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Comments 42751 to 42800:
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NASA GISS adjustments introduce warming bias
Apparently so. I've commented on the subject here.
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Watts' New Paper - Analysis and Critique
Continuing from an unfinished page here:
As I pointed out on a WUWT thread that claimed adjustments were distorting the data,
It could be argued that it’s better to look at raw temperature data than data with these various adjustments for known biases. It could also be argued that it’s worth not cleaning the dust and oil off the lenses of your telescope when looking at the stars. I consider these statements roughly equivalent, and (IMO) would have to disagree.
Various replies (arguments from authority, etc) followed, mostly ignoring the rather copious literature on time of observation bias.
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BaerbelW at 03:10 AM on 31 August 2013Where SkS-Material gets used - Coursera's Climate Literacy Course
Richard Alley's course I mentioned above has been postponed until January 6, 2014:
Energy, the Environment and Our Future - Penn. State University
"Get Rich and Save the Earth…Or Else! Learn about the past, present, and possible futures of human energy use."This suits me just fine as I won't have to juggle two courses running in parallel (I'm currently enrolled in University of Melbourne's "Climate Change")!
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dvaytw at 02:47 AM on 31 August 2013NASA GISS adjustments introduce warming bias
I'm assuming this page is under construction? I'm asking because I've just been hit with this line in a debate.
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Global warming...still happening
Tamino gave an even better summary later in the thread:
If you flip a coin 10 times and all 10 flips give "heads" then you've got strong evidence the coin is biased. If you flip a coin 10 times and record the result, then repeat that process 1000 times, and one of the "flip sets" is 10 heads, you do NOT have evidence of a biased coin. If you then report the single set of 10 which gave 10 heads, without mentioning the 999 sets of 10 which didn't, you're dishonest (maybe to yourself). Does that make it clear?
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Global warming...still happening
Regarding Santer et al and time required for trend significance, Tamino posted something very interesting a few years ago:
Cherry Snow - It turns out that if you cherry-pick an extrema starting point for your trend identification (as opposed to the more frequent values near the trend), the t-value needed to establish trend significance almost doubles.
In other words, if you select a trend point such as the 1998 El Nino as your start, as done over and over by 'skeptics', it distorts the statistics such that the trend over that period is less significant, so that what would be reasonable (say, 17 years) is insufficient due to that cherry-pick.
Cherry-picking extrema end points weakens trend significance, making the oft-repeated "16 year" claims even less meaningful - they have the least trend significance of any possible data selection of that length.
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Ari Jokimäki at 00:12 AM on 31 August 2013Global warming...still happening
VeryTallGuy #2: I think your interpretation of Santer et al. makes sense, but I'm not a statistics expert.
Chriskoz #5: Sorry, the vertical axis is indeed insufficiently labeled (but it's like that already in the Chapman et al. paper). The vertical axis shows Brightness Temperature.
I don't think I said anything about total outgoing IR, but only the "characteristic absorption frequencies of greenhouse gases". The study of Chapman et al. shows that the IR absorption of said greenhouse gases has increased over the ten year study period.
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One Planet Only Forever at 23:51 PM on 30 August 2013Global warming...still happening
The indepth presentation is interesting and infromative. However, I prefer a simpler statement.
The warming since 1998 can best be evaluated after the next signifcant El Nino of the magnitude that occurred in 1998 occurs. There are other variable factors influencing the surface temperature, but the global average surface temperature history shows very strong "bumps" in the global averages when significant El Ninos are acting.
So the implication that a specific minimum number of years of data is required to establish statistical significance is not correct. The major variable influencing factors need to recur in the data being evaluated, whatever time that takes.
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mitch at 21:43 PM on 30 August 2013Abraham et al. (2013) explore the known unknowns in the oceans and global warming
Ranyl in (1): The reason that researchers don't make these available in open access journals is because that there is a cost of about 2000 dollars to make them open access. Someone has to pay for the residual cost (after volunteer reviews, etc.) of editing, formatting, posting, and maintaining the journal archive.
If I charge the 2000 dollars to a grant, then I must either cut back the pay to myself or my students, or I must cut back the number of analyses that are done. There is no free lunch.
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chriskoz at 21:31 PM on 30 August 2013Global warming...still happening
Ari,
Last figure is unreadable, especially the axis legends.
At least I can imagine on horizontal axis the values of spectral numbers where known CO2 and H2O absorption bands are. But I have no clue what is on vertical axis.
And how do you read from said figure that total outgoing IR in the spectrum shown has decreased over last decade as implied by the caption?
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TonyW at 20:17 PM on 30 August 2013The Beginners Guide to Representative Concentration Pathways - Part 3
Sorry, I meant to add that it's really not so much reserves that matter but the likely rate of production, as fossil fuels get tougher and tougher to extract (e.g. oil sands might be an enormous reserve but they won't be produced at anything like the rate of conventional oil from similar sized reserves). -
TonyW at 20:14 PM on 30 August 2013The Beginners Guide to Representative Concentration Pathways - Part 3
It's not clear to me that any consideration has been taken of energy reserves in these pathways. For example, oil use in RCP8.5 is shown rising to double what it is today? That seems unreasonable, given that even though a peak of all liquids has not been experienced, the energy content of what is produced is not substantially different from 8 years ago. It may not be possible to increase the energy from oil much in the future. If this is true, then any pathway that projects much increase would be unusable. The same applies for coal use, given that the data on coal reserves is poor but some analyses I've seen suggest energy produced from coal could well peak before mid-century, even within a decade or two. Ditto natural gas, despite the hype of fracking (US dry gas production has stalled for the last 18 months, for example).Do the RCPs take account of plausible reserve scenarios at all? I think they need to -
Lanfear at 19:25 PM on 30 August 2013Abraham et al. (2013) explore the known unknowns in the oceans and global warming
The paper in question seems to be available here.
