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TonyW at 20:08 PM on 7 August 2013Toward Improved Discussions of Methane & Climate
Apparently, Shakhova and Semiletov have a paper to be published soon, in Nature. They seem very concerned about abrupt methane releases, so I'm sure that the paper will present more discussion points.
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MA Rodger at 19:20 PM on 7 August 2013How much will sea levels rise in the 21st Century?
jja @16.
I don't know if your 5m SLR by 2100 was a "throw-away" but I it is rather too high. While such a figure does appear in the lieterature, from Jim Hansen no less, do note that within Hansen & Sato 2011, the 5m rise is argued from the admitted position of it being "an improbable outlier." And the proposed non-linear solution from Hansen & Sato just makes matters worse as it requires an impossible 300mm SLR p.a. for the end of the century.
To achieve 5m SLR by 2100, indeed to achieve rates of SLR much above 20mm p.a. does require some explanation as to how the ice and the heat get together. To melt enough ice to achieve 50mm SLR p.a. would require roughly 5 ZJ p.a. which is not far from the entire energy imbalance today at the TOA. Sure the imbalance could get bigger in future decades but to expect more than 10-20% of it to get to the poles to melt ice? That does require explaining.
There is one mechanism that readily springs to mind. Ice bergs would work. They don't even need to melt to cause SLR, and bobbing round the tropics would get them to the heat as well as increasing the TOA imbalance so making more 'heat' available. But such ice berg speculation does require an answer to the question as to the source of these ice bergs because 5m of ice berg-induced SLR requires almost 2 million cu km of ice berg. That's a lot of ice.
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Riduna at 10:09 AM on 7 August 2013How much will sea levels rise in the 21st Century?
Thank you jja @ 16 - that explains everthing!
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Riduna at 10:05 AM on 7 August 2013How much will sea levels rise in the 21st Century?
William @ 15 ... "That sea level rise is for every degree that the sea warms".
Really? Then why is this not stated in the article?
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jja at 09:32 AM on 7 August 2013How much will sea levels rise in the 21st Century?
It should be noted that there are a few basic assumptions involved in the RCP4.5 assumption:
1. (Saviour Technology) CO2 carbon capture from coal plants will be implemented and emissions will be held steady state after 2035 with reduced emissions even during population growth after 2035. Current projections hold China to emit 180 GT of carbon by 2100.
2. Arctic sea ice loss rates will (magically) slow and then stop before summer seas become ice free in the arctic until after 2065 (projections around 2085) allowing for much less global albedo change and keeping summer arctic temperatures closer to the 20-year average.
3. Magically slower Arctic sea ice loss rates allow for a much slower arctic permafrost melt and associated natural emissions feedbacks.
4. Thermohaline current continues at only a very slightly decreased intensity, allowing for continued significant natural CO2 sink in the North Sea.
5. Boreal forests and boreal peat do not significantly contribute to natural emissions.
6. Greenland and Western Antarctic ice loss rates do not rise significantly due to natural feedbacks and the lack of saviour technology (CCS) to halt emissions.
7. Amazon forest carbon sequestration continues at current rates.
8. Climate forcing is consistent with a 2XCO2 sensitivity of 2.3 and not 4.3 'C per doubling of CO2 (Arctic Summmer sea ice free by 2030 scenario).
9. Natural methane sources do not increase significantly due to magically slow arctic sea ice loss.
as long as those assumptions hold true then we can stay within the RCP 4.5 scenario as well as expect only 1Metre of Sea level rise by 2100. Otherwise, the scenario is closer to 6-8C of average warming by 2100 with closer to 5Metres of sea level rise.
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william5331 at 06:17 AM on 7 August 2013How much will sea levels rise in the 21st Century?
(12) That sea level rise is for every degree that the sea warms. The 0.8 degree warming we have seen so far is in the atmosphere. Because of it's inertia, the huge sensible heat of water and the huge volume involved, it will take quite a while to see a degree warming in the sea.
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Andy Skuce at 04:42 AM on 7 August 2013Update on BC’s Effective and Popular Carbon Tax
More on the BC Carbon Tax
Mark Jaccard and another article discussing how carbon tax revenues should be spent.
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dr2chase at 01:22 AM on 7 August 2013How much will sea levels rise in the 21st Century?
@Agnostic - "Given this statement should we now be observing global mean sea level ~1.6 metres above the pre-industrial?"
