# What's The Straight Dope on Sea Levels? **URL:** \ **Category:** Factual Questions\ **Created:** [December 10, 2009, 2:47pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726 "2009-12-10T14:47:00Z")\ **Posts on this page:** 14\ **Page:** 2
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 11, 2009, 6:43pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/21 "2009-12-11T18:43:10Z")
> [@BrandonR](#): > > :dubious: Isn’t water one of the only substances that expands upon cooling, not upon heating? > > Edit: After Googling the thermal expansion properties of water, I see it acts “normally” above 4°C by expanding as it heats. Strange stuff. Yes. For the temperature ranges found in the upper levels of the ocean, water will expand as the temperature increases. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [December 12, 2009, 1:45am UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/22 "2009-12-12T01:45:29Z")
I’m not trying to offer anthing controversial, but on the way home tonight, listening to [NPR](http://www.npr.org/templates/story/story.php?storyId=120498442), you might want to visit Southern Florida pretty soon. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [December 12, 2009, 2:56am UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/23 "2009-12-12T02:56:38Z")
Well, the rate is tiny. At most 3mm a year, or about a inch a decade. (Some projected rates are higher, some lower). You would not notice 3mm. You would not notice an inch over a decade. They are trying to scare dudes.It is a very real problem\*, but a problem that will more affect our grandkids than us. - although figures very wildly. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 12, 2009, 3:12am UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/24 "2009-12-12T03:12:45Z")
> [@DrDeth](#): > > They are trying to scare dudes. Cite? Seems to me, what with the ignorance being flaunted around in this very thread, that _informing_ dudes is the simplest hypothesis consistent with the facts. Were you personally aware of the effect of water temperature on sea level, or is the info in this thread new to you? Does such thermal expansion frighten you? When you make relieving ignorance equatable to scaring dudes, you become a proponent of ignorance yourself. Surely that’s not your intent here at a place that’s been “fighting ignorance since 1973” is it, **DrDeth**? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 12, 2009, 3:17am UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/25 "2009-12-12T03:17:09Z")
> [@DrDeth](#): > > They are trying to scare dudes. [Moderating] Once again, let’s keep this factual. Comments like this are out of place in this discussion. Colibri General Questions Moderator ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [December 13, 2009, 5:47am UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/26 "2009-12-13T05:47:43Z")
> [@Squink](#): > > Were you personally aware of the effect of water temperature on sea level, or is the info in this thread new to you? Does such thermal expansion frighten you? I mentioned nothing at all about the effect of water temperature,😕 you’re apparently confusing me with another poster. I just stated what the rate of rise was, and thus that it wasn’t a big problem in the near future, nor is it something that would be noticeable to a casual observer. Or perhaps you disagree with my figures?😕 ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [December 13, 2009, 7:31am UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/27 "2009-12-13T07:31:26Z")
The Australian Bureau of Meteorology has on its site a PDF of [Annual Sea Level Data Summary Report](http://www.bom.gov.au/ntc/IDO60202/IDO60202.2008.pdf) for the The Australian Baseline Sea Level Monitoring Project. It states in part: _The IPCC AR4, 2007 estimates that global average eustatic sea level rise over the last century was 1.7 ± 0.5 mm/yr. From 1961 to 2003, the average rate of sea level rise is estimated as 1.8 ± 0.5 mm/yr. IPCC AR4, 2007 also recognises that sea level records contain a considerable amount of inter-annual and decadal variability. For instance, the average rate of sea level rise for the decadal period 1993 – 2003 based on satellite altimetry is 3.1 ± 0.7 mm/yr. Studies have shown that comparably large rates of average sea level rise have been observed in previous decades._ Note both the margin of error and the last sentence. Elsewhere it notes: _Sea level and climate can vary about a long-term climatological mean from one decade to the next. The project to date is yet to span two complete decades, so it is important to recognise that the sea level change observed over this time is largely a measure of decadal variability. Continued monitoring is needed to quantify the longer-term trend that is associated with climate change._ and also: _Although simulations of recent sea level rise (eg 1993 to 2003) are in reasonable agreement with observations, longer-term sea level rise has not been satisfactorily modelled. This implies a deficiency in the current understanding, which is partly related to the poor global coverage of high quality historical tide gauge records and the uncertainty in the corrections for land motions. The high-accuracy sea level stations installed for the ABSLMP will help address these issues in future._ ---
**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\ **Post date:** [December 13, 2009, 8:24am UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/28 "2009-12-13T08:24:22Z")
> [@don't ask](#): > > The Australian Bureau of Meteorology has on its site a PDF of Annual Sea Level Data Summary Report for the The Australian Baseline Sea Level Monitoring Project. > > It states in part: […] > Elsewhere it notes: […] Your selected quotes emphasize the current uncertainty in making precise estimates of the _amounts_ of sea level rise due to long-term climate change, which is a fair point. However, I think they somewhat misleadingly omit the report’s overall concurrence with the mainstream hypothesis that there **is** a long-term rising trend in average sea level, due to global warming: > [@](#): > > This is a long-term project designed to monitor sea level and > climate around the coastline of Australia. The primary goal is to identify long period sea > level changes, with particular emphasis on the enhanced greenhouse effect sea level > signal. […] > > Projections of future sea level rise, according