Dialing back the 10 foot hype – NOAA Tide Gauge Data shows no coastal sea level rise acceleration

… meanwhile California sea level rise “model study” claims 10 foot rise by 2100

Guest essay by Larry Hamlin

NOAA has just updated its coastal sea level rise tide gauge data including actual measurements through year 2016 which continues to show no evidence of coastal sea level rise acceleration.

These measurements include tide gauge data coastal locations for 25 West Coast, Gulf Coast and East Coast states along the Pacific Ocean, Gulf of Mexico and Atlantic Ocean, 7 Pacific island groups and 6 Atlantic island groups comprising more than 200 measurement stations.

The longest NOAA tide gauge data coastal sea level rise measurement record is at The Battery in New York with its 160 year long data record showing a steady rate of sea level rise of about 11 inches per century.

NOAA data provides assessments of the 95% confidence intervals at all measured locations which demonstrate the consistent behavior of location specific sea level rise over time and as well as showing that longer interval measurement periods provide tight ranges for the 95% confidence interval.

The 2016 updated NOAA tide gauge data includes four long time period (between 92 and 119 years) coastal locations for California at San Diego, La Jolla, Los Angeles and San Francisco. The actual measured and steady coastal rates of sea level rise at these locations vary between about 4 to 9 inches per century.

The UN IPCC AR5 WG1 report concludes in the Summary for Policymakers Chapter that:

“It is very likely that there is a substantial anthropogenic contribution to the global mean sea level rise since the 1970s. This is based on the high confidence in an anthropogenic influence on the two largest contributions to sea level rise, that is thermal expansion and glacier mass loss. {10.4, 10.5, 13.3}”

NOAA tide gauge coastal sea level rise data measurements encompassing the 46 year period from 1970 through 2016 do not support and in fact clearly contradict the UN IPCC AR5 WG1 conclusion regarding supposed man made contributions to increasing rates of sea level rise since the early 1970s.

Meanwhile here in California, the climate alarmist capital of the U.S.,  the Working Group of the Ocean Protection Council Science Advisory Team, supported and convened by California Ocean Science Trust have just released a new report “Rising Seas in California, An Update on Sea–Level Rise Science“ which is intended to provide statewide sea-level rise policy guidance.

The report has been widely hyped by climate alarmist main stream media  http://www.mercurynews.com/2017/04/30/oceans-rising-faster-than-scientific-forecasts/  based on the highly speculative and scientifically unsupported claim that sea levels at the states coastline could rise by 10 feet by the end of the century.

The new state report is based on projections derived from semi-empirical climate models which supposedly provide probabilistic assessments of coastal sea level rise for California locations.

The UN IPCC AR5 WG1 report dealt extensively with the many problems and shortcomings of sea level rise semi-empirical climate models (SEM’s) and provided a litany of significant and complex unresolved scientific issues.

Provided below are IPCC identified issues with SEMs as noted in various chapters of the AR5 WG1 report.

Summary for PolicyMakers Chapter:

“The basis for higher projections of global mean sea level rise in the 21st century has been considered and it has been concluded that there is currently insufficient evidence to evaluate the probability of specific levels above the assessed likely range. Many semi-empirical model projections of global mean sea level rise are higher than process-based model projections (up to about twice as large), but there is no consensus in the scientific community about their reliability and there is thus low confidence in their projections. {13.5}”

Technical Summary Chapter:

“Semi-empirical models are designed to reproduce the observed sea level record over their period of calibration, but do not attribute sea level rise to its individual physical components. For RCPs, some semi- empirical models project a range that overlaps the process-based likely range while others project a median and 95-percentile that are about twice as large as the process-based models. In nearly every case, the semi-empirical model 95th percentile is higher than the process-based likely range. For 2081–2100 (relative to 1986–2005) under RCP4.5, semi-empirical models give median projections in the range 0.56 to 0.97 m, and their 95th percentiles extend to about 1.2 m. This difference implies either that there is some contribution which is presently unidentified or underestimated by process-based models, or that the projections of semi-empirical models are overestimates.”

“Making projections with a semi-empirical model assumes that sea level change in the future will have the same relationship as it has had in the past to RF or global mean temperature change. This may not hold if potentially nonlinear physical processes do not scale in the future in ways which can be calibrated from the past. There is no consensus in the scientific community about the reliability of semi-empirical model projections, and confidence in them is assessed to be low. {13.5.2, 13.5.3}”

“There is low confidence in semi-empirical model projections of global mean sea level rise, and no consensus in the scientific community about their reliability. {13.5.2, 13.5.3}”

Sea Level Change Chapter 13: 

“Some semi-empirical models project a range that overlaps the process-based likely range while others project a median and 95th percentile that are about twice as large as the process- based models. In nearly every case, the semi-empirical model 95th percentile is higher than the process-based likely range.”

