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What drives uncertainties in adapting to sea-level rise?

Filed under: — stefan @ 17 March 2016

Guest article by Sally Brown, University of Southampton

Let me get this off my chest – I sometimes get frustrated at climate scientists as they love to talk about uncertainties! To be sure, their work thrives on it. I’m someone who researches the projected impacts and adaptation to sea-level rise and gets passed ‘uncertain’ climate data projections to add to other ‘uncertain’ data projections in my impact modellers work bag. But climate scientists do a good job. Without exploring uncertainties, science loses robustness, but uncertainties in combination can become unbounded and unhelpful to end users.

Let’s take an adaptation to sea-level rise as an example: With increasing scientific knowledge, acceptance and mechanisms that would allow adaptation to potentially occur, one would think that adaptation would be straight forward to implement. Not so. Instead of hard and fast numbers, policy makers are faced with wide ranges of uncertainties from different sources, making decision making challenging. So what uncertainties are there in the drivers of change, and can understanding these uncertainties enable better decisions for adaptation?

Prior to considering adaptation in global or regional models, or implementation at local level, drivers of change and their impacts (and thus uncertainties) require analysis – here are a few examples.

Between 1901 and 2010, global sea levels rose by 0.19±0.02m, albeit at varying rates and spatial distribution (Church et al. 2013) – these past values (including their uncertainty) are potentially much smaller than those associated with future projections. Whether this precise trend will continue is uncertain, but scientists are confident that sea-levels will continue to rise and accelerate due to global warming

My background is partly in geology, so I often recall the well-known quote referring to Earth’s history ‘the present is the key to the past’ (Hutton / Lyell). In sea-level science however it might be the other way around: ‘the past is the key to the present’. Kopp et al. (2016) recently found that from the late in the 20th century sea-levels have risen faster than in any of the previous 27 centuries. Further back in time again, sea-levels have risen at much faster rates during the end of the last ice age. Past rates of change, if used wisely, provide potential constraints of future projections, together with the many semi-empirical approaches to project future sea-level rise (e.g. Rahmstorf, 2007) which are typically greater in magnitude than those from process based models. Hybrid approaches have also been undertaken (e.g.  Moore et al. 2013, Mengel et al. 2016). Scientific knowledge input into process based models has much improved, reducing uncertainty of known science for some components of sea-level rise (e.g. steric changes), but when considering other components (e.g. ice melt from ice sheets, terrestrial water contribution) science is still emerging, and uncertainties remain high. Still, our understanding has a wide range of projections, particularly for high emissions scenarios as Jevrejeva et al. (2014) illustrates. Given emerging knowledge and changes in uncertainty, this leads me to the question, what are we adapting to, and when could this occur? Is it about 1m of rise by 2100? Or 1.4m?

Planning for sea-level rise does not just depend on how much waters rise, but also how land levels change. Glacial Isostatic Adjustment (GIA) occurs in response to retreating ice from the last glacial period, where around most of the world, land is subsiding at a fraction of a millimetre per year, compounding the problem of sea-level rise. In northern latitudes the reverse is happening – land is rising after being liberated from the mass of the ice sheets, again normally by less than 1mm/yr, but in places over 5mm/yr (Peltier et al. 2015). Land levels also change due to tectonics, natural compaction of soft soils as well as human influences.

I recently researched causes of subsidence in Bangladesh (Brown and Nicholls 2015) and struggled with the uncertainties, data errors, and in some cases, poor science when recording rates of subsidence. In Bangladesh, subsidence can be much higher than GIA – with 10mm/yr being a local norm, rather than an extreme rate. A major cause can be groundwater withdrawal resulting from the needs of a growing population. These factors can be spatially highly variable, even within a short distance. Additionally, rates of subsidence also change with time (Kaneko and Toyota, 2011). Subsidence is common in deltas and projecting relative change (particularly when causes vary or are unknown) remains uncertain.

ganges-india_attila-lazar Relative land level change is extremely important in low-lying delta regions.

When I undertake an impacts assessment, land elevation and population exposed to hazards becomes extremely important. Global elevation levels, such as from the Shuttle Radar Topographic Mission (Rabus, 2003) is an extremely helpful dataset. Elevation data has a resolution of tens of metres, and subject to errors which can mean important coastal features are omitted, such as entire small islands. Similar distribution issues occur with respect to population.

Projecting how population changes – per country and it’s spatial distribution – is an additional uncertainty, particularly as coastal population grows differently to those areas further inland (Neumann et al. 2015). Of course, there are changes in economic growth too – who could have imagined rapid growth seen in Asian cities over the last few decades? Whilst projections of socio-economic change can be made, these still have a wide range of implications in impact assessments and choices over adaptation.

All these factors and many more combine uncertainties resulting in different scenarios of change – each potentially likely to occur. Fed into impacts assessment, further uncertainties arise. But even faced with this, modelling and choosing the type of adaptation itself is uncertain, whether this involves ‘hard’ barriers, such as sea-walls, ‘soft’ protection including sand nourishment, accommodating sea-level rise by raising buildings, or even deliberately retreating from the sea. Furthermore, sea-levels won’t stop rising in 2100 – even under climate mitigation, so adaptation has to be a long-term investment. Nevertheless, engineering reasoning may question the scientific and financial values of adapting newly built infrastructure to sea-level rise over a 100-year timeframe, if the design life is far less than this. Adaptation therefore has to take a flexible modular approach, allowing for uncertainty, rates of change and investment choice. Long-term investment in infrastructure could become a cat-and-mouse game, where monitoring becomes increasingly important leading to reactive adaptation to avoid an unacceptable situation of escalating risk.

