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Steve L at 12:33 PM on 6 March 2010New observations find underwater Arctic Shelf is perforated and venting methane
The wikipedia article on atmospheric methane is pretty good (IMHO) and it has a table that may help to put some big picture perspective on this news. Approximately 3% of total methane added to the atmosphere is listed as coming from oceans (I'm not sure if there is now ~6% if these latest results are applied). Wetlands (including rice agriculture) account for 37%. Farm animals account for 19%. There are other contributors readers might find interesting. Anyway, the most optimistic thing I can think to write is that we have pleny of scope to cut back anthropogenic emissions elsewhere. Halving beef production (or trapping the gas of cows) should easily compensate for even a doubling of the amount of methane released from this area. Right?, I ask hopefully. Finally, does the paper indicate how sea life is responds to all this supersaturated water? Methane reacts with oxygen in the water, so presumably this region is anoxic. Right?, I ask somberly.Response: ...does the paper indicate how sea life is responds to all this supersaturated water?
No, it doesn't look at impacts of the rising methane. It's mainly concerned with the measurement of methane levels in the water and atmosphere above the East Siberian Arctic Shelf. -
Marcus at 12:28 PM on 6 March 2010New observations find underwater Arctic Shelf is perforated and venting methane
There is strong evidence that the Permian Extinction Boundary-where 95% all marine life died out-was caused by the melting of methane clathrates. Anyone else just a little bit scared yet? -
gallopingcamel at 12:28 PM on 6 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
doug_bostrom, (#120). Good story about the physicist; for a moment I thought you had tracked me down as my field is particle accelerators! It seems that we agree that it makes sense to get the data sets cleaned up. Will that change anything? Let's wait and see. I hope you agree with the idea that extraordinary claims require extraordinary evidence. Should we spend hundreds of billions of dollars unless the evidence is truly "unequivocal"? -
Tom W at 12:13 PM on 6 March 2010New observations find underwater Arctic Shelf is perforated and venting methane
Sry, Should be "sudden warming at the END of the Younger Dryas". -
Tom W at 12:12 PM on 6 March 2010New observations find underwater Arctic Shelf is perforated and venting methane
This new work is interesting and a bit scary. It will be interesting to see if any trends are detected in the next few years. But... Neither of the two papers to which you have linked support clathrate methane as the primary driver of sudden warming during the Younger Dryas, although they do not rule it out as part of a larger GHG feedback. A better example for the clathrate gun hypothesis might be the PETM. -
Jim Meador at 11:49 AM on 6 March 2010New observations find underwater Arctic Shelf is perforated and venting methane
Is there a temperature record for the water around the underwater permafrost? I would be curious to see the trends. -
John Bruno at 11:45 AM on 6 March 2010New observations find underwater Arctic Shelf is perforated and venting methane
Daisym, John clearly explained the mechanism through which AGW is melting arctic ice and allowing methane to be released from the benthos. It isn't that complicated. The thawing of terrestrial tundra permafrost is having the same effect. There is underwater permafrost because during the last ice age, sea level was lower than it is now. The permafrost was created, then it was submerged when sea level rose. Try googling "underwater permafrost" and you can learn all about it. -
Peter Hogarth at 11:19 AM on 6 March 2010Visual depictions of Sea Level Rise
Jeff, just to elaborate on your points a little, am I correct in stating that Jason 2 (for example) has all three tracking systems, (Dual GPS receivers, DORIS, and Laser ranging reflectors) and they are all independent? I know many of the 50 or so DORIS base stations are co-located (on the Earths surface) with GPS stations - some near tide gauges, and some of the handful of Laser Ranging stations are also co-located. The GPS receivers allow very high accuracy tracking of the altimeter satellites using the in view constellation of GPS satellites independent of the ground station data. Is it the case that tide stations and altimeters are ultimately independently locked into the GPS reference frame (for starters)? This detail is stretching my knowledge a bit thin... -
Admiral Memo at 09:43 AM on 6 March 2010A brief history of our iPhone app
I'll put my support in with those who want a Droid app. I've got one and I know already that once its Market gets enough apps, it'll give the iPhone a run for its money. The Droid is solid and can only improve from this point. -
Jeff Freymueller at 06:19 AM on 6 March 2010Visual depictions of Sea Level Rise
#56 RSVP. If you know the position of the satellite, and the distance from the satellite to the sea surface, then you know the position of the sea surface. So mainly you are asking about the first part. The two most important parts of determining the satellite orbit are the earth's gravity field, and the speed of light. Satellites can't wander about -- they obey the equations of motion subject to particular forces: earth's gravity field, solar radiation pressure on the satellite, etc. You integrate the equations of motion from a set of initial conditions, and then adjust the initial conditions (and, if needed, elements of the force model for drag, radiation pressure, etc) in order to fit data. The data here are your tracking data -- the satellite may have an onboard GPS receiver, or DORIS transponder, or a laser-ranging retroreflector. But you are measuring the distance between the satellite and various ground and/or space-based sites, and using this series of observations to estimate the satellite orbit. -
RSVP at 06:02 AM on 6 March 2010Visual depictions of Sea Level Rise