AINE, but no, not yet. "Next few centuries" is a somewhat vague term, and the bulk of our CO2 excess and temperature increase are both relatively recent (another vague term). For example, from two charts that Google found for me, in 1900 our world total yearly emissions were about 2Gt CO2-equivalent, 4Gt in 1930, 8Gt in 1960, and 16Gt in 1975 (this is eyeball addition of developing and developed). 25Gt in 2000, and 32Gt in 2010. So, roughly, doubling every 30 years, but with a special bonus kick from 1960-1975.
Charts:
Developed and developing CO2e
World wide CO2Also worth noting is that the thermal mass of the oceans is incomprehensibly large. After a discussion on Slashdot I went and did the math carefully -- if the ice caps could all be dumped into the ocean and melted (but not raised to room temperature) it would cool them by only 2 degrees C. And I really do mean "incomprehensible" -- my gut gives no guidance for those quantities, I really do need to just follow the math. I think that is one thing that helps climate-skepticism to persist -- my gut, and probably most other people's, simply says "no way, that can't be right." But simple physics and arithmetic says it is.
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Tom Curtis at 00:08 AM on 7 August 2013John Christy on High Temperature Records in the US
KR @5 (and others), Christy labels his graph as a graph of standing records as at Dec 31, 2012. Thus any record formed earlier in the period, but superceded, will not appear on the graph. That is, it is a graph of standing records, not of running records. The main article discusses the difference quite clearly. Importantly, for standing records, given no trend in the data, the probability of a record is the same in each year, no matter how close to the beginning or end of the record.
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Tom Curtis at 00:03 AM on 7 August 2013John Christy on High Temperature Records in the US
Christy has short changed us on relevevant information for this graph.
To begin with, he does not tell us how many stations were operational in each year.
The total record is 128 years long, but the records are only >80 years in length. That means that for some years, at least, not all stations used recorded data in that year. Straightforwardly, in each year, for each day, there can only be as many records as there are stations collecting data on those days. So, assume all records are 81 years long. In that case, the probability of a new record on any given day for each station is 1 in 81 (and a quarter that for February 29th); and the expected number of records given no trend is just the number of stations recording on that day times the probability of a record on that day. If you have twice as many stations recording on one day as on another, you would expect twice as many records on the former day compared to the later.
As it happens, we know the records are at least 81 years long, so therefore no record starts later than 1931, and no record ends earlier than 1975. Thus during the period 1931-1975, there are 974 records for each day (ignoring missing data). In contrast, prior to 1931 and after 1975 there may be fewer records, potentially much fewer records. To make a meaningful comparison across the years we need to know the number of stations active in each year; or better yet, Christy should have normalized the plot by the number of stations active in each year.
Secondly, Christy does not tell us the duration of operation of each station.
The probability of a record for each date on any give day is 1/(station record duration in years). Thus, if one station is in operation for the full 128 years, it only has a probability of 1/128 of a record on any given day, or only 63% of the probability of a daily record . Therefore in periods in which the majority of records are of greater length, the probability of an new daily record is deflated compared to periods in which they are of shorter length.
Thirdly, Christy does not tell us whether he is using adjusted or unadjusted data.
In the early part of the record, Stevenson screens were haphazardly deployed. A multitude of other factors also effect the record. The consequence is that if Christy is using the unadjusted data, he is inflating the early record due to contaminating factors.
Fourthly, Christy does not tell us the geographical distribution of the stations.
The stations of the USHCN are more thickly concentrated in the north east of the Contigous United States (CONUS) then elsewhere, and less thickly concentrated in the south west, particularly the wouth west excluding California. The result is that, with two years of equal mean warmth over the CONUS, with one being hotter in the north east and the other in the south west, the former will show more record high temperatures.
Finally, Christy does not tell us which version of the USHCN he is using.
Without that data, it will be difficult to reproduce his graph, and ensure that the 974 stations include all stations with greater than 80 years of duration.
Klaus Flemløse: Very good remarks. The John Christy statistics must be verified. I have added a remark in this respect to the blog. Do you have a better formulation than mine. ?
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John Christy on High Temperature Records in the US
Indeed, Christy is presenting rather deceptive un-normalized data. The longer the record for any particular station, the fewer records will be seen, with a probability of 1/n where 'n' is the number of observations - and that is the reason why the record highs he presents seem to indicate no rise in temperatures.
A far more useful statistic is the ratio of highs to lows, as discussed in Meehl 2009 (see a SkS article on the paper here); the ratio cancels out the number of observations, normalizing for the length of observation, and leaves behind trends in record observations.
[Source]
Once again, this demonstrates how selecting an accurate yet out of context subset of data (cherry-picking) can present misinterpretations of reality.
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Alexandre at 22:44 PM on 6 August 2013John Christy on High Temperature Records in the US
Of course: number of records is very different from a temperature time series, but it sounds a lot like the same to the layman.
