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Unforced Variations: July 2012

Filed under: — group @ 3 July 2012

Have at it.


561 Responses to “Unforced Variations: July 2012”

  1. 401
    MARodger says:

    sidd @387
    A plausible rate for SLR?
    AR4 continued the IPCC underestimation of SLR which I suppose allows the floodgates to be opened for spectacular SLR predictions. Pfeffer et al 2008 (abstract) Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise helpfully suggests an upper limit of 2 m by 2100.
    Stefan Rahmstorf discusses SLR having been part of a study looking at SLR under other IPCC scenario estimates based on temperature/SLR correlation. He breaks a forecast 1.2 m SLR by 2100 under IPCC A1B scenario (3.5 °C warming, the IPCC forecast was 0.35m) into – expansion 0.23 m (as IPCC), glaciers 0.40 m (two-thirds of the total such ice), polar land ice c. 0.50 m.
    This may present “plausible” but then there’s the WAIS that, as you say @392, sits patiently “on the other hand.”

  2. 402
    Hank Roberts says:

    Chris, you have to add _and_ subtract to end up with the total. You understand that right now, human fossil fuel produces about twice as much CO2 as is accumulating in the atmosphere, right?

    Biological cycling has been handling about half the excess CO2 we produce, for the moment. Biological cycling can change its rate very quickly — within limits we haven’t yet understood.

    The amount we produce from fossil fuel is not the same amount that accumulates in the atmosphere and oceans — and the fraction doesn’t stay the same over time.

    http://cgcs.mit.edu/research/focus-areas/oceans-ocean-atmospheric-coupling-and-carbon-cycling/

  3. 403
    sidd says:

    Now to return to my previous stipulation: that 80mm/yr SLR is the maximum possible

    if i recall correctly 0.5 to 1 W/m^2 radiative imbalance is about 1e22J/yr over the earth surface, whereas 1mm SLR/yr ~400GTon ice melt/yr ~ 1e18J/yr

    so a percent of a percent of the total radiative imbalance goes to melt ice, most goes into the oceans. How much could this fraction plausibly increase ?

    sidd

  4. 404
    Patrick 027 says:

    Re Chris Machens – if I have time I might check that video out, but … estimates vary but they’ve all been on the order of 0.2 Gt C / yr. Note this isn’t just what comes out during volcanic eruptions, and it may include oxidation of buried organic C (that is, excluding when humans are doing the same thing).

    The point, though, was that geologic emission (and the typically almost-balancing sequestration) don’t have much to do with deglaciations of the orbitally-forced sort – those CO2 changes are due to imbalances in fluxes among the surface/oceanic reservoirs in response to climate change, with a generally amplifying response given the way things have been set up recently.

    Of course, changes in CO2 over the longer term can be driven by changes in geologic emission as well as geologically-forced changes in sequestration (putting mountains up where tropical rains will fall, having wet flat areas with poor drainage to form coal, … or putting all your continents at the equator so that changes at higher latitudes don’t have as much effect… ) as well as climatologically/evolutionarily-induced changes in sequestration.

  5. 405

    Volcanoes emit between 150-260 (130-440 on the outside) million tons of CO2 per year
    Gerlach, 2011

    0.2 is well within the ballpark on the mean of the est.

  6. 406
    MARodger says:

    sidd @403
    Sorry. I perhaps went off in an unexpected direction @401
    The radiative imbalance number we agree but I’m not at all happy with your 400 Gtm.melt=1e18 J. I usually work with 300 Gt.melt=1e20 J, which is a rather different number. One familiar place to easily back my assertion is the PIOMAS page, bottom paragraph.
    If today there is some 700 Gt.melt divided equally between Greenland, Antarctica plus another 700 Gt.melt from Arctic sea ice loss (I’ve no idea about Antarctic sea ice loss), today’s percentage of global warming expended melting polar ice would be approaching 4%, with half contributing to SLR.