51.RSVP at 22:02 PM on 5 March, 2010 How do they position the height of satellites anyway? 52.Riccardo at 23:36 PM on 5 March, 2010 RSVP, you can find a general discussion on satellite positioning "here" Riccardo I went "there" (ie NASA), and they explain that they use microwave altimeters, computers, etc., all good to determine how far up the satellite is. That was not my question. I guess its a chicken and egg thing. How do you know how much the sea has risen or dropped if all you know is how far away you are from the Earth (even if you know to within 1 mm)? Especially when satellites are continually losing altitude and requiring repositioning? -
Doug Bostrom at 04:17 AM on 6 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
gallopingcamel at 02:57 AM on 6 March, 2010 I'm totally in favor of a ground-up redo of CRU's analysis, even if only necessary because 30 years ago few could see how fraught with suspicion and controversy such a relatively mundane data processing exercise could become. I'm sorry if I misread your remarks as cynical; the air these days is positively thick with not even risen as opposed to half-baked accusations of intentional misbehavior on CRU's part. I recently participated in another discussion with a fellow who insisted that losing any data raw or processed was the height of irresponsibility for a practicing scientist, especially one expending taxpayer dollars in pursuit of research. He identified himself as an active experimental particle physicist and it was clear from his examples he was (no surprise, accelerators==taxpayer money) relying on other people's money to conduct his research. He referred over and over again to his work in the 80's supporting his PhD thesis, how important it was to preserve detector data and the like, how his adviser would never have tolerated any loss. Finally somebody thought to demand he restore all of his raw data, algorithms etc. which of course he could not do, frankly admitting that was now impossible because of the passage of time. That's a particularly appropriate example, because the physicist in question found his own earlier work became unpredictably controversial in a later context and then of course could not produce every last iota of data collected decades before. The entire time I've been listening to the CRU badgering, I've been thinking about the proverbial glass house and stone throwing therein. Ignoring the statute of limitations, if the IRS decided I had some problem with my taxes back in 1980 both they and I would have the dickens of a time making a firm case to demonstrate every last dollar had been accounted for. As to the fundamental issue with dropped stations, I urge you to read carefully the work at the links I provided. -
Riccardo at 03:33 AM on 6 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
galopingcamel, the file with the UAH dataset quote the decadal trend in the last line. The number they give updated Jan 2010 is 0.130. -
gallopingcamel at 02:57 AM on 6 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
doug_bostrom (#115), I have never claimed that the dropped station issue will inflate or deflate the apparent rate of warming. To make that determination one would need the full data set as well as the truncated one. At the risk of repeating myself, my point is that a good scientist does not discard data without explaining why he is doing it. Phil Jones has made his excuses for the problems with HADCRUT3. We are still waiting for Tom Peterson to explain what is going on at NASA/GISS. With regard to NOAA/GHCN, take a look at "Digging in the Clay": http://diggingintheclay.blogspot.com/2009/12/physically-unjustifiable-noaa-ghcn.html P.S. Thanks for that link about wine growing on the other thread.....very interesting! -
Jeff Freymueller at 02:49 AM on 6 March 2010Visual depictions of Sea Level Rise
#54, Berényi Péter I do satellite positioning for a living. You are confusing the coordinate system with the tracking network. The tracking network deforms, the underlying coordinate system does not. The tracking network is a means of accessing the coordinate system, not the system itself. The context of the Leuliette paper is that earlier work (like Douglas) simply omitted all tide gauges that were thought to have vertical motions. This may be fine for the global rate, but leaves large swaths of the globe (like the North Pacific) with no tide gauge data, which causes problems at the regional scale. Here's the abstract of the Beckley et al. paper, which you can access for free (as you know): Mean sea level trends from TOPEX and Jason-1 altimeter data are recomputed using unified geophysical modeling and the new ITRF2005 terrestrial reference frame for the entire altimetric time series, with consistent orbits based on satellite laser ranging (SLR) and DORIS tracking data. We obtain a global rate of 3.36 ± 0.41 mm/yr over the 14 year period from 1993 to 2007. The regional sea level trends computed with the new reference frame show significant north/south hemispherical offsets of ±1.5 mm/yr relative to trends based on the previous 1995-era frame. Regional sea level trend comparisons for the time periods of 1993–1999 and 1999–2005 reveal strong basin-scale polarities and pronounced inter-decadal variability, with a relative increase in the global mean sea level trend of 1.5 ± 0.7 mm/yr in the latter seven years. As for the "paywall", your objection is over-the-top given that you could buy this article for $9 from AGU if you wanted, and if you email one of the authors they will almost certainly email you back a PDF if they don't already have a preprint version on their website. It is hardly locked up. If there is a research university where you live, you don't even need to set up a proxy. You should be able to walk into the library, go to the journals section, and make a xerox copy of the article for just the cost of xeroxing. Or if you are really serious about things, you can join AGU for $20 a year (only $7 if you are a student, I think) and get a cheap personal subscription (very cheap for complete access to all back issues of all AGU journals). I view it as a subscription that provides the revenue that allows a non-profit scientific society to continue to publish and function. If you want all published articles to be available for free, I would not mind at all, but somehow at least non-profit scientific publishing has to remain viable, and nobody pushing free access has proposed a believable way to do that. I don't really care what happens with the for-profit publishers; they are the ones who charge very high prices for subscriptions and individual papers. -