Early in the record you'll probably have a lot of record breaking. I'm sure no Olympics had as many Olympic records as Athens 1896...
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Jos Gibbons at 22:37 PM on 6 August 2013John Christy on High Temperature Records in the US
It’d be good to see a bar chart similar to Christie’s in which each of his bars’ height is divided by the number of years up to and including the year that bar occurs in, so the years can be fairly compared, and one would presumably see an obvious warming trend even by eye. Could anyone here post either such an image or tabulated data that could be used to build one?
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Buddy at 22:21 PM on 6 August 2013John Christy on High Temperature Records in the US
Isn't a more "accurate" measure of "land surface" climate change, the use of the RATIO of "new daily record highs" to "new daily record lows"? With the passing of time, the probability of new record highs AND new record lows.....drops. But in a warming climate, the RATIO will be > 1.0 over the longer term (decades and centurys).
The graphs linked below, show three time frames of the ratio of New Daily Record Highs....to New Daily Record Lows. The first link shows the ratio on a DECADAL time frame, and the second graph shows the ratio on a YEARLY time frame....and the third link shows the ratio on a MONTHLY time frame (for the previous 13 months).
DECADAL: http://climatechangegraphs.blogspot.com/2012/08/ratio-of-new-record-high-temps-to-new_30.html#!/2012/08/ratio-of-new-record-high-temps-to-new_30.html
YEARLY: http://climatechangegraphs.blogspot.com/2012/08/ratio-of-new-daily-record-high-temps-to.html#!/2012/08/ratio-of-new-daily-record-high-temps-to.html
MONTHLY (last 13 months): http://climatechangegraphs.blogspot.com/2012/08/ratio-of-new-record-high-temps-to-new.html
Not surprisingly.....there is "variability", and the shorter the time frame, the more the variability. However, on an annual basis or a decadal basis.....the upward trend is clear.
Klaus Flemløse: I have linked to this graphs in the last part of the blog post !
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bouke at 17:59 PM on 6 August 2013John Christy on High Temperature Records in the US
What do you mean by "The expected number of records for the current year is calculated by definition"?
KFL:I will change the this to "is calculated by 1/n"
What is a "balance year"?
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Andy Skuce at 11:48 AM on 6 August 2013Toward Improved Discussions of Methane & Climate
None of the references in the Guardian article point to observations of shallow gas hydrates on the ESAS. There are shallow gas hydrates (around 60 metres depth) reported in Yamal, some 2000 km away, but those are (according to the author) relict hydrates thought to have been formed when that area was overlaid by an icesheet (or a marine transgression) and have been preserved in a metastable form after disappearence of the icesheet (or regression of the sea). As far as I know, nobody has proposed those kinds of events in this part of eastern Siberia. On the contrary, the local sea level on the ESAS has risen since the last glacial maximum, submerging the permafrost that formed when the shelf was exposed land.
All of the references cited show that hydrates form below 200 metres depth in areas of permafrost. The Shakhova et al 2010 paper does not present any geophysical or sampling evidence for hydrates above 200m on the ESAS. Permafrost, yes, gas leaks yes, but not shallow hydrates.
There's little doubt that a warming climate will provide huge carbon cycle feedbacks in the Arctic, from both carbon dioxide and methane. MacDougall, Avis and Weaver have showed that, by the end of the century, feedbacks from thawing land permafrost will increase temperatures by 0.25 to 1.0 degree Celsius from carbon dioxide emissions alone. That's 174 billion tonnes of carbon emissions over the next several decades in their median case. For me, that's more worrying than conjectural methane eruptions from the ESAS. Having said that, I will be following the future research results there with interest and anxiety.
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johnroberthunter at 10:37 AM on 6 August 2013How much will sea levels rise in the 21st Century?
Two points:
(1)
"A draft version of the next report from the IPCC (AR5), due for publication in 2014, was recently leaked. Although the information is subject to change, the draft report says sea levels are likely to rise by between 29 and 82 centimeters by the end of the century, (compared to 18-59 centimeters in the 2007 report)."
- this is comparing apples with oranges. There are at least three differences in the ways in which each of these projections were derived: (a) the "18-59 centimetres" quoted for the 2007 report does not include an adjustment of 0-0.17 m for "scaled-up ice sheet discharge" which accounts for dynamic land-ice processes not otherwise simulated by the glaciological models, (b) the periods are different (roughly 1990-2095 for the 2007 projections and 1995-2090 for the AR5) and the "emission scenarios" are different (as indicated in the article; the highest "scenarios" being A1FI for the 2007 projections and RCP8.5 for the AR5). All these differences need to be taken into account before a meaningful comparison can be made.(2) The "in the pipeline" effect is predominantly due to the fact that a substantial proportion of the greenhouse gases that we emit stay in the atmosphere for a very long time (millennia). So it's as if we've turned up the heating to our house and left it on "high" - the house (and the Earth) takes a long time to come into equilibrium with this enhanced level of heating (e.g. the oceans have to warm and land-ice melts).