Many a time you can google these by putting the title of the paper in quotes, and then adding the filetype:pdf definition.
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VeryTallGuy at 19:20 PM on 30 August 2013Global warming...still happening
Let's then look at the trends recently.
I used GISS, and by my reckoning, there are *no* years in the past 33 where the trend is negative.
This applies whether the trend is defined as end – to – end, or least squares best fit.
Going for the least squares best fit approach, which seems more reliable, the last time there was a 17 year negative trend was 1976, and there are only 3 in the past 50 years (’67, ’68, ’76)
On that basis, there is nothing unusual whatever about the current “pause”, indeed it is expected and could even be argued as overdue.
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Ari Jokimäki at 19:14 PM on 30 August 2013Global warming...still happening
Thanks, Shoyemore. I think that there might be a separate article on that paper in SkS in near future.
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VeryTallGuy at 19:13 PM on 30 August 2013Global warming...still happening
I think the meaning of statistical significance has been misapplied to the current hiatus/pause.
As I understand Santer (please correct me if I'm wrong) defines statistical significance as a 95% probability of a positive trend over 17 years. As applied to a "pause" in surface temperatures during a period of rising Co2, let's define that as
"During a period when CO2 rises at 1.5ppm per year, we expect, for any given year, a 5% probability that the trend across the preceeding 17 years will display a zero or negative value"
Let's define modern warming as being over the past 50 years (during which time Co2 has risen at ca 1.5ppm/year)
We then *expect* one in twenty of the past 33 years (those where we can measure the previous 17) to show a negative or zero trend for the preceeding 17.
Our prediction is then that roughly one or two years of the past 33 will have a negative trend.
Feedback on if this is a correct interpretation of the science would be much appreciated.
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shoyemore at 17:31 PM on 30 August 2013Global warming...still happening
Ari,
This paper is causing some current stir ... it may be one you would like to comment on in the light of this excellent review of papers & perhaps add to your list.
Recent global-warming hiatus tied to equatorial Pacific surface cooling
Thanks.
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Tom Curtis at 14:14 PM on 30 August 2013Human CO2 is a tiny % of CO2 emissions
YubeDude @252, I am not aware of any use of O18 as a marker of CO2 of organic origin. Of course, I am not expert in the field, so that only means it has not made it into popular presentations (or the IPCC reports). Further, searching google scholar does not readilly turn up studies using O18 as a marker for the organic origin of CO2.
I suspect it is possible in principle. However, fractionation of O18 in respiration is a confounding factor, and likely to be stronger. Further, atmospheric O18/O16 ratios will vary more with time than than C13/C12 ratios due to the fractionation of O18 in water by evaporation and condensation. No doubt there are other complexities of which I am not aware as well.
Sorry I can't help anymore.
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YubeDude at 13:18 PM on 30 August 2013Human CO2 is a tiny % of CO2 emissions
TY Tom for the reply. I understand about the carbon ratio and the meaning what I am interested in is if CO2 also caries the O-18 marker that would link that particular molecule of CO2 directly to combustion and not just a sink release or another anthropogenic use of older carbon sources such as chemical manufacturing that is petro-chemically based.
I am wondering if O-18 has any merit whitin the topic as I see no mention or research that attempts to link or associate its presence with A-CO2.
No quibble on my part as to the evidence rather just a currisoity in regards to this darn O-18. Thanks in advace for any light you may be able to shed.
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jdixon1980 at 04:21 AM on 30 August 2013Abraham et al. (2013) explore the known unknowns in the oceans and global warming
ranyl @1 Sometimes they are free, like the Trenberth paper referenced at the end (Balmaseda et al.).
The journals probably can't afford to make every important paper free. But the amazing thing is the wealth of knowledge that you can get right here for free, thanks to so many highly qualified people who, as I understand it, donate their time in writing these posts, and who also frequently engage questions and criticisms down here in the comments section.
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jja at 02:25 AM on 30 August 2013How much will sea levels rise in the 21st Century?
in the link you posted the authors cite the A2r scenario, updated with current developing country projections: "
"The RCP8.5 is based on the A2r scenario (Riahi et al. 2007), which provides an updated and revised quantification of the original IPCC A2 SRES scenario storyline (Nakicenovic et al. 2000). With a few exceptions, including an updated base year calibration (to 2005) and a revised representation of short-term energy trends, especially in developing countries, the RCP8.5 builds thus upon the socio-economic and demographic background, resource assumptions and technological base of the A2r scenario."
if you look at the final values of CH4 and CO2 atmospheric concentrations in 2100 you will see that the A2 scenario is approximately 15% below the RCP 8.5 high error margin estimation. You will also find that the A1Fl concentrations match that value much more closely.