gallopingcamel at 02:31 AM on 6 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
Riccardo, (#116), your P.S. comment is puzzling to say the least. Are you talking about this document: http://wattsupwiththat.files.wordpress.com/2010/02/metoffice_proposal_022410.pdf Some see this as a PR or CYA exercise aimed at dousing the Climategate fire. Frankly I don't care what you call it as long as the data gets cleaned up and published in its raw state so that researchers can make their own decisions about what is good, bad or ugly. With regard to the UAH data set. The one I am looking at runs from 1978 to 2009. Over this 31 year period the trend is 0.05 degrees Celsius or 0.016 C/decade. In other words, not statistically significant. -
Berényi Péter at 02:16 AM on 6 March 2010Visual depictions of Sea Level Rise
#49 Peter Hogarth at 20:54 PM on 5 March, 2010 "as it stands is fundamentally flawed" Yes, I realize it is. The change in LoD caused by steric sea level change is negligible at first approximation. The steric part of the figure I have calculated should be multiplied by the ratio of depth with temperature change (1000 m?) and Earth's radius. It makes it more than three orders of magnitude smaller, microseconds instead of msecs. For eustatic rise (when water mass is changing), this is not the case. However, effect on LoD depends on latitude of source. If landlocked watermass makes its way into the ocean from latitude fi, actual delta_LoD is proportional to 1-1.5*cos(fi). Latitude 48 11 (N/S) is neutral, water from here has no effect on LoD. Poleward from there the coefficient is positive, increasing. At southern tip of Greenland (60N) it is 0.25, goes up to 0.8 for Norhern fringe (82N). Uneven latitudal distribution of landmasses can modify this relationship somewhat. Observed drift of pole is also a limiting factor, needs further care. Mass contribution to sea level rise, if any, should have been balanced between low and high latitudes. There was not much ice in temperate zone & tropics, so it is a limiting factor. As for steric rise, if half of 20th century rise (~10 cm) is attributed to thermal expansion and it occurred in the upper 1000 m of ocean, temperature rise should have been close to 1K (thermal expansion coefficient of water is ~10^-4 in realistic temperature range). To warm up 10^6 kg water by 1K, 4x10^9 J is needed. It can be supplied by a constant global 1 W/m^2 excess flux, concentrated to the oceans for a century. Way too much for last century, therefore considerably less than half of supposed rise could be steric. #40 Jeff Freymueller at 16:03 PM on 5 March, 2010 "the coordinate system itself does not deform due to plate tectonics" The coordinate system used by TOPEX/POSEIDON/JASON does deform and not just because of plate tectonics. It is linked to a set of only 64 tide gauges. Marine Geodesy, 27, 79–94 Calibration of TOPEX/Poseidon and Jason altimeter data to construct a continuous record of mean sea level change Leuliette, E., R. Nerem, G. Mitchum, 2004 see 2.2 Tide Gauge Calibration (pp. 9), especially the part on Douglas rate. Satellite datasets are dependent on it, GPS & DORIS calibration just "should be used at every gauge, and work along these lines is proceeding". At the moment slope is based on a single global assessment (Douglas, 1997) and historic rates of gauges. Would like to see GRL A reassessment of global and regional mean sea level trends from TOPEX and Jason-1 altimetry based on revised reference frame and orbits B. D. Beckley, F. G. Lemoine, S. B. Luthcke, R. D. Ray & N. P. Zelensky Unfortunately it is behind a paywall. I could set up a university proxy and have a look of course, but I don't do that. IPR (Intellectual Property Rights) is a devastating thing when applied to science. On a public site, in public debate only publicly available material should be used. In fact it should be that way for each & every scientific publication. -
Peter Hogarth at 00:22 AM on 6 March 2010Visual depictions of Sea Level Rise
HumanityRules at 11:10 AM on 4 March, 2010 My apologies, I forgot the Nerem 2009 link in 48. https://abstracts.congrex.com/scripts/jmevent/abstracts/FCXNL-09A02a-1728088-1-OceanObs2009cwp_final.pdf -
Tony Noerpel at 00:19 AM on 6 March 2010Every skeptic argument ever used
Hi BaerbelW Absolutely right. Interestingly, the lesson we should take from Y2K is that we asked our experts, computer analysts, to evaluate the problem and propose a solution. They did and we trusted them and did not question the need to invest some money in the solution. As a result, nothing bad happened and the investment in upgraded software most likely benefitted the economy rather than hurt the economy. In other words any economic argument not to respond to the problem were quite frankly baseless. With respect to AGW, humanity has asked our best experts to study the problem and propose solutions. They've done that. The IPCC report is one of the most incredible achievements of humanity. It is the first time our reaction to a serious problem was the application of critical thinking rather than say going to war (the Bush administration solution to peak oil for example). Economic arguments are again unsubstantiated and baseless, even on the very remote possibility that the IPCC report is wrong (say some value of epsilon greater than zero but smaller than say the probability that the Nats will win the world series every year for the next hundred