In June 2012, the National Academy of Sciences (NAS) released a long-awaited report establishing likely rates of sea level rise (SLR) over the 21st century. Projections were provided for the entire west coast of the US in the report titled Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future. Sea level along the California coast, south of Cape Mendocino, is projected to rise 4-30 cm (2-12 in) by 2030, relative to 2000 levels, 12-61 cm (5-24 in) by 2050, and 42-167 cm (17-66 in) by 2100. These projections are close to SLR projections on a global scale and were used to inform the analysis conducted for California's third major assessment on climate change, released July 31, 2012.
To illustrate this rate of sea level rise, we thought it would be useful to visualize this information in relation to historic rates of sea level rise. In the chart below you can visualize historic sea levels at the San Francisco tide gage, compared with the various projections presented in the report. Use the lower graph to select and zoom in on sections of the data and turn portions of the data on and off by clicking on the colored legend.
Find more about this data and chart at the bottom of the page. Some web browsers don't seem to like this graph, but it should work fine in Firefox, Chrome and Safari.
About this Data and Graph
Here in the Bay Area we are lucky enough to have one of the longest tide records on the West Coast, which for San Francisco stretches from July 1854 to the present. Monthly mean water levels were downloaded from the National Oceanic and Atmospheric Administration's Tides and Currents website. From this, the 5-month moving average of these monthly averages was calculated, to smooth out the graph and make it easier to detect trends in sea level rise. This graph is presented in terms of inches above or below the average level observed in 2000. You may notice a shift in the trend around 1897, which is likely attributed to a change in the datum, or the reference from which elevation measurements were made.
Since the start of the record, sea levels have risen at the San Francisco tidal gage by around 20 cm, or 8 inches. During El Nino years, sea levels rise significantly, such as in 1983 and 1997. It is during these times when the risk of flooding and coastal erosion is greatest - threats which will increase in frequency and magnitude as sea level rise progresses.
To create the sea level rise curves, the projections presented in the NAS report were fit to polynomial equations. Since expected sea levels were only expressed for the years 2030, 2050 and 2100, these curves allows us to estimate the projected rate of change in sea level in the intervening years. The NAS provided an expected rate of sea level rise, relative to 2000 levels, as shown by the middle orange curve, compared to an upper- and lower-bound estimate, in blue and light orange, respectively.
For questions or comments about this data visualization, please contact Ian Wren (email@example.com).