2. This is the limitation of science, in a non-linear environment. PIOMAS has been verified by Cryosat-2. This has not been utilized in the AR5. The non-linear response of multiple coupled systems to the loss of arctic sea ice will produce traumatic shifts that are unforetolled by the AR5. The paper I quoted is published in 2008, this is not a "new" paper.
3. Your estimates of climate sensitivity are based primarily on paleoclimate data. However, you do not have a statistically signficant number of sample points for the current climate regime. So, you throw out the anomalous data that indicates that there is a much higher climate sensitivity during interglacials. You justify this because you do not understand why a runaway warming did not occur if sensitivities were actually that much higher during the interglacials.
In addition, the issues that I have brought up are not uncertainties, they are unknowns. The difference is that the unknowns are not contained in the current models. The body of evidence indicates that these unknowns (defined as proesses with impacts that are determined to be real, potentially catastrophic, but currently undefined and so not included in the model) will have effect, and that the potential effects of their cumulative impacts will surpass even the worst case scenarios.
The 3,425 ZJ cumulative energy deposition is your value not mine. I assume a current TOA imbalance of .75 W/m^2 and a 2100 TOA imbalance value of 3.5 W/m^2 (linear and proportional to RCP 8.5). Yeilding an average TOA imbalance of 2.125 W/m^2 between now and 2100, producing the cumulative energy deposition of 2,939 ZJ. I used RCP 8.5 for continuity of discussion, I do believe that RCP 10.0 is more likely given the albedo and carbon cycle feedbacks (as well as emission scenarios) posited in @16.
6. The .44 TOA came from your post@ 43 when you said, "That formula predicts a current TOA energy imbalance of 0.44 W/m^2, and a 2100 imbalance of 1.76"
you did not show your math so I reproduce it here:
1. TOA imbalace will be have constant proportionality to RF between now and 2100 (you say this is conservative)
2. Current TOA is .63, RF is 1.635(to pre-industrial) Ratio is 35.8/100
3. you then used RCP 6.5 for your calculation, I used RCP 8.5
4. 8.5 * 35.8/100 = 3.27 W/m^2
5. If I use a starting TOA of .75 then my values are slightly higher for TOA in 2100 = ~3.57. The rate of warming from the last interglacial is approximately 200X slower than current warming rates. This is an undeniable truth. The ice will necessarily melt more slowly. The Milankovich cycles are not GHG driven events. I am sure you know this.
I would ask that future discussions by AR5 reviewers list clearly and succinctly whether or not the following unknowns are contained within their models.
1. The cessation of Anthropogenic SOx emissions in 2070
2. The reduction of the OTC by 80% in 2060 and its effects on North Atlantic carbon sink.
3. The effect of drought on the Amazonian basin by year 2050 on natural carbon sequestration
4. The potential for boreal peat carbon emissions in a +4C environment
5. The step-change in annual surface temperatures produced in the arctic for an ice-free state in the summer.
6. The total emission potential from the ESAS under a regime of consistent +10C water temperatures in late summer.
7. The localized ocean warming effect on the West Antarctic Ice Shelf under a regime of 80% reduction of the OTC.
8. The projections of Western United states drought under a regime of a summer ice-free arctic in 2030.
9. Accelerated Permafrost emissions due to an ice free summer state in 2030.
10. The effects of these non-analyzed carbon cycle and albedo feedback scenarios within an environment where Carbon Capture and Sequestration is NOT utilized by developing countries and ECS for 2XCO2 is actually 4.5C.The above would be a very useful study. It would also provide a reasonable basis for the collective mea culpa due to the human race (and the Nobel Committee) when the arctic ice DOES disappear in 2030 and catastrophic warming events begin to reveal these unknowns to be real and disasterous.
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joeygoze9259 at 01:25 AM on 30 August 2013Abraham et al. (2013) explore the known unknowns in the oceans and global warming
In abstract, states that sea level rise is at 3 mm/yr. This sounds low compared to other estimates I have read. see http://www.nap.edu/openbook.php?record_id=12782&page=244
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jdixon1980 at 01:12 AM on 30 August 2013CO2 limits will hurt the poor
A dissenter/denier/contrarian/whatever friend of mine keeps bringing up the issue of forgoing fossil-fuel based industrialization being a lost opportunity to alleviate the world's worst poverty. (We generally have these discussions on my Facebook timeline.) He also brings up the whole gamut of meritless "scientific" arguments (solar activity, Milankovitch cycles, cosmic rays, nameless "natural cycles," platitudes about "uncertainty/complexity") as well as the usual conspiracy theories about AGW theory being a commie plot to bring down the west, etc., all of which made it hard for me to take his poverty argument seriously for a long time.
