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The inevitability of sea level rise

Filed under: — stefan @ 15 August 2013

Guest post by Anders Levermann [via The Conversation]

The Conversation
Small numbers can imply big things. Global sea level rose by a little less than 0.2 metres during the 20th century – mainly in response to the 0.8 °C of warming humans have caused through greenhouse gas emissions. That might not look like something to worry about. But there is no doubt that for the next century, sea level will continue to rise substantially. The multi-billion-dollar question is: by how much?

The upper limit of two metres that is currently available in the scientific literature would be extremely difficult and costly to adapt to for many coastal regions. But the sea level will not stop rising at the end of the 21st century. Historical climate records show that sea levels have been higher whenever Earth’s climate was warmer – and not by a couple of centimetres, but by several metres. This inevitability is due to the inertia in the ocean and ice masses on the planet. There are two major reasons for the perpetual response of sea level to human perturbations.

One is due to the long lifetime and warming effect of carbon dioxide in the atmosphere. Once emitted carbon dioxide causes warming in the atmosphere over many centuries which can only be reduced significantly by actively taking the greenhouse gas out again. This is because both the amount of heat and carbon dioxide the ocean can absorb is reduced, and so the temperature stays up for centuries or even millennia. Of course, not cutting emissions would exacerbate the problem even further.

The other reason is that both the ocean and the ice masses are very big and a warming of the surrounding atmosphere will only penetrate slowly, but inevitably, into them. As a consequence their sea level contribution continues even if the warming does not increase. Sea level rise over the last century has been dominated by ocean warming and loss of glaciers. Our recent study indicates that the future sea level rise will be dominated by ice loss from the two major ice sheets on Greenland and Antarctica – slumbering giants that we’re about to wake.

levermann2013

Graph: Sea level rise contributions over 2000 years from: ocean warming (a), mountain glaciers (b), Greenland (c) and Antarctic (d) ice sheets. The total sea level commitment (e) is about 2.3m per degree of warming above pre-industrial.

It is easier to understand a future world that has adjusted to a new equilibrium of higher temperatures than it is to understand the dynamic (perhaps rapid) transition from today’s world to a warmer one. That is why we used physical models for the ocean, the mountain glaciers and the big ice sheets to compute how the systems would be different if the world was warmer.

What we found was that for each degree of global warming above pre-industrial levels the ocean warming will contribute about 0.4 metres to global mean sea-level rise while Antarctica will contribute about 1.2 metres. The mountain glaciers have a limited amount of water stored and thus their contribution levels off with higher temperatures. This is over-compensated for by the ice loss from Greenland, so that in total sea level rises quasi-linearly by about 2.3 metres for each degree of global warming (see figure).

How fast this will come about, we do not know. All we can say is that it will take no longer than 2,000 years. Thus the 2.3 metres per degree of warming are not for this century. They need to be considered as our sea level commitment – the sea level rise that cannot be avoided after we have elevated global temperatures to a certain level.

Ben Strauss of Climate Central has considered the different possible future pathways that society might take and computed which US cities are at risk in the long-term. He poses the question as to what year, if we continue with greenhouse emissions at current rates, we will have caused an inevitable sea level rise that puts certain cities at risk.

According to his analysis, within the next few years Miami in Florida will be committed to eventually lie below sea level, while our future actions can still decide on whether we want to one day give up cities such as Virginia Beach, Sacramento, Boston, Jacksonville or New York City.

This is a decision society has to take for future generations. We will need to adapt to climate change in any case, but some things we will not be able to adapt to. Society needs to decide whether we want to give up, for example, the Tower of London, or to put the breaks on climate change so that we don’t have to.

Weblink: The New York Times has a good current article on this issue.

Anders Levermann is department head at the Potsdam Institute for Climate Impact Research, Germany


198 Responses to “The inevitability of sea level rise”

  1. 101
    Alan Millar says:

    Comment by MA Rodger — 23 Aug 2013 @ 4:10 AM

    Well here is a graphical view of total emissions since 1751.

    http://www.earth-policy.org/indicators/C52

    I think it demonstrates very clearly the significant percentage of man’s total emissions that have been issued this century. You can work out the exact percentage from the data if you wish.

    Like I said this basically uncontrolled continuation of our emissions this century must have lead to the changes in global temperatures that have happened during the same period. This is surely in line with theory which inextricably links the two phenomena together. Or are you suggesting some other linkage?