years.) I take issue with coal geologist writing: "Admittedly, some who concur with AGW do so on the basis of faith or prejudice, and are equally as dogmatic as many of those who reject AGW." As a matter of fact, besides the handful of people (not even too many of the commenter’s here) virtually all people do not have the training and time to properly evaluate climate physics and the IPCC report, sorry. People who accept this report are entirely rational and sane. People who like George Will, Senator Inhofe, Glen Beck, Marc Morano, and the clownish Third Lord Viscount Monckton of Benchley, who deny the science based on maybe the stuff they forgot from a junior high school earth sciences course, are in denial. Referring to them as deniers is being accurate. If anybody thinks they can have a rational discussion based on science and fact with such people if only we adopt a better name for them besides the rather appropriate “denier” is deluding himself. I suggest you try it. I have. Pick a local elected official who denies AGW and make an appointment to discuss it with them. By all means arm yourself with the best science. You will find out that they will tell you how wonderful the Inhofe 400 prominent scientist report is despite the obvious fact that they haven't actually read it. (It wasn't ever actually meant to the read and I doubt Inhofe, Morano and Dempsey even read it.) And they will have some unkind things to say about Al Gore. And they will mention one or two of the more ridiculous denier arguments (water vapor is 98% of the GHG effect, in the 70's.., Mars is warming.., GCRs, it will hurt the economy to do anything about it, the hockey stick was debunked, it's the sun, or worse). These they believe unquestioningly while insisting on being called "skeptical". What we are struggling with here is that the human brain may not be wired to avoid self extinction. Of coure, we have no choice but to press on. Check this out: http://www.sciencemag.org/cgi/content/abstract/327/5970/1246 Best regards Tony -
Jesús Rosino at 00:07 AM on 6 March 2010Temp record is unreliable
We can add to "other lines of evidence for rising temperatures" also indirect evidence you mentioned elsewhere: - Greenland and Antarctica show net ice loss - Acceleration of glaciers in Greenland and Antarctica, particularly within the last few years. - Sea-ice loss in the Arctic is dramatically accelerating - Accelerating decline of glaciers throughout the world. - Rapid expansion of thermokarst lakes throughout parts of Siberia, Canada and Alaska - Disintegration of permafrost coastlines in the arctic - Poleward migration of species - Poleward movement of the jet streams (Archer 2008, Seidel 2007, Fu 2006) - Widening of the tropical belt -
Riccardo at 23:36 PM on 5 March 2010Visual depictions of Sea Level Rise
RSVP, you can find a general discussion on satellite positioning here -
RSVP at 22:02 PM on 5 March 2010Visual depictions of Sea Level Rise
How do they position the height of satellites anyway? -
Peter Hogarth at 21:11 PM on 5 March 2010Visual depictions of Sea Level Rise
Steve L at 07:32 AM on 4 March, 2010 I have been looking for a good visual of the North/South Seasonal variation. CSIRO has something on their fine website. http://www.cmar.csiro.au/sealevel/sl_drives_seas_dec.html -
Peter Hogarth at 20:54 PM on 5 March 2010Visual depictions of Sea Level Rise
Berényi Péter at 13:23 PM on 5 March, 2010 I admire the working and effort (and charts), but your "spherical shell" argument as it stands is fundamentally flawed. Much of the estimated 3.3 mm/yr rise is "steric", ie due to processes that cause an increase in ocean volume without a change in mass, mainly through changes in temperature (thermal expansion) and salinity. The remaining "eustatic" rise, does refer to mass increase (at least in the oceanographic community). This is changes in land runoff, including glaciers and ice sheets but as has been pointed out above, this is a re-distribution of mass, and only a proportion of this will effectively move in latitude. There is recent work on this (I'll look), some references submitted by others above (thanks Jeff). Again, look at the GLOSS summary linked in the post. The Geodetic guys are well represented. The ITRF reference frame is a virtual co-rotating frame, not referenced to the Earths surface as such, but to its "centre" (or very close). For full fetails see http://itrf.ensg.ign.fr/general.php -
Peter Hogarth at 20:03 PM on 5 March 2010Visual depictions of Sea Level Rise
HumanityRules at 11:10 AM on 4 March, 2010 You make a fair general point, but this is not a case of one data set correcting another which then validates the first! The tidal station data are relative (Land level-Sea Level) so to make them absolute we need land vertical offset corrections for individual samples, or vertical velocity estimation corrections for extended time series. As I briefly said, most recently this is done with nearby fixed stations which use GPS (see Woppelmann 2009 linked in post) or DORIS satellite systems that are ultimately referenced back to and integrated with other geodetic systems using SLR (Satellite Laser Ranging) or VLBI (Very Long Baseline Interferometry). These systems are all used to generate a stable geocentric reference frame such as the International Terrestrial Reference Frame (ITRF). Once a sufficient number of vertically bench marked tidal stations are available (there are currently around 300) it is possible to “calibrate” (I’ll use this word rather than “correct”) the independent satellite altimeters as their raw data are in a sense “orbit referenced” to allow global coverage - which the tide stations obviously cannot give. It is also fair to suggest that the altimeters are not perfect and are subject to all sorts of error sources, however once calibrated, their output is independent of the tidal stations and not subject to ongoing trend correction using tidal station increases as you might be suggesting. Thus in turn they could then be used to estimate vertical offsets for tide