I'm not even sure that alleviation of poverty argument is a good argument against aggressive emissions reductions. It's just that I haven't been able to find any satisfying discussion of it on the web. This may be because the kind of analysis I would ideally like to see would probably take a lot of experts a long time to put together: I would like to see analysis of an emissions pathway that at least a majority of scientists would consider prudent (i.e., at a bare minimum avoiding any significant risk of a "Hell on Earth" scenario within the next X number of years - 100? 150?, such as requiring mass evacuations of coastal cities and low-lying island nations, etc.) in terms of what increase in power generation per capita can feasibly be distributed to the poorest regions of the world within the constraints of that emissions pathway by X date, what the difference is (if any) between that increase and the increase that would be feasible by X date in a free-for-all scenario with no emissions restrictions, and what that difference implies in terms of a sacrifice in quality of life (if any) that today's poor will have to make for the sake of avoiding climate catastrophe. I have no idea what that kind of analysis would entail, or whether it might take so long or depend on so many political unknowns (for example) that it wouldn't be worth doing, but I would like to see somebody take a stab at it.
Of course, there is another elephant in the room, which is that if our rate of consumption of global resources across the board already far exceeds Earth's ability to replenish them (see "Earth Overshoot Day," "Ecological Debt Day," which the Global Footprint Network says that we hit this year on August 20), then it's frightening to think what would happen if every country in the world had a population that consumed like America's or Europe's populations. This doesn't change the fact that some people live on appallingly little and consume far less than their fair share of resources, but it would be crazy to pursue policies aimed toward making sure that everybody in the world overconsumes to the same degree as I do in America. They have a right to scale up consumption, but not to our current level, and I have no right to remain at my current level of consumption. Reducing inequality is a noble goal, but if the Global Footprint Network is anywhere close to right, then reducing inequality will have to involve meeting somewhere in the middle or we are screwed.
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Tom Curtis at 21:18 PM on 29 August 2013How much will sea levels rise in the 21st Century?
jja @50:
1) RCP 8.5 is based on the IPCC AR4 A2 scenario (see discussion at the top of page 34).
2) Treating every newly published result that suggests worse outcomes than the consensus as gospel is not science, it is advocacy. Publication in only the first step, and until a result has had a chance to be reviewed by the scientific community at large, and responses published, or the results accepted and cited, they should be regarded as provisional at best. That you are not only seizing on such results but ignoring (equally provisional) results that point in the other direction shows very clearly that it is not the science driving your view point.
3) It is true that the ice and snow albedo feedbacks are larger than expected in the models. The models, however, include many feedbacks with significant uncertainties - and just be chance we would expect some to be under-estimated and some over-estimated. Pointing to one that is under-estimated and concluding from that that the climate sensitivity is under-estimated without out a full survey of the evidence with regard to all feedbacks is, again, not science but advocacy. Afterall, from the nature of uncertainty we expect there to be some under-estimates, and finding one tells us nothing about the overall balance.
4) Measurements of climate sensitivity from paleodata by their nature include all feedbacks. Therefore, the evidence from that source is unaffected by findings regarding the strength of particular feedbacks. If we find one feedback to be stronger, then of necessity the balance of remaining feedbacks must be weaker because the total effect of all feedbacks are already included in the estimate. As an ECS of 3 +/- 1.5 C per doubling of CO2 is a robust result from paleoclimate analysis of ECS, finding an enhanced ice and snow albedo feedback does not make an ECS greater than 4.5 C per doubling of CO2 appreciably more likely.
Given points (3) and (4), I think there can be no doubt that your scenario is a "worst case" scenario, and is not supported by the current balance of scientific evidence (no matter how well supported by a cherry picked sample of that evidence).
5) Contrary to your supposition, the 2110 ZJ (RCP 8.5) result "assumes" a TOA energy imbalance of 0.686 W/m^2 in 2014, and is consonant with Trenberth's result (although notice again your selection of the largest available value as being bedrock). The 3425 ZJ (RCP 10) result "assumes" a TOA energy imbalance of 1.115 W/m^2 for 2014. Between them, therefore, they bracket the Trenberth result, and by your logic the RCP 10 value is an overestimate. Therefore, take that value and you still need to propose a mechanism to raft a volume of ice equal to 44% of the volume of Greenland's Ice Sheet. You refuse to confront this absolute necessity in your scenario, and until you do you don't have a theory worth considering.
6) I note in passing that your maths regarding energy balances is all over the place, and way off. Thus, in your comment @47 you claim my linear estimate based on RCP 8.5 and ECS2xCO2 as assuming a current TOA energy imbalance of 0.44 W/m^2 (it actually assumes 0.6 W/m^2). You further claim that using an current imbalance of 0.75 W/m^2 would result in a mean annual imbalance of 3.65 W/m^2. The correct value is 1.525 W/m^2.
Finally,
7) Your explanation of why ice sheets melted slower coming out of the last glacial amounts to asserting that ice sheets melted slower because ice sheets melted slower (ie, the albedo reduced slower). The reasoning is circular and provides no support for your hypothesis, and gives us no reason to ignore the lessons of the past.
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chriskoz at 21:00 PM on 29 August 2013The Beginners Guide to Representative Concentration Pathways - Part 3
In find the belief in CCS by (van Vuuren et.al. 2011) surprising. Especially if you look at Figure 14: RCP2.6 in 2100 burns twice as much coal as has been in 2000. Is it realy realistic that so much coal be burned and yet the CO2 will decline from a peak of about 450ppm in mid century to current 400ppm level? That's contradictory or relying on CCS (technology not yet proven) doing this miracle. That's like the reliance on future generations to perfect that technology to 100% efficiency or to start scrubbing CO2 from the air.