    Alan

  2. 102
    Alan Millar says:

    Comment by MA Rodger — 23 Aug 2013 @ 4:10 AM

    Well here is a graphical view of total emissions since 1751.

    http://www.earth-policy.org/indicators/C52

    I think it demonstrates very clearly the significant percentage of man’s total emissions that have been issued this century. You can work out the exact percentage from the data if you wish.

    Like I said this basically uncontrolled continuation of our emissions this century must have lead to the changes in global temperatures that have happened during the same period. This is surely in line with theory which inextricably links the two phenomena together.
    Or are you suggesting some other linkage?

    Alan

  3. 103
    Hank Roberts says:

    for MA Rodger and Alan Millar, you’re both right.

    starting at
    http://www.realclimate.org/index.php/archives/2013/08/the-inevitability-of-sea-level-rise/comment-page-2/#comment-404645

    The 30 percent figure is CO2 increase in the atmosphere since the beginning of the industrial revolution: https://www.google.com/search?q=industrial+revolution+co2+30+percent

    Yes, human activity started boosting CO2 before the industrial revolution, but that was not -fossil- carbon; that was from forests and fields and topsoil and peat and whale oil — everything we ate, burned, and wasted — changing where the biosphere held carbon.

    That was being handled by natural cycling, dissolved in the ocean, and slowly increasing CO2 in the atmosphere.

    Then — industrial revolution — we started burning coal and fossil oil and dumping fossil methane into the air.

    Biogeochemical cycling has handled half of -that- as well. So far.

  4. 104
    Mal Adapted says:

    Alan Millar:

    I mean if people on here weren’t prepared to do this, people who know the future disastrous consequences of rampant energy use, how could you expect other people to do so who are not so aware of this or who even are not so convinced of such future events.

    Why, through a carbon tax, or some method of pricing fossil fuels to internalize their full costs. That way wouldn’t require other people to be aware or convinced of the consequences of rampant energy use, as long as government taxing authority can be asserted. Once the full costs are internalized, the invisible hand can take over.

    Unless you think that the problem can be solved through individual efforts. If so, I presume you’re unacquainted with the Tragedy of the Commons, of which AGW is a classic example.

  5. 105
    Alan Millar says:

    Comment by Mal Adapted — 23 Aug 2013 @ 3:35 PM

    So people who are absolutely convinced of a coming catastrophe and are evangelical about the need to change behaviours, will actually only change their personal behaviour if forced to by taxation? The justification for this being that, why should they change if others are unwilling and they cannot do it on their own.

    Do you agree with this viewpoint?

    It doesn’t seem to me to be the most inspiring or convincing message to the less convinced.

    Alan

  6. 106
    Hank Roberts says:

    > Do you agree with this viewpoint?

    Yes, I think sea level rise is definitely going to happen.
    Believe it or not.

  7. 107
    Chuck Hughes says:

    We seem to be mired in political inaction. How long will this continue? It may be a little off topic but it does mention sea level rise.

    http://consortiumnews.com/2013/08/20/will-the-american-right-kill-us-all/

  8. 108
    MA Rodger says:

    Hi Hank Roberts @103.
    I did wonder if our guest Mr Millar was thinking atmospheric increases while saying emissions. But his comment @101 shows he didn’t (or doesn’t) mean that at all.
    As for when to place the “Industrial Revolution” the common time is the eighteenth century. Of course that isn’t very exact. I like the idea of timing it to the coke-powered iron production by Abraham Darby in Coalbrookedale, he being the first person (outside China) to dream up uses for fossil fuels that weren’t just cooking or heating houses. That would put the revolution as happening on 10th January 1709. But in climatology 1750 is the year used (eg by IPCC).
    As for the the 30% figure (which is as you demonstrated still encountered); it is a tad behind the times. (I do get the strong impression that our Mr Millar is living in the past.) A more up-to-date figure would be 395/280 = 41%.

  9. 109
    MA Rodger says:

    Alan Millar @101.

    You wrote @93 “Indeed we have emitted more than 30% of the whole total of man’s emissions since the industrial revolution.” This was ambiguously worded so it is helpful that you comment now (at last) allows us to know what you are on about.
    I can thus tell you that you are wrong. Using the data you point to, emissions this century (even if you include the year 2000) are not “more than 30%” as you claim, and the ratio will be reduced further if emissions from changing land use are also accounted for.

