Guest Post by Willis Eschenbach [See update at the end]
Since publishing my last two posts here and here on the Church and White (“C&W”) 2011 sea level dataset, some folks have queried why I didn’t use the Church and White 2013 dataset instead. The answer is simple. It’s because of the hockeystick.
What hockeystick, you might ask? Why, the C&W hockeystick … the figure below shows the difference between the C&W 2013 and the C&W 2011 data.
Figure 1. Red line shows the difference between the sea levels of the two C&W datasets. Larger values show where the 2013 dataset has higher sea levels than the 2011 dataset.
Now, I can understand the slight, ~ ± 1 mm differences between the two datasets in most of the record. They’ve recalculated with a slightly different algorithm, or maybe used a somewhat different mix of tide gauges and weights, with resulting small differences.
And I can understand the offset in most of the record, where the 2013 data is generally about 2 mm less than the 2011 data. It’s an anomaly so the zero point doesn’t matter.
What I don’t understand is the blade of the hockeystick from about 1992, the start of the satellite sea level era, to 2009 when the C&W 2011 record ended.
It looks to me like they’ve munged the data in order to make the data take up a smooth transition from the smaller acceleration of the tidal gauge record to the larger acceleration of the satellite record. That way, they could claim that the tide gauges and the satellite data agree … and if that is the case, I can only say bad scientists, no cookies …
Anyhow, that’s the only explanation I can think for this hockeystick … suggestions gladly accepted.
[UPDATE] I thought I might point out the biggest problem we have with sea level estimates, which is the lack of data. Here’s a graph showing how many tide gauges we have by the number of years of data that they have:
So for example, there are only 35 tide gauges which have 120 years or more of data … and that only gets us back to about the year 1900.
Not only that, but because the tide gauges are on land, the world’s oceans are only sampled around the edges and on a few islands …
Here’s another look, this time at how many gauges we have going at any given time:
Note that at the maximum, only half of the tide gauges in the historical record were in operation.
I bring this up to point out that we simply cannot place much faith in the tidal gauge data to provide any “global” average sea level rise.
Here, amazingly, we’ve had rain again. It hardly ever rains this late in the spring in Northern California, and the redwood forest around our house is redolent with the earthy odors of new growth and old decay … I blame global warming. After all, global warming has been blamed for a host of bad things from low birth rates to volcanic eruptions, so why not balance the scales by blaming it for a lovely gentle late spring rain?
Best of this wonderful wet world to you and yours,
MY USUAL REQUEST: When you comment, I ask, beg, implore, request, and importune you to QUOTE THE EXACT WORDS THAT YOU ARE DISCUSSING so we can all understand who and what you are talking about.
DATA: The C&W data is here, h/t to Nick Stokes for finding it.