With this, adaptation remains a choice or an opportunity which may not be available to all. Better decision making is enabled by making policy makers aware of the wider range of uncertainties, possibilities and options available. This includes how best to apply for and utilise climate change adaptation funds for developing nations, so that intelligent choices can be made to encapsulate uncertainty.


Adaptation is a manner of choice, mixed with local needs

In recent years there has been a push towards climate services to provide forecasts or projections of long-term change to enable adaptation. I think this is a welcome development as it indicates that climate change is becoming more accepted within the international community leading to action. It’s important to remember that climate change is not the only issue and multiple uncertainties exist in other fields that can sometimes be greater than the climate signal alone, leading to deep uncertainty.

So, to answer my question ‘what uncertainties are there in the drivers of change, and can understanding these uncertainties enable better decisions for adaptation?’, perhaps it as apt to quote Albert Einstein: ‘The more I learn, the more I realise how much I don’t know’. The quest to reduce uncertainty (and my frustration!) continues.

Sally Brown is a Senior Research Fellow at the University of Southampton, UK and a member of the Tyndall Centre for Climate Change Research.


Anuar, N. (2015). 20 skylines of the world: then vs now. Accessed August 2015.

Brown, S. and Nicholls, R.J. (2015). Subsidence and human influences in mega deltas: The case of the Ganges–Brahmaputra–Meghna. Science of The Total Environment, 527-528, 362–374. DOI: 10.1016/j.scitotenv.2015.04.124

Church, J.A., Clark, P.U., Cazenave, A., Gregory, J.M., Jevrejeva, S., Levermann, A., Merrifield, M.A., Milne, G.A., Nerem, R.S., Nunn, P.D., Payne, A.J., Pfeffer, W.T. Stammer, D. and Unnikrishnan, A.S. (2013). Sea Level Change. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Stocker, T.F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S.K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P.M. (eds.)). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Jevrejeva, S., Grinsted, A. and Moore, J.C. (2014). Upper limit for sea level projections by 2100. Environmental Research Letters. 9, 104008. DOI:10.1088/1748-9326/9/10/104008

Kaneko, S., and Toyota, T. (2011). Long-term urbanization and land subsidence in Asian megacities: An indicators system approach. In: groundwater and subsurface environments: Human impacts in Asian coastal cities (Taniguchi, M. (ed.)). Springer, Japan.

Kopp, R.E., Kemp, A.C., Bittermann, K., Donnelly, J.P., Gehrels, W.R., Hay, C.C., Mitrovica, J.X., Morrow, R.D., Rahmstorf, S. and Horton, B.P. (2016). Temperature-driven global sea level variability in the Common Era. Proceedings of the National Academy of Sciences of the United States of America. doi: 10.1073/pnas.1517056113.

Mengel, M., Levermann, A., Frieler, K., Robinison, A., Marzeion, B. and Winkelmann, R. (2016). Future sea level rise constrained by observations and long-term commitment. Proceedings of the National Academy of Sciences of the United States of America.

Moore, J.C., Grinsted, A., Zwinger, T. and Jevrejeva, S. (2013). Semiempirical and process-based global sea level projections. Reviews of Geophysics. 51 (3), 484–522. DOI: 10.1002/rog.20015

Neumann, B., Vafeidis, A.T., Zimmermann, J. and Nicholls, R.J. (2015). Future coastal population growth and exposure to sea-level rise and coastal flooding – A global assessment. PLoS ONE 10 (3), e0118571. DOI: 10.1371/journal.pone.0118571

O’Neill, B.C., Kriegler, E, Riahi, K., Ebi, K.L., Hallegatte, S. Carter, T.R., Mathur, R. and van Vuuren, D.P. (2014). A new scenario framework for climate change research: the concept of shared socioeconomic pathways. Climatic Change, 122 (3), 387-400. DOI: 10.1007/s10584-013-0905-2

Peltier, W.R., Argus, D.F. and Drummund, R. (2015). Space geodesy constrains ice age terminal deglaciation: The global ICE-6G_C (VM5a) model. Journal of Geophysical Research – Solid Earth, 120 (1), 450-487. DOI: 10.1002/2014JB011176

Rabus, B., Eineder, M., Roth, A. and Bamler, R. (2003). The shuttle radar topography mission—a new class of digital elevation models acquired by spaceborne radar. ISPRS Journal of Photogrammetry and Remote Sensing, 57 (4), 241-262. DOI: 10.1016/S0924-2716(02)00124-7

Rahmstorf, S. (2007). A semi-empirical approach to projecting future sea-level rise. Science, 215 (5810), 368-370. DOI: 10.1126/science.1135456

United Nations (2014). Adaptation Fund. Accessed August 2015.

177 Responses to “What drives uncertainties in adapting to sea-level rise?”

  1. 51

    Jim Steele, #45–“I am not sure who is denying the science, you are [sic] Titus?… How is that science denial?”

