### Science Story: the Making of a Sea Level Study

Filed under: — group @ 6 April 2010

Guest commentary by Martin Vermeer

On December 7, 2009 the embargo expired, and my and Stefan’s joint paper ‘Global sea level linked to global temperature’ appeared in the Proceedings of the U.S. National Academy of Sciences. It had been a long time coming! But this post is not so much about the science as about the process, and about how a geodesist from Helsinki and an oceanographer from Potsdam, who to this day have never even met, came to write, to the surprise of both of us, a joint paper on sea level rise.

My own entry into climatology happened only a few years ago. A significant trigger was RealClimate, which I had learned to appreciate as one of the rare reliable Internet sources amidst the junk. Contributing to the oft-slandered science is my small ‘thank you’ and revenge as a scientist.

As I remember, it was the commenter calling himself Rod B. who enquired, sometime August 2008, what the story really was with Rahmstorf (2007). Trying to answer, I ended up reading the paper and getting interested. What seduced me was the simplicity of this, so-called semi-empirical approach: linear regression of sea level rise dH/dt against temperature T, yielding two unknown parameters: a regression coefficient a, and an intercept, or ‘equilibrium temperature’, T0. See our Ups and downs of sea level projections for a more detailed explanation.

The curve of temperature as a function of time over the 20th century has three parts: a steep rise in the beginning, a flat middle part commonly attributed to aerosols, and a very steep upswing at the end. Physically one would expect for the curve of the sea level rise rate dH/dt as a function of time to look rather similar, as indeed it does: this justifies the Rahmstorf (2007) approach of regressing the one against the other. Looking more carefully however one sees that the dH/dt curve has slightly more of an S-like shape, turning downward in the middle, before swinging up again at the end.

This suggested to me that, in addition to a proportionality to temperature T, sea level rise would also contain a term proportional to the time derivative of temperature, dT/dt. In other words, global sea level would be a good global thermometer, but with a ‘quirk’. I could even think of a physical mechanism for such behaviour.

I contacted Dr. Rahmstorf, proposing the idea: one would expect the ocean surface to warm up rapidly to completion, contrary to the deep ocean and the continental ice sheets. This would argue for a term, in addition to the secular a (TT0) term, of form b dT/dt. Stefan’s response was cautious; not surprising, as being something of a media figure in Germany surely means that he has to contend with his share of cranks. But he suggested I look myself into the idea, which I subsequently did: in for a penny, in for a pound.

I downloaded Stefan’s script, modified it, did the first computations with the same real tide gauge and temperature data Stefan had used — surprise: negative b. Hmmm, strange. That was for real data from the real Earth; what would happen if I applied the extended relationship to simulated data from the same general circulation model (actually, an Earth system model) for the period 1900-2100 that Stefan had used in his paper for testing his relationship? This model was in one essential way very much simpler than reality: it completely lacked the contribution of land ice melting to sea level.

Stefan helpfully sent me Matlab snippets and model output, and indeed I got it all working. What was more, the disagreement found by Stefan for the late 21st Century — between sea level rise as predicted directly by the model, and indirectly through the semi-empirical relationship between temperature and sea level rise — went almost completely away when using the new, extended relationship. With a positive value for b, just as expected from theory for an ocean surface water response.

 Global sea level against time. Top, sea level rise, bottom, sea level itself. Red, sea level from observations; blue, with uncertainty band, the fit from global temperatures using our new relationship; black, the fit using Stefan’s original relationship. The thin red wiggly curve shows annual sea level values.

That was encouraging, but what again about the real data? Remember that this is real observational data from tide gauges, altimetric satellites and meteorological stations, warts and all, with a very imperfect spatial sampling both for the tide gauge data and for the surface temperature data. Nothing like the clean, formally perfect model output of truly global mean surface temperature and sea level.

At that point I was about to give up.

I remembered however Stefan mentioning a ‘reservoir correction’ and decided to see if that made a difference. It was not hard to find Chao et al. (2008), who had painstakingly compiled a list of all man-made reservoirs the world over, and the amount of water stored in them. I fitted a simple arctan function through their water storage curve and added that to Stefan’s already extended script. All that water, up to 30 mm sea level equivalent, that should have been in the ocean was progressively kept bottled up on land as dams were being built: a known correction that should be applied.

Wow. Introducing the b term had already improved the Pearson correlation r of fit from 90% for Stefan’s original relationship to 97%; nice, but hardly on its own compelling. Bringing in the Chao et al. man-made reservoir correction brought it up to 99.2%!

Slowly it dawned upon me that, hey, maybe I’m on to something real here, something based in physics: it seems the world ocean can be a remarkably good global thermometer, once you get to know its quirks.

 The world ocean, a pretty good global thermometer (drawn using GMT).

Stefan relates the moment when he realized that I had something worth publishing: January 16, when he saw the results of the ‘millennium run’ that I had done on the data he had sent me. All of the volcanic explosions over the last thousand years, which were translated first into top-of-atmosphere radiative forcing and then turned into sea water thermal contraction and a drop in modeled sea level, were faithfully reproduced in the sea levels obtained from the model temperatures by my new relationship! A beautiful performance on what are large, rapid and erratically occurring excursions in both global temperature and sea level. And that’s how Stefan came on board.

With the small number of independent data points we needed to make sure we were not ‘fitting an elephant‘, so I read up on statistics during winter 2008/2009, and in particular, information theoretical methods like the Akaike Information Criterion. The model intercomparison was useful for just that. I’m not the only one studying these ideas, and I learnt a lot from tamino and James Annan’s Empty Blog. Jaynes (2003) was also on my 2009 Christmas reading list; Hypothesis testing, null and alternative hypotheses, confidence bounds and all that, is a traditional approach to statistics that is easily misunderstood and often misused. Statistical refutations of “silly null” hypotheses abound — like the silly null of no relationship between temperature and sea level rise. If this sounds all cryptic to you, I don’t blame you. Pick up Jaynes (2003), it’s an eye-opener.

As part of his contribution, Stefan tightened up the draft paper to be suitable for submission to Nature. Nature gave us some very helpful reviews which we used to further improve our manuscript. The most useful reviewer remark had to do with the extraction of water from underground aquifers, a process potentially almost as important as the artificial reservoir storage that we did take into account — only, nowhere in the literature was there an equally painstaking accounting exercise to be found as what Ben Chao and colleagues did for the reservoirs. So, we settled for a sensitivity analysis, skillfully whipped up by Stefan.