    If I may, let me chew a while on that 4%….
    The 4% will surely increase as (i) global warming starts getting to grips with ice, resulting in (ii) the ocean warming being robbed of energy through a reduction in the rate of surface warming (although that is quite a slow process). For big (i)-type processes, this would result in surface warming halting and even cooling. (I don’t see this as counter-intuitive as suggested @387, although perhaps I’m approaching the phenomenon from the other way round. I will have to check out ‘Heinrich events’. Thank you for the lead Anonymous Coward.)
    My ‘25% going into melt (yielding 20mm SLR pa)’ was only a guess & is now looking too large. The figure from Rahmstorf of 500mm SLR from polar land ice by 2100 (linked @401) would mainly apply to the end of the century so the 20mm is perhaps high but isn’t a silly number.
    For the 25%, I was working on a fixed radiative imbalance (I took it as 0.6 W/m-2) but this will increase with our increasing rate of emissions. The imbalance will also increase with the (i) & (ii) above.
    So the 20mm pa by 2100 may be on the high side when applied to SLR from melt & the 25% of energy imbalance is seemingly worse, approaching silly. To get a more realistic figure without guessing yet again would require the numbers used for net radiative imbalance by the likes of AR4. Or Vermeer & Rahmstorf 2009. do mention the future reduced % of SLR from thermal expansion suggesting the % of SLR from melt will (very) roughly triple by 2100 but presumably this triples the land ice melt (so 2% triples to 6%) for a 1.2 m rise. (If you double that 6% to 12% you pretty much double the SLR, as melt is (I calculate, but it does need checking) ~50 times more energy-efficient at SLR than is thermal expansion.) And this is in the context of a 1.2 W/m-2 radiative imbalance by the end of the century.
    ….and swallow.

  7. 407

    AN Australian Antarctic scientist has made a climate studies breakthrough by examining how the earth warmed up after the last Ice Age.

    Dr Pedro says the study of natural warming only underlines the speed at which human-created climate change has occurred.
    He says 8000 years’ worth of natural CO2 increases have been created in the 200 years since the industrial revolution.
    “Just as the steady increase in CO2 helped to melt the ice caps and warm the earth out of the ice age, the rapid increase now in CO2 is also driving up temperatures, only at a much faster rate,” he said.
    “What we’re doing now is over a hundred times faster.”

    Read more: http://www.news.com.au/technology/sci-tech/aussie-antarctic-scientist-in-climate-studies-breakthrough/story-fn5fsgyc-1226434145677

  8. 408
    sidd says:

    Mr. MARodger says on the 24th of July 2012, at 6:43 AM:

    ” 300 Gt.melt=1e20 J ”

    You are of course, correct, I was wrong.

    So, approx 1% of the integrated radiative imbalance/yr is enough to melt the equivalent of 1mm/yr SLR from land ice. I agree with you that increasing this fraction to 25% seems implausible. Could it go as high as 10% into melting land ice ? I tend to think not, but lets see where we get using that as an upper bound.

    This argument seems to indicate that MWP1A level event is implausible from radiative imbalance alone melting land ice and supports the contention that AIS must have had a role. Today, we see few barriers to remaining WAIS exporting itself into the ocean, or the ocean undermining WAIS on its way to the Byrd Basin behind PIG and Thwaites.

    So how fast can WAIS collapse ? (leaving aside those bits of EAIS which also have deeeeeep holes under them. For now.) ANDRILL sees timescales on the order of 1e3 yr in previous collapses. 7 m in 1e3 yr from WAIS ~ 7mm/yr + 10 mm/yr (very high estimate for GRIS) is 17mm/yr, slow compared to MWP1A, but fast enuf to drown a great deal.

    Now to EAIS. I dont see any way that EAIS contribution can exceed WAIS. Add another 7mm/yr for EAIS ? Now we get to 25 mm/yr SLR, a meter every 40 yr, closer to MWP1A rates.

    Lastly: Again relying on aging memory, I seem to recall that Bindschadler posited that the 1e3yr time to collapse WAIS should be taken as an upper estimate. In which case, MWP1A seems even more possible.

    sidd

  9. 409

    Re MARodger @406
    Rahmstorf probably attributes ice sheet disintegration into his projection? Also it would help if we can attribute the melt amount to their respective sources, when discussing melt rate/SLR.

    Re Rate of Climate Change
    James Hansen lecture on “The last 65 million Years” was referring apparently to the equilibrium state of that time. Where Dr Pedro’s study is focusing on a climate change episode.

    That we are 2 magnitudes above pre-historic climate changes is exactly what we can observe and why past projections have been underestimated. With positive feedback’s attributing more as we progress, we can assume that we get another uptake of magnitude for the rate of change (emission/temperature).