“Despite the successful calibration and evaluation of semi-empirical models against the observed 20th century sea level record, there is no consensus in the scientific community about their reliability, and consequently low confidence in projections based on them. {13.5.2, 13.5.3, Figure 13.12}”

“Semi-empirical models (SEMs) project sea level based on statistical relationships between observed GMSL and global mean temperature (Rahmstorf, 2007a; Vermeer and Rahmstorf, 2009; Grinsted et al., 2010) or total RF (Jevrejeva et al., 2009, 2010). The form of this relationship is motivated by physical considerations, and the parameters are determined from observational data—hence the term ‘semi-empirical’ (Rahmstorf et al., 2012b).”

“SEMs do not explicitly simulate the underlying processes, and they use a characteristic response time that could be considerably longer than the time scale of interest (Rahmstorf, 2007a) or one that is explicitly determined by the model (Grinsted et al., 2010).”

“The semi-empirical approach regards a change in sea level as an integrated response of the entire climate system, reflecting changes in the dynamics and thermodynamics of the atmosphere, ocean and cryosphere; it does not explicitly attribute sea level rise to its individual physical components. SEMs use simple physically motivated relationships, with various analytical formulations and parameters determined from observational time series, to predict GMSL for the 21st century (Figure 13.12 and Table 13.6) and beyond, from either global mean SAT (Rahmstorf, 2007a; Horton et al., 2008; Vermeer and Rahmstorf, 2009; Grinsted et al., 2010; Rahmstorf et al., 2012b) or RF (Jevrejeva et al., 2009; 2010, 2012a).”

“The GMSL estimates used for calibrating the SEMs are based on the existing sparse network of long tide-gauge records, and are thus uncertain, especially before the late 19th century; these uncertainties are reflected in the observational estimates of the rate of GMSL rise (Sections 3.7 and 13.2.2).”

“Consequently, the projections may be sensitive to the statistical treatment of the temporal variability in the instrumental record of sea level change (Holgate et al., 2007; Rahmstorf, 2007b; Schmith et al., 2007). Rahmstorf et al. (2012b) reported that GMSL projections for the RCP4.5 scenario for 2100 (Table 13.6) varied by ±0.04 m when the embedding dimension used for temporal smoothing during the calibration was varied within a range of 0 to 25 years.”

“SEM projections will be biased unless contributions to past GMSL rise which correlate with but are not physically related to contemporary changes in the predictor variable (either global mean SAT change or RF) are subtracted from the observational sea level record before the cali- bration (Vermeer and Rahmstorf, 2009; Jevrejeva et al., 2012b; Rahm- storf et al., 2012b; Orlić and Pasarić, 2013).

“These include groundwater depletion due to anthropogenic intervention and storage of water by dams (Section 13.3.4), ongoing adjustment of the Greenland and Ant- arctic ice sheets to climate change in previous centuries and millen- nia (Section 13.3.6), and the effects of internally generated regional climate variability on glaciers (Marzeion et al., 2012a; Church et al., 2013, Sections 13.3.2.2 and 13.3.6) and ice sheets (Section 13.3.3.2). For instance, Jevrejeva et al. (2012b) found that their median projections for 2100 were reduced by 0.02 to 0.10 m by excluding some such contributions.”

“Making projections with a SEM assumes that sea level change in the future will have the same relationship as it has had in the past to RF or global mean temperature change. The appropriate choice for the formulation of the SEM may depend on the nature of the climate forcing and the time scale, and potentially nonlinear physical processes may not scale in the future in ways which can be calibrated from the past (von Storch et al., 2008; Vermeer and Rahmstorf, 2009; Rahmstorf et al., 2012b; Orlić and Pasarić, 2013). Two such effects that could lead to overestimated or underestimated projections by SEMs have been discussed in the literature.”

“The higher estimates from the SEMs than the process-based models used here for the long-term projections are consistent with the relation between the two modelling approaches for the 21st century (Figure 13.12).”

“Section 13.5.3 concluded that the limited or medium evidence supporting SEMs, and the low agreement about their reliability, provides low confidence in their projections for the 21st century. We note here that the confidence in the ability of SEMs is further reduced with the length of the extrapolation period and the deviation of the future forcing from the forcing of the learning period (Schaeffer et al., 2012), thus decreasing confidence over the long time frames considered here.”

The California main stream media climate alarmist articles about the new sea level rise study projections ignored these many thorny issues.

The new state sea level rise report contains many significant qualifications and uncertainties that are addressed but none of which are revealed by California main stream media alarmist articles.

Regarding the headline grabbing 10 foot sea level rise claim which is based on accelerated Antarctica ice melt the report notes the following:

“These projections may underestimate the likelihood of extreme sea-level rise, particularly under high emissions scenarios, so this report also includes an extreme scenario called the H++ scenario.”

“The probability of this scenario is currently unknown, but its consideration is important, particularly for high-stakes, long-term decisions.”

