Talk:Sea level rise

Opening

Can some explain how the sea level rise is documented here in the opening line? Source 1 says "no acceleration during the last century has been detected" and source 2 says "Multi-century sea-level records and climate models indicate an acceleration of sea-level rise, but no 20th century acceleration has previously been detected."

Am I missing something? —Preceding unsigned comment added by IzmirEkmek (talk • contribs) 01:03, 2 February 2010 (UTC)

Factors known to affect sea level (SL)

Singer lists three factors (first two are from IPCC):

The contribution to SL rise of the past century comes mainly from three sources: (i) Thermal expansion of the warming ocean contributed about 4 cm; and (ii) the melting of continental glaciers about 3.5 cm. (iii) The polar regions, on the other hand, produced a net lowering of SL, with most of this coming from the Antarctic. (The mechanism is intuitively easy to understand but difficult to calculate: A warming ocean evaporates more water, and some of it rains out in the polar regions, thus transferring water from the ocean to the polar ice caps.) The surprising result: When one simply adds up all these contributions (neglecting the large uncertainties), they account for only about 20 percent of the observed rise of 18 cm. The climate warming since 1900 cannot be the cause of the SL rise; something is missing here. (Singer)

global warming and sea level rise

What about the effects of human-induced global warming on SL rise? Will it really increase the rate above its natural value, as predicted by the IPCC? We do have a handle on this question by observing what actually happened when the climate warmed sharply between 1900 and 1940, before cooling between 1940 and 1975. The answer is quite surprising and could not have been derived from theory or from mathematical models. The data show that SL rise slowed down when the climate warmed and accelerated when the climate cooled. Evidently, ocean-water thermal expansion and mountain-glacier melting were less important than ice accumulation on the Antarctic continent (which lowers SL). (ibid.)

Flat out WRONG

Quote: Increasing temperatures result in sea level rise by the thermal expansion of water and through the addition of water to the oceans from the melting of continental ice sheets. -- part of initial description as of June 16, 2009
The latter part is potentially correct, but the first claim, "thermal expansion", is just flat out wrong. Water is atypical, in that its solid form is more voluminous than its liquid form. This has been used for centuries as a means of breaking down large rocks in fields into more manageable (i.e., movable) pieces. In the winter, you pour water into the cracks, and, when it freezes, it expands, breaking the rock apart. This is also a prime reason for road deterioration in the north, when melted rain gets into cracks and then freezes in a successive cold spell. An iceberg has less volume of water than the volume of the berg. Any sea-level rise must come from snow/icepack which is above sea level (or at least not contributing to it by being a part of the oceans due to land formations)
I've removed this part of the description as a result. I think that the rest of the article needs to be much more carefully vetted if such an obvious fact was missed.
Also, this article probably needs to be included and cited:
http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo544.html
OBloodyHell (talk) 16:37, 16 June 2009 (UTC)

It was talking about thermal expansion of water, the runny stuff. Would you care to revert? Pterre (talk) 16:53, 16 June 2009 (UTC)

Well Pterre took the words ;-) Look at your reference btw. which say much the same. --Kim D. Petersen (talk) 16:54, 16 June 2009 (UTC)

To OBloodyHell: The reason is that no phase change takes place. Water does not become monotonously more voluminous as it gets colder: it contracts. It then expands when it becomes crystalline. Awickert (talk) 17:07, 16 June 2009 (UTC)

Yeah, I think OBloodyHell just read it wrong. Smkolins (talk) 17:52, 16 June 2009 (UTC)

Actually it's a bit problematic as water reaches its max density at 3.98 C. Either side of that it expands. So... the mean temp of water in the region of interest decides if melting ice causes an increase or decrease in volume -right? MarkC (talk) 08:23, 22 June 2009 (UTC)

Well OK, but the region of interest is the world's oceans. Pterre (talk) 08:57, 22 June 2009 (UTC)

To clarify, we are not just talking about expansion of melt water, but expansion of water everywhere. Pterre (talk) 09:11, 22 June 2009 (UTC)

Dumb Question: has anyone considered the size of the ocean is changing due to plate tectonics? Make the pond smaller and the sea level will rise. KVB —Preceding unsigned comment added by 154.5.113.3 (talk) 04:43, 21 December 2009 (UTC)