  10. 410
    SecularAnimist says:

    A Science Daily article about the study mentioned by Chris Machens above is here:

    http://www.sciencedaily.com/releases/2012/07/120723162707.htm

    The Climate Of The Past abstract with a link to the full study in PDF format is here:

    http://www.clim-past.net/8/1213/2012/cp-8-1213-2012.html

    “Here, we focus on the last deglaciation, 19 000 to 11 000 yr before present … we show that the increase in CO2 likely lagged the increase in regional Antarctic temperature by less than 400 yr and that even a short lead of CO2 over temperature cannot be excluded. This result, consistent for both CO2 records, implies a faster coupling between temperature and CO2 than previous estimates, which had permitted up to millennial-scale lags.”

  11. 411
    Unsettled Scientist says:

    Gavin,

    I want to thank you for the way you’ve dealt with Dan H. recently. When you gave the UC sea level link, I tried to bookmark it only to realize I had previously done so. This made me realize that instead of just leaving it in my bookmarks I should take an hour or so and go through the material on their site. I definitely have a better understanding now of GMSL, how satellites measure the sea level, the need for a glacial isostatic adjustment and how that makes GMSL smaller than it would be simply from melt water and thermal expansion, how RSL is more meaningful for local planning due to some of these effects (like how NOLA is sinking faster than the sea is rising).

    I just wanted to point out that your efforts aren’t just about correcting the wildly incorrect. Inquisitive people are paying attention to what you write and using it as a guide for learning. I generally seek out main posts, and contributor replies here, they have a higher guarantee of value to me as I try to learn about the natural world.

    Once again, Thank You.

  12. 412

    The overall lower atmosphere of the Arctic is warming:

    http://www.nasa.gov/topics/earth/features/greenland-melt.html

    Its not a surprise, the warming is gradual and is related to sea ice thinning which means sudden rapid sea ice extent melting.

  13. 413
  14. 414
    Jim Larsen says:

    Have any of the models shown the ability to melt so much of Greenland’s surface by 2012ish?

    On the maximum sea level rise through ice melt, some of the most vulnerable ice is in shelves and sea ice. That quantity would have to be subtracted, right?

  15. 415
    sidd says:

    Mr. Jim Larsen writes on the 24th of July, 2012 at 10:28 PM:
    “… some of the most vulnerable ice is in shelves and sea ice. That quantity would have to be subtracted, right?”

    Yes, altho I imagine that summer Arctic sea ice will be a distant memory in a decade, and there are a bunch of other things bring the estimate down. But I am primarily interested in upper bounds on SLR/yr assuming all the heat comes from radiative imbalance, how fast can we get it into land ice. Of course, the ocean is much cleverer than me and might move some of its stored heat into the land ice from underneath or thru rain …

    sidd

  16. 416
    jgnfld says:

    @141 I am not a physicist but I think the correct way to look at this is not to subtract meltwater from floating ice as to not add it in in the first place.

    Thermal expansion would still apply to the melted water just like the rest of the ocean, of course.

  17. 417
    Paul S says:

    […Where for instance do you get a current ‘2-2.5 mm/yr’? You know as well as I do that all of the satellite data sets show more than 3mm/yr. – gavin]

    I wouldn’t be quite so dismissive of Dan on this point. If you look at different trend periods to present in the satellite data there is a steady drop for later start dates, suggesting that 1993 occurred at a local minimum, inflating any trends drawn from it. It seems likely that the “true” underlying current rate is between 2.5-3mm/yr. (ok, he may have lowballed a bit, but what do you expect?)

  18. 418
    Jim Larsen says:

    415 Sidd,

    So in your scenario, Ross et al are already gone. Ocean currents won’t be what they are, and WAIS is highly susceptible to erosion. Glaciers will be un-buttressed. Greenland won’t be white as its surface will melt every spring.

    Instead of global budget, what about calculating GIS, WAIS, and EAIS’ summer insolation, then “just” add in for glacial transport, wind, and ocean currents? In an ice-free ocean, all ice which hits the ocean melts quickly enough. I’m sure there’s plenty of energy in such an ocean to handle any influx of bergs. So the vision of an ice-filled ocean isn’t too far off. The ocean will fill to the extent needed to melt all incoming ice.

    The other problem, erosion of the grounding line, doesn’t immediately change sea level much, but it weakens the ice above. WAIS will get riddled. Any collapses would result in tsunami-style SLR.