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Riduna at 10:26 AM on 6 August 2013How much will sea levels rise in the 21st Century?
“For every degree of warming, sea levels will rise by more than 2 meters in the next few centuries. The Earth's temperature has already risen 0.8 degrees C over pre-industrial temperatures.”
Given this statement should we now be observing global mean sea level ~1.6 metres above the pre-industrial?
AR4 estimates of mean sea level rise are notable for excluding the contribution made by the mass loss of polar ice sheets. Will the IPCC rectify this in the forthcoming AR5?
Given that mass loss from both the WAIS and GIS are accelerating and already exceed some modeling, how confident can one be of the prognosis that mean sea level will rise by no more than a maximum of 1.5 metres this century?
How does mean sea level rise this century predicted in this article compare with the certainty of a 2°C average global temperature rise and the possibility of a 4°C-6°C rise before 2100?
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Tom Curtis at 09:04 AM on 6 August 2013Toward Improved Discussions of Methane & Climate
Also with reference to the Guardian article, the claims that the Arctic was not ice free in the summer during at least part of the Eemian are very likely wrong. I base that claim on the facts that there is solid evidence that the Arctic was ice free in summer durring the Holocene Climactic Optimum when temperatures were comparable with current temperatures, but major ice sheets persisted, such that albedo forcing in the Arctic was less than currently. Further, current temperatures are sufficiently high (or very close) to force an ice free summer. The Eemian had a more extended period that was at least as warm as current temperatures, and those of the HCO and more likely than not, was slightly warmer. Given that, it is implausible that the Arctic was not ice free in summer during at least part of the Eemian.
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TomR at 08:53 AM on 6 August 2013How much will sea levels rise in the 21st Century?
I'm not an expert, but I think "in the pipeline" refers to excess heat that will be retained by the carbon dioxide and other GWGs in the future even if we stop increasing the 400 parts per million already in the atmosphere. That CO2 will be there an average of roughly 400 years. Also, it's not that 90% of all the sun's energy is absorbed by the sea, but that 90+% of the excess heat retained by planet Earth that is absorbed by the sea. The majority of the sun's energy is reflected or is radiated back into outer space. Unfortunately, the small excess absorbed and not radiated back into outerspace is going to wreck massive destruction on our planet, including the U.S. and its population.
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perwis at 07:28 AM on 6 August 2013How much will sea levels rise in the 21st Century?
I mean *good* post
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perwis at 07:26 AM on 6 August 2013How much will sea levels rise in the 21st Century?
Good and important stuff! Thanks!
Typos: "RPC" should be "RCP"
Rahmstorf 2011 compares a number of different studies, most seem larger than Jevrejeva 2011.
Aslak Grinsted discusses the very long term in a recent goof post:
http://www.glaciology.net/Home/Miscellaneous-Debris/glacierprojections
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rootsmusic at 06:37 AM on 6 August 2013It hasn't warmed since 1998
For all the posts I read about the warming trend having apparently stabilized I don't find any arguments for enthalpy as a sink consuming vast amounts of excess atmospheric heat. I've only had a basic technical physics education so, while I feel a bit out of my class trying to contribute something substantive to the discussion, a review of the chapter on Properties of Heat and Heat Transfer in my physics text raised my eybrows relating to this topic.
1 calorie of heat will raise the temperature of 1 gram of water 1 degree Celsius.
Effect of Enthalpy - To raise a gram of water the degree across which it changes state from ice to liquid requires 80 calories in order to break down the crystaline structure of the ice.
Eighty times as much is an enourmous increase in heat consumption and since enthalpy is taking place in the worlds ice packs it can be considered work that the global heat is doing. While it's somewhat valid for the denier to observe a levelling off global atmospheric temperature, wouldn't it be helpful to direct their attention to the fact that the world's ice has been melting at an alarming rate at the same time this "levelling" has been apparent? In my somewhat elementary view the world's ice is a great heat sink which, at its melting point, is consuming enormous amounts of excess heat from the atmosphere and from sea water. This is the work the heat is accomplishing. This is basic physics and I believe most deniers have the mechanical aptitude to wrap their minds around that concept. I haven't seen this accounted for in any climate science articles or graphs. I just think that, if my physics isn't off the mark, if enthalpy does account for a significantly stabilizing effect on global temperature, then it might be helpful to spin some easy to read and understand pictures about it.
