Tide Gauge Evidence: Sea Levels
Rose Faster Before 1950 Than Since
In recent years it has become increasingly apparent that tide gauge measurements of sea level rise often do not align with climate model expectations.
The models are predicated on the assumption that anthropogenic CO2 emissions, which have risen explosively since about 1950, are the drivers of modern sea level rise.
Evidence from observed sea level trends have not been cooperating with this narrative, however.
Tide gauges indicate there has been a substantial overall reduction in the rate of sea level rise since about 1950 rather than the expected substantial acceleration.
For example, UK oceanographer Simon Holgate reported a 29% deceleration in global sea level rise rates from the first half of the 20th century (1904-1953) to the second half (1954-2003)
Holgate, 2007 “The rate of sea level change was found to be larger in the early part of last century (2.03 ± 0.35 mm/yr 1904–1953), in comparison with the latter part (1.45 ± 0.34 mm/yr 1954–2003).”
A small sampling of regional tide gauge results (SW Pacific, Japan) affirm the deceleration of sea level rise since the mid-20th century, and indicate the highest rates of sea level rise occurred before human CO2 emissions began accelerating rapidly.
Gehrels et al., 2012 “Between 1900 and 1950 relative sea level rose at an average rate of 4.2±0.1 mm/yr. During the latter half of the 20th century the reconstructed rate of relative sea-level rise was 0.7±0.6 mm/yr. Our study is consistent with a similar pattern of relative sea-level change recently reconstructed for southern New Zealand.”
Sasaki et al., 2017 “Sea level variability around Japan from 1906 to 2010 is examined using a regional ocean model, along with observational data and the CMIP5 historical simulations. The regional model reproduces observed interdecadal sea level variability, e.g., high sea level around 1950, low sea level in the 1970s, and sea level rise during the most recent three decades, along the Japanese coast. … That the wind-induced sea level rise along the Japanese coast around 1950 is as large as the recent sea level rise highlights the importance of natural variability in understanding regional sea level change on interdecadal timescales.”
A reconstruction of global-scale rates from tide gauges (Jevrejeva et al., 2008) dating back to 1700 also reveals a deceleration in the rate of sea level increase since 1950.
Rates Of Recent Rise For 2,133 Global-Scale Tide Gauges: 1.04 mm/year
According to a comprehensive analysis (2,133 tide gauges) of Permanent Service for Mean Sea Level (PSMSL) data, the current (2014) global mean sea level rise rate is a little more than 1 mm/year.
Parker, 2015 “The nominal satellite altimeter-based determination of the absolute global mean sea level is actually a computational result rather than a direct observation. It is obtained by correcting the satellite altimeter raw signal with algorithms having many features in common with the climate models. Regardless of any modeling problems, Carter et al. (2014) pointed out that estimates of sea-level change from satellite-collected data remain problematic, because of the many uncertainties in data collection and processing. In particular, there is inconsistency between the results derived by different research groups, with all results depending upon the accuracy of complex adjustments, some of which lack in- dependent verification, plus the severe problem that the signal being sought may be less than the noise level of the data being used. Many corrections applied to all satellite altimeter measurements of sea-level since 2003 had the effect of changing a sea-level record that showed no trend or a gentle rise into one that projects high rates of rise.”
“The latest PSMSL Table of Relative Mean Sea Level Secular Trends update 14-Feb-2014 (www.psmsl.org) proposes the relative rates of rise computed for 2133 tide gauges of variable record length (maximum 183 [years], minimum 21 [years], average 56.5 years) with the more recent, shortest readings collected mostly in areas of subsidence and a strongly non uniform geographical coverage. The average relative rate of rise of the 2133 tide gauges is 1.04±0.45 mm/year“
NOAA’s ‘Believed’ Rates Of Recent Rise From Tide Gauges: 1.7-1.8 mm/year
Adding NOAA’s ‘Believed’ Modern Rate To The Long-Term Rate Trend
Trends In Human CO2 Emissions Rates (GtC/year)
Non-Correlation: Sea Level Rise Rates & CO2 Emissions Rates
Reconstructed Trends In Total Solar Irradiance 1700-2013
“Deterministic models based on the stationary periods confirm the results through a close relation to known long solar minima since 1000 A.D. and suggest a modern maximum period from 1940 to 2015. The model computes a new Dalton-type sunspot minimum from approximately 2025 to 2050 and a new Dalton-type period TSI minimum from approximately 2040 to 2065. … Periods with few sunspots are associated with low solar activity and cold climate periods. Periods with many sunspots are associated with high solar activity and warm climate periods.”
Apparent Correlation: TSI And (Lagged) Sea Level Rise Rate Changes
Apparent Correlation: TSI And Northern Hemisphere Temperatures