  19. 419
    Jim Larsen says:

    Sidd,

    Imagine Greenland in a slightly(?) warmer world. In summer it will be an isolated pocket of 0C while temperatures all around are much higher. Lots of rain, which, along with the melt water will carve huge river systems into the ice and/or moulins throughout…

    Here’s another path to an estimate. If we assume that surface area is the dominant variable for melting and that small ice caps and glaciers are currently in the condition where we get maximum melt, then the graph halfway down shows the smalls contribute ~63% from an area of ~3%. Account for inefficiencies of scale and you’ve got something, or not.

    http://nsidc.org/cryosphere/sotc/sea_level.html

  20. 420
    Jim Larsen says:

    Oops, it’s scheduled to get worse for the small ice caps and glaciers, so that’s another big variable to add.

  21. 421
    sidd says:

    RE:WAIS and ocean intrusion into previously unknown rift
    http://www.nature.com/nature/journal/v487/n7408/full/nature11292.html

  22. 422

    It seems likely that the “true” underlying current rate is between 2.5-3mm/yr.

    Oh sure, and if you look here in 2010 sea level is obviously falling, but in 2011 it’s really cranking again, well above 3 mm/year. Cherry season is over, it was an early season this year. A better question to ask is what happened in 2010?

  23. 423
    J Bowers says:

    Loss of Arctic sea ice ‘70% man-made’

    Study finds only 30% of radical loss of summer sea ice is due to natural variability in Atlantic – and it will probably get worse
    […]
    Looking across all his simulations, Day found that the 30% figure was an upper limit – the AMO could have contributed as little as 5% to the overall loss of Arctic ice in recent decades.

  24. 424
    Hasis says:

    “…what happened in 2010?”

    My understanding was that the water moved inland:

    http://www.jpl.nasa.gov/news/news.cfm?release=2011-262

  25. 425

    Questions, in particular for Ray PH if he has the time.

    We have a discussion going on elsewhere about what causes stratospheric cooling. My own understanding is that there are two factors: (1) diminished IR in the CO2 wavelengths coming from the upper troposphere below (the “enhanced greenhouse effect”) and (2) increased emission from the stratosphere in the CO2 wavelengths due to increased CO2 in the stratosphere itself.

    My questions are: (a) Is this an accurate statement and (b) which of these factors, if either, contributes more to stratospheric cooling, reduced energy-in from below or increased energy-out from within?

  26. 426

    Follow-up Note: This is of course ignoring changes in ozone, which is another topic. The question purely relates to how increases in CO2 in the atmosphere cool the stratosphere.

  27. 427
    jgnfld says:

    Goddard has [edit. thanks for alerting us, but we’re not interested in publicizing this sort of nonsense at the site]

  28. 428
    Dan H. says:

    Thomas,
    You seem to be trading one type of cherries for another. Using a one-year trend to make your point seems rather short-sighted. While the satellite data shows an overall 3.1 mm/yr rise since 1993, the rate of increase during the first half of the data is 50% higher than the second half. Further (as pointed out by Paul and myself), the rate for the years prior to the satellite data show much lower SLR. Over the past 30 years, global mean sea level as increased at an average of ~2mm/yr has shown in this graph provided earlier by Gavin.
    http://www.cmar.csiro.au/sealevel/index.html

    While some may conclude that this is in disagreement with the recent satellite data, it is not. The overall data shows decadal averages of ~1mm/yr for the first decade, close to 4mm/yr during the middle decade (the start of the satellite record), and about 2mm/yr for the past decade (including the most recent data).

    Over the past half century, SLR has average about 2 mm/yr.

    http://www.real-science.com/wp-content/uploads/2011/12/ScreenHunter_08-Dec.-13-21.41.jpg

  29. 429

    “Goddard has…”

    Oh, the hours of innocent amusement in filling that particular elipsis!

    And. I swear, Captcha says “hescoff further!”

  30. 430
  31. 431
    Mike says:

    Can someone help me with this engineer’s opinion?

    Water vapor records are available from every weather observation station – but are never used as the climate ‘scientists‘ like to incorrectly use temperature as a metric for heat energy which the gullible and scientifically ignorant media get excited about.

    The CO2 global warming hypothesis is based on the claim that CO2 ‘traps heat in the atmosphere’. Yet atmospheric temperature is NOT a measure of heat content. Such people not only use temperature, they average the temperature showing their complete lack of understanding of physics.