Nature turned us down, like they do over 90% of manuscripts; had they accepted, the paper would have been out already in summer. We resubmitted to PNAS who obtained three further helpful reviews, the paper was improved yet again and finally published in December. As it happens, this landed it right on top of the Copenhagen meeting.

Stefan tells me that we have exchanged over a thousand emails in the run-up to this paper. I see some poetry in that number being close to that of the East Anglia stolen email selection. Easy, informal email plays a vital role in the work of climatologists, and the loss of trust in its confidentiality could be very disruptive for the science: if the internal discussions of an authoring team would have to be expressed with the same care as the finished product, not a lot of authoring would get done.

Would I have dared, or managed successfully, to submit to a top journal all on my own? Hardly. It is an illusion to think that you can just enter a field that’s not your own and become a productive researcher, whatever you might read or what denialists-of-service may pretend. There is a lot of domain knowledge involved, and precious little of it is simple. In this case, I did learn a lot (and I continue to do so), but this takes both a willingness to learn, and great teachers. RealClimate, and the community it represents, are an indispensable resource for that.

Still waiting for Al Gore’s cheque…

P.s. Over at Nature Stefan has a commentary on sea level today.

References

Martin Vermeer and Stefan Rahmstorf (2009): Global sea level linked to global temperature, Proceedings Nat. Acad. Sci. 2009 vol 106 no. 51 pp. 21527-21532, DOI: 10.1073/pnas.0907765106, open access link

Jonathan Overpeck and Jeremy L. Weiss (2009): Projections of future sea level becoming more dire, Proceedings Nat. Acad. Sci. 2009 vol. 106 no. 51, pp. 21461-21462, DOI: 10.1073/pnas.0912878107 link.

Stefan Rahmstorf (2007): A Semi-Empirical Approach to Projecting Future Sea-Level Rise, Science 315, 368-370, DOI: 10.1126/science.1135456 link

B.F. Chao, Y.H. Wu and Y.S. Li (2008): Impact of Artificial Reservoir Water Impoundment on Global Sea Level, Science, 320, 212-214 link

Edwin Jaynes (2003): Probability theory: the logic of science. Cambridge University Press, ISBN 0-521-59271-2.

### 237 Responses to “Science Story: the Making of a Sea Level Study”

1. 151
Gilles says:

G. the warmer : “The scenario you linked to in #128 is one such scenario but it’s not realistic.
A halfway-realistic scenario in which temperatures decrease soon enough to mitigate a large SLR would in my opinion involve a combination of the following:
1) emissions reductions
2) CO2 sequestration
3) geoengineering
I don’t think one of these on its own would realistically be enough with current technology unless perhaps extreme measures are taken. For instance I don’t think emissions can be reduced to anywhere close to zero in the forseeable future.”

I regret you don’t give any quantitative estimates : in this topics, everything is a question of numbers. Could you give an example of which temperature decrease could be reached , with which amount of GtC burnt/sequestrated , and which limit (quantitatively) on the SLR we could hope to stay within in the next centuries, if Stefan and Martin are correct ?

2. 152
Tim Joslin says:

Martin,

A fascinating post for lots of reasons. It seems to me that introducing your second term b.dT/dt into the equation is a step forward.

However, I don’t believe b is negative in the real world. This would imply a sudden sea-level rise of several mm following a cooling event, such as one caused by a volcanic eruption, which is not observed.

I suspect a problem with your water storage adjustment based on Chao et al. My initial impression, reinforced by having looked into the topic in a little more detail since you posted (see see the entry on my own blog), is that the water storage behind dams quantified in Chao et al is exceeded in magnitude by the combined effects of ground water pumping, land-use change and over-exploitation of surface water resources. The Aral Sea alone (not even including the water table in the surrounding region) lost around 1000km3 from the 1960s to c.2000, nearly 10% of the Chao et al estimate for total water storage. Fred Pearce’s book When the rivers run dry is a good read about water use (though annoyingly includes no references).

I suspect that statistically the problem occurs over the period from the 1940s to the 1970s when temperatures were flat or declining slightly. Clearly, b has to explain most of the variation in the rate of sea-level change when temperatures are fluctuating around a constant level, as over this period. Over the rest of the instrumental record, sea-level is rising (at least when smoothed), and a and b can be adjusted to fit the data.

In the real world, the rate of sea-level rise must have been declining from the 1940s to the 1970s (e.g. see the slowing rate of retreat of glaciers in IPCC Fig 4.14). Your water storage adjustment appears to produce an increase in the rate from the early 1960s. If this did not in fact occur, it seems to me that your method of determining b by the best fit to the data might well lead to an erroneous result.

To establish b more accurately would need a global inventory of all water stores including those in ecosystems such as wetlands and forests (as Pearce notes, most water is held in soils) not just those included in Chao et al.

It also occurs to me, though, that, while we’re preparing the full water inventory, it might be possible to establish b by use of the fact that it explains more variation than parameter a the shorter the time scale (Fig 3 in the Vermeer & Rahmstorf paper shows a lot of smoothing), though the approach would be less textbook and more back of envelope. The fit would not be highly significant because of noise in the data, but the best fit to the annual data and that smoothed over a small number of years would surely give the best approximation to b (you could increase the years of smoothing until b becomes stable). This could then be applied to the smoothed data, the best fit to that giving a good approximation to parameter a (which I suppose would have to be fed recursively into the analysis of the less smoothed data) and telling us something about the accuracy of the water storage adjustment.

3. 153
Anonymous Coward says:

Hank (#145),

Thanks for the link. But, the way I read them, the letters are indeed about temperatures. The thing is, the more I look into it the more I find the Matthews letter unserious.