station data where there is no nearby GPS station. Cross validation is certainly part of the process. This is not to say that all of the many sensors are not continually checked and calibrated, or that further corrections will not be made. However the possibility of a major error or drift having remained hidden over the past 17 years over several different satellite sensors is quoted as “unlikely”. On your point about recent acceleration, there are (of course) decadal changes in gradient throughout the historical tidal records, but the papers listed in the post give the rationale behind the reported recent increase being more significant than previous “decadal” changes. In general, it is obvious even by inspection that the shape of the long term average for the extended time series is an upwards curve, though of course this should not be substituted for careful analysis, and “long term” is relative! The “slowing down” was something I saw from commentators on blog sites, and was (I believe) based primarily on a couple of years worth of the then current Jason 1 data (from University of Colorado, the standard ASCII data outlet). There may well be references for this (or other previous accelerating or decelerating mini-trends in the data set), and if so I have not excluded these out of any deliberate bias, but simply because the mainstream consensus of expert opinion that I am exposed to (and have tried to communicate to a wider audience) has moved on. The best overview on the complete “system” is The Global Sea Level Observing System (GLOSS), Merrifield 2009, linked in the post. Also: OceanObs09 – Community White Paper. Observations of Sea Level Change: What have we learned and what are the remaining challenges?. Nerem 2009 -
Riccardo at 19:04 PM on 5 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
gallopingcamel, good that you (almost) admitted that the temperature record isnot affected by the dropped stations. For the rest, i'm not defending the supposed "abandoned position" of good archive management (they were talking about a different issue than station dropping), I do not know how they do it. But what i'm interest in as a citizen that has to take decisions, or better, express opinions is the scientific value of their work. It proved to be at the very least good enough. Finally, I agree that all these discussions on the temperature records are bogus given that we now have independent satellite data set. The skeptic's beloved UAH dataset gives a decadal trend of 0.13 °C/decade, RSS 0.16 °C/decade. Both a strong confirmation of the quality of the surface stations datasets which should stop once and for all the chattering on this non-existent issue. P.S. There's no "do over" proposal due to archive mismanagement. Read the proposal they presented at the WMO meeting. -
Mike F at 18:17 PM on 5 March 2010Every skeptic argument ever used
Question. Why do you think that the majority of the people, especially the more educated, choose to be ignorant of climate change. Or rather choose not to accept the possibility of climate change and won't adapt to it. i.e. Why are skeptic arguments so successful? -
Steve L at 18:13 PM on 5 March 2010Visual depictions of Sea Level Rise
daisym -- I think over short time scales only warming (and therefore thermal expansion of water and melting of land ice) causes global sea level to rise globally. There are some positive feedbacks too, if you like a less simple answer. What causes the warming is a topic covered on other pages on this site (hint: greenhouse gases and black carbon very likely play a role). Also, there's this fun thing. -
Doug Bostrom at 18:09 PM on 5 March 2010Visual depictions of Sea Level Rise
Steve L at 17:51 PM on 5 March, 2010 Duly added to Links page. Your trophy is here: Links for 'Wine grew in England in Roman times'
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Steve L at 17:51 PM on 5 March 2010Visual depictions of Sea Level Rise
Hi John, do you have a webpage for the English vineyards skeptic talking point (I won't call it an argument)? To respond to Camel I have to go to one of your competitors: RealClimate Jul2006 RealClimate Nov2006 -
Doug Bostrom at 17:40 PM on 5 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
gallopingcamel at 16:24 PM on 5 March, 2010 There's been quite a bit of analysis done on dropped stations of late, leaving the Great Needle of Credibility pointing at the empty mark for the notion of dropped stations inflating the record of warming temperatures. I think this has already been mentioned in this thread? Undoubtedly somewhere else, in any case. To shift the Great Needle of Credibility away from the empty mark with regard to dropped stations inflating the record of warming temperatures, one would need to refute as opposed to ignore these three independent investigations: A simple model for spatially-weighted temp analysis The 1990s station dropout does not have a warming effect False Claims Proven False -
daisym at 17:07 PM on 5 March 2010Visual depictions of Sea Level Rise
Peter Hogarth #14: Thanks for the expanded scale for the graph at Fig 1. This graph is wonderful in its simplicity and ability to help visualize sea level rise. I see three distint sections on the graph. One, is for the essentially flat plot from 1700 to 1800; then two, an increasing rate of rise from 1800 to 1900; then three, a steady rate of rise from 1900 through 2010. A couple of questions come to mind as I see this. Given that sea level rise occurs slowly over time, something must have happened between 1700 and 1800 to cause sea levels to rise as shown beginning at about 1800. Whatever was the cause ameliorated after 1800 to the steady rise that began at about 1900 and continues, today. This begs the question, is the sea level rise shown on the graph of manmade or natural origin? And if manmade, it seems that sea levels should be rising at an increasing rate, as we see fron 1800 to 1900 due to the development of industry and transportation, but that doesn't seem to be the case. How certain are we that we know what causes sea levels to rise? -