    The word “inextricable” is not usually found within scientific statements. You are claiming that a “basically uncontrolled continuation of our emissions this century” is “inextricably” linked by theory with the “changes in global temperatures that have happened during the same period.” I have to say this is a theory of which I am unaware. And I find that strange as I usually keep abreast of developments within climate science.
    So, far from “suggesting some other linkage,” I am entirely ignorant of your inextricable link or of the theory from which it derives.
    Perhaps you could explain this theory of yours or provide a reference to it.

  10. 110
    Radge Havers says:

    So what works better, top-down or bottom-up solutions; is that the question?

    IMO we tend to romanticize grass-roots activism, which under special circumstances can organize to effect. But everything in society is systemic. The libertarian notion that radical individualism, given sufficient cheerleading, will always automagically generate some kind of utopia, never a swamp, is suspect. It seems about as likely as throwing a bunch of nuts and bolts into a box and expecting it to go out and mow the lawn.

    If AGW is one inconvenient truth, two more are how necessary good government is to assist in solving large, complicated problems and how it gets broken and bought out by corrupt interests.

  11. 111
    SecularAnimist says:

    Killian wrote (#94): “Nobody wants to hear it, but the greatest part of the answer is to use a whole lot less.”

    According to the latest analysis from the Lawrence Livermore National Laboratory, “the U.S. is just 39 percent energy efficient … more than half (61 percent) of the energy that flows through our economy is ultimately wasted.”

    Which means that we in the USA could cut our total energy consumption by more than half, with NO reduction in our “use” of the services that energy provides — simply by eliminating outright waste.

    And keep in mind that the vast solar and wind energy resources of the USA are much more than sufficient to produce ALL the energy that we currently consume.

    GHG emissions from energy generation are not the whole problem, but they are a huge part of the problem, and the reality is that they can be rather easily eliminated by making efficient use of available carbon-free energy sources, with no need whatsoever to resort to extremes of austerity in our use of energy.

  12. 112
    Hank Roberts says:

    > Perhaps you could explain this theory of yours

    Elsewhere please.
    You guys are tag-teaming distraction from the topic, a specific paper with the author here to take questions.

    Leave off so we hear more from the real scientists, eh?

    (why yes, I am the cranky you-kids-offa-my-lawn type, why do you ask?)

  13. 113
    prokaryotes says:

    Sea Level Rise Found to Cause Slope Collapse, Tsunamis, Methane Release Link

    And regarding messaging of outcomes: Climate Change Alarm is Needed and Climate Scientists Aren’t Sounding it Loud Enough Link

  14. 114
    Mal Adapted says:

    Alan Millar, most recently:

    So people who are absolutely convinced of a coming catastrophe and are evangelical about the need to change behaviours, will actually only change their personal behaviour if forced to by taxation?

    Alan Millar, previously:

    I have no doubt that the majority of people on here, who are predicting an apocalyptic future for mankind unless we change our habits, have personally got rid of their gas guzzling cars and wouldn’t even consider using aircraft to get around. I am sure they will have made their houses as energy efficient as possible and don’t use things like air conditioning unless they are generating the power from renewables.

    You are likely correct about the majority of people here, if by “here” you mean frequent commenters on this blog. Do you really not understand that even if all RealClimate commenters were to model the needed behavioural changes conscientiously, the future would be no less apocalyptic if the unconvinced (whether because of ignorance or active denial) don’t change as well? Do you think that paying a carbon tax is worse than global climate catastrophe? I’m afraid you’ll need to convince us of that.

  15. 115
    sidd says:

    Many comments here belong in the unforced variations thread.

    Let me return to the Leverman paper.

    1) I see that they use a model by Pollard for Antarctica. As I uncerstand it, that model has no basal hydrology. But we see sub ice water in many places in Antarctica. Is this a problem for the model ?

    2) Was there any hysteresis seen in the Greenland or Antarctica models ?

    sidd

  16. 116
    Robj says:

    1. While a bit too cheery, I think this is one of the cheerier articles I have read in a long time. I think it is not an accident that utilities are now desperately trying to claw back on reverse metering and any subsidies.
    http://www.csmonitor.com/Business/In-Gear/2013/0602/Will-solar-power-kill-utility-companies-They-think-so.

    2. On the emissions despair motif (waaaa–we can’t do anything but die), the IPCC has modelled various emission scenarios for 20 years. What we do, individually and by policy does matter. And one would opine that if solar and wind options are driven down in cost by 1st world adoption, 2nd world adoption will quickly follow. It is no accident that China is rather desperately incentivizing both solar and wind.