The Caldeira & Kalding paper it cites doesn’t show what is claimed. It doesn’t explain how its ocean and CO2 flux model works (are SSTs even considered as a factor in the flux?) and I wouldn’t give it too much weight but in any case it simply doesn’t support his case. It has two unrealistic BAU-looking scenarios simulated and graphed for instance. Eyeballing them I see one emissions path peaking at 80% more GtC/year than the second but atmospheric CO2 peaks at only 15% more. Obviously 80% more emissions didn’t result in anything like 80% more forcing early on. As to the longer term, the forcing from the emissions paths (which have the same amount of carbon emitted over time) converge only 150-250 years after the fast emissions peak with this relatively simple model.
None of this is unexpected I think but it doesn’t support Matthews’ contrarian claims. The claims are verified when you get closer to equilibrium but that’s long after the forcing has peaked and, so far as I can tell, the model does not have slow feedbacks such as permafrost or ice sheets melt which would put the fast emissions scenarios on a path to higher temperatures and higher CO2 concentrations due to the higher temperatures during the first two or three centuries.
As far as I can determine, the one case that’s legitimately made in these letters is a case against delaying emissions cuts (loading the oceanic CO2 sink has a long-term cost essentially). But, while Matthews’ cavalier statements could also be used to argue against emissions cuts, I don’t think the output of these models could legitimately be used that way (nevermind their lack of realism).

I won’t rant endlessly about Matthews’ letter but there’s one thing I need to say. We have discussed how his recent claim that there is no global warming commitment is presposterous, in part because it ignores aerosols. But look at his justification for ignoring aerosols this time (in the mehodology section): “Our calculation also assumes that climate forcings other than CO2 emissions have had little influence on atmospheric CO2 concentration. This is a reasonable assumption given a near-cancellation over the past century of positive non-CO2 greenhouse-gas forcing and negative aerosol forcing.” This in the context of 1000-year simulations. The mind boggles. This assumption is going to work out great with methane after emissions finally drop (whether it be because of policy or depletion)!

4. 154
Anonymous Coward says:

Gilles (#151),

I’m sorry but there is too much uncertainty over the long-term impacts for a non-specia_list to kid around with numbers like this.
But feel free to combine Matthews (which makes everything so much simpler) with Rahmstorf & Vermeer: Feed 0.0017 centigrade multiplied by net GtC emitted (after substracting GtC sequestrated that is) into their SLR model. I wouldn’t give much weight to the result but you’d have numbers, and numbers based on the litterature instead of my musings to boot!
When it comes to “the next centuries”, the biggest uncertainty is future social and technological development anyway. I think we can agree about that.

I think the one number worth repeating is 350. Unlike GtC and the like, this number doesn’t hang on assumptions and modelling.

5. 155
Gilles says:

AC “Gilles (#154),
I’m sorry but there is too much uncertainty over the long-term impacts for a non-specia_list to kid around with numbers like this.”

I don’t think that multiplying a derivative by a relaxation time to get an order of magnitude of the global variation is exceptionally tough, nor that it requires to be a “specia_list” of the domain, since it involves only basic properties of rather simple differential equations. If this is your only argument to contradict mine, I’m afraid I wouldn’t consider that you could bring much information to me – which doesn’t imply any other personal judgement about you, of course.

6. 156
Anonymous Coward says:

Don’t be silly, Gilles: you know you need the temperature curve over the next two centuries to get the SLR. Obviously the uncertainties I was talking about regarding the climate concerns how you get from GtC to temperatures.

You have presented no “argument” by the way.

7. 157
Gilles says:

if the equations of Stefan and Martin are correct (implying dL/dt >= a (T-To) ) , obviously one only needs a lower limit on the temperature to get a lower limit on the SLR. So which lower limit of the warming do you consider as reasonable for the coming centuries, for reasonable hypothesis of fossil fuels consumption ?

8. 158
Martin Vermeer says:

Tim Joslin #152,

thank you for your interesting thoughts.

However, I don’t believe b is negative in the real world. This would imply a sudden sea-level rise of several mm following a cooling event, such as one caused by a volcanic eruption, which is not observed.

Actually, not quite true… see Grinsted at al. 2007. More relevantly perhaps, if the apparently negative b is related to a time delay as we suspect, your argument doesn’t apply either.

About the ground water (aquifer) extraction, yes, this is probably of similar order of magnitude as the reservoir storage. However, it is not just the magnitude that matters; it is also the shape of the curve as a function of time, and the shape of the reservoir correction is very special. It leads to the quality of fit becoming very much poorer when it is not applied.

What the shape of the curve of ground water extraction is, we can only guess; it could be such that the quality of fit is unaffected and the correction is absorbed into the estimated parameters — and yes, that could mean that b becomes less negative. We just don’t know at this point. For the three test functions we used in the SI (Table S1), what happened was that indeed the quality of fit was almost unaffected, and the correction was absorbed into the estimated coefficients, mostly a.

The problem with your final proposal is the natural-variability noise in the data, which blows up if you take the smoothing time much below 15 years. We looked at that a bit, and are weary of trying to extract more information from the sea level data than is there… we would really need a good, independent ground water inventory.

9. 159
Anonymous Coward says:

Gilles,
I’m not following you. If you do not make any other assumption or hypothesis than “reasonable” fossil fuels consumption, pretty much everything is possible over 200 years. I suppose a lower limit would be -0.5 centigrade (that is half a degree of cooling). I figure there’s no reason to aim lower than -0.35 and I round it down in case a future geoengineering program overshoots a bit. I don’t believe such an outcome is likely but I can’t rule it out either. It is becoming less likely every year however.

10. 160
Gilles says:

“Gilles,
I’m not following you. If you do not make any other assumption or hypothesis than “reasonable” fossil fuels consumption, pretty much everything is possible over 200 years. I suppose a lower limit would be -0.5 centigrade (that is half a degree of cooling). ”

But when you say “I suppose”, is it only wishful thinking, or do you have a real agenda to reach that ? we hear interesting things here !

11. 161
Martin Vermeer says:

> and are weary of trying to extract

Wary, actually ;-)

12. 162
Anonymous Coward says:

When I wrote “I suppose”, I meant “I figure there’s no reason to aim lower”. More cooling could in principle be acheived through geoengineering.
It’s not “wishful thinking” nor my “agenda”: it’s futurology. Two centuries is a long time.
While I would tend to support politicians willing to fund research in carbon sequestration and geoengineering, my agenda, based on what can actually be done here and now, is Hansen’s: opposing coal and unconventional oil at every turn, deep emissions cuts through fee & dividend and pilot biomass burial programs. The target I’m proposing for the next century is 350, which would probably not deliver cooling or a stable sea level. Future generations will take up that challenge if they choose to.