    The enthalpy ( heat capacity ) of the atmosphere varies considerably with humidity. A misty Louisiana Bayou at 100% humidity after an afternoon storm with the temperature at 78F will hold twice as much heat energy as the air in the Arizona desert at close to zero humidity but at 100 F . This is important as it takes far less heat energy to raise the temperature at the poles where the air is very dry than it does in the tropics where the air is very humid. Averaging these atmospheric temperatures is generating a meaningless number. It is quite probable that a day starting at a low temperature with mist or radiation fog which then ‘burns off’ to a ‘warm’ afternoon actually has no significant change in atmospheric heat content as the enthalpy in the morning is extremely high with liquid water droplets and in the ‘warm’ afternoon is low with drier air.

    A correct metric for Atmospheric Energy Content would be an integral ( adding up ) of the atmospheric heat content in kilojoules ( Kj ) per kilogram ( Kg ) over the 24 hour period. This can be worked out using the existing station records using existing ‘wet bulb’ / dew point temperatures to obtain the humidity and thus the enthalpy of the air; then using the temperature to calculate the Kj/Kg. Even better just use ocean heat content as the top few meters of ocean hold as much heat as the entire atmosphere. But the climate ‘scientists‘ know these metrics do not support the cause so they keep every body arguing about minutiae of time of day of temperature measurements, adjustments of temperature measurements etc. to prevent the gullible from realizing that atmospheric temperature is not the right metric and that average global atmospheric temperature is meaningless.

    http://www.friendsofscience.org/assets/documents/FOS%20Essay/Climate_Change_Science.html#Water_vapour

  32. 432
    Hank Roberts says:

    Irony is still dead.

    “… the rise in mean sea level has thus been estimated as 3.18 mm/year …” from the page cited above at

    http://www.cmar.csiro.au/sealevel/index.html

  33. 433

    Over the past half century, SLR has average about 2 mm/yr.

    And now it is nearly 3.2 mm/yr. In 2011 it was 5 mm/yr. In 2010 it was decreasing, apparently, which is disturbing. In the recent past it has been as much as 30 mm/yr. Theory and historical records clearly indicate that this recent acceleration of sea level rise isn’t going to stop and that what we are witnessing now is a reorganization of ocean currents and heat reservoirs. Very serious stuff to even the moderately informed. There is approximately 70 meters of sea level rise in the pipe, and plenty enough identified carbon reserves and entrained methane to melt it all.

    You can flail around all you want, Dan, it’s both amusing and entertaining, but my recommendation to you is stick with what you know best – Christianity.

  34. 434
    Unsettled Scientist says:

    Sphaerica (Bob),

    Here are some links that I think will help you out:

    http://www.atmosphere.mpg.de/enid/20c.html

    “Why does the stratosphere cool?

    “There are several reasons why the stratosphere is cooling. The two best understood are 1) depletion of stratospheric ozone, 2) increase in atmospheric carbon dioxide.

    “Cooling due to the greenhouse effect

    “The second effect is more complicated. Greenhouse gases (CO2, O3, CFC) absorb infra-red radiation from the surface of the Earth and trap the heat in the troposphere. If this absorption is really strong, the greenhouse gas blocks most of the outgoing infra-red radiation close to the Earth’s surface. This means that only a small amount of outgoing infra-red radiation reaches carbon dioxide in the upper troposphere and the lower stratosphere. On the other hand, carbon dioxide emits heat radiation, which is lost from the stratosphere into space. In the stratosphere, this emission of heat becomes larger than the energy received from below by absorption and, as a result, there is a net energy loss from the stratosphere and a resulting cooling. Other greenhouse gases, such as ozone and chlorofluorocarbons (CFC’s), have a weaker impact because their concentrations in the troposphere are smaller. They do not entirely block the whole radiation in their wavelength regime so some reaches the stratosphere where it can be absorbed and, as a consequence, heat this region of the atmosphere.”

    A couple other links that might be useful:

    http://www.wunderground.com/resources/climate/strato_cooling.asp

    http://scienceofdoom.com/2010/04/18/stratospheric-cooling/

  35. 435
    SecularAnimist says:

    Mike wrote: “Can someone help me with this engineer’s opinion? Water vapor records are available from every weather observation station – but are never used as the climate ‘scientists‘ like to incorrectly use temperature as a metric for heat energy which the gullible and scientifically ignorant media get excited about.”

    So it is your “opinion” that climate scientists deliberately deceive the public by deliberately choosing “incorrect metrics”, and it is apparently also your “opinion” — as I infer from your use of scare quotes around the word “scientist” — that climate scientists are not really scientists.

