Friday, June 16, 2017

Pacific Tide Gauge Charts Show No Acceleration in Sea Level Rise

Californians are constantly bombarded with apocalyptic articles on sea level rise. A reporter, Sarah J. Black, for our local weekly newspaper, the Independent Coast Observer, had a very long article, "Studies show climate change could transform Mendonoma (Mendocino and Sonoma counties)," in their June 9, 2017 issue. In a section on sea levels, the ICO averred that: "The 20th Century saw sea levels rise at 1.2 to 1.7 mm per year, and those rates doubled after 1990, 'and the rise continues to accelerate,' researchers found."

"Currently rates are at 3.4 mm per year,' greater than anytime over the past thousand years,' the report reads."

Concerning the 3.4mm/year,  I had previously looked at 108 tide gauge records worldwide, and found a mean of 0.9mm/year and median of 1.1mm/year. Seventy-three of the records were at 1.8mm/year or less, and only 10 at 3.4mm/year or more. The average length of each tide gauge record was 90 years.

Besides my study using readily available resources open to all on the internet, a Hebrew University of Jerusalem study ( found mean sea levels rising by 1mm/year. For 35 percent of tide gauges, sea levels rose on average by 3.8mm/year. However, sea levels were stable for 61 percent of tide gauges, and fell on average by almost 6mm/year for 4 percent of tide gauges.

NOAA keeps records on 199 tide gauges which have been active this century. The average sea level rise rate is 1.08 mm/year for that set of gauges – one third of the claimed University of Colorado 3.2mm/year trend. Eighty-six percent of the tide gauges show sea level rise slower than 3.2mm/year.

Sea level, according to the GRACE gravitational anomaly satellites, has been falling (Peltier et al., 2009). During the eight years of ENVISAT’s operation, from 2004-2012, sea level rose at a not very scary 1.3 inches per century, or 0.33 mm/year.

Nicola Scafetta of Duke University found that sea level is subject to 60-year cycles and concludes that the human impact on sea level is too small and is statistically insignificant.

Another study found primarily that unsustainable groundwater use contributed a sea-level rise of about 0.77mm /year between 1961 and 2003.

Armed with all these studies, including the US government NOAA one, showing sea level rise at a rate less than a third of the rate posited in the ICO, I then decided to look for signs of acceleration in rates. Again, the NOAA provided convincing proof that they were not in the form of tide gauge graphs for cities worldwide. I selected twenty-five tide gauges scattered over the pacific, and found only two that had rates higher than 3.4mm/year. 

I have posted all twenty-five charts below for two purposes. One: each chart shows the rate of sea level rise in mm per year for its location. Two: you can visually determine for each chart if there is a doubling of the rate after 1990, as claimed in the report cited by the ICO. There is none. If you doubt this, look closely at each straight line fitted to the observations. A doubling after 1990 would appear as a cluster of observations above the line, not as observations both above and below the line.

The San Francisco chart below is interesting at several levels. It is the longest tide gauge record in the Western Hemisphere, began in 1854. Its highest level was third-four years ago in 1983, over two inches higher than in 2015, and 2016 is lower than 2015. Does it look like the rate of sea level rise doubled after 1990?