13. 163
Completely Fed Up says:

“161
Martin Vermeer says:
16 April 2010 at 12:54 AM

> and are weary of trying to extract

Wary, actually ;-)”

I prefer the first one…

14. 164
C. Streif says:

@AC, Eric: I am afraid the discussion about Matthews here is partly too complicated for the likes of me.
I had not realised that Matthews (2009) was controversial. Are you saying, essentially, that the conventional position is that emissions trajectory is a more important determiner of temperature outcomes than total cumulative carbon emissions? (The point I had wanted to make with citing Matttews was simply what’s in the title of the paper: global warming will be proportional to cumulative emissions, which I thought had been contested earlier.) Certainly I had not wanted to say that there won’t be ocean acidification or additiolnal effects on the biosphere (this is simply not what the paper is about.)
I was a bit surprised/confused by the reaction because it’s not that unsusual to see total emissions targets mentioned in climate change discussions. I had not been aware that that position is “contrarian”. The Matthews paper wasn’t reported as contrarian in the press. (The BBC reported it as giving politicians easy-to handle numbers to use for planning emission cuts) Also, there is another paper that Matthew co-wrote with K. Caldeira, who to my knowledge isn’t a contrarian. That paper, “Stabilizing climate requires near-zero emissions”, 2008, is also relevant to the point I had originally wanted to make, eg: we do have to cut to zero sometime in the second half of this or early in the next century if we want to stabilize climate at or below two degrees. If Matthew’s premises are right, it is not enough to reduce global yearly emissions by half (or some such number) to stabilize climate at or below two degrees. THis would only postpone the moment when we have to wean ourselves completely from fossil fuels for a few decades. So if Matthews is right, it really is a choice between reaping the benefits of fossil fuels and take the consequences, or doing without them and avoiding some consequences (not all, because it will already be to late for some.) I had understood Gilles to be saying something like that.
If all of this is doubtful/controversial, please give me some legit sources that enlighten me.
What I do see is that Matthews disagrees with Plattner on the question whether there is a warming commitment. I myself, with my layperson’s understanding, find Matthews’ assumption that there is practically no commitment improbable, as albedo feedbacks from melting and reduced snow cover should intensify for a while even after an emissions stop, and as the drop in aersols (no more coal) should result in some more warming as well; although clearly Matthews must have some of these factored in because unless for feedbacks the temperature should begin to fall immmediately after a stop in emissions and it doesn’t in his models. (see his other paper on climate change commitment).
But certainly if there is commitment it just strengthens Gilles’ position (as I understood him) that we realistically can’t stop sea level rise for the next few centuries even with strong mitigation.
Maybe someone from the RCteam could help here. And in your replies, please remember: I am an environmentally interested, scientifically literate layperson, not a climate speciali st.

15. 165
Completely Fed Up says:

“But certainly if there is commitment it just strengthens Gilles’ position (as I understood him) that we realistically can’t stop sea level rise for the next few centuries even with strong mitigation”

So if we can’t, which is better:

Year X 1m rise
Year X+Y 2m rise
Year X+2Y 3m rise

Year X+30Y 31m rise
OR
Year X 1m rise
Year X+Y 2m rise
Year X+2Y 4m rise

Year X+30Y lots m rise

?

16. 166
David B. Benson says:

Completely Fed Up (165) — The rise will be S-shaped and the maximum pssible is about 80 meters.

17. 167
Completely Fed Up says:

Dai, if we keep increasing CO2 concentrations, we get a higher and quicker rising S curve than if we stopped.

This was the illustration.

18. 168
Completely Fed Up says:

PS technically, if we raise temps enough, then for gassy enough definitions of “water”, our water level will be over 11km high.

But some would say this is good: look at the lovely steam baths the Swedish enjoy!

19. 169
Anonymous Coward says:

C. Streif (#164),

I’m not saying that the “emissions trajectory is a more important determiner of temperature outcome than total cumulative carbon emissions”. I’m saying that slowing emissions so as to limit atmospheric concentrations over the whole period would result in less warming than if the same amount of carbon was emitted faster, especially if slow feedbacks are considered. Please refer to the references I’ve already given (IPCC AR4, Hansen’s “Target CO2” paper).
The main reason why emissions should be slowed has little to do with climatology anyway. Slower emissions opens the opportunity for more drastic cuts at a later date and therefore lower cumulative emissions should that be deemed necessary. Also, years of R&D will be needed before serious sequestration programs could be started (if they’re ever started) and geoengineering would at best be even slower to jumpstart. Such programs would have the most impact around the peak of the temperature curve and fast emissions shift the peak closer to the present.

Gilles used the “total emissions” concept to argue against emissions cuts (see post #108). In my opinion, he’s not abusing a useful policy tool. He’s only stating explicitely the politically incorrect reason why this policy metric is being pushed. Recall that most wealthy countries have already failed to meet their Kyoto emissions rates. This “total emissions” business can be used as yet another delaying tactic: we’ll cut more later and we’ll meet the target just as well as if we cut now. Matthews’ simplification of the science is evidently politically motivated and it’s not surprising it’s popular.

Even if Matthews’ climatology was right, cutting emissions to zero is not necessary to acheive any reasonable target. The paper you’re talking about uses the phrase “near-zero emissions” which is not the same thing. Consumption could obviously be prolonged for an arbitrary amount of time (not just decades) with the right decline rate. Since it’s easy to come up with valuable applications for fossil fuels for which there is no efficient substitute on the horizon, you’re granting ready-made arguments to the delayers by insisting on zero emissions.
And since sequestration compensates for burning fossil fuels, I would also encourage you to use the phrase “net emissions” so as to allow for continued use of fossil fuels on a large scale if needed. It may also be worth pointing out that cutting on frivolous uses over the next decades would preserve the limited resource for truely valuable applications in the future, over centuries if needed.

As to the sea level, I think we all agree that mitigation alone can not realistically stop its rise, only the acceleration of its rise.

20. 170
Gilles says:

““But certainly if there is commitment it just strengthens Gilles’ position (as I understood him) that we realistically can’t stop sea level rise for the next few centuries even with strong mitigation”

So if we can’t, which is better:”

well, if limiting FF use has strictly no inconvenience, the answer is obvious. If it is the case, we should stop them immediately. Which “nobody advocates” (that’s the usual reply). So if nobody advocates it, it means that stopping FF HAS some inconvenience. So the answer to your question is not obvious. It’s a question of balance. Knowing that the sea level rise is unavoidable, and that all constructions and artifacts of civilization have a finite lifetime, it demands some precise comparison between the real cost of diminishing FF and the real marginal cost of increasing the SLR during an average lifetime of what could be threatened. I don’t have the answer, you probably don’t have it, and nobody has it either. Not a good starting point to convince people.