    Let’s go back and reread:

    “…scary unfounded hypothesis usually associated with current global climate change propaganda…”


    “…Questioning the wild claims of sea level rise when our local topographical studies…”

    So we have the name-calling of peer-reviewed research papers which specifically attempt to quantify probable global trends as “scary”, “unfounded”, “propaganda”, and “wild”, all on the basis of alleged incompatibility with empirical evidence from “local topographical studies.”

    Then we read Don Barber’s link and find that, lo and behold, there is peer-reviewed evidence of a 20th-century acceleration of SLR in NZ, and also that it is in fact consistent with those ‘local studies’ Titus cited.

    Somehow, I’m reminded of this famous incident in the life of Samuel Johnson.

  2. 52
    Victor says:

    re Titus et al.:

    “These new results indicate that relative sea levels in New Zealand have been rising at an average rate of 1.6 mm/yr over the last 100 years – a figure that is not only within the error bounds of the original determination, but when corrected for glacial-isostatic effects has a high level of coherency with other regional and global sea level rise determinations. There continues to be no evidence of any acceleration in relative sea levels over the record period.”

    “An updated analysis of long-term sea level change in New Zealand,” by
    J. Hannah:

  3. 53
    Alf says:

    Can you tell Hull city council all this please, because the place looks destined to become an artificial reef by 2100.

  4. 54
    John McCormick says:

    There will be certainty when Miamians complain about the salty taste in their drinking water.

  5. 55
    Marco says:

    Victor @52 *could* have told us that the paper he cites is from 2004, with the data only going up to 2000.

  6. 56
    John West says:

    Edward Greisch says:
    “What is really going to happen: Civilization is going to collapse about a century before sea level rise has reached a meter.”

    Hyperbole much?

    The ingredients of civilization

    Many different elements must come together before a human community develops to the level of sophistication commonly referred to as civilization. The first is the existence of settlements classifiable as towns or cities. This requires food production to be efficient enough for a large minority of the community to be engaged in more specialized activities – such as the creation of imposing buildings or works of art, the practice of skilled warfare, and above all the administration of a centralized bureaucracy capable of running the machinery of state.

    Civilization requires at least a rudimentary civil service.

    In the organization of a civil service, a system of writing is an almost indispensable aid. This is not invariably the case because at least one civilization, that of the Incas in Peru, will thrive without writing. But the development of writing greatly enhances civilization. And with a script comes history.

    Read more:

    So, SLR is going to render mankind unable to produce food efficiently enough for a significant percentage of the population to be engaged in pursuits other than food production, completely lose the ability to read and write, and make the existence of towns and cities untenable?

  7. 57
    Geoff Beacon says:

    Robin Johnson @21

    I’m pleased you mention the carbon due to building.
    A problem often avoided by those that discuss low carbon living is the embodied carbon in the infrastructure. The carbon cost of building conventional homes in the UK is nearly 100 tonnes CO2 for a three 3 bedroomed house. For an electric car it is about 12 tonnes CO2e per car.

    These are big items when compared to the IPCC remaining carbon budgets. That is when these budgets are assessed on a per person basis. When divided by the number of people in the world, the budget for a 1.5°C rise in global temperatures is about 30 tonnes CO2e. The budget for 2°C is about 100 tonnes CO2e.

    Embodied carbon could easily spend these budgets. “

    We ought to be grateful to the poor people in the world who don’t live in brick and cement houses or buy cars – even electric ones.

    (See The carbon cost of achieving low carbon lifestyles )

  8. 58

    #52–Which paper is an update from 12 years ago, now. It may be a respectable effort, but it is certainly not even close to the latest word.

  9. 59

    Further re #52–

    A quick search on Google Scholar of citations of the Hannah paper cited by Hank and by Victor fails to turn up any newer research on the topic. So, sadly, it seems possible that there’s nothing newer on NZ SLR.

    On the other hand, there is a research opportunity for somebody.

  10. 60
    Hank Roberts says:

    There’s no doubt the ice caps are melting, and will continue to do so, until a while after CO2 gets brought down one way or another. There’s no doubt that meltwater is going to raise sea level faster. Is there a breakpoint in the trend line? Ask a statistician, but use current data not the 2004 data.

    We recommend that for planning and decision timeframes out to the 2090s (2090–2099):

    a base value sea-level rise of 0.5 m relative to the 1980–1999 average be used, along with
    an assessment of potential consequences from a range of possible higher sea-level rise values. At the very least, all assessments should consider the consequences of a mean sea-level rise of at least 0.8 m relative to the 1980–1999 average.

    For longer planning and decision timeframes beyond the end of this century, we recommend an additional allowance for sea-level rise of 10 mm per year beyond 2100.

  11. 61
    Mal Adapted says:


    What’s that got to do with “arguments from consequences”?

    From your first comment here:

    All falls on our taxes…As Joe public will ultimately foot the bill

    That is the fallacious argumentum ad consequentiam, as sea level is either rising or not, without regard for your taxes. If sea level actually is rising, then your taxes will be affected, whether your local government makes an effort to be prepared or ignores the problem while the costs of SLR mount.