  17. 117
    Dave123 says:

    This is a response for various posts by Alan Miller-

    For some of us the objective is to preserve as much of our present ‘behavior’ as possible. There are simply not enough of us to create a market that someone will respond to. Carbon taxes or cap-and-trade are means of creating demand that results in reduced carbon footprint goods and services.

  18. 118
    Chris Dudley says:

    I think we have to look on this as a long term strategy to gain a permanent republican majority. The takings clause of the Constitution requires just compensation for use of eminent domain. So it would be expensive to eliminate the urban democratic districts just by taking them. But property law says that land lost to permanent inundation is simply no longer property. Thus, conversion of these districts to federal waters can occur with no compensation at all. House congressional seats long held by democrats can be eliminated and republicans can gain a permanent advantage. While some republican coastal second homes may be lost as well, it won’t be a loss in the district in which the republicans vote.

  19. 119

    #118–Really? One hopes the voters themselves won’t be inundated, in which case they’ll just change voting patterns in other districts.

    Or was that a smile I didn’t ‘see?’

  20. 120
    Filip Hondekyn says:

    I live in the Lowlands near the sea in the West of Europe. My ancesters (German tribes that had replaced the Romans) invented flood protection in the 9th century.
    As a results, their descendents were able to deal with all the sea level changes from the early middleages until now (Dunkirk transgressions and regression afterwards) . We have the best nautical engineers and the best dredging companies in the world. My homeland is extremely vulnerable to climate change, yet we have been able to maintain our high standard of living for more than thousand years. We do not fear the future as we are well prepared for sea level changed. And we can help the rest of the world with our advanced floodprotection technology.
    Optimism is a moral duty (Popper).

  21. 121
    Ray Ladbury says:

    Optimism may be a duty, but realism must be a prerequisite to optimism.

  22. 122
    Eric Rowland says:

    As noted in the post, warming and SLR have a long lifetime. In human terms, it will certainly be multi-generational. As in any war, some locations will be saved and other sacrificed early on. Some locations will, over time, receive devastating assaults and others will succumb to the slow ravages of wind and water damage and other relentless environmental insults. The outcome will be an influx of refugees moving to higher ground. These refugees will be largely dependent on Federal and State support. Staying within the context of your argument, this is where the on-going expenses will be incurred. I can’t imagine a scenario for the US where mitigation will be more expensive than remediation.

  23. 123
    wili says:

    “Pessimism of the intellect, optimism of the will.” (Gramsci)

    Though I admit that the latter is getting harder to muster.

    Protecting the Lowlands during relatively stable sea level conditions, impressive as that has been, is a completely different thing from protecting them (and all other near or below sea level areas) from ever increasing sea levels and increasingly stormy seas.

    (On the other hand, the apparently ever-optimistic reCaptcha says: arranged astypedZ)

  24. 124
    prokaryotes says:

    As in any war, some locations will be saved and other sacrificed early on. Some locations will, over time, receive devastating assaults and others will succumb to the slow ravages of wind and water damage and other relentless environmental insults.

    It also means that land is flooded, land is lost to coastal erosion – dependent on the new SLR regime. This means that vast amounts of possible new environmental contamination will occur when modern human settlements become lost to the sea. The ecosystem response will likely contribute to growing ocean dead zones and could induce another feedback from increased decomposition rates and the availability of higher amounts of organic content. For instance, just to visualize one serious implication means to understand how we plan to bring nuclear power plants to higher grounds.

  25. 125
    patrick says:

    @124 It used to be that floods were water emergencies. Now they’re one-way runaway combinatorial toxicity events–and becoming more so.

  26. 126
    Greg Simpson says:

    For instance, just to visualize one serious implication means to understand how we plan to bring nuclear power plants to higher grounds.

    I can’t see this, at least, being much of a problem. Can any operating nuclear reactor not handle a 3′ rise in sea level? Will any existing nuclear reactors still be operating ~85 years from now when the sea will have risen 3’? It’s a very slow process, so we have plenty of time for planning about this.

  27. 127
    prokaryotes says:

    Greg Simpson

    I can’t see this, at least, being much of a problem. Can any operating nuclear reactor not handle a 3′ rise in sea level? Will any existing nuclear reactors still be operating ~85 years from now when the sea will have risen 3′? It’s a very slow process, so we have plenty of time for planning about this.