21. 171
Gilles says:

AC ;:”When I wrote “I suppose”, I meant “I figure there’s no reason to aim lower”. More cooling could in principle be acheived through geoengineering.
It’s not “wishful thinking” nor my “agenda”: it’s futurology. Two centuries is a long time.”

AC, I have nothing against futurology, but please do it in a coherent way. If we find a way of strongly reducing the CO2 concentration and inverting the temperature curve, it would also mean that CO2 is no more a problem. Hence that we shouldn’t worry too much about what we burn now. So again I don’t see a clear case where we could change the future by acting on our current consumption. Either we can’t stop the SLR below a few meters and we won’t be able to stop it anyway – or we find a way of stopping it and it will work anyway. In no hypothesis would the future of SLR strongly depend of our FF consumption in the next decades :this is not the relevant parameter.

22. 172

Gilles (171),

If we find a way of strongly reducing the CO2 concentration and inverting the temperature curve, it would also mean that CO2 is no more a problem. Hence that we shouldn’t worry too much about what we burn now.

BPL: Your “[h]ence” is a non sequitur.

1. We don’t know of any such method. It may take 100 years for one to come along. That would be too late. The climate would already be wrecked, along with human civilization.

2. We may be close to tripping the geophysical feedbacks (e.g. melting clathrates) that will make the problem impossible to fix. The time to reduce CO2 emissions is NOW. Not some unspecified future date. Hope is nice, but stupidity is counterproductive.

23. 173
Completely Fed Up says:

“So again I don’t see a clear case where we could change the future by acting on our current consumption.”

Here’es one, oh blind master:

If we don’t consume so much now, it will not have been consumed now in the future. This means we don’t have to undo that consumption.

You never acted like this when you “passed” your degree, did you, ‘cos this sort of “thinking” would have you chucked out.

24. 174
Completely Fed Up says:

“So if nobody advocates it, it means that stopping FF HAS some inconvenience. ”

And if continuing FF use has some inconvenience, then this must mean we MUST STOP NOW.

Or please show me that there is no inconvenience with using fossil fuels.

Hint: Exxon Valdes.

25. 175
Anonymous Coward says:

BPL (#172).

Strictly speaking, no “methods” would be needed. CO2 atmospheric concentration would drop without intervention (unless nasty feedbacks are triggered) and most AR4 models have temperature falling slowly without intervention as well (though they may be badly wrong).

Some methods such as loading the stratosphere with sulfate aerosols are known to affect the climate although no efficient implementation has been devised yet. On the other hand, many biomass sequestration methods have been implemented on a scall scale and there is no reason to believe they wouldn’t affect the climate on a large scale. Though CCS coal plants are controversial, even inefficient CCS would be carbon negative in combination with biogas for instance. And so on…
None of this amounts to a ready-made, scalable and efficient climate management program of course and there may well be better methods which are unproven or totally unknown but it’s not accurate to state that “we don’t know of any such method”. If you want a reference, Hansen et al. briefly outlines some methods in the “Target CO2” paper for instance.

26. 176
Gilles says:

CFU:”“So if nobody advocates it, it means that stopping FF HAS some inconvenience. ”

And if continuing FF use has some inconvenience, then this must mean we MUST STOP NOW.

Or please show me that there is no inconvenience with using fossil fuels.

Hint: Exxon Valdes.”
CFU, show me something without any inconvenience. Even eating can produce diseases. So stop eating.

I have no binary world : YOUR world is binary (fossil fuels are evil, stopping them is good). My world is complex, and I humbly recognize that I don’t know enough to tell mankind what to do. I admire you so much to know so perfectly what it should…

27. 177
Gilles says:

“BPL: Your “[h]ence” is a non sequitur.

1. We don’t know of any such method. It may take 100 years for one to come along. That would be too late. The climate would already be wrecked, along with human civilization.

BPL, we focus here on the problem of sea level rise. Please don’t make me explain again everything from the beginning !

28. 178
EFS_Junior says:

#107 Philip Machanick says:
9 April 2010 at 6:16 AM

“Waqidi Falicoff #66: Maunder minimum? Tell your buddy to check out the latest satellite AMSU-A data as explained at my blog.

As to your direct question, why is it reasonable (as in the blog you refer to) to set dH/dt to a constant? Note that the author’s logic requires a temperature trend growing as exp(-at/b). This is a growth rate that rapidly converges to zero, unless you reverse the sign by making one of the multiplied constants (a or b) negative. Big surprise: it results in constant sea level rise when you plug it into the equation given in the paper covered here. Oh and the author fibs slightly about using the same constants as in the paper in his own calculations. In the paper, b = 2.5”

and

# 120 Waqidi Falicoff says:
9 April 2010 at 2:35 PM

“To 90 (Efs_Junior) and 107 (Philip) Thanks for your comments. I have passed them on to my colleague.”

#121 Philip Machanick says:
9 April 2010 at 3:50 PM

“Waqidi Falicoff 120: my comments got snipped partway through for some reason. This is a small fraction of the problems in the article you referred to. Your colleague should download the spreadsheet if he (or she) has any numeracy at all and will find that the whole thing is a total fraud: the formulae for the graphs on the site bear no relationship to the calculations in the spreadsheet.”

Upon further investigation the integration will be correct for SLR and SLR if you use a very small dt ~ 0.0001 years, but still the assumed temperature curves are ad hoc, and produce ludicrous values for temperature before even the end of the 20th century.

But the ad hoc temperature curves really don’t do anything if you look at the spreadsheet(s) and their value for gamma (there are now 5 parts at climatesanity, but I’m just discussing the first three parts) is equal to one, this means that the first term of their eq 4 (with gamma = one as per the spreadsheets);

http://climatesanity.wordpress.com/2010/03/27/rahmstorf-2009-off-the-mark-again-part-2/

is (1 – gamma) * and desired temperature profile (temperature profile doesn’t matter as (1 – gamma) = (1 – 1) = 0!

Also the backward finite difference isn’t calculated correctly (small error introduced), they should use a central diffenence with any 3- 5- 7- or 9-point stencel.

I used a 9-point stencel with dt = one year (same as spreadsheets), but you don’t need to do this. Just calculate a*(Toffset – To) to arrive at the annual SLR slope per year.

D’oh!