    Well, based on the fact that you welcomed yourself to these comment pages by slandering and insulting climate scientists, you definitely need help, that’s for sure. But you will probably need to consult a mental health professional to get the kind of help you need.

  36. 436
    Unsettled Scientist says:

    Mike, you just ranted about people not understanding physics while also saying enthalpy is heat capacity? Heat capacity is the amount of energy required to change the temperature of a gas. Enthalpy is the total energy content of a system.

    Hank, irony lives!

    Mike, also note that the conversations of the news media are driven by polemics, ideologies, etc. and do not relate the conversations scientists wish to have and are having amongst themselves. When it comes to physics, engineers are usually pretty bad at the language. For example, in thermal physics we would only consider conduction and radiation to be energy transfer mechanisms, while engineers consider convection also to be one. A physicist will make the distinction that convection does not transfer energy, it only transports it within in the system. Transfer vs transport. So we need to be careful about applying engineering language to physics. When engineers say “you don’t understand the physics” they really mean “you don’t understand the engineering” but it takes a physicist not an engineer to point this out.

  37. 437
    Unsettled Scientist says:

    Dan H. I would never use real-science as a reliable source of information, luckily your link is broken. Just do a little searching and see that Steve Goddard is like some sort of anti-science/troll/satirist. And apparently that site was either hacked or faux hacked earlier this year. Whatever is going on with that site, it’s not trustworthy.

  38. 438
    Dan H. says:

    Unsettled,
    That plot comes from the Church & White 2011 data, whereby they state that the trend since 1961 is 1.9mm/yr. See the link provided by Gavin above. The most recent decade is similar to the past half century. Yes, SLR accelerated during the 1990s (up until ~2002). However, many people have failed to notice that the SLR has decelerated recently, instead, preferring to include the timeframe of highest SLR in their calculations in order to show a continued acceleration. Others have noticed this cherry picking and pointed it out above.

  39. 439
    RickA says:

    443 Thomas Lee Elifritz:

    “There is approximately 70 meters of sea level rise in the pipe . . .”

    Over what time frame?

    The sea has been rising for 20,000 years, and has risen over 120 meters over that time.

    Obviously the sea rose much faster from 20,000 years to about 8,000 years ago than it is presently rising – but there has been many meters of melting in the pipeline for 20,000 years.

    After all, we are in an interglacial – isn’t this to be expected?

  40. 440
    RickA says:

    I just saw this headline in my Google reader:

    Students discover methane seep ecosystem
    from ScienceDaily: Latest Science News
    During a recent oceanographic expedition off San Diego, graduate student researchers discovered convincing evidence of a deep-sea site where methane is likely seeping out of the seafloor, the first such finding off San Diego County.

    My question is how much methane is seeping naturally into the atmosphere – and how much of the warming over the last 150 years can be attributed to natural methane seeps?

    Has anybody looked at this?

  41. 441

    #431–Mike, you might also note that:

    1) specific humidity has been increasing:

    http://www.sciencemag.org/content/310/5749/841.abstract

    2) ocean heat content has been increasing:

    http://oceans.pmel.noaa.gov/

    These facts would seem to be rather at odds with the perspective you describe.

    And about ‘average’ temperature–would you regard the statement (linked below) that 2.59 persons live in the ‘average’ US household as ‘meaningless?’

    http://quickfacts.census.gov/qfd/states/00000.html

  42. 442

    RickA, #439–“Has anybody looked at [natural methane seepage?]

    Yes, of course. To give you a small start on the research, here is a Google search of “global-methane-budget”–40,000-odd hits, and I see research on the first page going back to 1991.

    Have fun!

    http://scholar.google.com/scholar?hl=en&q=global+methane+budget&btnG=&as_sdt=1%2C11&as_sdtp=

  43. 443

    Unsettled Scientist,

    Thanks, but I had already read two of those links, and the third added nothing. I understand the mechanisms perfectly. My question is purely one of relative influence; which factor is dominant (if either), the effect of less IR reaching the troposphere from below or the effect of increased IR “leaking out” from within the stratosphere.

    I can find no reference that quantifies the two effects (and perhaps there is none, because the result comes from a complex model run that does not bother to separate them).

  44. 444
    Hank Roberts says:

    Rick A. — natural methane seeps, like natural volcanos, are part of the background that has held fairly steady over the time span humans have been affecting the planet. These things have been studied a lot, there’s much of interest to read, e.g.
    http://scholar.google.com/scholar?hl=en&num=100&ie=UTF-8&q=methane+seep+rate+time
    but the natural background, before we started warming up the ocean, hasn’t been highly variable on human time scales.