    And speaking of alarmist language:

    The problem we have to deal with is local authorities trying to find ways to get needed projects funded by central government and the like. Or cover up past failure. The whole exercise gets politicized using scary unfounded hypothesis usually associated with current global climate change propaganda.

    I don’t know about your local politicians, but New Zealand is consistently ranked one of the least corrupt countries in the world by Transparency International. And according to the Heritage Foundation, a conservative American think tank, “The country is renowned for its efforts to penalize bribery and ensure a transparent, competitive, and corruption-free government procurement system.” Perhaps you’re more suspicious of your government than you need to be.

    In any case, you are free to ignore “alarmist” propaganda and pay attention only to the refereed publications of climate scientists, whose skepticism of unfounded hypotheses can be relied on. If you repeat current global climate change denialist propaganda here, though, you should expect to be called a denier.

  12. 62
    Phil Scadden says:

    Victor, Titus, Hannah’s analysis of tide gauge data to 2001 is not in dispute, (cited in the Gerhels 2008 paper), but Gerhels provides the larger context. NZ is also not immune to more recent sealevel rise since 2001. However, given NZ tectonic and glacial history, I would argue that it is not exactly the best place in the world to be projecting global conclusions about sealevel rise from. I have heard John Hannah be skeptical (in true sense of the word) about the accuracy of satellite altimetry but I wonder if that is still the case since the advent of Jason 2 data.

  13. 63
    Robin Johnson says:

    @Paul Segal #44 – You are correct, PETM has been estimated at 4 Bt/year for an extended time whereas we are doing 30+ Bt/year. We want to melt the ice caps and don’t feel like waiting. My point is that BAU for several more decades would equal the total CO2 released during the PETM event. And then we would get a 5C rise in temp that would likely eventually melt the EAIS which would be 35+ meters of sea level rise. That is my PETM comparison. Interestingly – the PETM was not known to be a mass extinction event.

    @57 Geoff – You make critical points. Getting to carbon neutral is going to be wee bit challenging [i.e. REALLY hard], so we have to make hard choices about what to save and how to replace it with more efficient stuff. It is daunting.

  14. 64
    Titus says:

    Don Barber @46
    Don’t see any relevance of the “2008 GRL paper”. Interesting but does not address the lack of any acceleration (and indeed some deceleration)in the recorded data of the last 100yrs or so.
    My only comment is that the rate they come up with (2.8mm/yr) is on the high end of most other studies and the actual observed data (nearer 2mm/yr).

  15. 65
    Titus says:

    Kevin McKinney @51
    You appear to have missed the plot. Scary language is used by media, politicians, activists and the like (which I’m sure you see enough to agree).
    When the scientific studies and actual data disagree, the problem is that those bringing this to their attention are called deniers.
    I thought my observation and experience here would be useful to the discussion.
    As for Don Barbers link see my previous reply.

  16. 66
    Titus says:

    Ray Ladbury @50 says: “Jim Steele, Titus has a long record of denying the science of climate change–as do you”

    Hmm. I have sited from scientific data and studies. When alarmist language is used about our sea levels and local topographic data says otherwise and anybody who disputes it is called a denier then something has gone terribly wrong.
    I’m thinking you to could be part of the problem under discussion here.

  17. 67
    Paul Segal says:

    Robin I suppose my take is life on the planet rather than planning for how it affects our assets which makes this off topic. No the PETM is not noted for a mass extinction but we are in one now and there are many ecosystems fairly well perturbed. An extremely fast rate of climate change puts more pressure on an ecosystem than a slower one, a short search will find that general conclusion. If we continue with BAU or the rates continue to climb like BAU then is not going to be a PETM look alike from the point of view of the other life here.

  18. 68
    Hank Roberts says:

    > last hundred years
    Oh, why not use the last thousand to smooth out the trend?

  19. 69
    JIm Steele says:

    @ Ray Ladbury

    You wield the denier label like a club as if it is a substitute for a robust scientific discussion. Fabricating my “long-record of denying” is dishonest on your part. I simply find natural climate variability is more often the driver of observed change, and believe we need 20 more years of observation to better evaluate how sensitive the climate is to rising CO2.

    You claim it is disingenuous to look at localities. But the global average rise in sea level is a chimera of many factors acting differently at various locations. A full accounting is required before we can accurately attributed causes. Is Antarctic gaining or losing ice? To debate that is not denial! How much is groundwater contributing to sea level rise? Some claim that extraction is now adding “net terrestrial contribution to increase to +0.87 (0.14) mm yr” If so, then global warming is not contributing as much to sea level as others assert. To debate that uncertainty and disagreement with your limited analysis, should never be confused with denial. In fact such debates make for better science.

  20. 70
    JCH says:

    titus, etc., they are among people around the blogs who think this RC article by Sally Brown is all about there being no significant SLR threat because of uncertainty… not now, and not for the rest of this century. They think all Sally Brown thinks can happen is 100 times 3.0mm, or 11 inches by 2100. They think this article means Sally Brown thinks climate scientists are exaggerating the threat, and they are shocked that RC is allowing her to chastise them.

  21. 71
    Jim Eager says:

    John West @56: So, SLR is going to render mankind unable to produce food efficiently enough for a significant percentage of the population to be engaged in pursuits other than food production…

    No, not likely, it’s far too slow, but sufficient disruption of the planet’s hydrologic cycle might well do it though, since large scale agriculture is utterly dependent on predictable and reliable precipitation at the right place and time, and civilization is completely dependent on agriculture.