At any rate, I don't have the capability to scale the above argument up to the climate equation and am interested to know if it's valid and how significant is it? I don't like to think about what the temperature graphs will look like when the ice packs are gone.
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Chris Colose at 06:26 AM on 6 August 2013Toward Improved Discussions of Methane & Climate
Thanks for the comments everyone.
I've seen the Guardian's most recent response. I still think it conflates many different issues, including varying sources of CH4 releases (e.g., in his point #7, the 2009 Science paper he references with respect to the Younger Dryas are talking about wetlands, not hydrate destabilization), and still presents no evidence for a significantly new Arctic methane source to the atmosphere....again, observed methane emissions around the Arctic are not evidence that they are a new source. The point #4 about highest CH4 levels in 800k is due to direct anthropogenic activity, not hydrate destabilization, and renewed growtth in atmospheric CH4 has been attributed to a few different factors (Dlugokencky has recent literature on this). If a positive hydrate feedback exists, it is currently very small and not emerging clearly.
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Hyperactive Hydrologist at 05:04 AM on 6 August 2013How much will sea levels rise in the 21st Century?
"In the pipeliene" relates to the thermal inertia of the polar ice sheets which will potetially take hundreds or even thousands of years to stabalise in a warmer world.
I persionally think that the RCP 8.5 is currently the most likely scenario based on current and commited emissions. I also think there should have been RCP 10 scenario. Maybe this can be looked at in CMIP6.
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How much will sea levels rise in the 21st Century?
DJon - Good point, the opening post text is incorrect (I was responding just to michael sweets comment). The text should say something like:
"Even if we were to stop emitting greenhouse gases tomorrow, the oceans would continue to rise, driven by the remaining TOA imbalance."
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BWTrainer at 04:29 AM on 6 August 2013How much will sea levels rise in the 21st Century?
It's important to keep in mind this is the global average. Localities may see twice this.
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franklefkin at 03:06 AM on 6 August 20132013 Arctic Sea Ice Extent Prediction
Why didn't you step in the ring? You're not going to make it worse by pulling a Goddard and claiming long-term recovery based on one year, are you?
It's not really fair for me to guess now when it looks like most of these guesses were made months ago.
As to the Goddard ref.... 1 year data point does not a trend make.
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Rob Honeycutt at 02:52 AM on 6 August 20132013 Arctic Sea Ice Extent Prediction
I remember saying earlier this year that I thought this year would actually break last year's minimum. I'm probably going to be wrong on that point, but there are still about 6 weeks of rapid melt left.
And I noticed just today there is a shift in direction in the NSDIC chart... toward more rapid melt.
I should probably be on that list with Paul and Michael at 3m sq km.
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DSL at 02:17 AM on 6 August 20132013 Arctic Sea Ice Extent Prediction
Nope. You're sniping from the audience. Why didn't you step in the ring? You're not going to make it worse by pulling a Goddard and claiming long-term recovery based on one year, are you?
Want to predict GISS L-OTI anomaly for July?
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Djon at 02:13 AM on 6 August 2013How much will sea levels rise in the 21st Century?
@KR You didn't quite answer Michael's question. The current wording "Even if we were to stop emitting greenhouse gases tomorrow, the oceans would continue to rise, driven by the heat already stored." doesn't seem to be saying that future sea level rise is inevitable as a result of future heating that will continue until the atmosphere warms up enough for the outgoing TOA energy flow to balance the incoming energy flow. It seems to be saying that the heat that is already stored in the oceans would cause additional future sea level rise even if atmospheric temperatures were to immediately become stable.
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franklefkin at 01:44 AM on 6 August 20132013 Arctic Sea Ice Extent Prediction
Let's summarise:
Kevin - 5,000,000
dwr - 4,250,000
Roger D - 4,200,000
scaddenp - 4,100,000
KR - 4,040,000
DSL - 3,900,000
Michael sweet & Paul W - 3,000,000
L Hamilton - 2,300,000
Eternal Consumption - 1,110,00
Did I miss anyone? Quite a range. Anyone care to change their quess?
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Bob Loblaw at 00:56 AM on 6 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
dvaytw:
Apart from MA Rodger's comment, perhaps it helps to know how heat content and temperature are related. The graphs above are actually changes in heat content, relative to a baseline. This has to be the case, as the oceans did not have negative heat content in the 1960s.