    Whatever ecosystem the students discovered may be the the first in San Diego County, good for them. It’s not a new source of methane. It’s of biological interest.

  45. 445
    Hank Roberts says:

    oh, specific answer for Rick A., yes, people have estimated how much methane contribues to warming, e.g.
    http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-spm-2.html
    then take into account how much is natural vs. the estimates of human fossil fuel contribution of methane (natural gas burned, leaked, flared) and dams (which capture vegetation in deep cold water where it can rot producing methane, lacking sufficient oxygen), etc.

  46. 446

    Over what time frame?

    Over the timeframe that it takes to melt that ice. If even a fraction of the carbon reserves are emitted into the atmosphere, total melting is inevitable.

    Nothing short of a Solar L1 occultation disk or restriction to reasonable levels or a drawdown of the carbon dioxide will prevent total melting of our ice reserves from occurring. It’s guaranteed. There is no way to deny this.

    I can’t give you exact values in ppm right now, but it will soon be known. I’ll just say that 600 to 1000 ppm will be really bad.

  47. 447
    Unsettled Scientist says:

    Dan H. You completely ignored what I wrote and just repeated yourself. My two points were: 1) There is no plot, your link is broken. 2) You’re link is to a horrible site. I wasn’t talking about SLR. I’m letting other people deal with the issue of SLR, I’m dealing with the issue of your choice of sites. But we can let that die now, no need to clutter up with a continued discussion of that bad site.

    Public Safety Announcement, I would avoid clicking around the real-science website, if you try to click the search tab, it pops up a window to some random apparently identity theft website. It really a bad place to go clicking. That happens if you click in blank space too, nasty site.

  48. 448
    MARodger says:

    sidd @408
    It does appear sensible to me to consider the potential collapse of ice sheets like WAIS individually & I’d tend to the view that such events are to be expected in the longer term rather than the shorter term. (A view so far based on zip.)
    But this unsupported view raises another point that I feel is being taken less seriously than it should (& here I am in accord with the Jim Hansen message). To me, analysis is almost obsessed with calculating the SLR by 2100 and so ignores the almost inevitably big SLR in the following centuries that will result from the more ‘conventional’ melt processes. If ice sheet disintegration is a threat on a multi-century timescale, over the same timescale the metre+/century (or metre++) SLR from melt is just as siginficant but almost inevitable.
    Studies (like AR4) project SLR to 2100 and then go no further. Or if they do, they generate little discussion. (For instance, how often is AR4 figure 10.34c discussed?)
    While I might get all sarky about Jim Hansen’s 5m rise by 2100, I am in accord with his broader meaasge that a +5m rise is inevitable simply from the temperature rises we cannot avoid causing. I only disagree with the speed he predicts for such SLR to happen.

  49. 449
    MARodger says:

    Mike @431
    It’s always fun to see somebody with such a grasp of physics as yourself showing an interest in climatology. You will of course be aware that SST is a water temperature measurement somewhat resembling your preferred method of measuring an Ocean Surface Heat Content. Due to the relative size of ocean area, this sort of data represents 70% of any global average temperature.

    Of course this does leave land temperature data still measured in a manner you expressly object to.

    I would suggest that if you wish to combine surface temperature with surface specific humidity, it is probably best not to look at relative humidity readings from the upper atmosphere (like in the pretty graph you linked to) which are both not relevant to your purpose or, for the higher altitude readings, not considered to be that reliable. Perhaps HadCRUH is the sort of dataset you should be looking at, providing surface specific humidity. And would you look at that? Surface specific humidity globally is on the rise. And by the looks of it, the increase is most pronounced over land masses.
    So I assume that means you have now the convincing evidence you sought that demonstrates global warming is happening after all.

  50. 450
    RickA says:

    #446

    If all ice sheets melted, I think that is only 80 total meters in additional sea level rise. So your 70 meters is assuming almost all ice melting.

    I don’t see that happening over time frame of hundreds or even thousands of years – but only over millions of years).

    In addition, Greenland is bowl shaped, is it not, so a bunch of ice would stay in the bowl or turn into a lake.

    Second, East Antarctica just won’t melt – raise the temperature 11C and it is still below freezing their year-round.

    So I guess I am just questioning your 70 meter figure and over a time frame of?? Millions of years??


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