Locally, tectonics result in uplift and subsidence, as does mantle flow in response to changing glacial and water loads (see this paper, for example). Globally, tectonics is a very minor player; a way to think of why this is is because expansion of ocean basins (from seafloor spreading) is generally matched by subduction, so the ocean volume stays pretty much constant. There are fluctuations in ocean volume due to ocean geometry as ocean basins reconfigure themselves, but none that are important over the 100+ years that we're talking about. Awickert (talk) 15:16, 21 December 2009 (UTC)

In many places, effects of tectonics and global warming are generally dwarfed by the isostatic adjustments resulting from the melting of the continental ice sheets (the "last ice age"). In fact, sea level would DROP near Greenland if the ice cover melted, as the gravitational pull from the ice actually raises the sea level locally. 173.161.195.122 (talk) 21:52, 6 May 2010 (UTC)

Category:Climate crisis

Recently, this article was taken out of Category:Climate crisis. I am baffled by this action. An article "about the current and future rise in sea level associated with global warming" is NOT part of Cat: Climate Crisis? Is today Opposite Day?--CurtisSwain (talk) 19:37, 11 November 2009 (UTC)

It was also recently added (last several hours) and is a relatively recently-created category (2 months ago), and the category has a decidedly non-neutral name. It also seems that the climate crisis category is a small eclectic collection of global warming-related topics, and topics that people think are related to global warming but really aren't (or are only tangentially, or perhaps maybe sort of under a couple of conditions but it's not really statistically significant) like the "floods" category. Awickert (talk) 20:01, 11 November 2009 (UTC)

Agree. So, adding this article to the category helps to improve it as this one actually belongs.--CurtisSwain (talk) 20:12, 11 November 2009 (UTC)

Or actually IMO adding this to the "climate crisis" category is redundant to having it in the "effects of global warming" category; I'm thinking off the top of my head that there should maybe be a climate change activism category, maybe "Action on climate change" (which is being considered for deletion now).... In any case, it seems that the science is well categorized, there are some scattered categories for the politics, and that adding this article to a half-baked, poorly-defined, weasel-worded (IMO) category is not the best course of action. What might be better is consolidating the politics into categories that are parallel to the science categories. I'm going to comment on the CfD for "Action on Climate Change". Awickert (talk) 20:45, 11 November 2009 (UTC)

Actually, I take some of that back. The "global warming" and "climate change" categories are really crufty too. So really it seems that there are too many of these darn things floating around, and little order to them. Awickert (talk) 20:48, 11 November 2009 (UTC)

Overcategorization is human nature. -Atmoz (talk) 21:52, 11 November 2009 (UTC)

Please see my linked discussion of the Future sea level rise issues, the same thing applies to this article.

http://en.wikipedia.org/wiki/Talk:Future_sea_level

Montestruc (talk) 07:59, 13 December 2009 (UTC)

Merge proposal

• Oppose - Someone tagged Future sea level to be merged with this article. I don't know why, since the editor did not given a reason. Both articles are already long, and a merged article would be too long (100K). --Geronimo20 (talk) 08:11, 15 December 2009 (UTC)

Tags removed per lack of support --Geronimo20 (talk) 20:18, 30 December 2009 (UTC)

Barometric corrections to satellite measurements

An article in the Journal of Atmospheric and Oceanic Technology[1] suggests that there is a significant correction to the rate of sea level rise due to atmospheric pressure changes. In Table 3, the authors give a rate of 0.5 mm/yr using their recommended method of correcting the TOPEX/Poseidon data over a limited time series versus 0.7 mm/yr for the standard method. This article is about 10 years old, so should have been incorporated in the more recent literature. This article has been extensively cited. Does anyone know if this needs to be considered in computing mean sea level changes using satellite data? At the very least, it points to potential uncertainty in the use of satellite measurements. Drphysics (talk) 18:06, 30 December 2009 (UTC)

Yes, the inverse barometer correction is applied to satellite sea level measurement:

"A correction is made for the "inverse barometer" effect, where sea level is depressed in areas of high atmospheric pressure, and vice versa"

http://www.cmar.csiro.au/sealevel/sl_meas_sat_alt.html --Giorgiogp2 (talk) 20:35, 12 February 2010 (UTC)

Suggestion

I think this article could use a graph like the one from this post. It's a 380,000 year reconstruction of Red Sea sea levels (Siddall et al. 2003), with a temperature reconstruction from Vostok. I could contribute the graph myself, if you just point me to instructions on how to build graphs suitable for Wikipedia. Joseph449008 (talk) 15:04, 12 February 2010 (UTC)

I wonder if it would be more appropriate in Sea level article, as that article covers a historic perspective, while this one is more focused on the present and near future. --SPhilbrickT 23:38, 12 February 2010 (UTC)

To the extent that it relates to global warming, this is probably the right article. It does have a "past sea level rise" section, after all. Joseph449008 (talk) 00:35, 13 February 2010 (UTC)

Proposed change to lede

The current lede states that " Thermal expansion, which is well-quantified, is currently the primary contributor to sea level rise and is expected to be the primary contributor over the course of the next century."