I would rather expect that the renewable mixture (hydro/PV/thermal/wind/etc) to take a large chunk of energy in RCP2.6, basically replacing that big chunk of coal. Said renewables, boosted with gas to balance their intermittent nature, are proven, existing technology. But they actually take the smallest chunk in future energy mixture among all scenarios on Figure 14. How could it be, given RCP2.6 is the most agressive mitigation scenario? Does it mean that the authors "do not believe" in this technology as opposed on their reliance on CCS?
I think that either RCP2.6 on Figure 14 is erroneous, or my knowledge about CCS is incomplete: i.e. CCS is proven to be possible on 100% scale and as cheap as to successfuly outcompete the renewables by 2100. Can someone convince me to the latter?
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ranyl at 18:17 PM on 29 August 2013Abraham et al. (2013) explore the known unknowns in the oceans and global warming
Shame the paper is behind a paywall.
Would have been nice to able to read such an important topic.
Why don't researchers with such important works make them available in name of open access and proper knowledge distribution at this critical time?
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Nick Stokes at 16:17 PM on 29 August 2013The Skeptical Science temperature trend calculator
Thanks, KR
That's a surprising difference for just three extra years in the a/c calib period.
I'm not sure why, but I now get 1.57+-0.44 C/cen for Had 4 start 1980, default a/c calib (1980-2010), and no change if I switch to 1980-2013 calib.
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jja at 15:19 PM on 29 August 2013How much will sea levels rise in the 21st Century?
Tom Curtis @ 49
I am not manufacturing a worst case scenario from the clothe. The AR5 is fundamentally flawed due to unmodeled parametes (i.e. todays revelation that expected ocean acidification will lead to an additional .4C warming by 2100 due to DMS reductions and ice albedo positive feedbacks happening 6 decades before the current worst-case scenarios). Globally induced warming due to summer arctic sea ice loss will produce a non-linear behaviour in warming resulting in a step-change in warming prior to 2050. Hence the TCR is estimated higher for 2013-2050 than from 2050-2100. The ECS taken as a whole is higher for 2XCO2 than from 2XCO2 to 4XCO2. The carbon feedbacks listed in @16 coupled with the lack of CCS implementation and current projected global CO2 emissions produce a Carbon Burden of 1200PPMv by 2100. Methane burden will also increase significantly due to permafrost release and Stratospheric OH depletion increasing CH4 persistence.
These are all real and ocurring and not modeled under RCP 8.5The 2110 ZJ figure that you determined was conservative due to non-frontloading of Arctic albedo as well as the fact that you start from a lower figure than the one determined using more accurate ARGO data by Trenberth. (TOA of .75 W/m^2). The primary driver of this change in the rate of energy accumulation is the albedo change produced by the Arctic sea ice melt.
The RCP 8.5 is the A1Fl scenario as far as I can read the emissions profiles, not A2
The RCP temperature response profile models a relative linear change in temperatures. The arctic albedo and associated carbon feedbacks beginning in 2020 and peaking in 2040 will produce a decidedly non-linear response. The front-loading of deposited energy and temperature increase will greatly increase the rate of OHC deposition in the early years. basically a doubling of current RCP 8.5 projections between now and 2050 and a quadrupuling between 2050 and 2100 from current scenarios.
The temperature rise from LGM (post dryas) to Holocene Climatic Optimum was approximately 4C and occurred in 2.5k.y.a. We are talking about a 4C rise in 170 years (post 1880). The reason it is different now is that we are at the tail end of a 10 k.y.a. interglacial. if you want to look at historical analogies, the closest I can find is the Ice shelf collapse that ocurred at the end of the Eemian interglacial 125,000 years ago.
The reason the ice albedo feedback calculation is different now is because the incremental annual change between 1982 and 2012 (and I project from 2012 to 2030) will provide as much global albedo shift as over 1,000 years of warming during the transition from the LGM toward the Holocene climate optimum.
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Greenhouse Effect Basics: Warm Earth, Cold Atmosphere
Mea culpa, I often work with electronic state changes and that is my default vocabulary (in error in this case). Those are more visible/UV in range.
Vibrational (near/far IR), rotational (far IR/microwave) and combinational modes are involved in thermal IR. Radiation times for these modes are on the order of 7-15*10-6 seconds at 1atm.
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citizenschallenge at 14:40 PM on 29 August 2013Fasullo (2013) Seeks Some Levelheadedness Regarding Sea Level Variability
I'm sorry, I screwed that up "Global Sea Level: An Enigma" is by Dr. Walter Munk -
it's a so-so lecture, OK - but it's the following lecture that's the real eye opener.
~ ~ ~ ~ ~ ~ ~
"In Search of Lost Time: Ancient Eclipses, Roman Fish Tanks and the Enigma of Global Sea Level Rise"
"Jerry X. Mitrovica, Ph.D., is a Professor of Geophysics in the Department of Earth and Planetary Sciences at Harvard University, a Fellow of the American Geophysical Union, and the Director of the Earth Systems Evolution Program of the Canadian Institute for Advanced Research. ..."
