The original detrended sea level rise rate graphs for this post was off by a factor of 12!. This greatly changes my conclusion. Incorrect information is now crossed out and is followed by corrected information in red.
Tide gauge data for the 20th century indicates that the average sea level rise rate was 1.8 mm/year. Satellite data from 1993 to present indicates a sea level rise rate of about 3 mm/year. This is part 3 of a series of posts looking for the acceleration necessary to reconcile those two facts
I am working under the theory that by detrending sea level data from individual (local) sites and averaging with other regional sites it should be possible to extract changes in regional rise rates while bypassing the question of what the “true” rise rate is for that region.
Conclusion: There is no convincing sign of a late century acceleration in the sea level rise rate in the tide gauge data from the Japan.
Conclusion: The rise rate during much of the satellite era has been much higher than the average for part of the 20th century for which data is available.
I looked for tide gauge data along the coast of Japan such that it covered at least the period from 1955 to 2008 with 90% of all monthly data accounted for. The following image shows the seven sites that met this criteria. The circles show a weighting threshold of 300 km.
Seven sites used in this analysis. Circles show 300 km weighting threshold
The following plot shows the qualifying data spread out for easy comparison. The key at the right shows the RLR data filenames.
Sea level data for all seven sites.
Data reduction and detrending
The following animation shows the transition through raw data, removal of the yearly signals, detrending, Gaussian smoothing and conversion to derivative (rise rate).
Here are the removed yearly signals and the weighting.
Yearly signals removed from Japanese RLR data
Number of files and effective weighting based on 300 km threshold.
Lets take a closer look at the detrended rise rate data and look for an acceleration in the satellite data era…
The very weak argument could be made that there was a rapid acceleration around 1985, but the resulting sea level rise rate was only about 0.25 mm/year higher than the average for the last half of the century. There was also an even greater acceleration around 1965, and sea level rise rate around 1970 was as high or higher than than in the 1990s. Finally, the 0.25 mm/year increase in the rise rate is only about 20% of the difference between the average global tide gauge rise rate for the 20th century (1.8 mm/year) and the satellite data (1993 to present) rise rate (about 3 mm/year).
So, I conclude that the Japanese data does not reconcile the difference between the 20th century tide gauge data and the satellite data.
The tide gauge data covering the part of the satellite data era (1993 to present) clearly shows a rise rate that is far greater than the average rise rate for the entire time period covered by the tide gauges. The period from 1993 to about 2003 may have a rise rate around 3 mm/year greater than the average, but after that the rise rate seems to fall again. Note that form about 1965 to 1975 the rise rate was also very high. This data from Japan does reconcile the difference between the satellite data and the average tide gauge data.
The following graphs show the sea level data from the Soma tide gauge station in Japan with the seven station shown above. Soma is the tide gauge station closest to the Fukushima nuclear reactors. The images speak for themselves.
20th century rise rate average of 1.8 mm/year
1. Church and White Global Mean Sea Level Reconstruction
2. Links to Church and White sea level data
Satellite data (about 3 mm/year)
CU Sea Level Research Group
RLR tide gauge data
Permanent Service For Mean Sea Level