    We’re already well down that path and recall that most large cities have on-hand food stocks for only a few days at most, so that significant percentage of the population engaged in pursuits other than food production is more vulnerable than you seem to think.

    We can handle the odd year like 2010 when drought reduced the Russian wheat crop by a quarter, flood wiped out a substantial portion of Pakistan’s crop, and then Autsralia’s that winter, but what about when it starts to happen year after year?

    Right now a turbo charged el Nino is drying out much of southeast Asia’s rice fields as the monsoons fail to materialize. You might want to read Davis’ Late Victorian Holocausts to wake you from your complacency.

  22. 72
    Jim Eager says:

    And here is Lloyd’s 2015 emerging risk report on Food System Shock:

    the Global Sustainability Institute at the UK’s Anglia Ruskin University predicts that catastrophic food shortages, triggered by a combination of climate change, water scarcity, energy crisis, and political instability might lead to a virtual collapse industrial civilization by 2040. The model explores short-term scenarios of policy decisions by simulating social-economical-environmental systems, including the impact of climate-induced drought on crop failures and food prices. The model was successfully used to simulate the multiple factors–including the great Russian drought of 2010–that made the 2011 Arab Spring uprisings more likely. These uprisings caused major unrest in at least twelve nations, and forced rulers from power in Tunisia, Egypt, Libya, and Yemen.

    We ran the model forward to the year 2040, along a business-as-usual trajectory based on ‘do-nothing’ trends—that is, without any feedback loops that would change the underlying trend. The results show that based on plausible climate trends, and a total failure to change course, the global food supply system would face catastrophic losses, and an unprecedented epidemic of food riots. In this scenario, global society essentially collapses as food production falls permanently short of consumption.

  23. 73
    Robert Davis-Vasquez says:

    Thank You!

  24. 74
    Solar Jim says:

    What drives uncertainties? Well, whether the rise will be 50 feet or 150 feet. After all, according to several scientific analysis, at close to 500 ppm,equivalent today, fifty feet is all but baked in. Now we get to watch the heating of melting arctic ice, soon to be gone in summer, turn into sensible heating.

    Sure would be nice if western thought were sensible. As the article demonstrates, no such luck. Save your concrete (a “climate change” material).

  25. 75
    Theo says:

    Layman observation: My area receives 720 Megga litres of rain per quare km per year, but the law only allows about 6ML of water in dams. I assume that this is to keep the rivers flowing and leave water for downstream properties. But these properties also receive the same rain, so they don’t really need mine, maybe other than flushing their waste? My local river alone discharges 5000ML of slightly dirty fresh water each year and tries to flood the town just about every year. Can a change to Water Harvesting Laws have any effect on SLR? There would be an army of willing workers to take advantage of such a change. Would only need 285 km2 to offset Greenland current average runoff?

  26. 76
    Digby Scorgie says:

    #60 Hank

    Your comment reminds me that our authorities in New Zealand do seem to be paying attention to the effects of climate change, even if they’re not doing much to curb our emissions.

    We live on the east coast of the South Island and my wife works at the local library. She reports that last week the senior managers in the council attended a meeting where climate change, and specifically sea-level rise, was discussed. Our council, at the very least, is not complacent about the problem.

  27. 77
    Ray Ladbury says:

    Several folks here have pointed out why you are wrong. You can either listen to them or remain deluded. Your choice.

  28. 78
    Ray Ladbury says:

    Jim Steele,
    When one’s conclusion is at odds with those of all the smart people in a field, failure to reexamine one’s process is denial. You are a textbook case. You sound just like the creationists saying, “We just interpret the evidence differently.”

  29. 79
    Hank Roberts says:

    > I simply find … and believe

    Which appears to be science denied, finding what you believe.

    You should try showing your work.
    Tamino is a good example, try emulating his analyses.

  30. 80
    Hank Roberts says:

    > only allows about 6ML of water in dams.
    > I assume that this is to keep the rivers flowing

    Why assume when you can check? Could be they leave space behind dams for possible flooding — for instance if your watershed is a snowpack, it’ll either melt slowly if the weather stays cold, or melt suddenly in warm spring rains and send a lot of water downstream.

    Your meteorology may vary, of course.

  31. 81
    Titus says:

    Mal Adapted @61 says: “New Zealand is consistently ranked one of the least corrupt countries in the world”
    Yep and we are very proud of that. Thanks for raising.

    Problem here are the Green party activists who wield a lot of influence as our current National party relies on them for support. They attack everybody who goes against the consensus, science or no science just blindly shout ‘denier’ whenever questions are raised.