Now, to get the change in heat content, you simply take the change in temperature, multiply it by the heat capacity (in J/kg/degree or J/m3/degree, whichever you prefer), and then multiply that by the number of kg (or m3, whichever you used for heat capacity), and magically you have now converted temperature changes (in degrees) to heat content changes (in Joules). To a first approximation, you could consider heat capactiy of water to be a constant for all the ocean, and then the temperature-->heat content conversion and averaging becomes one of weighting the layer temperatures by the volume or mass in each layer. It's alittle more complex when you start to take the slight variations in heat capacity due to temperature, denisty, etc., into account, but it doesn't change the big picture.
Granted, my PhD thesis (partly) involved developing a numerical model for heat transfer, so I may know a bit more about this than most, but does anyone here really think that a person that who thinks Ocean Heat Content is "very different from temperature" should be considered a reliable source? Maybe it's a surprisingly different thing to a Blog Scientist, but it's high school physics. It doesn't take much to conclude that Eschenbach is in way over his head.
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dvaytw at 00:39 AM on 6 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
Ohhh... that comment went over my head the first time. Thanks!
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How much will sea levels rise in the 21st Century?
michael sweet - "In the pipeline", or as I prefer to call it, "unrealized warming", is the change in temperature required to cancel out the current top of atmosphere (TOA) energy imbalance. It is in effect the difference between the GHG changes and the lagged climate response, mostly due to the thermal mass (inertia) of the oceans.
If climate forcings stopped changing right now, there would still be warming until the oceans caught up with previous forcing changes. As it stands, however (under current economic outlooks), changes in forcings are remaining well ahead of the climate response.
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saileshrao at 00:20 AM on 6 August 2013Toward Improved Discussions of Methane & Climate
Nafeez Ahmed's response in the Guardian is well worth reading.
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MA Rodger at 23:37 PM on 5 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
dvaytw @54.
Coinsidently, I think that's been covered up-thread @38. Still it is perhaps wothy of repeating being such a forehead-smackingly stupid piece of analysis (although you need not look far on Wattsupia to find similar stuff).
The fool was only "quite surprised" to find that a number as big as 205 could be converted into three numbers as small as 45+60+100. But only being "quite surprised" didn't stop him yet again making a fool of himself. He was after all a fool so he couldn't wait to tell the rest of the class. 'Look,' he said 'Look how the wiggles on the graph stay so close to the line at the bottom when I split the numbers up. How fantastic this arithmateratic is - numbers made small by cutting them up into seperate pieces!'
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michael sweet at 21:06 PM on 5 August 2013How much will sea levels rise in the 21st Century?
Excellent post. Many of these numbers are lower than others I have heard.
I find the first paragraph in "whats in the pipeline" to be a little confusing. Is the future sea level rise caused by heat already absorbed or is it from the current energy imbalance caused by greenhouse gases already emitted?
Hopefully scientists will forecast sea level rise more successfully than they have forecast Arctic Sea Ice.
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TonyW at 20:54 PM on 5 August 2013How much will sea levels rise in the 21st Century?
It would be interesting to see how "the most likely" estimates of sea level rise have changed over the years. Are these increasing as the science gets better? -
John Russell at 19:24 PM on 5 August 2013Toward Improved Discussions of Methane & Climate
Nafeez Ahmed has just responded to what he calls "Skeptical Science's unusually skewered analysis" in this new Guardian article.
It seems to me that when it comes to Arctic methane there's much uncertainty, and the wise course is to hope for the best but plan for the worst. Having strong opinions on this particular issue is backing oneself into a corner.
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chriskoz at 18:58 PM on 5 August 2013How much will sea levels rise in the 21st Century?
I want to nitpick on your AR5 date: you mention 2014.
But the part of AR5 relevant to this article (WG I: The Physical Science Basis) should be ready in September 2013, so just one month from now. So readers will not wait for the official document for as long as you imply.
The other parts of AR5 (WG II, WG III & synthesis) to be released successively until Oct 2014, will be mostly irrelevant to this article or not changing anything.
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dvaytw at 18:49 PM on 5 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
Guys thanks again for all input. I was wondering how you'd respond to this point from the Eschenbach article:
"The good news is that we’re measuring ocean heat content (OHC), so it’s very different from temperature. We can simply subtract the changes in the 700 metre level OHC from the 2000 metre level OHC changes, and what is left is the change in heat content for the layer from 700 metres down to 2000 metres. Can’t do that with temperature. Figure 3 shows the same OHC data as in Figure 2, except split out into distinct and separate layers, at the same scale. as Figure 2...