    Here are 2 articles from last year on this topic Sea Level Rise Brings Added Risks to Coastal Nuclear Plants and Nuclear Power Plant Flood Risk: Sandy Was Just a Warm-Up

    Not sure where you get the 3′ increase but projected are up to above 2 meters (till 2100), which does not include potential non linear developments. Further is SLR not uniform, which means that in areas such as the US East Coast, SLR is 25% more pronounce.

  28. 128
    Lichanos says:

    In the scheme of things, how important is the Tower of London? Is affection for a medieval monument the criterion for societal decisions of this magnitude?

    I can do without Miami, assuming that the real estate moguls don’t see the writing on the wall and move their investments elsewhere, i.e. inland, which would, incidentally, preserve their lock on the beachfront.

    Society makes decisions, without acknowledging them, about future generations all the time. Sometimes cities die because of them: take a look at Detroit, MI. It’s not all that unusual in the history of civilization. Nor has it brought on the end of civilization.

    None of this is intended as a critique of your scientific arguments, but conclusions regarding politics you draw from them are not based in any recognition of the history and development of civilization and how it comes about. You speak in the tone of Jor-El before the catastrophe, or Hari Seldon of the Foundation Series: nobody heeds your prescient warnings! Those are fictional creations – get real.

  29. 129
    Lichanos says:

    Oh, forgot this too – most of NYC is well above the present or projected sea level. It’s only those portions of the city on made land that we we would lose.

  30. 130
    Hank Roberts says:

    > robertscribbler, recommended (or perhaps merely pointed to) by prokaryotes

    says
    > the shallow East Siberian Arctic Shelf …. structures
    > in these regions are already emitting …. methane ….

    Good so far

    > … from undersea hydrate stores.

    Citation needed; he’s still assuming hypothetical shallow water hydrates to make the scary story hugely more scary than the science supports.

    Yes methane is a big scary story.
    No, it’s not 160x scarier than science supports.
    It’s puny next to coal.

    Don’t distract people from the real problem. Dammit.

    Problem is — being enthusiastic, sincerely caring, utterly convinced about the world’s woes and the need to fix the problem — isn’t enough, if you want people to trust you as a reliable source of good information.

    Having your heart in the right place doesn’t improve how you think.

    You need to check the stuff you point to, not just point to it and say, awesome, look, if that were true it’d be just awful.

    Reality is scary enough.

    We need facts.

  31. 131
    Doug Bostrom says:

    Greg Simpson: Can any operating nuclear reactor not handle a 3′ rise in sea level?

    As long as there’s no weather, absolutely. Assuming rest of geophysics comes to a screeching halt there’s nothing to worry over.

  32. 132
    MA Rodger says:

    A 28 min interview a couple of day’s back (BBCi link here – may be restricted to UK) on BBC Radio 4’s ‘The Life Scientific’ with Jo Haigh of Imperial College, an atmospheric physicist. How she’d cope with deniers like Lichanos @128/129 (and she is quite strong on using that term “denier”) would appear to be ‘politely’. Perhaps we should accept that when deniers like Lichanos at least admit in argument that SLR is happening, that is a small step in the right direction.

    “And the idea that the IPCC is some sort of consensus body of mad green scientists who are all trying to, um, have their own agenda, er, work through government or something I don’t know, is quite ludicrous. I mean, you know what its like when you put a load of scientists together in a room, they are not going to decide to agree with each other together. In fact they are each going to decide to be clever and decide to disagree with each other. So consensus is very very hard to achieve and the fact that they come up with some sort of general agreement means you can be pretty sure that that’s been worked through well.”
    Q- What is the current consensus then amongst scientists about how are climate is changing? Are we doing enough to avert a potential disaster in years to come?
    A – No. Not at all. No. Precious little. All the science shows that unless we do something more radical the temperature is going to carry on increasing.

  33. 133
    Dave says:

    I wrote a comment @71 about 10 days ago and hadn’t revisited until just now. I read that some identify me as a Troll, some dismiss me and some responded to at least part of what I was trying to say.

    My point, however inadequately put, was to suggest that there is inevitability about changes to the climate that are coming – that we have/are, in actuality, done/doing nothing that will change that.

    Does anyone here believe that CO2 ppm is going to reduce in the next 50-100 years?? Does anyone believe that, globally, the initiatives agreed and undertaken are actually going to reduce CO2 in that period?