  32. 82
    Titus says:

    Kevin McKinney @59 says: “it seems possible that there’s nothing newer on NZ SLR. On the other hand, there is a research opportunity for somebody”

    Hmm. When local observational data, scientific studies and engineering professionals all agree that current sea level rise is at historical average (albeit showing a statistically insignificant decline) I think we can put off spending on further research until our conditions warrant.
    Try telling that to our Green activists:)

  33. 83
    Mal Adapted says:

    Jim Steele:

    You wield the denier label like a club as if it is a substitute for a robust scientific discussion. Fabricating my “long-record of denying” is dishonest on your part. I simply find natural climate variability is more often the driver of observed change

    Jim, just how did you “find” that natural climate variability is more important than anthropogenic forcing? Did you review all the available evidence collected by trained, disciplined scientists over two centuries, and perform appropriate statistical analysis? Have you considered all possible sources of error? Have you subjected your finding to the unsparing scrutiny of other climate scientists, by submitting it for publication in appropriate peer-reviewed journals, or debating it at, say, the annual AGU meeting or other formal venues? If so, you’d realize that “robust scientific discussion” has already led to a lopsided consensus of working, publishing climate scientists that the observed rise in global mean surface temperature in the last 50 years is largely or entirely due to anthropogenic forcing.

    For reasons that no doubt seem good to you, including a belief that “the politics of global warming have been misguiding conservation efforts”, you’ve rejected the expert consensus. That you feel competent to do so despite your rather modest CV suggests that you’re afflicted with the Dunning-Kruger effect, like so many AGW-deniers who over-estimate their own competence and are unable to recognize genuine competence in others. Do you understand that it’s not random blog participants that you need to engage, it’s the community of scientific experts that have specialized in climate change? FWIW, I can assure you that political beliefs will have no part in robust scientific discussion with them.

    As (dog help us) a middle- and high-school science teacher, one hopes you taught your pupils that science is a way of trying not to fool yourself (“The first rule is you must not fool yourself, and you are the easiest person to fool.” – Feynman, who else?). Presumably you taught them that it rests on the dual foundations of empiricism and inter-subjective verification – “peer review”, IOW. Now, if thousands of expert climate scientists have reviewed your finding and failed to verify it, then either you’re right and the others are all wrong, or you’re fooling yourself. Which do you think the rest of us consider more likely? Do you begin to see why you’re being labeled a denier?

  34. 84
    Richard Caldwell says:

    Jim quoting Lloyd: In this scenario, global society essentially collapses as food production falls permanently short of consumption.

    Richard: That’s impossible, of course. Now, falling short of desired consumption is another (very good) thing. There’s nothing like Their imminent starvation to decrease the amount of food we need to send overseas to trade for raw materials. In any case, there’s nothing which says we must share, and nothing which says we have to allow refugees. It’s rather easy to put up a fence, gun down anybody who tries to cross, and throw those who “make it” back into the scrum. Empathy is a choice, as least when it comes to action. There’s no scientific reason to not simply let large portions of Africa, the Mideast, and other areas where idiots failed to plan properly for our spewing of CO2 depopulate. As if population reduction to fight global warming is difficult or even requires much effort. When it’s Profitable and the alternative is civilization’s collapse (which is defined as “I can’t drive a sportscar-fast SUV”), why not, eh? Watching Europe struggle with the mere trickle of folks from tiny Syria is interesting. All that hand-wringing and trouble when sitting back and eating popcorn while watching the free entertainment is all that’s required is silly. Besides, letting folks migrate from low-spewing areas to high-spewing areas is scientifically stupid. We’ll be just fine as long as They all die. (Yes, Miamians are part of They) Walls are our future and Donald Drumpf is prescient.

  35. 85
    Torsten Käll says:

    Can anyone please explain to me what I’m missing because looking at satellite data from university of Colorado ( obvious that the annual sea level rise is contained at 3.3 mm/year. That equates to 330 mm/100 year. A scary number I’m sure but nowhere near those catastrophic 3 to 6 meters I can read about here.

  36. 86
    Geoff Beacon says:

    Jim Eager @71 makes good points.

    We should integrate food production in our neighbourhoods and only rely on long distribution chains for small luxuries and emergencies. We should replace the agribusiness monoculture with more diverse local food production making this work by using local economic incentives.

    In the “special period” in Cuba they managed to feed the population with healthy diets. We should seek to find financial mechanisms that would do this in a market economy.

    Making planning work differently suggests targets for new prototype neighbourhoods based on these parameters

    % of residents employed locally
    % of food produced locally
    % of goods bought from local retailers
    Social class of the residents.
    Average weekly travel distances.
    A measure of ecosystem services
    Average carbon footprint of residents
    Protection of ecosystems

    Developers pay on penalty clauses when the settlements fail.

    PS. I know some decent sites near London high enough to survive at least 10m of sea level. Is this high enough for this century?

  37. 87
    Theo says:

    @80 from me @75: Thanks Hank, but the essence of my question is simple:

    Can us retaining more water on land have a useful effect on SLR ?

    (Like more dams, locks on rivers and other water retaining techniques like Keyline, Rice paddies and Permaculture?)

  38. 88

    TK @ 85: Can anyone please explain to me what I’m missing because looking at satellite data from university of Colorado ( obvious that the annual sea level rise is contained at 3.3 mm/year. That equates to 330 mm/100 year. A scary number I’m sure but nowhere near those catastrophic 3 to 6 meters I can read about here.

    BPL: What you’re missing is that the rate is rising, which means accelerating (2nd time derivative, not 1st). What you’re also missing is the possibility that the relation is highly non-linear and may involve catastrophic changes along the line, in accordance with chaos theory involving domains never observed. We don’t know how greatly the initial conditions affect the long-range outcome, but the more we learn, the less good it looks.