~ ~ ~
"... Mitrovica will describe the important role these archaeological treasures have played in the understanding of sea-level rise and how they help scientists both "fingerprint" sources of recent sea level changes and make more accurate projections of future sea levels. ..."
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citizenschallenge at 14:31 PM on 29 August 2013Fasullo (2013) Seeks Some Levelheadedness Regarding Sea Level Variability
Great description, thanks.
~ ~ ~
If this topic interests you, check out:
Jerry Mitrovica, Harvard University on YouTube
SacklerColloquia
Finger Prints of Sea-level Rise
~ and ~
UCTV
Global Sea Level: An Enigma - Perspectives on Ocean Science
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The Skeptical Science temperature trend calculator
Nick Stokes - According to the Trend Calculator ("Show advanced options" dropdown), the default ARMA(1,1) coefficient calculation is derived from 1980-2010 data. Using 1980-2013 the reported trend is 1.56 ±0.42 °C/century, rather closer. I suspect the difference is due to different ARMA(1,1) calibration periods, with the arima function using the entire period by default.
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Tom Curtis at 12:12 PM on 29 August 2013How much will sea levels rise in the 21st Century?
jja @47 & 48, you may be seeking a worst case scenario, but you cannot just manufacture such scenarios from the whole clothe. For instance, using the RCP 8.5 forcings, and a transient climate response pegged to give a 4 C increase in temperature by 2050 as per your specification, and a equilibrium climate response of 4.5 (ie, the upper end of plausible values), the cumulative energy gain from the TOA energy imbalance from now till 2100 is 2110 Zettajoules. Thus my conservative estimate of midrange values is well within error of your "worst case" scenario. An "RCP 10.0 scenario" will only increase that to 3425 Zettajoules. In both cases, your 5 meter sea level rise requires far more than 5% of the energy stored in the system.
Further, thermal expansion of the ocean linearly correlates to increased temperature. The A2 scenario (approximately equivalent to the RPC 8.5 scenario) has an upper estimate for thermal expansion of 0.35 meters. Allowing for your greater temperature increase, that rises to 0.56 meters, well short of the 1.67 meters you assume. Therefore melting of ice must make up 4.44 meters of sea level in you 5 meter scenario. In consequence, your scenarios require the melting of the equivalent of 44% (RCP10) - 50% (RCP 8.5) by ice rafting in excess of that from normal melt and calving of icebergs. In total, you require the melting of the equivalent of 64% of Greenland's ice in just 90 years. Even your worst case scenarios do not make this plausible. You still require a well justified mechanism for such massive ice rafting.
Finally, you simply do not adress the issue of past precedents. The rate of sea level rise durring the transition from the last glacial to the holocene can be (very conservatively) estimated at 0.16 meters per century. With twice the mass of ice melted during that period than is currently available to melt from all ice sheets, and with the ice at lower latitudes and hence having a stronger ice albedo feedback, why did the ice melt so slow if you think a 5 meter sea level rise in less than a century is plausible? You are expecting 30 times the melt rate, and far more than that towards the end of the century. And you are expecting this with a weaker albedo feedback.
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Nick Stokes at 09:13 AM on 29 August 2013The Skeptical Science temperature trend calculator
KR,
Thanks, I should have looked more carefully at the discussion above. I did run the same case using ARMA(1,1)
arima(H,c(1,0,1),xreg=time(H))
and got 1.52+-0.404, which is closer to the SkS value, although still with somewhat narrower CIs.
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jdixon1980 at 08:53 AM on 29 August 2013CO2 limits will hurt the poor
Above I say "there is a very uncomfortable balancing of policy considerations to be done."
By that I don't mean to imply that I think the right course is unclear, necessarily. If it's between slowing (not halting, mind you) the alleviation of the worst poverty in the world by only allowing/helping those regions to industrialize mostly if not exclusively through non-emitting energy sources like wind/solar/hydro/geothermal/yet-to-be-perfected fourth generation nuclear/current riskier nuclear, on the one hand, and on the other hand destroying the stability of the climate to the point where mass extinction is a near certainty and the very survival of humanity is in question, obviously it is a no-brainer - we should choose not to destroy the planet.
It would be even more of a no-brainer if alleviation of poverty can be done just as rapidly and effectively without fossil fuels (using all those other energy sources) as with fossil fuels, though I doubt that is the case.
So I guess my question is, how much agreement is there as to the so-called "tipping points" that would highly likely lead to mass extinction / survival of civilization being in question? To the extent that it is "speculative," does that even matter, considering we should err very much on the side of caution when the planet is at stake?
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jdixon1980 at 08:34 AM on 29 August 2013CO2 limits will hurt the poor
skept.fr @1 I share your objection. The fact that CO2 rise and the resulting global warming impacts will disproportionately harm the poor is clear, but that is not inconsistent with the the notion that emissions reductions/limitations/caps will disproportionately harm/burden the poor. So there is a very uncomfortable balancing of policy considerations to be done.
I understand that carbon budgets proposed for climate mitagation tend to be more generous for developing countries, as they ought to be from both an equity/fairness standpoint (atmospheric CO2 being for all intents and purposes cumulative, rich countries have already heaped on way more than our fair share to keep the total within acceptable limits), and a utilitarian standpoint (people in subsaharan Africa, for example, obviously stand to improve their lives a lot more by emitting a little more CO2 than we stand to be burdened by emitting a lot less CO2).