However, while thermal expansion is expected to contribute more than half the increase in the coming century, it isn't the primary contributor currently.

From AR4 page 409, "Thermal expansion is projected to contribute more than half of the average rise,..." but "During recent years (1993–2003), for which the observing system is much better, thermal expansion and melting of land ice each account for about half of the observed sea level rise,"

I propose the following replacement sentence: At the end of the 20th century, thermal expansion and melting of land ice contributed roughly equally to sea level rise, while thermal expansion is expected to contribute more than half the rise in the upcoming century.

I also intent to remove the subsequent sentence, "Glacial contributions to sea-level rise are less important, and are more difficult to predict and quantify" as it is no longer needed.

Current footnote 8 doesn't support the claim, or at least I couldn't find it as it is the AR4 chapter on Climate models, not the chapter on Sea Level. I will add the reference to the Sea Level chapter

Any objections?--SPhilbrickT 23:32, 12 February 2010 (UTC)

The change sounds good - glacial contributions are definitely important; I actually don't remember the relative contributions but I trust that you're right. The only thing that I'm concerned about is that AR4 didn't include glacial dynamics, see this paper, I can send you a PDF if necessary. But go ahead and make the change - it will be better than the current version. Awickert (talk) 02:23, 13 February 2010 (UTC)

How ironic. I started with Criticism of the IPCC AR4; as I think the organization needs some work. One paragraph contains the sentence "The IPCC AR4 estimates explicitly exclude the influence of the melting of ice sheets." I don't think that is literally correct, and the supplied reference isn't all that helpful, as it doesn't really point to a source. I'm guessing they are getting at glacial dynamics, and I started searching AR4 to find the exact reference. While searching, I came across the Sea Level Rise article, which lead me to this proposed change. However, my real interest is in reading about glacial dynamics, so yes, I'd love to see that paper. (I have enabled the email option)--SPhilbrickT 02:41, 13 February 2010 (UTC)

OK - I'm actually not all that knowledgeable about this topic (other than the very basics), FYI. I'll send you an email, and if you reply (I can't attach things in wiki-emails), I'll send it over. Awickert (talk) 18:48, 13 February 2010 (UTC)

Thermal expansion is fairly easy to quantify but not dramatic. Various estimates of rather more SLR in the coming century (Hansen, Rahmstorf) would rely on more glacial melt. So be cautious William M. Connolley (talk) 19:22, 13 February 2010 (UTC)

Good point. One of the concerns about the AR4 report is the possibility that their sea level estimates may be too low, as a result of not fully considering the impacts of glacial dynamics. Which reminds me, another editor promised to send me a paper on the subject, and I haven't received it, so I’ll have to follow-up. I wonder if we should add a caveat to this sentence, acknowledging that some experts felt that the melting of land ice could be materially higher than the AR4 estimates? The problem is, that probably universally true (this is, for every AR4 conclusion there are some experts with higher indications and some with lower), so we’d need a special reason to privilege this caveat.SPhilbrickT 15:36, 22 February 2010 (UTC)

Withdrawn paper

An IP added a statement referring to the recently withdrawn paper (which I reverted). However, I don't believe that paper was even used in support of this article, so the added comment comes out of left field. Of equal importance is that the withdrawal is due to errors, and it isn't yet clear what will happen to the conclusions when the errors are addressed. If this paper had been notable in itself, it's withdrawal might be notable. It wasn't.SPhilbrickT 02:28, 23 February 2010 (UTC)

The IP has probably been reading the std skeptic blogs William M. Connolley (talk) 08:36, 23 February 2010 (UTC)

See-also Talk:Global_warming#Climate_scientists_withdraw_journal_claims_of_rising_sea_levels and other circles William M. Connolley (talk) 16:18, 23 February 2010 (UTC)

Someone arrogantly asserts in hidden text that there is no controversy about this topic. This is obviously not the case, and the deleted material demonstrates it. The note "nobody cares" is inappropriate, too. —Preceding unsigned comment added by Goodranch (talk • contribs) 03:58, 24 February 2010 (UTC)