I have a much better Excel spreadsheet than ClimateSanity has (tou’ll just have to trust me on this or I can send you a copy).

I’m now off to shoot down Parts 4 & 5 & however many parts that ClimateSanity choose to throw up.

Also since the assumed equation is deterministic, it is directly integrable without the need to use numerical finite differences (just a restatement from my previous post).

29. 179
EFS_Junior says:

#107 Philip Machanick says:
9 April 2010 at 6:16 AM

“In the paper, b = 2.5″

No.

b = 2.5 is obtaied in the section titled;

Testing the Dual Model on Simulated Future Sea-Level Rise.

which ClimateSanity does not use, what ClimateSanity does use are from the actual (smoothed) sea level record (“For sea level we use the data of Church and White (18) as adopted by the IPCC.”) from the V&R (2009) section;

Testing the Dual Model on Observed Data.

“The parameter values obtained are To = -0.41 +/- 0.03 K, a = 0.56 +/ 0.05 cm/(a * K), and b = -4.9 +/ 1.0 cm/K.”

NOTE: ClimateSanity (parts 4 and 5) are GIGO, the ad hoc curves they assume are not continuous with the prior time series of actual temperature data (in FEA this is called C0, C1, C2, C* continuity across element boundaries), the ad hoc temperature curves jump suddenly from the prior smoothed temperature time series (technically these ad hoc curves don’t even pass the C0 continuity test).

For example, I’ve fitted exponential curves to the entire C&H (2006) raw data that produce total temperature rises of 2, 4, and 6 degrees C in 2100 AD. Using the same constants from V&R (2009) and get very reasonable SLR and SLRR in 2100 AD (similar, but not the same as V&R (2009)).

30. 180

Gilles (177): BPL, we focus here on the problem of sea level rise. Please don’t make me explain again everything from the beginning !

BPL: And I’m pointing out that sea-level rise is a long-term problem, whereas drought is here and now and getting worse. Il faut manger.

31. 181
Gilles says:

BPL : OK, we’ll discuss that on the next thread about droughts ! I think we have a problem anyway with the demographic growth, independently of CO2 concentration. Here again depletion of fossil fuels, and increasing prices of gasoline and fertilizers, will probably be the most crucial problem in the next future.

32. 182
Completely Fed Up says:

“CFU, show me something without any inconvenience. ”

That was rather my point.

You dismiss renewables because they have an inconvenience:

#170 “So if nobody advocates it, it means that stopping FF HAS some inconvenience”

But now it’s all “well, EVERYTHING has inconvenience”.

So how does FF inconvenience draw us to any conclusion.

You don’t listen to a word you say, do you.

33. 183
Gilles says:

CFU : I don’t see your point. Everything has inconvenience, and things have also more or less advantages. The only inconvenience of renewables is that they can simply not support by themselves the industrial society. It’s not an inconvenience, it more a disability. That’s physics, how can you change it ?

34. 184
Completely Fed Up says:

“CFU : I don’t see your point. Everything has inconvenience, and things have also more or less advantages”

Which you “forgot” when talking about the inconvenience of leaving fossil fuels.

How inconvenient.

“The only inconvenience of renewables is that they can simply not support by themselves the industrial society.”

You keep repeating this canard but it’s completely unsupported and false.

“That’s physics, how can you change it ?”

No, that’s complete made up bollocks, and you won’t change it to reflect reality.

35. 185
C. Streif says:

AC (#169):
Dear AC, I certainly see eye to eye with you on immediate action (because reduction will have to be gradual to be practicable) and on avoiding frivolous use NOW. (I have done so for a long time, my yearly emissions according to the Greenpeace calculator: 4,5 tons.) And by the way I for one live in a country (Germany) that has met its Kyoto targets.
But with a long-lived gas like CO2, what I don’t see is how stabilization can be reached without getting down to zero emissions (from fuel combustion) for at least a few centuries, unless of course one uses large-scale sequestration, but then again, carbon caption and storage is not a proven technology at this point in time , even less so than nuclear fusion (which I am not waiting for to solve the climate problem, or are you?). The “proven” alternatives (like reforestation) yield far too little sequestration to make a meaningful difference. (Unless you use more arable land than the earth possesses.)
I have cited Matthews to make the point that total emissions are what counts, there is also this: http://www.nature.com/nature/journal/v458/n7242/full/nature08019.html , saying that “the relationship between cumulative emissions and peak warming is remarkably insensitive to emissions pathway (timing of emissions or peak emissions rate).” See also this http://www.nature.com/nature/journal/v458/n7242/full/nature08017.html which also usees cumulative emissions to calculate climate effects (from Stefan’s institute, so please don’t tell me it’s contrarian or “politically motivated”).
To support your argument that we won’t have to cut as radically if we cut soon, you refer me to AR4 (what chapter?) and “Hansen’s target CO2” paper. I recently read the Hansen paper. If I remember rightly, Hansen (2008 or 2009) argues that we should stabilize at 350 ppm.
Now accepting 350 as target CO2, let’s do a calculation. Current emissions (2004, Wikipedia) are in the range of 27 gigatons CO2 (=. 7,4 Gigatons C) which translate to a rise of ca. 2 ppm per year, more than double what it was in the sixties. The percentage taken up by the biosphere has so far stayed largely constant with rising emissions, so even with sinking emissions there will always be a percentage that stays in the air. One older Hansen paper (which I took a few notes from at the time) assumes a more or less constant if (to my mind) a bit high relationship of 2,1 Gigatons C giving a rise of 1 ppm CO2.
So if even a massive cut of more than two thirds (from over 7 Gigatons down to 2,1) still gives us a yearly rise of one (or more probably 0.6) ppm, how do we get back to 350 ppm and climate stabilization without fuel emissions per capita cut back almost to nil? Remember, we will soon have a population of 9 billion whith a rising living standard who will engender lots more land use change and methane and co2 from cement even if they don’t use more fossil fuels.
Rereading the 2009 (Target CO2) Hansen paper now, I find it actually supports my argument. Hansen says: “Stabilizing atmospheric CO2 and climate requires that net CO2 emissions approach zero”.
That was my point all along. See also further down: “Thus, moderate delay of fossil fuel use wil not appreciably reduce long-term human-made climate change. Preservation of a climate resembling that to which humanity is accumstomed will require that most remaining fossil fuel carbon is never emitted.”