Jeff Freymueller at 17:05 PM on 5 March 2010Visual depictions of Sea Level Rise
Darn it. I read my own graph wrong. Glacier Bay collapse was ~8 mm of global sea level rise, and most of that from 1800-1900 (about 10% of global rise over that time). The regional component mentioned above was ~15 mm but over about 1850-2000, so about another 5 mm within 1800-1900, leading to 15-20% of the total, not 30%. I didn't deal with Charlie A's anthropogenic or not question. Sea level rise tells you it is warming, whether anthropogenic or not. To get at the anthropogenic component, you need to explain the various contributions to sea level rise -- see the Cazenave presentation and paper referenced in the main post -- and see what component of those are due to anthropogenic warming. -
gallopingcamel at 16:49 PM on 5 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
Fortunately, the surface station data sets such as GHCN are not as important as they once were because satellite measurements have been accumulating for 37 years. Satellite measurements diverge significantly from the three main (independent?) surface station data sets. For example, John Cristy (UAH) has published a data set that shows significant cooling since 1998 in sharp contrast to James Hansen's much publicised Hockey Stick presentations. When Hansen says that "Catastrophic" warming is taking place, Joe Sixpack wants much more of it, at least where he lives. Mother Nature plays such cruel tricks! -
Jeff Freymueller at 16:47 PM on 5 March 2010Visual depictions of Sea Level Rise
#39, Charlie A. asks about 19th century sea level rise. I estimate about 70 mm of sea level rise, 1800-1900, from the graph -- just eyeballing. Close to 30% of that 19th century sea level rise came from Alaska and coastal British Columbia. About 10% came from the collapse of the glacier/icefield system in Glacier Bay, Alaska (3000 cubic km of ice lost, equivalent to 8 mm global sea level rise), and about 20% from the rest of the surrounding area. Whatever the global extent of the Little Ice Age, it was certainly significant in Alaska, and the glaciers and icefields have been shedding mass rapidly since 1750-1800. The main cause for the rapid response is probably not melting but rather tidewater glacier dynamics leading to very rapid retreat and dumping ice into the ocean, where it melts. This is not a purely temperature-driven effect, but an amplified response to warming caused by positive feedbacks. Reference for the last paragraph is Larsen et al. (2005), in Earth and Planetary Science Letters (I'm a co-author). -
Jeff Freymueller at 16:30 PM on 5 March 2010Visual depictions of Sea Level Rise
#38 Bern, for the effects on sea level of geoid change and changes in shape due to changes in the rotation axis with post-glacial rebound, you could start with the Science Daily article on the Feb 2009 paper by Jerry Mitrovica (link above in comment #23). As for the effects on earth rotation, I did some searching around. For effects on length of day, check out Landerer et al. (2007) in Geophysical Research Letters (http://www.agu.org/journals/gl/gl0706/2006GL029106/). You can download a non-formatted preprint for free at http://www.mpimet.mpg.de/fileadmin/staff/landererfelix/landerer_07_GRL.pdf. They say the effect has been -0.12 milliseconds over the last 200 years. The effect on the position of the earth's rotation axis is covered in a 2009 paper from Landerer et al. in the same journal. Probably available in preprint form on the same website, if you can't get the journal. -
gallopingcamel at 16:24 PM on 5 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
John Cook, thank you for your gracious reply. I promise to moderate my metaphors. Riccardo, (#108) you may be right. The results may be unchanged by discarding over 80% of the data before starting the analysis. However, you can't be sure of that until the full data has been compared to the truncated data. My point was something completely different. Scientists who discard most of the available data before starting their analysis need to provide cogent explanations for their actions. CRU, NASA, and NOAA failed to do that. You are defending a position that has already been abandoned by the professionals. Reto Ruedy at NASA and Phil Jones at CRU have admitted to poor data base management and sloppy analysis. Inhofe gives a glimpse of this in his "Minority Report" but you need to read all 274 pages of the HARRY_READ_ME.txt file to get your arms around the bungling and incompetence at the UEA. It gets worse! The UK "Met Office" recognises that the historical climate data is hopelessly compromised so they propose a "do over". If you are right the conclusions will remain unchanged after the "do over". Let's wait and see. -
Jeff Freymueller at 16:03 PM on 5 March 2010Visual depictions of Sea Level Rise
#34 Berényi Péter, Bern (#38) is right, and your calculation is an overestimate. Most of the sea level rise is either thermal expansion (some change in moment of inertia as some mass is moved outward) or from melting land ice. In both cases, the change in the moment of inertia is definitely smaller than your calculation because the mass now in the ocean was already at about 1 earth radius. You have to take your value and subtract the effect of removing the mass of the water from where it WAS. You are only partially right about the coordinate system. All sites on the surface move due to plate tectonics, but the coordinate system itself does not deform due to plate tectonics. The relative positions of those sites are measured daily to weekly, with a precision at the few mm to centimeter level, by 4 independent global measuring systems. Orbits of the altimetry satellites (and others) are determined both through laser ranging and radiopositioning (GPS and sometimes DORIS). There are always technical concerns with any kind of work when you aim for the highest precision, but the error bars on the altimetry estimate already include the best error estimates available for these uncertainties. -