  39. 89
    Omega Centauri says:

    Torsten @85.
    Current SLR is roughly your stated 3.3mm/year. But its been accelerating, and there is every reason to think the acceleration will continue for some time. The climate isn’t done heating up, and ice sheet response is thought to be nonlinear, so there are multiple lines of reasoning which point to significant increase in the melt rate. There is of course a lot of uncertainty about the details, that affect the melt rates, we just don’t know how quickly warmer seawater will undercut floating glaciers, and buildup of darker older snow/ice layers will increase the amount of absorbed sun light. There is even a biological component whereby bacterial communities can darken the ice surface during the melt season. A lot of reasons to be concerned about future melt rates, but not very good science to model it with.

  40. 90
    Robin Johnson says:

    @85 Torsten –

    Most of the sea level rise for the last 200 years is attributed mainly to thermal expansion and hence slow and steady. The melting being discussed above is mostly related to the Ice Sheets. Thermal Expansion will contribute potentially 1-4 meters depending on how hot things get.

    Mountain range glaciers (Alaska, Andes and Himalayas) will likely melt out, but this is relatively negligible. Even if they completed melted it would contribute less than 0.25 meter to sea level rise.

    Next up are the three enormous Ice Sheets:

    GIS (Greenland Ice Sheet) 7.2 Meters if completely melted
    WAIS (West Antarctic Ice Sheet) 4.8 Meters if completely melted
    EAIS (East Antarctice Ice Sheet) 55+ Meters

    They are the big drivers. GIS and WAIS were both completely melted out (from well-established evidence) 3+ million years ago when the Earth was just 2-3C+ warmer than today. EAIS remained stable but was thinned by ~500 meters. Sea level was 25 meters higher as a result.

    Plate tectonics have changed the ocean currents since the Pliocene and so maybe we’ll see a different result. Current evidence is that WAIS is unstable and will melt eventually. How long will it take? Uncertain. More science/modeling will hopefully yield an answer that will give us plenty of planning time…

    GIS – nobody knows yet. Again more science needed. It is definitely melting and accelerating.

    EAIS – stable for 35 million years. But 5C rise? Then maybe not.

    It really is scary. There is evidence that Ice Sheets collapse rapidly not slowly when there is a rapid temperature change. We may get to find out the hard way.

  41. 91

    Titus, #82

    When local observational data, scientific studies and engineering professionals all agree that current sea level rise is at historical average (albeit showing a statistically insignificant decline) I think we can put off spending on further research until our conditions warrant.

    And how do you expect to know when ‘conditions warrant,’ if you aren’t even looking?

    Truly, it’s incredible how you blind yourself. By your own account, you’re not looking at anything thing except ‘local conditions’, and apparently you aren’t looking at all the ‘scientific studies’ either, since there’s been one cited above with rather different conclusions.

    “Still a man hears what he wants to hear/ And disregards the rest.”

  42. 92

    Torsten, #85–

    Can anyone please explain to me what I’m missing because looking at satellite data from university of Colorado ( obvious that the annual sea level rise is contained at 3.3 mm/year. That equates to 330 mm/100 year. A scary number I’m sure but nowhere near those catastrophic 3 to 6 meters I can read about here.

    Torsten, why do you think that extrapolation from a 20-year trend line is likely to prove reliable over even the next 20 years, much less the next 80?

    StatIstically, I don’t think that there is ‘proof’ that acceleration in sea level rise, though there is some evidence that it *may* be happening. for example:

    But there are solid physical reasons to expect acceleration–the radiative imbalance is growing along with the concentrations of GHGs; we are shedding reflective ice from the cryosphere; our warming atmosphere is holding more water vapor, a potent GHG; and we are melting permafrost and frozen soils to release methane. These are all feedback loops; more GHGs, more warming, more ice loss, more permafrost melt, more GHGs. Et cetera. And there’s the possibility of more feedbacks kicking in: changes to the carbon cycle which raise GHGs further, dynamic ice loss effects kicking in to raise sea level directly.

    No-one knows exactly what *will* happen, but it’s a pretty good bet that there’s nothing ‘inevitable’ about the observed 20-year trend–and an even better one that deviations are more likely in the direction of an acceleration of the trend.

  43. 93
    Dan Miller says:

    #85 Torsten: Try this: Assume that 1mm of the 3.3mm/year is due to melt from Greenland and Antarctica. Now assume that the rate of melting of those ice sheets is doubling every 5 or 10 years, as the sparse data seems to imply. So for 5 year doubling, 1mm becomes 2mm in 5 years, 4mm in 10, 8mm in 15 years, etc. You’ll soon see that you get about 3 feet of SLR around mid-century and way more than that in 2100. It’s a little better with 10 year doubling but that only buys you a bit of time. Exponentials are not your friend.

    Some scientists have disagreed with Dr. Hansen’s paper and said the physical mechanisms for continued doubling of melt are not there. But Dr. Hansen has responded that it is certain that multi-meter per century SLR has occurred in the past with forcing less than we are causing now. As Michael Mann has said, we ignore Jim Hansen at our peril.

  44. 94
    Titus says:

    Ray Ladbury @77 says: “Several folks here have pointed out why you are wrong. You can either listen to them or remain deluded. Your choice.”