    Unless China, India, Brazil, etc get on board and reduce their CO2 production then, in reality, the initiatives being implemented by “the West” will not contribute to an overall reduction. Does anyone disagree with that? Does anyone think that’s going to happen?

    I am not saying we shouldn’t do everything we can (in the west) but it will never, realistically, be enough.

    Just so you know, I haven’t been on an aeroplane for over 5 years, I drive less than 2000 miles a year. I am a vegetarian and eat less than 1500 calories per day. I recycle as much as possible and produce very little rubbish or food waste. My wife and I have produced two kids – which will replace my wife and I when we are gone. Any of you have more than two kids? I am happy to put my personal carbon footprint up against any contributor/commentor on this site.

    And that’s the point isn’t it. It doesn’t matter (in reality) what I do – its what the rest of you do – and you aint doing enough to prevent the inevitable.

    So, coming back to my point, if we believe that 2 degrees of warming is now “locked in” in the next 100 years – what should we be doing now to deal with the issues that we result from that predetermined warming? Which Islands are going to go under and what are we going to do with that population? Where should we stop allowing building development near threatened coastlines? etc etc. Alternatively, where, around the world, are we going to build coastal or flood defenses that will cope with the predicted sea level rise? Where will water and food availability be problematic and what are we going to do about that. Will there be areas with greater water and food production capability?

    As an aside, and hopefully an observation of the blindingly obvious, it is clear that the single factor that is most responsible for AGW – is the growth in the human population here on earth! If our population was where it was 50 years ago – then AGW would probably not be an issue. The estimated, continuing rapid rise in the human population is the single main factor that has/will cause the problems envisaged.

    So, here we go. What would be the affect of limiting every person on the planet to having one child (for clarity, that’s two per couple). What would that achieve? Is that a more achievable goal than other initiatives? … and so on.

  34. 134
    sidd says:

    Miles et al: doi:10.1038/nature12382

    The biggest player, EAIS, more labile than thought.

    ” … the vulnerability of large parts of the EAIS margin requires urgent reassessment.”

  35. 135
    SecularAnimist says:

    Lichanos wrote: “most of NYC is well above the present or projected sea level. It’s only those portions of the city on made land that we we would lose”

    If the New York City sewer system is flooded and eight million people cannot flush their toilets, the city is uninhabitable.

  36. 136
    flxible says:

    What would be the affect of limiting every person on the planet to having one child (for clarity, that’s two per couple).
    Do the math, 2+2 doesn’t = 2. There are many living humans with grandchildren and great-grandchildren, and even great-great-grandchildren. Your 2 children will be having children long before you and your spouse are dead, and count on those grandchildren having grandchildren soon after your demise, if not before. The only way to stop population growth [as China has found] is to stop reproducing. So in reality, it does matter what you do, your ‘footprint’ includes adding more humans to the current population, which you rightly perceive as the root of the problem.

  37. 137
    Doug Bostrom says:

    …only those portions…

    “Only” is like “just.” Four letters to cover up what we don’t really want to think about.

  38. 138
    Filip Hondekyn says:

    “Protecting the Lowlands during relatively stable sea level conditions…”. Sea level conditions of the North Sea have never been stable, transgressions, regression and floodings have repeatedly caused massive damage in known history. Read about “Floods in the Netherlands” and “the Dunkirk Transgressions”. Cities and villages disappeared in the sea, others lost their connection to the sea and became economically irrelevant. That’s why flood protection is omnipresent in urban developments near the sea since more than thousand years. “Open” cities such as New York are unthinkable in the Lowlands.

  39. 139
    MA Rodger says:

    Dave @133
    You are presenting the most bizarre ideas here. And they are also way off topic, although you are not alone in that on this thread.

    You assert that is “blindingly obvious” that AGW can be blamed on population growth, indeed the “continuing rapid rise in the human population is the single main factor that has/will cause the problems envisaged,” having previously pointed the finger at “China, India, Brazil, etc” as offenders who will blow all chances of sorting AGW if they don’t “get on board and cut their CO2 production”.

    It is true that if there were 700 million humans and not 7 billion of us, we would have to be busier burning fossil fuels to do a proper job with achieving AGW. But beyond the theoretical, this is hardily a useful idea. And then to suggest that we Westerners are not the true offenders in all this – that is a rather distasteful idea, mainly because it is so untrue.