“Before 2050, differences in sea-level rise projections under different emissions scenarios are minor but they diverge significantly past mid- century. After 2050, sea-level rise projections increasingly depend on the trajectory of greenhouse gas emissions. For example, under the extreme H++ scenario rapid ice sheet loss on Antarctica could drive rates of sea-level rise in California above 50 mm/year (2 inches/year) by the end of the century, leading to potential sea-level rise exceeding 10 feet. This rate of sea-level rise would be about 30-40 times faster than the sea-level rise experienced over the last century.”

“As described above (Section 3.1.1), these projections may underestimate the probability of extreme Antarctic ice loss, an outcome that is highly uncertain but, given recent observations and model results, cannot be ignored.”

“Accordingly, we have also included an extreme sea-level rise scenario, which we call the H++ scenario. This is an unknown probability, high consequence scenario such as would occur if high rates of Antarctic ice loss were to develop in the last half of this century. When decisions involve consequential infrastructure, facilities or assets, we advise that extra consideration be given to this upper end of potential sea-level rise outcomes”

“The obvious question is: how confident can we be in the recent model projections? First, it should be emphasized that the model ensembles (Figure 10) hinge on the performance of a single ice-sheet model and a single climate model. Furthermore, the ensembles do not explore the full range of parameters in the ice sheet model.Thus, the ensembles do not provide a true probabilistic assessment of Antarctica’s possible future.”

“While much progress observing and modeling the ice sheet has been made in recent years, the precise magnitude and timing when Antarctic might begin to contribute substantial sea level should still be considered deeply uncertain.”

“Regardless of uncertainty in model physics, one of the greatest sources of uncertainty lies in which future greenhouse gas scenario will be followed; so even if the physical model were perfect in its representation of the natural world, there would still be major uncertainty in the Antarctic ice sheet’s future.”

The alarmist claims of 10 foot California sea level rise by the end of the century suggested by this report and highlighted by the media have no established scientific basis and represent nothing but conjecture and speculation.

Regarding the reports projections in general the following significant uncertainties are addressed:

“For projections over the next few decades, we do not expect the role of models and scenarios to be as crucial to pin down. However, as we move into the more distant future, our ability to guess what society will do diminishes, different models will be more or less dependable, and the processes generating our extreme scenario will unfold.”

“As a result, our ability to quantify uncertainty through formal probability distributions decreases. We therefore include a qualitatively different scenario (H++) whose likelihood we cannot characterize at this time, and note that quantified probabilistic projections need to be taken as an evolving representation of our understanding, open to updates and modifications especially in the tails of probability distributions. In this context of likely continued and unquantifiable uncertainties, incorporating long-range planning for sea-level rise in decisions is increasingly urgent.”

“Depending on the time horizon being considered, different sources of uncertainty play smaller or larger roles in projections of sea-level rise [48]. For long-term changes (second half of this century and beyond), the choice of model and scenario of anthropogenic greenhouse gas emissions significantly affect the outcome. By comparison, for short- to mid-term projections (within the next two or three decades), variability in the Earth’s climate system, which would exist even in the absence of human-driven changes, is the predominant source of uncertainty.”

“As for climate system drivers at large (e.g., ENSO, storms), the question boils down to assessing possible future changes and their statistical characteristics. At the moment, uncertainties in modeling outcomes are large and there is not robust evidence that the internal variability of these phenomena will change significantly under future scenarios [52]. As mentioned, the interplay of these different sources of uncertainty is not unique as we move from short- to mid- to long-term horizons for our projections.”

“Estimated probabilities of particular outcomes are increasingly less robust — in the sense of comprehensively covering the range of expected outcomes and firmly quantifying their relative probability — as we lengthen those horizons, and we move into climate scenarios of unprecedented nature as far as anthropogenic forcing is concerned”

The states new sea level rise report may be intended to provide California coastal sea level rise policy guidance but the very significant qualifications, limitations and uncertainties reflected in the report but unaddressed by the climate alarmist media clearly demands that planning efforts utilizing the reports projections must be done with great caution.

This is particularly true given the extensive NOAA coastal sea level tide gauge data for California locations showing no evidence of coastal sea level rise acceleration despite the claims of the UN IPCC that man made actions have been increasing the rate of sea level rise since the early 1970s.

[UPDATE] As these things happen, I’d written about this sea level question and was about to post it, but Larry has done it first, and likely better. I trust he won’t mind my adding one graphic from my now superceded post showing what the sea level would have to do to get to a ten foot rise by the year 2100 …

And from my now unnecessary post …

How can any rational human being believe this kind of nonsense? The CO2 has been rising strongly since about 1940 or so … but in that 75 year period, the rate of sea level rise is basically unchanged. If CO2 were going to do something to sea level rise, it would have happened long ago.

I weep for the death of science … of course, this claim will be used to force people to do all kinds of crazy things if they want to build near the coast.

My best to all, and my thanks to Larry for an excellent exposition.

w.