Arguments
How much is sea level rising?
What the science says...
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A variety of different measurements find steadily rising sea levels over the past century. |
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Climate Myth...
Sea level rise is exaggerated
"We are told sea level is rising and will soon swamp all of our cities. Everybody knows that the Pacific island of Tuvalu is sinking. ...
Around 1990 it became obvious the local tide-gauge did not agree - there was no evidence of 'sinking.' So scientists at Flinders University, Adelaide, set up new, modern, tide-gauges in 12 Pacific islands.
Recently, the whole project was abandoned as there was no sign of a change in sea level at any of the 12 islands for the past 16 years." Vincent Gray).
Gavin Schmidt investigated the claim that tide gauges on islands in the Pacific Ocean show no sea level rise and found that the data show a rising sea level trend at every single station. But what about global sea level rise?
Sea level rises as ice on land melts and as warming ocean waters expand. As well as being a threat to coastal habitation and environments, sea level rise corroborates other evidence of global warming
The blue line in the graph below clearly shows sea level as rising, while the upward curve suggests sea level is rising faster as time goes on. The upward curve agrees with global temperature trends and with the accelerating melting of ice in Greenland and other places.
Because sea level behavior is such an important signal for tracking climate change, skeptics seize on the sea level record in an effort to cast doubt on this evidence. Sea level bounces up and down slightly from year to year so it's possible to cherry-pick data falsely suggesting the overall trend is flat, falling or linear. You can try this yourself. Starting with two closely spaced data points on the graph below, lay a straight-edge between them and notice how for a short period of time you can create almost any slope you prefer, simply by being selective about what data points you use. Now choose data points farther apart. Notice that as your selected data points cover more time, the more your mini-graph reflects the big picture. The lesson? Always look at all the data, don't be fooled by selective presentations.
graph from Church et al. (2008)
Other skeptic arguments about sea level concern the validity of observations, obtained via tide gauges and more recently satellite altimeter observations.
Tide gauges must take into account changes in the height of land itself caused by local geologic processes, a favorite distraction for skeptics to highlight. Not surprisingly, scientists measuring sea level with tide gauges are aware of and compensate for these factors. Confounding influences are accounted for in measurements and while they leave some noise in the record they cannot account for the observed upward trend.
Various technical criticisms are mounted against satellite altimeter measurements by skeptics. Indeed, deriving millimeter-level accuracy from orbit is a stunning technical feat so it's not hard to understand why some people find such an accomplishment unbelievable. In reality, researchers demonstrate this height measurement technique's accuracy to be within 1mm/year. Most importantly there is no form of residual error that could falsely produce the upward trend in observations.
As can be seen in an inset of the graph above, tide gauge and satellite altimeter measurements track each other with remarkable similarity. These two independent systems mutually support the observed trend in sea level. If an argument depends on skipping certain observations or emphasizes uncertainty while ignoring an obvious trend, that's a clue you're being steered as opposed to informed. Don't be mislead by only a carefully-selected portion of the available evidence being disclosed.
Current sea level rise is after all not exaggerated, in fact the opposite case is more plausible. Observational data and changing conditions in such places as Greenland suggest if there's a real problem here it's underestimation of future sea level rise. IPCC synthesis reports offer conservative projections of sea level increase based on assumptions about future behavior of ice sheets and glaciers, leading to estimates of sea level roughly following a linear upward trend mimicking that of recent decades. In point of fact, observed sea level rise is already above IPCC projections and strongly hints at acceleration while at the same time it appears the mass balance of continental ice envisioned by the IPCC is overly optimistic (Rahmstorf 2010).
Basic rebuttal written by doug_bostrom
This rebuttal was updated by Judith Matz on September 13, 2021 to replace broken links. The updates are a result of our call for help published in May 2021.
Last updated on 5 July 2015 by pattimer. View Archives
[DB] "if the scientists are really interested in how much ocean water there is"
You tread dangerous ground here. If you are going down the path you are implying (fraud/conspiracy) then take this whole conversation to a more appropriate venue (many dozens exist). This forum is about the science of climate change. No room exists for implications such as this. FYI.
[DB] Steve, we have all been through this before. You focus on insignificant timescales (while ignoring the contextual greater picture) and fixate on minutiae without a good grounding and background. Perhaps more time researching, reading and studying would bear more useful results than the current approach.
[DB] Then we are at impasse. Whether due to a lack of background in climate science and statistics (I give you more credit than that) or an ideology discordant with the science, you continually prosecute an agenda of conspiracy and fraud rather than discussing the science itself.
I reiterate: if you wish to have an open dialogue about the actual science of climate change, then you are welcome to participate here. Your present course is unacceptable.
Your choice on how this plays out.
[DB] "I stated the obvious, and you tell me I'm on dangerous ground."
Re-read my response to you above. If you are again implying that fraud & conspiracy are obvious then we are done.
[DB] In addition, per Willis and Leuiette (2011):
Also from Hamlington et al. (2011, J.Climate):
[Emphasis added to each.]
Santer et al, DelSole et al and Hamilton et al. (and probably others) all point toward a minimum sample period of 16 years or so increase the SNR. Anything less than 10 years is meaningless, a chasing after the wind.
H/T to the mighty Albatross...
[DB] "What I'm doing is painting a picture of what it is that needs to be explained to those of us in this world that are skeptical of what we are told about climate change."
Then paint that picture to those at UCAR. I'm very certain that they will be able to explain things to "skeptics".
[DB] "What's your point?"
The point Steve has been trying to make is one of conspiracy and fraud on the part of UCAR. However, he is reduced to making them via veiled insinuations, because he knows any more open accusations won't survive moderation.
It has become very tiresome.
[DB] The moderator deleted your comment because:
[DB] Fixed image. Html posting tips are here.
As a tip for images, place your URL address desired between both sets of "" in the string below:
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If sea level was falling, Earth would be in an ice age and that wouldn't be nice for any of us.
Earthling, does that fact somehow make rapid sea level rise somehow benign?
DSL,
What Earthling is saying is that because starvation is bad for you, obesity must be good. Or because drought is bad, flooding must be good. This seems like the appropriate place for that argument.
If he's worried about ice ages, perhaps he should ponder the selfishness of squandering what could have been a useful geoengineering resource to future generations faced with an imminent glaciation; carefully burning fossil fuels to enhance the greenhouse effect just enough to maintain temperatures in the face of declining northern-hemisphere insolation due to the Milankovich cycles may well be the most cost-effective method for them to do so, if those resources are still around at the time.
Gads - Joe D'Aleo is on a The Weather Channel comment stream trying to convince people that Morner is a "the top world expert" in sea level. I quote:
"Also see http://www.jcronline.org/doi/pdf/10.2112/JCOASTRES-D-10-00157.1 where after studying tide gauges (instead of relying on failing models) they conclude: Our analyses do not indicate acceleration in sea level in U.S. tide gauge records during the 20th century. Instead, for each time period we consider, the records show small decelerations that are consistent with a number of earlier studies of worldwide-gauge records. The decelerations that we obtain are opposite in sign and one to two orders of magnitude less than the+0.07 to+0.28 mm/y2 accelerations that are required toreach sea levels predicted for 2100 by Vermeer and Rahmsdorf (2009), Jevrejeva, Moore, and Grinsted (2010), and Grinsted, Moore, and Jevrejeva (2010)."