Hat-tip: Kenneth Richard
The site allows user-friendly observation of sea level rise trends at locations across the world using spreadsheet data direct from NOAA and PSMSL, as it is designed to be similar to Paul Clark’s popular interactive temperature graph site (woodfortrees.org).
Sea levels rising less than half as fast, no acceleration!
Stunningly, contrary to the claims of the modeled reconstructions of sea level rise (with “adjustments” added), actual physical measurements indicate that sea levels are rising at rates well less than half the claimed rates when including GIA “adjustments” and satellite altimetry modeled reconstructions.
The best estimate is a median global mean sea level value of 1.48 mm/yr, or less than 6 inches per century.
SeaLevel.info is a one-stop source for sea-level information. The spreadsheets consolidate data from NOAA, PSMSL and other sources, to simplify examination of tide-gauge data for long term sea-level trend analysis.
The site writes:
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 1.017 mm/year (median 1.280), but the GIA adjustments add an average of 0.665 mm/year, giving a total “adjusted” average trend of 1.682 mm/year, which rounds to 1.7 mm/year, which happens to exactly equal a very widely-quoted figure for 20th century sea-level rise.”
The site here also writes that sea level is not rising everywhere, and:
The measured rate of coastal sea-level change varies from -17.59 mm/yr at Skagway, Alaska to +9.39 mm/yr at Kushiro, Japan. The average, as measured by the world’s best long-term coastal tide gauges, is just under +1.5 mm/yr (about 6 inches per century).”
SeaLevel.info wonders about the often ballyhooed figures of 3.3 mm/yr (13 inches per century), based on satellite altimetry measurements of sea-level, rather than coastal sea-level measured by tide gauges. It writes that satellite altimeters “measure the wrong thing”:
Their measurements are distorted by “sea-level rise” caused by thermal expansion when the upper layer of the ocean warms. But that is a strictly local effect, that doesn’t affect the quantity of water in the oceans, and doesn’t affect sea-level elsewhere (e.g., at the coasts). Sea-level rise only matters at the coasts, but satellite altimeters are incapable of measuring sea-level at the coasts. They can only measure sea-level in the open ocean. Tide gauges measure sea-level at the coasts, where it matters. Also, tide gauge measurements of sea-level are much higher quality than satellite altimetry measurements.
SealLevel.info adds that “satellite measurements of sea-level are of questionable reliability, and vary considerably from one satellite to another” and that tide gauges are more reliable because “some of the tide-gauge records of sea-level measurements are nearly ten times as long as the combined satellite measurement record, and twenty times as long as any single satellite measurement record.”
According to SeaLevel.info, the NOAA has done linear regression analysis on sea-level measurements (relative sea-level) from 225 long term tide gauges around the world, and found that “there’s been no sign of any acceleration (increase in rate) in most of those tide-gauge records, in over three-quarters of a century.”
The site summarizes:
The rate of measured sea-level rise (SLR) varies from -17.59 mm/yr at Skagway, Alaska, to +9.39 mm/yr at Kushiro, Japan. 197 of 225 stations (87.6%) have recorded less than 3.3 mm/yr sea-level rise. At 47 of 225 stations (20.9%) sea level is falling, rather than rising. Just 28 of 225 stations (12.4%) have recorded more than 3.3 mm/yr sea-level rise. The average SLR at those 225 gauges is +0.90 mm/yr. The median is +1.41 mm/yr.
MSL = 1.48 mm/yr