    Oh my. I have to ask you Ray, to point out even one of these ‘several’ who say I’m wrong. In fact their comments and links only go to strengthen my case.

    I came here to add some of my personal experience in dealing with the subject in hand. Inadvertently you have actually acted out that experience in your responses. Like it or not, you are part of the problem

  45. 95
    Aaron Lewis says:

    In planing for SLR, we should allow for contingency, in case the climate science has made a mistake and SLR occurs sooner, rather than later. For example, climate models assume a CH4 atmospheric half-life of ~12.5 years, so they use the 100-year CO2 equivalency of 28, rather than the annual equivalency of 84. It is more prudent to use the CH4:CO2 equivalency of 84 for planning and public policy.

    Fifty years ago, when I first measured atmospheric CH4, the concentration that I got was ~1 ppm. If the climate model assumptions are correct on a practical basis, then current atmospheric concentration would be less than 0.25 ppm. It is not. Looking at well calibrated data for the last 25 years (e.g., ) we see that CH4 has consistently increased.

    Certainly much of the CH4 in the atmosphere over the last 25 years is from human releases, and California and other states are considering laws on CH4 releases, but many states are not. The world is now warmer and wetter, and we have better than anecdotal reports that feedback CH4 releases are now occurring (e.g., plumes of CH4 in lakes and oceans).

    In short, a prudent planner would treat the CH4:CO2 equivalency as ~84, meaning that current greenhouse gas concentrations are over 560 ppmve CO2, and current forcing is close to 3.6 w/m2. That is the forcing that will melt permafrost this summer, releasing CH4 this year, setting the stage for more CH4 and water vapor in the atmosphere, next summer. As a result, all of the standard climate models understate the rate of global warming. Then, all ice models, and sea level rise models using the output of standard climate models also understate the rate of change.

  46. 96

    Torsten Käll #85… keep reading. Sea level rise is not linear, it is exponential. Most of the rise now is attributed to warming, expanding water. Look for the increasing rate of ice cap melt. Figure the rate of increase. Google search “sea level rise projections” Check the source material.

  47. 97
    Jim Eager says:

    Torsten Käll, what you are missing is that the slope of the curve for sea level rise over the last century was concave, meaning sea level rise accelerated. And since you have missed this acceleration you have assumed that the rate will remain at 3.3 mm/year for the rest of this century, despite ongoing observations of increases in ice mass loss in Greenland and parts of Antarctica. Very short sighted assumption, that.

  48. 98
    Jim Eager says:

    Actually, the quote came from Dr Jeff Master’s summary of the Lloyd’s report at WeatherUnderground here:

    Sorry for stuffing that up.

    But to Richard Caldwell’s dark sarcasm, let me add a sobering thought:
    As we’re seen, starving populations will not starve quietly and complacently. But walls and fences will not be enough. India and Pakistan have already exchanged artillery duels over water in the form of the glaciers that feed the Indus river. Keep in mind that both states possess nuclear weapons.

  49. 99
    Victor says:

    Titus, Jim Steele, et al:

    Regarding the right of non-climate specialists to speak out on any of the issues raised on this blog, let me cite some excerpts from a particularly insightful Scientific American article titled “Evaluating scientific claims (or, do we have to take the scientist’s word for it?)”:

    “Scientific knowledge is built on empirical data, and the details of the data . . . can vary quite a lot in different scientific disciplines, and in different areas of research within those disciplines. However, there are commonalities in the basic patterns of reasoning that scientists in all fields use to compare their theories with their data. . . In other words, even if I can’t evaluate someone else’s raw data to tell you directly what it means, I can evaluate the way that data is used to support or refute claims. I can recognize logical fallacies and distinguish them from instances of valid reasoning. Moreover, this is the kind of thing that a non-scientist who is good at critical thinking (whether a journalist or a member of the public consuming a news story) could evaluate as well. (

  50. 100

    A little algebra puts Hansen et al’s estimate right in the ballpark of what we should expect– 6-9 meter sea level rise from a 1 K temperature excursion. What follows is reprinted from a post I made on Eli’s blog, with some infelicities edited:

    Hart (1978) gives the following rough relation for the fraction of Earth’s surface covered by ice, going from satellite data available at the time:

    f(ice) = [(328 – Ts) / 70]^5

    for Ts = 288 K (the assumed mean global annual surface temperature of Earth), this gives 6.1%. For a 1 K rise, this becomes 5.4%.

    The volume of grounded ice on Earth is 2.934 x 10^16 m^3. The melting of 7/61 of this releases 3.37 x 10^15 cubic meters. Since fresh water is denser than ice by a factor of 1000/917, this becomes 3.09 x 10^15 m^3.

    Earth’s total area is 5.10066 x 10^14 m^2, of which 70.8% is water (Sellers 1965, p. 5). Thus, spread out over the ocean, the new ocean height rises 8.56 meters, and spread out over the whole globe, 6.06 meters. Hansen et al.’s figure is thus just in the ballpark of what it should be.

    Hart MH 1978. The Evolution of the Atmosphere of the Earth. Icarus 33, 23-39.

    Sellers WD 1965. Physical Climatology. Chicago IL: Univ. of Chicago Press.