Maintaining units for ease of comparison

The article talks mostly in mm except for 4 places where is used cm. I've changed those all to mm so that it's easier for reader to make direct comparisons insteaf of us randomly switching between units. If you notice any other weird units I'd encourage you to do the same. Lot 49a^talk 14:52, 23 February 2010 (UTC)

Deletion of material demonstrating that there is controversy

{{rfctag|sci}}

Some editors are violating Neutral Point of View by removing references in reliable sources to the recent move by Nature Geoscience to retract a study which predicted a sea level rise due to global warming. These editors claim that there is no controversy over predictions of sea level rise, and removed the references with snide comments like "nobody cares." Some outside intervention is needed at this article. Goodranch (talk) 15:17, 25 February 2010 (UTC)

Am I understanding correctly that the paper is not currently being used as a reference in the article? If so, then there is no issue. If someone is pushing to include a reference to the article on account of it currently not being published, then that clearly does not meet notability requirements. Many, many papers are not published and/or haven't passed peer review. We do not list them off as "evidence against a theory" for obvious reasons. Kevin Baas^talk 16:05, 25 February 2010 (UTC)

It was published, then retracted due to acknowledged errors. The retraction was unprecedented and received significant press coverage:[2][3][4] Goodranch (talk) 02:56, 26 February 2010 (UTC)

that's incorrect use of the word "unprecedented". Unprecedented means that it has not happened before. Clearly this is not the first time a paper was retracted due to errors. As to the press: given the nature of the report and the specious logic you've already expressed, conservative radicals are bound to jump all over it. So there's nothing all to surprising there. And in any case you just anaswered my question in the affirmative. Which also means the title of this section is wrong: this isn't a matter of "deletion" it's a matter of non-insertion. i.e. it's not being "removed" it's being prevented from being "added". (and with good reason: it doesn't meet WP:RS and WP:NOTABILITY.) I would call that "disingenous" and "intentionally misleading". Also, as has been pointed out in past discussions (and the record shows this), the retraction due to acknowledged errors does not in th eleast bit "demonstrate that there is a controversy". So the title is doubly-misleading. Kevin Baas^talk 14:08, 26 February 2010 (UTC)

This is the first time that Nature Geoscience has retracted a paper due to errors, so it is unprecedented, as the press coverage says. The press coverage also demonstrates that there is a controversy. You may not like the press coverage, but most of Wikipedia seems to be sourced to press coverage. --Goodranch (talk) 16:03, 27 February 2010 (UTC)

Let's be careful with the use of the word "unprecedented". It isn't unprecedented to withdraw a paper, not even unprecedented to withdraw a climate science paper. It's only unprecedented at this single journal, which, IIRC, is relatively new. So the "unprecedented" label is really not very meaningful.--SPhilbrickT 15:26, 15 March 2010 (UTC)

The paper was never used here, so its retraction is of no interest here. It might, perhaps, be of some interest at the Nature article? FWIW, the paper (had it been accurate) would have been quite a low-side constraint on SLR; that it has been retracted *raises* the "on average" prediction of future SLR, it doesn't lower it William M. Connolley (talk) 17:30, 27 February 2010 (UTC)

Responding due to the RfC, Just my 2¢. The article states that there are uncertainties. The retraction was made due to well-specified reasons that affected the predictions in that article. There appears to be no dispute among scientists about whether or not sea levels are due to rise, but rather by how much, and how fast, and whether or not the causes are anthropogenic. The article appears to say that well. Seeing Goodranch proposed content in the editorial history, I agree with Connolley on this occasion that the addition is of no interest here. On a side-note, I agree that the retraction is unprecedented, but that in itself is not particularly interesting or notable regarding this article. An article that describes in detail the methodologies used for estimating sea level rise may wish to describe the boundaries of the errors of that paper; most especially how they were made, and why they were made. But the retraction itself does not seem particularly relevant. (20040302 (talk) 13:58, 3 March 2010 (UTC))

• Responding to the RFC (please word RFC requests more neutrally in the future: "Include a brief, neutral statement of the issue below the template."): the retraction of a single paper seems to be an issue too minor to address in this article. The current content of the article and one of the sources cited by Goodranch make it clear that this paper was only a fairly small component of the overall field of research. To discuss the retraction of study that is uncited in the article neems an unnecessary diversion. — Scientizzle 15:35, 16 March 2010 (UTC)