Claims are only possible by cherry-picking the multidecadal oscillation with a short time window
Guest essay by Albert Parker
From the “every trick is legitimate to prove the flood will come” department, another example of cherry picking the short time window to misrepresent the natural oscillations of the sea levels. This time the place where global warming is producing three times higher rates of rise is Southeast Florida. In a paper Wdowinskia, Braya, Kirtmana and Wub  they claim “the average rate of sea level rise in Southeast Florida increased from 3 ± 2 mm/yr prior to 2006 to 9 ± 4 mm/yr after 2006”.
The alarmism is obviously mounting, as a recent article from NPR demonstrates. 
“Miami Beach is one of the nation’s cities most vulnerable to climate change — and its leaders are doing something about it. The city, a national leader in addressing climate, has begun to make improvements aimed at protecting residents from rising sea levels. In South Florida, the rate of sea-level rise has tripled over the last decade, according to a new study from the University of Miami. The rising seas raise questions for many about whether the resort community has a future”.
The 3 ± 2 mm/yr prior to 9 ± 4 mm/yr after 2006 statement is profoundly incorrect for assigning climate-scale trends, based on the use of a very short, cherry-picked time window of only 10 years that magnifies the latest positive phasing of the oscillations along the East Coast of the United States.
Without sufficient data of good quality spanning time windows long enough to clear the trend of the inter-annual, decadal and multi-decadal oscillations, there is no chance to compute a meaningful trend of relative sea level rise by fitting the monthly average mean sea levels (MSL) [3-6]. We proved already in the previous essay that a minimum 60-70 years of continuous data collected without major perturbations to the instrument are needed to infer reliable trends.
That is the case with Miami, as seen in Fig.1, the tide gauge data there stopped in 1981, but for the 50 years it did record, there was no evidence that the trend accelerated except for a brief pulse between 1940 and 1950.
Still, many alarmists continue to cherry pick the few years of data in a time series to prove the sea level are rising at “unprecedented” rates, thus confirming how bad we are burning fossil fuels, main reason why mother nature will punish us with the flood.
This latest claim is easily debunked by analyzing the data where they are measured over a significant time span without major issues in KEY WEST. This tide gauge has 104 recorded years over a time span of 104 years for a completeness of 100%. The first year is 1913, the last year is 2015. Fig.2 shows the MSL, the long term trend computed by using all the data (SLR), and the relative rate of rises based on a short time window of 10 years (SLR10) in different key times.
The longer term trend computed by using all the data is +2.36 mm/year.
The SLR10 changes significantly already month-by-month, and dramatically year-by-year or decade-by-decade. Over the years, the SLR10 has fluctuated between +12.93 and -7.05 mm/year.
In 2015 the SLR10 is certainly +11.81 mm/year.
However, in 2009 the SLR10 was +0.54 mm/year.
Going back in time, in 1943 the SLR10 was +0.96 mm/year.
Then, in 1948 the SLR10 was +12.93 mm/year.
Finally, in 1956 the SLR10 was -6.71 mm/year.
It is wrong to claim a SLR of +11.81 mm/year since 2006, and only +2.36 mm/year before, as even larger SLR with 10 years time windows were previously recorded in the past, and then these values were always followed by much smaller values.
Note that in Fig.3, the NOAA plotted trend for the 100 year period is nearly identical to that of the trend in Miami, shown in Fig.1.
The sea levels are clearly oscillating about the same constant sea level trend and it is therefore more appropriate to say that in Key West the sea levels have been oscillating since 2006 as they did before.
1. S. Wdowinskia, R. Braya, B. P. Kirtmana, Z. Wub (2016), Increasing flooding hazard in coastal communities due to rising sea level: Case study of Miami Beach, Ocean & Coastal Management, 126:1–8.
3. A. Parker (2013), Oscillations of sea-level rise along the Atlantic coast of North America north of Cape Hatteras, Natural Hazards 65(1):991-997. DOI: 10.1007/s11069-012-0354-7.
4. A. Parker (2013), SEA-LEVEL TRENDS AT LOCATIONS OF THE UNITED STATES WITH MORE THAN 100 YEARS OF RECORDING, Natural Hazards 65(1):1011-1021. DOI: 10.1007/s11069-012-0400-5.
5. A. Parker, M. Saad Saleem and M. Lawson (2013), Sea-Level Trend Analysis for Coastal Management, Ocean & Coastal Management 73: 63–81. Doi:10.1016/j.ocecoaman.2012.12.005.
6. A. Parker and C.D. Ollier (2016), COASTAL PLANNING SHOULD BE BASED ON PROVEN SEA-LEVEL DATA, Ocean and Coastal Management. Doi: 10.1016/j.ocecoaman.2016.02.005.
7. NOAA Tides and Currents http://tidesandcurrents.noaa.gov/sltrends/sltrends.html