Charlie A at 15:42 PM on 5 March 2010Visual depictions of Sea Level Rise
@Carrot Eater #27: It is hard to attribute particular increases in the sea level rate-of-rise to particular warming events. The Jenreva chart in comment #14 shows the acceleration in sea level rise starting in the late 1700's. AGW in 1800?? Church and White 2006 say "Another approach, given the clear change of slope at ~1930, is to do linear regressions on the two halves (1870–1935 and 1936–2001) of the record. The slopes are 0.71 ± 0.40 and 1.84 ± 0.19 mm/yr respectively, implying an acceleration of 0.017 ± 0.007 mm yr^-2 (95%). That simple analysis shows a greater than doubling in rate of rise taking place in the 1930s. Huge amount of AGW in 1930 ?? Church and White's 2006 paper, "A 20th century acceleration in global sea-level rise" only had data starting in 1870, but his best fit to the data was a quadratic with acceleration starting before the start of his 1870 data start. The paper, available as pdf has a graph plotting the sea level rate of rise with 10 year smoothing. The main post above references Jevrejeva 2008, but didn't list the title: "Recent global sea level acceleration started over 200 years ago?" The bottom half of figure three shows a graph similar to Church and Whites sea level rate-of-rise variation graph, except that it shows the roughly 60 year period on an upward trend going back to 1700. See http://www.pol.ac.uk/psmsl/author_archive/jevrejeva_etal_1700/2008GL033611.pdf Figure 3. So were we experiencing sea level rate of rise acceleration due to AGW back in 1700 ? If the sea level acceleration of today is an extension of the Jevrjava graph starting from 1700, why are we so certain that today's acceleration is anthropogenic? -
Bern at 14:43 PM on 5 March 2010Visual depictions of Sea Level Rise
Berenyi Peter, I haven't delved too deeply into your analysis, however one point occurs to me - I think your analysis would be absolutely correct if the water for sea-level rise were being added to the Earth, however it's not - it's a redistribution of existing mass. Some from Greenland, some from Antarctica. I wouldn't have thought the distribution was anything like being even, either, due to rotational oblateness effects (or whatever you call it). Does anyone know of a reference that looks into this aspect of SLR in detail, taking all the effects into account? It's a very complicated situation... -
gallopingcamel at 14:34 PM on 5 March 2010Senator Inhofe's attempt to distract us from the scientific realities of global warming
It has been fun but my last two replies failed to post. I was hoping that this site would not resort to censorship on the lines of "Climate Progress". Sad! All that remains is to wish you well; "live long and prosper".Response: I deleted the "religious zealots" comment as that violates the "no ad hominem" policy. Ditto for the previous comment likening scientists to "used car salesmen". You will notice that comments that express skeptic views without making value judgements are not moderated. -
gallopingcamel at 14:08 PM on 5 March 2010Visual depictions of Sea Level Rise
Berenyi Peter, wow! Way above my pay grade! -
gallopingcamel at 14:04 PM on 5 March 2010Visual depictions of Sea Level Rise
John Cook, the high numbers for the IPCC's predictions on sea level rise are dependent on temperatures rising at unprecedented rates. If you believe in scary temperature rise scenarios then rapidly rising sea level predictions are plausible too. We need to revisit this in 2020; by then I may agree with you (or perhaps vice versa). Steve L, my apologies for making this "Camel Centric". Nah! Just kidding. Back in 1325 my ancestors were paying taxes to Edward III in Littleham-by-Bideford (Devon, UK). Historians tell us that they were mostly drinking wine that was inexpensive and of high quality rather than beer that people consume in modern Devon. I hope that the IPCC will be proven right so that temperatures will rise to the point that my many relatives will give up their beer/whisky habits in favor of wine and growing seasons will be extended in the higher latitudes. -
Philippe Chantreau at 14:01 PM on 5 March 2010Visual depictions of Sea Level Rise
The Munk paper referenced above is over 8 years old (sent of review in 2001). What are the follow ups? -
Berényi Péter at 13:23 PM on 5 March 2010Visual depictions of Sea Level Rise
I can believe relative sea level changes measured by satellites, more or less. However, absolute rates are highly dubious. Earth's moment of inertia is 8x10^37 kgm^2. There is a continuous loss of rotational angular momentum due to tidal breaking (angular momentum lost goes into orbital angular momentum of Moon, Earth-Moon distance is measured to increase by 38 mm/year). It is supposed to slow down Earth's rotation, i.e. increase LoD (Length of Day) by 2.3 msec/century. On the other hand, historic record of solar eclipses for the last 2700 years indicate a 1.7 msec/century inrease in LoD. The difference is due to glacial rebound. Land formerly covered by ice sheets rises (Canada, Scandinavia), mantle material moves to the North, closer to axis to support it, moment of inertia decreases. A -0.6 msec/century change in LoD implies a 7x10^-9 relative decrease in moment of inertia per century (-5.6x10^29 kgm^2 in absolute numbers). A sea level rise of 3.3 mm/year increase measured by satellites increases Earth's moment of inertia. The mass of a 3.3x10^-3 m thick spherical shell of radius 6.37x10^6 m and having density 10^3 kg/m^3 is 1.7x10^15 kg. Moment of inertia for spherical shell is 2/3*M*R^2, i.e. 4.55x10^28 kg/m^2. In fact about 70% of Earth is covered by oceans, so actual increase in moment of inertia due to sea level rise is more like 3x10^28 kg/m^2/year. It is only an order-of-magnitude calculation, so latitudal distribution of ocean basins is considered uniform. It implies a 3.3 msec/century increase in LoD. As the secular increase is 1.7 msec/century, it would mean a 5 msec/century recent rate. Nothing like that is seen.
