About SeaLevel.info
SeaLevel.info is your one-stop source for sea-level information (and a lot of other climate-related information).
On the Data page you may:
1. Search for a tide gauge location by PSMSL ID, NOAA ID, or full or partial station name (i.e., location name, e.g., "Honolulu"). ↑
2. View Excel-compatible spreadsheets of data about tide gauges with sea-level measurements:
* You can sort the spreadsheets in various ways by clicking column headers.
* Scroll to the bottom to see some summary info.
For any tide gauge which you identify, either by searching or by clicking on the station name in one of the spreadsheets, there are many options available. You may:
- View a graph of sea-level measurements from that location.
- Follow links to the NOAA and PSMSL pages for that tide gauge.
- Select the data source (PSMSL and/or NOAA).
- Apply boxcar or triangle smoothing to the sea-level graph.
- Calculate linear and quadratic regressions (line/curve fitting).
- View graphical representations of the linear and/or quadratic regressions.
- View confidence intervals and/or prediction intervals for the regressions.
- Adjust the date ranges used in the regression calculations and/or displayed on the graph.
- Adjust the appearance of the graphs (color scheme, line thickness, etc.)
- View or suppress a juxtaposed graph of CO2 measurements, to see what effect CO2 has had on sea-level rise or fall at that location.
For example, here's Honolulu, with the default options:
Click on the link to see the analysis page for Honolulu's sea-level data. Note the regression results further down the page a bit, on the right. As you can see, the slope and acceleration calculated are:
linear trend = 1.547 0.204 mm/yr
acceleration = 0.000714 0.013419 mm/yr²From the slope we can see that over the 117 year history of that tide gauge, sea-level has been rising an average of 1.547 ±0.204 mm per year (i.e., 5.3 to 6.9 inches per century). (That's very typical, BTW.)
The confidence interval is broader than the rate of acceleration, so it should properly be reported as "no statistically significant acceleration or deceleration" (which is also typical).
In this next version the graph I've replaced the linear trend and confidence intervals with quadratic, and I've also enabled "prediction intervals" in the graph. Because the acceleration is negligible, the quadratic regression is almost a perfectly straight line:
https://sealevel.info/MSL_graph.php?id=Honolulu&boxcar=1&boxwidth=3&thick&linear=0&lin_ci=0&quadratic=1&quad_ci=1&quad_pi=1 Note: There's a link on the right side of the page, to a video explaining the distinction between "confidence intervals" and "prediction intervals."
Here is the graph with linear trend, but thicker traces:
https://sealevel.info/MSL_graph.php?id=1612340&thick Note the "previous" and "next" buttons at the upper-right and upper-left corners of each page, to view other locations.
Here it is without the green CO2 graph juxtaposed:
https://sealevel.info/MSL_graph.php?id=1612340&thick&co2=0 Here it is in black & white, with thick traces:
https://sealevel.info/MSL_graph.php?id=1612340&thick&colors=2
(Several other color schemes are also available.)Here it is with 3-month boxcar smoothing & thick traces:
https://sealevel.info/MSL_graph.php?id=Honolulu&boxcar=1&boxwidth=3&thick Here it is with the regression analyses restricted to measurements since January 1900:
https://sealevel.info/MSL_graph.php?id=Honolulu&boxcar=1&boxwidth=3&thick&c_date=1930/1:2025/12 Note that the data which was excluded from the calculations is graphed with a lighter shade of blue, and a double-dagger footnote is added to the page:
‡ Light blue data is excluded from regression calculations
The spreadsheets here consolidate data from NOAA, PSMSL and other sources, to simplify examination of tide-gauge data for long term sea-level trend analysis.
I hope they're useful to you! If you spot errors, or if you have suggestions about how I can improve this site, please let me know.
Warning: These tools are a work in progress, and there are still many rough edges. For instance, earthquakes aren't accounted for, and they can seriously distort the regressions. Here's the most dramatic example I've seen:
https://sealevel.info/MSL_graph.php?id=Seward
Why I built these tools?
(History of this site: https://sealevel.info/history.html)
A gentleman named Paul Clark in the UK has created an excellent site for analyzing and graphing temperature data, but nobody had yet created one for sea-level data. That was a significant lack, because temperature and sea-level measurements are the two most important types of data relevant to the “climate change” debate, and coastal sea-level measurement data are of much higher quality than the temperature data. ↑
One interesting observation is that GIA (PGR)† adjustments are often nearly as large as the averaged actual measured sea-level trends! The average of the measured trends for NOAA's 2012 set of 239 tide gauges is ≈1.2 mm/year (median ≈1.4 mm/year), but the GIA adjustments add an average of 0.567 mm/year, giving a total "adjusted" average trend of 1.764 mm/year, which is almost exactly equal to the very widely-quoted 1.7 or 1.8 mm/year figure which is frequently claimed to be the rate of 20th century sea-level rise. (See the "Averages" summary line at the bottom of each of the spreadsheets, and scroll-right.) This confirms the late John Daly's observation that:
"The impression has been conveyed to the world's public, media, and policymakers, that the sea level rise of 18 cm in the past century is an observed quantity and therefore not open to much dispute. What is not widely known is that this quantity is largely the product of modeling, not observation, and thus very much open to dispute, especially as sea level data in many parts of the world fails to live up to the IPCC claims."
Notes:
Note #1: Some features of this web site do not work properly with Internet Explorer 8 and earlier. However, it works well with recent version of Chrome, Firefox, Safari, Opera, and most other modern web browsers, including many small-screen devices such as smart-phones and eReaders. Most features also work with Internet Explorer 11 & Edge. It might also work reasonably well with Internet Explorer 9 & 10, but I don't regularly test with those browsers.
Note #2: Technologies used for this site include the Python, Javascript, PHP, and occasionally Perl programming languages; Google Visualization/Chart tools; Microsoft Excel HTML spreadsheet format.
Note #3: The photo of kitesurfers off Kanaha Beach, on Maui, is used with the gracious permission of the photographer, Patti Cadiz of HST Windsurfing.
Note #4: When you see this little symbol ↑ on the sealevel.info web site, it's a link directly to the paragraph or section that you're reading. (E.g., all of the entries in the glossary have those links.)
Dave Burton
Cary, NC USA
(alt)
M: +1 919-244-3316
†GIA stands for "Glacial Isostatic Adjustment," and PGR stands for "Post-Glacial Rebound." For our purposes, they are synonyms.