36. 186
C. Streif says:

Gilles, #183: What you say is true for biomass (which, unless it’s waste biomass, nobody in their senses advocates any more). Or do you mean the storage problem with wind an solar? That is certainly solvable, only at the moment storage is a bit expensive; also, using a large grid that has for eample wind from the french atlantic coast as well as from the ukraine, and solar from morocco as well as turkey, will reduce the storage needs . I have not seen a single study that says that wind and solar combined can’t run an industrialized economy according to “physics”. On the contrary, the German physical society supports solar power generation in the sahara. The problem is that it’s expensive, and thatb redesigning the infrastructure for a complete switch is also very expensive (and it does use more land than nuclear or fossil). So one would have to do the switch over several generations. And presumably countries were people are still dying because of malnutrition and that have lotsb of cheap coal don’t havge enough incentives to switch because possible future benefits of mitigation don’t outweigh its present drawbacks.

37. 187
Completely Fed Up says:

“And presumably countries were people are still dying because of malnutrition and that have lotsb of cheap coal”

And they are dying despite cheap coal. They are also the least likely to be able to survive changes in the climate. Being poor is better than being dead.

Also consider that they don’t have invested capital in the old technology: mobile phone penetration in Africa beats many “first world” countries (including the USA) because they don’t have lots of copper wires and so rollout of wireless access is cheaper than buying and laying copper.

38. 188
Anonymous Coward says:

C. Streif (#185),

Regarding zero emissions, I think my point is obvious but I will elaborate: even if only the total cumulative emissions mattered (which is clearly not the case), it does not follow that emissions need to be brought down to zero to limit this total. 50 years at 100% of a baseline emission rate gives you the same total amount as 100 years at 50% or 80 years at 40% followed by 360 years at 5%.
Hansen indeed says “requires that net emissions approach zero”. This is not the same thing as bringing net emissions to zero and certainly not the same thing as stoppoing to use fossil fuels (recall the “net” part). Note also that I’m not talking about a “moderate” delay in fossil fuel use: I’m talking about delaying it so as to minimize the atmospheric fraction which requires delaying it to a significant fraction of the timescale of CO2 diffusion in the oceans (about 1000 years).

It seems we also have different socio-economic assumptions. I do not believe that a 9 billion population with rising material standards of living is likely. Nor do I believe that a two-thirds emissions cut would be particulary “massive” or challenging over several decades.
The big Saudi oil fields are not representative of the fossil fuel reserve. Much of the reserve is nearly useless, unstable and/or hard to get, small desposits that are hard or impossible to exploit economically and so on. I believe most of the resource is likely to stay in the ground irrespective of policy. I also believe the quality, easily accessed stuff will be burned sooner or later. This also informs my opinions about appropriate policies which is why I believe coal needs to be the main target and that Germany should therefore not be held up as an example.
It’s not any kind of achievement to meet Kyoto targets when the FDR uses the DDR’s quota. In my opinion, there’s a streak of denial and flight to fantasy in Germany with regards to electricity issues. The comparison with France is striking.

Humanity has sequestered carbon since ancient times and fossil fuels are the product of geologically ancient carbon as well. Biochar was famously used by amerindians for instance. Carbon sequestration through photosynthesis is well understood. Reforestation is not sequestration.
CCS is proven too, contrary to your assertion. Check the Wikipedia or something. Anyone not ideologically motivated to the point of blindness can see that. If you’re being honest, you need to upgrade your skepticism and to reconsider your choice of sources.
Frankly, I find it rich to claim that sequestration methods are not proven in order to propose a fantasy as an alternative. Technically and socially, nobody knows how to do reduce fossil fuel consumption to zero. Fossil fuel have no proven and scalabe substitutes for many valuable applications. Sequestration is realistic in comparison.

You quote Matthews but it’s not clear you’ve understood the argument. The flux of CO2 to the oceans (the biospehere is more complicated) is a function of atmospheric concentration and not of emissions as such. Matthews’ whole point is that the more carbon is emitted, the larger the share that’s going to remain airborne. The reverse is also true. Barring nasty feedbacks, there is therefore an emissions rate at which the atmospheric concentration falls and that’s not even close to zero as you imply.

Again, I would recommend against quoting papers and especially abstracts in this fashion. I did the same thing for kicks with the Matthews paper and Eric went “?!?”. You need to look at the context carefully. Usually these kind of statements are only true in particular conditions and so on. Words like “remarkably” are also meaningless while the models’ output is quite eloquent if presented well and doesn’t necessarily support the spin that’s put on it.
I think it’s also obvious that a paper talking about 2C, the G8, policies and so on is politically motivated. Hansen is politically motivated too of course… only I like his politics.
But when the paper you reference says that a cumulative emissions target is more robust to scientific uncertainty than a concentration target, it’s transparently dishonest. What is achieved by ignoring uncertainties? Cumulative emissions is an accounting notion that plays no physical role in the climate system. It legitimzes irresponsibility whereas feedbacks need to be taken into account in order to reach a concentration target. Concentrations have a real effect and we can therefore infer reasonable targets from paleo evidence (see Hansen et al.). We have no such basis for limiting cumulative emissions.
Much of the litterature gives too much weight to abstract models and arbitrary statistics when it comes to formulating policy and ends up ignoring the biggest climate risks. Watch out for that! I don’t have a problem with purely scientific papers that use an unrealistic framework but when scientists advocate policies we need to call them on it whether they’re doing it in scientific journals or not. Slowing emissions in the short run and reaching lower atmospheric concentrations of GHGs in the long run is what mitigates these risks in the real world.

39. 189
Gilles says:

CFU : ”
Which you “forgot” when talking about the inconvenience of leaving fossil fuels.How inconvenient.”

sorry to contradict you, I didn’t “forget” that. That’s exactly the question I’m asking: how inconvenient? meaning, at which level the use of fossil fuels will bring more inconvenience than advantages ? of course this can be answered only if you make a rather precise balance between them, which is obviously not the case if you simply state “FF are bad”.

“The only inconvenience of renewables is that they can simply not support by themselves the industrial society.”
You keep repeating this canard but it’s completely unsupported and false.”

OK, let me know the objective facts that show that the development of industrial civilization is more correlated with the average temperature, or rather the temperature change , than with the use of fossil fuels ? “objective fact” means a quantitative method (correlation or whatever you want) which is blindly applied in the same way on these two parameters.