to an assessment of global coupled ocean-atmosphere climate computer models in IPCC AR4, 2007, ranges from 0.18 to 0.59 m at 2090-2099 relative to 1980-1999. These projections include contributions from thermal expansion and land ice contribution. In all scenarios the thermal expansion contribution accounts for around 75% of the total sea level rise. Thermal expansion is expected to continue well after climate stabilises because of the large heat capacity of the ocean. Yes, it’s true that the precise amount of sea level rise _to date_ that can be _unambiguously_ attributed to long-term anthropogenic climate change cannot currently be determined, as it’s pretty small and gets swamped in shorter-term fluctuations. However, the basic physics underlying the mainstream hypothesis of a predicted long-term sea-level rise due to anthropogenic climate change is AFAICT fairly uncontroversial: namely, 1. significant anthropogenic increases in greenhouse gases warm the atmosphere; 2. the warmer atmosphere warms the ocean; 3. the warmer ocean water expands, causing average sea levels to rise. (Land-based ice melting plays a part in the rise as well, but the thermal expansion is the biggest factor.) So if the OP is trying to find out what the scientific evidence is for average global sea levels having **already** detectably risen **specifically** as a result of anthropogenic global warming, the answer AFAIK is, “not much”. But if the OP wants to know what the scientific evidence is for predicting that average global sea levels **will** continue to rise by a significant amount over the next century **specifically** as a result of anthropogenic global warming, then AFAIK the answer is, “pretty good”. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [December 13, 2009, 6:02pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/29 "2009-12-13T18:02:11Z")
> [@Kimstu](#): > > 1. significant anthropogenic increases in greenhouse gases warm the atmosphere; > . What % of _all_ greenhouse gases are anthropogenic? Not just CO2, include water vapor, etc. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 13, 2009, 6:32pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/30 "2009-12-13T18:32:32Z")
> [@DrDeth](#): > > What % of _all_ greenhouse gases are anthropogenic? Not just CO2, include water vapor, etc. [Moderating] Once again, I would rather this not develop into a general debate about global warming. As anyone familiar with the debate knows, while an important greenhouse gas, water does not persist in the atmosphere the same way as CO2 and other greenhouse gas does, and is thus not equivalent. I regard your raising this issue as an attempt to sidetrack the thread. If you want to discuss whether global warming is or is not occurring, do so in one of the threads in GD. Colibri General Questions Moderator ---
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [December 13, 2009, 6:39pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/31 "2009-12-13T18:39:19Z")
> [@DrDeth](#): > > Well, the rate is tiny. At most 3mm a year, or about a inch a decade. (Some projected rates are higher, some lower). > > You would not notice 3mm. You would not notice an inch over a decade. They are trying to scare dudes.It is a very real problem\*, but a problem that will more affect our grandkids than us. > > - although figures very wildly. It’s not the rate that’s worrying; it’s the acceleration. Check out the Quirks & Quarks episode linked by another poster fur further explanation and discussion. ---
**Author:** ![Gymnopithys](https://avatars.discourse-cdn.com/v4/letter/g/fbc32d/32.png) [@Gymnopithys](https://boards.straightdope.com/u/Gymnopithys)\ **Post date:** [December 13, 2009, 7:15pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/32 "2009-12-13T19:15:23Z")
Some proponents of the Expanding Earth theory argue that midocean ridges “smoker vents” contribute to a rise in sea level: \*"The midocean LUVs vigorously extrude new basaltic seafloor and virgin new water via “black smoker” vents, plus an unknown, but prodigious, amount of other gases, minerals and heat as byproducts of the expansion process. … The LUVs are now the single greatest source of new water filling the expanding ocean basins, so research is needed to determine whether new ocean basin growth is keeping up with the increasing volume of new water. "\* > **[What's The Straight Dope on Sea Levels?](https://boards.straightdope.com/sdmb/showthread.php?t=543314)** > > One of the claims made by global warming proponents, is that the melting of land-based ice sheets (glaies, ice caps) will rase the level of the worlds oceans. Presumably, this should be a measurable effect, yet outside of anecdotal claims, thee... (I don’t know what LUV stands for) ---
**Author:** ![The\_Urban\_Spaceman](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@The\_Urban\_Spaceman](https://boards.straightdope.com/u/The_Urban_Spaceman)\ **Post date:** [December 13, 2009, 7:20pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/33 "2009-12-13T19:20:47Z")
Individual components of sea level rise are provided as a [table](http://img692.imageshack.us/img692/9582/slrs.jpg) within the latest IPCC report([AR4, 2007](http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_report_the_physical_science_basis.htm)). Note that the most recent estimates for Greenland Ice Sheet loss (1995-2007) exceed that in the IPCC report by a factor of _c._ 3.5. ---
**Author:** ![The\_Urban\_Spaceman](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@The\_Urban\_Spaceman](https://boards.straightdope.com/u/The_Urban_Spaceman)\ **Post date:** [December 13, 2009, 7:56pm UTC](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726/34 "2009-12-13T19:56:06Z")
LUV stands for _linear underwater volcano_, a term used by the vanishingly small number of eccentric theorists who still advocate the [expanding Earth hypothesis](http://en.wikipedia.org/wiki/Expanding_Earth). The term fissure volcano is used by ordinary geologists in describing these features. The expanding Earth hypothesis has no serious scientific support or geological evidence in its favour. Not only is it discredited, but if the Earth were supposedly expanding this would increase the volume of the ocean basins, leading to a relative sea level fall. Invoking it as an explanation is nonsensical. [Previous page](https://boards.straightdope.com/t/whats-the-straight-dope-on-sea-levels/520726.md?page=1)