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What's up with this?

There is much excitement among the green fraternity this morning over a new paper that claims to have found an acceleration in sea-level rise that is even more dramatic than previously thought.

Stop yawning at the back there.

As usual, a brief perusal beyond the headlines reveals a considerably more nuanced story. The paper is based on tide gauge records and finds a slow increase over the 20th century of just over 1mm/year. This is rather less than some previous estimates.

However, the authors go on to say that:

Our analysis, which combines tide gauge records with physics-based and model-derived geometries of the various contributing signals, also indicates that GMSL rose at a rate of 3.0 ± 0.7 millimetres per year between 1993 and 2010, consistent with prior estimates from tide gauge records4. The increase in rate relative to the 1901–90 trend is accordingly larger than previously thought; this revision may affect some projections11 of future sea-level rise.

I'm a bit bemused by this. Why would they use a different methodology for 1993-2010 to the one they used for 1901-90? Why would they want to combine data with "physics based and model-derived geometries"? Do the tide guages show any acceleration or not?

Perhaps the text of the paper will explain if someone can send it over or leave a comment.

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Reader Comments (64)

Sea Level rose faster in the 20s and 30s.

Jan 15, 2015 at 5:27 PM | Unregistered CommenterBruce

There is no need to worry.
Obama is on the job!

"This was the moment when the rise of the oceans began to slow, and our planet began to heal"

Jan 15, 2015 at 5:35 PM | Unregistered CommenterGordon

Paul Homewood.

"Now, all of a sudden, this work is just cast aside (and not actually disproven, I note) in favour of some model based nonsense."

I've noticed that too, and it's become a bit of bee in my bonnet. I don't know of any other science where a peer reviewed paper is accepted as gospel truth by the scientists at the drop of a hat. The Hockeystick was of course the first, but their is a pattern. The authors are usually v. young in terms of their careers (Mann had only just got his PhD) with no body of work behind them. Yet when Newby and GleamintheI produce a paper using "interpolated" data because the real data isn't good enough (which is clisci speak for "gives the wrong answer") and it shows "it's worse than we thought" their senior colleagues momentarily stop their applications for grants and hail the work of these hitherto unknown, and sometimes unpublished, scientists, as a massive breakthrough. In what other science does this happen?

Jan 15, 2015 at 5:37 PM | Unregistered Commentergeronimo

Bruce, you can't expect computer models to use real data. It is difficult enough to feed the models, enough homogenised data, to get the politically correct result, that the models were programmed to achieve, without unnecessary complications such as natural variability.

That is what Computer Generated Real Climate Science is for. They use experts in Computer Generation, and some of their output is so incredibly unbelievable, it really defies credibility, and believablity.

Jan 15, 2015 at 5:58 PM | Unregistered CommenterGolf Charlie

I'll believe in sea level rise when the sea reaches the prom at Southport. For those that don't know the sea only comes up to a quarter mile of it now & that's at high tide with a wind behind it.

Jan 15, 2015 at 7:04 PM | Unregistered CommenterTom Mills, Watergate?

Jan 15, 2015 at 7:17 PM | Unregistered CommenterPaul

Why do they need a new model?

If sea level rise is caused by heat uptake in the top layers of the ocean, then surely 'projecting' that is an integral part of 'projecting' future atmospheric temperature so must have been done already.

Jan 15, 2015 at 7:48 PM | Unregistered CommenterJake Haye

When the authors refer to 'model-based geometries' they may be referring to the International Terrestrial Reference Frame (ITRF). The first ITRF was created in 1992 and the most recent in 2008, hence sea levels can only be referred to a common datum close to these dates, leading, possibly, to the choice of 1993-2010 for the most accurate methodology.

Trying to guess the parameters of a TRF prior to 1992 and going back to 1901 would obviously require a model (physics-based?).

Is this what they have done?

Jan 15, 2015 at 8:40 PM | Unregistered CommenterBilly Liar

Forgot the link to the ITRF:

Jan 15, 2015 at 8:43 PM | Unregistered CommenterBilly Liar

Sherlock1 / Geronimo: the cry of, “It’s worse than we thought…” could actually be considered to be uncannily accurate. Each new scare that they drag, screaming and kicking, into the limelight, appears to be based on a science considerably worse than the one before. Yep, it is most definitely worse than we thought.

Jan 15, 2015 at 9:49 PM | Registered CommenterRadical Rodent

This is highly interesting to me. In 2008 I saw a report by Chao, Yu, and Li in Science (April 11th) that sea level rise had been linear for the previous 80 years and the slope of the rise was 2.46 millimeters per year. Their value was corrected for water held in storage by all reservoirs built since 1900. I had just seen Al Gore's movie in which he claimed a 20 foot sea rise on the way. That is why I was looking for data on it and came upon this paper. Of course I immediately sent in an article correcting Gore, to both to Science and to Nature, and got thrown out without even a pretense at peer review. These people report an overall trend of 3.0 +/- 0.04 millimeters a year which is really quite close to what Chao, Yu, and Li reported seven years ago. I am not sure how much difference correction for water held in storage would amount to. But as I said then, something that has been linear for 80 years is not about to change anytime soon.And that is basically what these data show. I recommend going with Chao, Yu, and Li and ignoring the slight differences they laboriously unearthed.

Jan 16, 2015 at 2:04 AM | Registered Commenterarno-arrak

It's a recurring theme. Decades of observational research is discarded in favour of an assumption loaded model based study. Referees aren't doing their job unless they ask how the model may be reconciled with the previous findings in the literature.

Jan 16, 2015 at 3:35 AM | Unregistered CommenterWill Nitschke

What is it with climate psientists?
They are always "lowering the past" to make today look more "extreme".

Jan 16, 2015 at 11:32 PM | Unregistered CommenterDon Keiller

"...Stop yawning at the back there..."

I wasn't yawning...

Well, maybe I was, but that was because I started the crossword when I read the words 'acceleration in sea level rise'.

Why is it that alarmists believe that buggering the incredibly massive volumes of salt water or multi-altitude challenged atmospheric temperatures will simultaneously 'make their fortunes and careers' plus prove the most catastrophic prognostications regarding civilization.

The alarmists rates of analytic accuracy and prognostication success make Nostradamus appear omniscient.

Jan 19, 2015 at 4:30 AM | Unregistered CommenterATheoK

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