Quoting AC : ” Technically and socially, nobody knows how to do reduce fossil fuel consumption to zero. Fossil fuel have no proven and scalabe substitutes for many valuable applications. ”

(I would precise of course : nobody knows how to keep our way of life while reducing FF consumption to zero. There is absolutely no issue in reaching this target with a return to the ancient way of life. )

C. Streif : “I have not seen a single study that says that wind and solar combined can’t run an industrialized economy according to “physics”.

well, try to say that to chinese people ?

On the contrary, the German physical society supports solar power generation in the sahara. The problem is that it’s expensive, and thatb redesigning the infrastructure for a complete switch is also very expensive (and it does use more land than nuclear or fossil).”

It is not only the problem of price. The other problem is that electricity is far from solving all problems. Ask yourself why airlines company do not switch to electrical planes, that would be of course easily insensitive to volcanic ashes, to take a hot example. Every oil spike has resulted in an economic recession, although there was of course no shortage of electricity – explain me why the existence of expensive solar electricity could have change the littlest thing in that !! we simply do not lack electricity.

40. 190
Completely Fed Up says:

“sorry to contradict you, I didn’t “forget” that.”

Then why did you say that we couldn’t move from fossil fuels because it would be inconvenient?

You “forgot” that every change is in some ways inconvenient. Because mentioning that in that post would be… inconvenient.

41. 191
42. 192
Gilles says:

CFU : “Then why did you say that we couldn’t move from fossil fuels because it would be inconvenient?”

I don’t see where I said that. We can (technically ) obviously move away from the fossil fuels-actually we will for sure. I said this will be impossible to keep our standard of living without them. The fact that many people – including you- are so reluctant to accept this idea is just the sign that it is very hard to accept that our civilization could recede durably. And this is the precise reason why I don’t think that people will do it willingly – before being forced by nature.

43. 193
Comletely Fed Up says:

“I don’t see where I said that. ”

No, you never do admit to what you’ve said, do you.

#170 “So if nobody advocates it, it means that stopping FF HAS some inconvenience”

44. 194

Gilles (192): We can (technically ) obviously move away from the fossil fuels-actually we will for sure. I said this will be impossible to keep our standard of living without them.

BPL: Yes, you say this over and over and over and over and over until our heads want to explode. But you’ve never given a convincing argument that it’s true. A high standard of living may well depend on using lots of energy. It does NOT depend on using lots of FOSSIL FUEL energy.

45. 195
Completely Fed Up says:

“A high standard of living may well depend on using lots of energy.

Comment by Barton Paul Levenson”

In any case, such a dependency is only a loose coupling.

With more problems in such a statement as, as another poster pointed out, the definition of “standard of living” has not yet been proposed.

46. 196
Gilles says:

“BPL: Yes, you say this over and over and over and over and over until our heads want to explode. But you’ve never given a convincing argument that it’s true. A high standard of living may well depend on using lots of energy. It does NOT depend on using lots of FOSSIL FUEL energy.”

Q : if there is no problem in producing lots of energy without lots of fossil energy, why should we produce ANY fossil fuel at all, and why don’t we forbid them simply just now?

Other related question : can you explain why all other forms of energy are optional for industrial countries (meaning you can find industrial countries without nuclear, without hydro , without wind, without solar, ), but not a single one without fossil fuels ?

rather unlikely that fossil fuels would just be cheaper than everything else everywhere (including in those countries totally deprived of them), but not much cheaper for crucial industrial uses, isn’t it?

but I guess : known facts don’t prove anything for you – hypes on the consequences of average global temperature, whose global influence on industrial societies as a whole isn’t proved by ANY fact, is much more credible.

47. 197
Anonymous says:

May I please know where you got the data values to make that graph?

48. 198

Gilles (196): Q : if there is no problem in producing lots of energy without lots of fossil energy, why should we produce ANY fossil fuel at all, and why don’t we forbid them simply just now?

BPL: I didn’t say there was “no problem” to it. Obviously we need to spend the time, money and labor to switch over. We can’t just shut off fossil fuel use. We should, however, phase it out as fast as possible.

Gilles: Other related question : can you explain why all other forms of energy are optional for industrial countries (meaning you can find industrial countries without nuclear, without hydro , without wind, without solar, ), but not a single one without fossil fuels ?

BPL: For the same reason that you could find lots of countries in 1600 without firearms, but none without swords. That was the traditional weapon, used all over the world. It did not, however, mean that it was not advantageous to soldiers and nation-states to switch to firearms.

Gilles: rather unlikely that fossil fuels would just be cheaper than everything else everywhere (including in those countries totally deprived of them), but not much cheaper for crucial industrial uses, isn’t it?

BPL: I can’t quite parse that sentence, so I don’t know how to respond to it.

49. 199
Gilles says:

“BPL: I didn’t say there was “no problem” to it. Obviously we need to spend the time, money and labor to switch over. We can’t just shut off fossil fuel use. We should, however, phase it out as fast as possible.”

But do you agree we could rather easily shut off nuclear energy (even in France !) , wind energy, and solar panels without great difficulties, replacing them with fossil fuels, and that without more labor and money that what is needed to develop them ?

so obviously something is different with fossil fuels. What is different is obvious : all other energies produce only electrical power (for which FF can also be used). But hydrocarbons have uses that cannot be entirely fulfilled by electricity. Full stop. You may desire that the reality should be different, but thinking that it will obey your desires is just childish. Again, there is no modern society without FF,there has been nowhere and never, and believing this has no particular meaning is just ignoring reality.

BPL: I can’t quite parse that sentence, so I don’t know how to respond to it

I elaborate (again) : the fact that NO industrial country has developed without FF means that, at least for some applications, FF aren’t easily replaceable.

This is NOT true for all applications, since for electricity generation, some of industrial countries have almost completely used other forms of energy (hydropower or geothermal power namely).

So the fact that BOTH
a) when it was possible, fossil fuels have indeed been replaced by other means for some specific needs
AND
b) they have never been replaced for other specific needs

proves that they are indeed very difficult to replace for needs b),(because if not there is no reason why they wouldn’t have been already replaced like a) ).

Hence I don’t see how you justify your confidence that it must be possible. You haven’t any known facts that support it.

50. 200
François says:

AFP reports that the Director of Dhaka’s CEGIS considers that the rise of sediments from the Himalayas would enable most of the Bangladeshi coastline to rise on par with the sea level.
Any clue about the actual level of sedimentation vs delta sinking?