Obviously it wouldn't benefit the most disadvantaged for richer countries to continue BAU, unless you buy into some kind of global trickle-down benefit that they will get from our marginally greater prosperity and thus greater charity/aid/whatever.
But it seems to me that the question remains to be addressed here whether mitigation of future harms from CO2 outweighs the benefits to today's poor of allowing them to rapidly industrialize by the cheapest means possible.
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MThompson at 07:50 AM on 29 August 2013Greenhouse Effect Basics: Warm Earth, Cold Atmosphere
Phil @78,
Thank you for your answer. I was indeed inquiring about KR@72 statement that "The electron relaxation time for a CO2 molecule is on the order of 10-6 seconds ..."
Furthermore, it seems that 10e-6 seems much too slow for relaxation of electronic states, and rather too fast for IR vibrational states.
Gratitude for furthering my education on this,
-M
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Phil at 07:02 AM on 29 August 2013Greenhouse Effect Basics: Warm Earth, Cold Atmosphere
KR and MThompson,
The excited electronic states of CO2 do not play a particular role in the Greenhouse effect. Any molecules that are in excited electronic states will have slightly different vibrational frequencies and so will add to the breadth of a vibrational band. However the fraction of molecules in excited electonic states will be small (as given by the Boltzmann distribution)I wonder whether MThompson was refering to KR's comment about "electron relaxation time" @72 which I must admit does seem out of place
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Greenhouse Effect Basics: Warm Earth, Cold Atmosphere
MThompson - Those IR active vibrational quantum states are exactly what is involved in the greenhouse effect. [ For those not familar, nothing like the classics as a starter: Martin and Barker 1932, The Infrared Absorption Spectrum of Carbon Dioxide, is a good place to look ]
Those IR active vibrational states (which exclude lengthwise compression/expansion vibrations, as they don't change the electronic moment of the molecule and hence don't absorb/radiate) absorb/emit thermal range EM, with multiple wavelengths in each from different excitation states. These are further expanded by various spectral broadening effects (too many to briefly list).
Beyond that, I'm not certain what you are asking. Any IR active gas can and will act as a greenhouse gas, restricting radiation to space to an altitude where the remaining gases above have something less than a 50% chance (to a first approximation) of absorbing a particular upward photon - and due to the lapse rate, that altitude will be cooler than the surface atmosphere, meaning less energy radiated to space than would be the case in an atmosphere transparent to that wavelength. The overall effect is just a reduction in effective emissivity of the surface to space, and hence a higher temperature required to radiate the incoming energy back out, to maintain conservation of energy.
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jja at 06:30 AM on 29 August 2013How much will sea levels rise in the 21st Century?
(correction to 3. above)
Subsequently, I have a worst case scenario of temperatures 1.5C higher than the RCP 8.5 worst case scenarios for 2050 and 2.5C for 2100. This earlier increase in global surface temperatures causes an exponential increase in OHC deposition (and ice melt!), leading to a tripling of total cumulative OHC energy deposion and resultant thermal expansion by 2100. 3X RCP 8.5 worst case scenario is 1.23M. My RCP worst case scenario is closer to 10.0 (see below).
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jja at 06:26 AM on 29 August 2013How much will sea levels rise in the 21st Century?
Tom Curtis
(first let me thank you for your responses and for challenging my math skills as well as my understanding!)
1. Agreed, intentionally left out as original calculation involved water not ice, this value was assumed negligible and within error estimates.2. This is true, the rate of volume increase of water from 0C to 10C is less than from 10C to 20C. The amount of water volume compared to the total volume capacity of the world's oceans is also negligible so this value is insignificant (thought slightly negative)
3. B2 scenario is not part of the discussion we are looking at worst case (according to the scenarios I posted @ 16) A1F1 in AR4 is maximum of .41M thermal Expansion and AR5 is looking like RCP8.5 maximum of .38M of thermal expansion. AR5 RCP 8.5 expects a worst case scenario 2.5C warming by 2050 above 1880 levels and ~5C warming at 2100 above 1880 levels. In their scenarios they expect arctic sea ice to last to 2080. In my scenario, the arctic sea ice becomes summer-ice free by 2020 (june 21) and may 1 ice free by 2030. In RCP 8.5 this happens in 2080. Subsequently, I have a worst case scenario of temperatures 1.5C higher than the RCP 8.5 for 2050 and 2.5C for 2100. This earlier increase in global surface temperatures causes an exponential increase in OHC deposition (and ice melt!), leading to a tripling of total cumulative OHC energy deposion and resultant thermal expansion by 2100. 3X RCP 8.5 worst case scenario is 1.23M. My RCP worst case scenario is closer to 10.0 (see below).
4. This is the key. What percent of warming will contribute to ice melt and what will contribute to expansion. Fundamentally, the variance in projections of future TOA imbalance and cumulative energy deposition in the ecosphere between now and 2100 are the only key questions for sea level rise. If the cumulative energy deposition is much greater than projections then the energy balance can be 98% ocean and 2% else and still gain 5M of rise. The real issue is how much energy will be placed into the biosphere in the next 86 years.