I was quite surprised by this result. Once I split the information up so that I could see the changes in each of the layers separately, much of the apparent change post-2001 disappeared. In Figure 2 there’s not a lot of change in 2001." -
chriskoz at 13:05 PM on 5 August 20132013 SkS Weekly News Roundup #31B
Recent marine life study by CSIRO (reported for example here and here) reveals the poleward migration pace by marine species (7.2km/y) outpacing that of the land species (6km/y) indicating the AGW impact on upper ocean waters be greater than that of surface air.
Another indication, that the latest denialists' bunkum point that "global warming has stopped for 15 years" is irrellevant to the issue at hand. It looks to me that AGW warming impact on ocean, including acidification will be greater than on land. And it is final time to start judging the changes in the ocean as primary indicators of the pace of AGW. And let's cease proclaiming the nonsense that "global warming stopped" over and over again. Unfortunately, the deniaslist who refuse to accept the fact the athmosphere holds less heat than the ocean will always have trouble understanding such simple indicator.
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Richard Komorowski at 10:41 AM on 5 August 2013Where SkS-Material gets used - Coursera's Climate Literacy Course
Thanks for the info, Baerbel. I'm already registered for both of them, so I expect we'll be meeting again on the forums.
Cheers
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Riduna at 10:38 AM on 5 August 2013Toward Improved Discussions of Methane & Climate
Will – Thanks for the ref. to interview with Dr Shakhova Deweaver
@ 9. – on your point 3: When onshore permafrost melts from the surface down, underlying permafrost inhibits drainage with the result that shallow water covered surfaces are produced. Methane produced beneath the water-table in anoxic conditions vents directly to the atmosphere unoxidised.
However, CH4 produced in the presence of oxygen, particularly where sphagnum moss is present, are largely oxidized and enter the atmosphere as CO2. It can be concluded from this that during early stages of permafrost loss most methane produced as a result of permafrost loss will enter the atmosphere as CH4 but as loss continues at greater depth and surface drainage occurs CH4 will be increasingly oxidized to CO2. Lawrence et al (2005) estimate that permafrost covering ~9.5m km2 will have thawed to a depth of 3 meters by 2100.
On your point 4: Most of the Siberian continental shelf is covered by water ≤ 50 metres deep. Methane escaping from the seabed vents to the surface through a water column which is too shallow to bring about any oxidation before it reaches the sea surface and enters the atmosphere. For CH4 escaping from the seabed to oxidize a water column of at least 200 metres is required. Methane escaping from the seabed west of Svalbad from depths of 200-400 metres is very largely but not fully oxidized or absorbed by ocean water before reaching the surface but even from these depths some CH4 is present at the surface.
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Leland Palmer at 07:58 AM on 5 August 2013Toward Improved Discussions of Methane & Climate
About the graph of the single large release in the original article-
Nice graph. It's somewhat reassuring, actually, visually.
But how does it correspond to reality?
What if that single large release of methane sets off additional releases, of various magnitudes, via increased greenhouse forcing and stimulation of both chronic and large scale individual releases?
What if that large release severely degrades the hydroxyl radical oxidation mechanism, and causes additional greenhouse forcing and a slower return to chronic methane release behavior?
What if those atmospheric chemistry effects leading to increased forcing, as postulated by Isaksen's modeling, set off additional methane releases?
Why should we limit ourselves to a single large release event scenario, when each large release could both amplify chronic releases and possibly stimulate additional large releases, via positive feedback?
What if increases in both CO2 and methane concentrations lead to higher temperatures, increasing water vapor concentrations, amplifying the combined effects of all the greenhouse gases on radiative forcing? This postive correlation between CO2 concentration and water vapor concentration is well accepted by most climate scientists.
The methane concentration graph that results could look like a jagged series of peaks, climbing up, and up, and up...
And not come down...for maybe a hundred thousand years, as apparently happened during other possible methane catastrophes, such as the End Permian.
Life could regain its former diversity...in several tens of millions of years.
Except that the sun is hotter now, than it was during the End Permian, by maybe two or thee percent- an effect that James Hansen says is equivalent in forcing to around a thousand ppm of CO2.
Apparently James Hansen has a new paper coming out, which I have not yet been able to gain access to on the web. The Guardian reports (July of this year):
The world is currently on course to exploit all its remaining fossil fuel resources, a prospect that would produce a "different, practically uninhabitable planet" by triggering a "low-end runaway greenhouse effect." This is the conclusion of a new scientific paper by Prof James Hansen, the former head of NASA's Goddard Institute for Space Studies and the world's best known climate scientist.
The paper due to be published later this month by Philosophical Transactions of the Royal Society A (Phil. Trans. R. Soc. A) focuses less on modeling than on empirical data about correlations between temperature, sea level and CO2 going back up to 66 million years.