We have data for the last three centuries (hail to astronomy).
Earth's moment of inertia varies wildly, but there is not much trend in it. The 1.7 msec/century secular trend perhaps, nothing else. Sea level rise is undetectable.
It can mean two things. Sea level is either not rising, at least not on a rate compatible with satellite data or haphazard changes in shape & internal mass distribution of Earth just mask it.
The two things may even be connected. Satellite measurements show large regional differences in sea level change. It may be just the underlying mantle.
The coordinate system used by satellites is not rigid (in fact rigid rotating coordinate system can not even exist). It is calibrated (and re-calibrated because of orbital drift) to a selected set of "fixed" points on Earth. But those points are not really fixed (relative to what?), they are just fixed to the surface.
The question is far from being settled, slope of satellite altimetry is rather arbitrary.
PNAS 2002
Twentieth century sea level: An enigma
Walter Munk
-
Jeff Freymueller at 11:38 AM on 5 March 2010Visual depictions of Sea Level Rise
Camel: What Steve L said, plus: 6. Most of the sea level rise from the last glacial maximum was over by about 6000 years ago. So your average is meaningless, because the average rate of rise from about 6000 years ago to a few hundred years ago was very close to zero (much closer to 0 than 2-3 mm per year is). Advanced human civilzations rose AFTER sea level stabilized, which also would have stabilized shorelines, near-coastal river gradients, etc. -
Steve L at 11:24 AM on 5 March 2010Visual depictions of Sea Level Rise
Dear Camel: 1. The "or more" is important; 2 m is a lot. 2. Not much infrastructure was at risk 9000 years ago. 3. If glaciers covered Canada, sea level would be lower. 4. But that won't happen: ice-age postponed 5. It's not all about you and your house. -
gallopingcamel at 10:40 AM on 5 March 2010Visual depictions of Sea Level Rise
Satellites provide us with great precision in the measurement of sea levels. Since the start of the satellite record the rate of rise has averaged 3.2 mm/year, in good agreement with other methods. Trying to put this in perspective, the 21st century sea level rise could be 0.3 meters or more. Is that a catastrophe? During the 20th century sea levels rose by ~0.2 meters so maybe we do have a problem as the rate appears to be rising. My understanding is that sea levels have risen by 110 meters in the last 9,000 years as the planet recovered from the last Ice Age. That works out at an average of 1.2 meters per century. Thus looking at the big picture, the current rate of rise is quite low and certainly not unprecedented. I live in Florida and at the current rate of rise my home will be at sea level in 1,000 years but by then we will probably be more worried about the glaciers covering most of Canada.Response: A rise of 30 cm by 2100 is not what the peer-reviewed science is telling us. Sea levels will not continue to rise at a linear 3.2 mm per year but are accelerating, primarily due to accelerating ice loss from the Greenland and Antarctic ice sheets. Satellite gravity measurements are already observing accelerating ice loss from both ice sheets (Velicogna 2009).
Once the contribution from ice sheets are taken into account, two entirely independent analyses (one using past sea level behaviour, the other using ice sheet dynamics) find the expected sea level rise by 2100 to be between 80 cm to 2 metres (Vermeer 2009, Pfeffer 2008). . This sea level rise will be more than inconvenient to many millions of people.
You make a good point that sea level rise has changed dramatically in the past. In fact, the past tells us volumes about how sea level responds to temperature. What it tells us is that ice sheets are very sensitive to changes in temperature. Consider that our lower emission scenarios predict a warming of around 1 to 2°C. This is approximately the same as the temperatures during the last interglacial, around 125,000 years ago. At this same time, sea levels were at least 6 metres higher than current levels.
In other words, while we expect sea levels to rise 80cm to 2 metres by 2100, sea level rise won't stop there. They will continue to rise and at our current emission trajectory, we expect sea level rise of at least 6 metres. There is uncertainty over how long this will take - likely centuries. I imagine future generations will not look kindly at the late 20th Century/early 21st Century generations who ignored these multiple lines of peer-reviewed evidence for dramatic sea level rise. -
ProfMandia at 05:09 AM on 5 March 2010Every skeptic argument ever used
John, I just added three of my own links. Can we plug our own links? Climate Models & Accuracy Global Cooling? The Scientific ConsensusResponse: Definitely! In fact, for the time-pressed climate blogger, I would encourage your readers to submit your webpages to the directory. The more links we can get into the directory, the more useful a resource it will be.
Not to mention hopefully it will get more traffic and google ranking for your website. -
Berényi Péter at 05:05 AM on 5 March 2010YouTube video on the empirical evidence for man-made global warming
Two more Annals of Glaciology 5 1984 Impurities in Snow: Effects on Albedo and Snowmelt (review) Stephen G Warren PNAS Soot climate forcing via snow and ice albedos James Hansen and Larissa Nazarenko, November 4, 2003
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