5. Your estimate of TOA above implied a .44W/m^2, Hansen and Soto says it is probably closer to .63 +/- .15 but recent analysis by Trenberth would indicate an even greater value due to increased rates of OHC gains that were undervalued by Hansen and Soto. So a probable current TOA would be closer to .75 +/- .15 W/m^2.
your calculation stated that current values are .44 TOA and 1.63 RF increased linearly to an RCP 6.5 and 8.5 of 1.76 and 2.3 W/m^2 respectively. You state that a linear assumption is generous on your part. (conservatively assuming worst case).My scenario assumes a significantly decreased global albedo in 2020 and a much cloudier winter arctic than now. It also assumes an exponential decline in SOx emissions beginning in 2050. These two factors alone account for over 2W/m^2 increased RF by 2070. So the linear TOA imbalance is actually a much less conservative estimate. I also expected a significant increase in anthropogenic fraction for CO2 abundance as natural carbon sinks collapse. So my analysis is actually an RCP 10.0
But still, using your linear analysis and only having an RCP 8.5 but having current imbalance as .75 not .44 we get a final imbalance of 3.65 and a similar average energy deposition to my calculation at the bottom of @44.
If, however we use a more accurate and advanced rate of arctic ice melt, as well as the other assumptions I provided in @16 you will see that the non-linear increases in RF beginning in 2020 and peaking around 2050 will front-load the rates of energy depostion leading to a much higher value than those calculated even in @44. -
MThompson at 05:36 AM on 29 August 2013Greenhouse Effect Basics: Warm Earth, Cold Atmosphere
@72
KR, Please help me understand which excited electronic states are playing a role in the greenhouse effect. I only familar with the IR vibrational quantum states.
Much appreciated.
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John Fasullo at 01:32 AM on 29 August 2013Fasullo (2013) Seeks Some Levelheadedness Regarding Sea Level Variability
Hi Chris,
Thanks for the feedback. Yes, the answer regarding other such drops in the historical record is complicated by the fact that our observations prior to GRACE and ARGO are incomplete, and prior to altimetry, are exceptionally so. We know that no comparable events occurred in the altimetry record. The gauge record of sea level is quite noisy on interannual time scales and so it is of limited use for identifying other events. There are comparable dips to that in 2010-11, but their credibility is highly questionable as they occur often and likely result from noise, not signal. And so what data to use?
If we were to argue that other events would require anomalous rainfall over Australia's interior basins comparable to that in 2010-11, then we could use the rainfall record to infer such sea level drops. In this case 1973-74 appears to be a comparable interval. Nonetheless, the assumption that the dips can only occur when Australian rainfall is high is questionable. Perhaps models will provide some perspective on this, and this is a possibility we are now exploring. Stay tuned!
In terms of 'dominant contributor', yes we did establish a % contribution. It varies somewhat depending on which GRACE product you use and at what time you evaluate the contribution. At the peak of the event, Australia made up about 50% of the storage +anomaly, with South America and North America, contributing about 30% and 20% respectively. But the anomalies in the Americas were relatively short lived whereas Australia's persisted for over a year. So at these longer time scales, Australia's influence was not only dominant, but solitary and unique.
Thanks for the informative/constructive feedback everyone! It is nice to read a blog where facts are the focus.
John
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dana1981 at 00:28 AM on 29 August 2013The Beginners Guide to Representative Concentration Pathways - Part 3
Note that we now have a 'Guide to RCPs' button in the left hand margin.
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The Skeptical Science temperature trend calculator
Nick Stokes - As per Foster and Rahmstorf 2011, the noise process is computed as ARMA(1, 1), not AR(n), as a simple autoregressive model turns out to underestimate autocorrelation in the temperature data. See Appendix 1.
This is discussed in the Trend Calculator overview and discussion.
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Nick Stokes at 23:18 PM on 28 August 2013The Skeptical Science temperature trend calculator
Kevin,
I've been puzzled about the 2σ confidence intervals on your calculator. They seem to have a high spread. I checked, for example, Hadcrut 4 from Jan 1980 to Jul 2013. The SkS calc says 1.56+-0.47 °C/Cen. But if I use the R call
arima(H,c(n,0,0),xreg=time(H))
with n=0,1,2 for AR(n), I get
1.56+-0.131, 1.55+-0.283, 1.53+-0.361
Your se seems higher than even AR(2). -
mitch at 21:31 PM on 28 August 2013The Beginners Guide to Representative Concentration Pathways - Part 3
Excellent summary--I was dreading the task of wading through the primary literature to put together a lecture on the RCP's. I assume that something is also included in the upcoming IPCC AR5 assessment report, but that is not yet available.
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ubrew12 at 19:52 PM on 28 August 20132013 SkS Weekly News Roundup #35A
The link to 'Kevin Trenberth's take on climate change' is not working for me.
I found a valid link at
http://minnesota.publicradio.org/features/npr.php?id=214198814
Moderator Response:[JH] Link fixed. Thanks for bringing this glitch to our attention.
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dvaytw at 18:41 PM on 28 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
Got it guys, thanks!
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Andy Skuce at 15:39 PM on 28 August 2013Toward Improved Discussions of Methane & Climate
Michael Tobis rebuts Nafeez Ahmed:
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