Given that efforts to exploit available fossil fuels continue to accelerate, the paper's principal finding - that "conceivable levels of human-made climate forcing could yield the low-end runaway greenhouse effect" based on inducing "out-of-control amplifying feedbacks such as ice sheet disintegration and melting of methane hydrates" - is deeply worrying.
The paper projects that global average temperatures under such a scenario could eventually reach as high as between 16C and 25C over a number of centuries. Such temperatures "would eliminate grain production in almost all agricultural regions in the world", "diminish the stratospheric ozone layer", and "make much of the planet uninhabitable by humans."
Hansen seems to think destabilization of the hydrates via a mixture of chronic and multiple large releases over several centuries is a realistic possibility, with final effects far beyond what Chris Colose or David Archer and his collaborators think is possible. -
Andy Skuce at 05:15 AM on 5 August 2013Toward Improved Discussions of Methane & Climate
TonyW@26
Indeed there is gas seeping to the surface from deep sources on the ESAS. A paper by Cramer and Franke (2005) documented this very nicely, with sea-bed samples, gas analyses and deep seismic reflection data. I really do not know why this paper is not cited more widely, since it seems to me to be much more through and detailed than subsequent papers on the ESAS.
Yes, the methane migrates up gas chimneys through the permafrost, some of which are related to faults. However, this gas release is slow and steady, as evidenced by the fact that it is still ongoing in deeper-water parts of the shelf in the northern Laptev Sea, where there is no permafrost. It might well be the case that melting of the permafrost cap will eventually perforate it in places where it is currently continuous, but this will take time and even when it happens, what we will end up with is what we see in the N Laptev Sea and not a sudden outburst.
Here's a section from the Cramer and Franke paper, showing gas chimneys, deep structure and permafrost in the central Laptev Sea:
I have written about sub-cap methane in a series of SkS articles: Part1, Part2, Part3 and Part4. In the last one, I speculate on the origin of methane on the ESAS and give my (blogger's) assessment of the relative importance and timing of GHG emissions resulting from a thawing cryosphere. I think that the one we have to worry about most in this century is the thawing of onshore permafrost and the emissions of CO2 and CH4 that will come from biodegradation of thawed organic matter. There will be some additional releases of thermogenic methane coming from perforation of permafrost caps on land and in shallow seas, but the quantities and the timing of these releases is uncertain. Emissions from hydrates in the deep sea, under and within permafrost and (maybe) under ice sheets, may well prove substantial over longer timescales.
I would have had no problem with the Whiteman et al article if they had portrayed it as a what-if model of an unlikely worst-case-imaginable scenario. But they did not qualify it that way, instead they wrote (my emphasis, references removed):
As the amount of Arctic sea ice declines at an unprecedented rate the thawing of offshore permafrost releases methane. A 50-gigatonne (Gt) reservoir of methane, stored in the form of hydrates, exists on the East Siberian Arctic Shelf. It is likely to be emitted as the seabed warms, either steadily over 50 years or suddenly. Higher methane concentrations in the atmosphere will accelerate global warming and hasten local changes in the Arctic, speeding up sea-ice retreat, reducing the reflection of solar energy and accelerating the melting of the Greenland ice sheet. The ramifications will be felt far from the poles.
which I think is irresponsible.
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Andy Skuce at 03:13 AM on 5 August 2013Toward Improved Discussions of Methane & Climate
People should take the post by Potomac Oracle with a grain of salt since it is scientifically incoherent. Note that the site that it was referenced from is full of anti-vaccine nonsense.
I was taken, though, with the image of formaldehyde crawling along the floor into "open widows".
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wili at 03:07 AM on 5 August 2013Toward Improved Discussions of Methane & Climate
One more point/set ofquestions:
Hasn't this been a particularly long interglacial?Doesn't that mean that the relative warmth from this long period has had thousands of years now to penetrate deep into the permafrost?
Doesn't that likely make the permafrost more susceptible now to sudden shocks like seismic activity...than it has been in the past, both during the Holocene and during other, shorter interglacials?
Thanks ahead of time for any light anyone can throw on any of these areas. -
Rob Honeycutt at 02:57 AM on 5 August 2013An accurately informed public is necessary for climate policy
Terranova @63... The point of asking the question was to suggest that, at least on a certain level, Obama's statement of AGW being dangerous is inclusive of what is represented by the larger body of published research.
Whether AGW is dangerous was not an explicit aspect of Cook13, but you could easily state that it is implied by the body of research. Thus, Obama's tweet is not far from the mark, and therefore a justifiable inclusion.
Moderator Response:[JH] We've beaten this horse to death. Let's move on to another topic.
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