task 1) and along the west coast of the United States (Task 2). Processes that have only transient effects on sea level (e.g., tides, tsunamis) were considered only if the nature of the process affects trends in sea level (e.g., changes in frequency of intensity of storms [Task 2a]). Coastal impacts or measures to lessen them were considered only in the context of summarizing what is known about how coastal habitats and natural and restored environments respond to and protect against future sea-level rise and storms (Tasks 2b and 2c).
2 Jeanine Jones, California Department of Water Resources, personal communication, December 3, 2008.