    If you take the historical cumulative emissions for each country in the world (Gapminder is one source.) and take the 16 top offenders, 4 of them are your offending non-Western countries with bulging populations. They are responsible for 16% of all historical CO2 emissions and today have a combined population of 2.6 billion.
    The other 12 countries are Western (if you can include Russia & Japan in such a description) responsible for 63% of all historical CO2 emissions with a combined population of 970 million. The top dog in all this is the good old US of A (31% missions all on their lonesome) with the good old Brits and the Belgians not far behind in per capita terms.

    The emissions that drive AGW are not a result of population, or of rising population but a result of high fossil fuel use, a practice at which us Westerners need no lessons from non-Western societies. We have the hang of that already. And when we eventually begin to significantly decarbonise our society, the non-Western world will no doubt be following close behind.

  40. 140
    dhogaza says:

    flxible – the replacement fertility rate is generally accepted to be a bit over 2 births per woman per lifetime (the expectation that over large numbers of births, close to one of those will be a girl).

    “per couple” doesn’t really matter, it’s the fertility rate per woman that matters, but when a couple is together for their reproductive life and have two kids, it works out to be the same.

    The fact that kids have kids before parents die etc etc affects how long it takes for equilibrium to be reached, that’s all.

    The same principles apply to other species and is a rather basic element of population ecology.

  41. 141
    Mal Adapted says:

    flxible, in response to Dave:

    So in reality, it does matter what you do, your ‘footprint’ includes adding more humans to the current population.

    And those humans, your offspring, will each have their own footprints, as will their offspring, on into the future. The discounted present value of all those future footprints must be charged to your own. Whereas the footprint of a childless person declines to zero on that person’s death.

    While I’m at it, why does anyone think their genes are worth reproducing, anyway?

  42. 142
    flxible says:

    dhogaza, Note Mal Adapteds elaboration – and note that although China has had a “one child” policy for 30 years [for some of their populace], the population there has not reached “equilibrium” yet, it is still growing. The point is ecology involves more than population numbers, those numbers are not ecologically sustainable now, and even less so as we go forward.

  43. 143
    Jim Larsen says:

    140 dhogaza said, “The fact that kids have kids before parents die etc etc affects how long it takes for equilibrium to be reached, that’s all.”

    Not in this case. Human life spans are increasing. I’ve read that the first person to live to 200 has probably already been born. Double life span and you double population. Can you say 15 billion?

  44. 144

    #133–Dave, I don’t think anyone here thinks that adaptation won’t be (or isn’t) necessary. But it’s also not sufficient. Mitigation *has* to happen. And yes, I believe that it will happen–though how soon, how much, and how adequate remain open questions. (Indeed, as I indicated in my original response, I believe it is happening now, in incomplete but meaningful ways.)

    And, for what it is worth, I disagree that “the single factor that is most responsible for AGW – is the growth in the human population…” The growth of population is enabled–ie., partly caused–by the the burning of fossil fuels. And though population growth does factor into ecological footprint, it does not primarily drive it.

    Consider China: population growth has been slowing during the last couple of decades–precisely the period during which and GDP and GHG emissions have been surging.

    http://www.data360.org/dsg.aspx?Data_Set_Group_Id=201

    “What would be the affect of limiting every person on the planet to having one child (for clarity, that’s two per couple). What would that achieve?”

    Well, if China’s experience is a guide, and considering the above graph and the fact that ‘one child’ was mandated in 1979, to a reasonable approximation, we’d see a stable population in about 40 years, one about 40% higher than today. (Of course, China excluded!)

    “Is that a more achievable goal than other initiatives?”

    I doubt it, but it’s far too late in any case.

  45. 145
    Hank Roberts says:

    > human life spans are increasing
    On average, yes — but maximum possible life span for an individual?

  46. 146
    Steve Fish says:

    Re- Comment by Jim Larsen — 30 Aug 2013 @ 7:32 PM

    “I’ve read that the first person to live to 200 has probably already been born.”

    Where did you read this? Science fiction is not a good basis for environmental and social planning.

    Steve

  47. 147
    Susan Anderson says:

    Looking at all the off topic discussion here and wondering if it would be out of order for this amateur to weigh in, instead I thought I would ask if anyone has addressed or is thinking about this news:

    http://www.climatecentral.org/news/newly-discovered-greenland-mega-canyon-sends-water-to-the-sea-16415
    (h/t Tenney Naumer)
    “Greenland “Mega Canyon” Sends Water to the Sea” (nice graphic)

    (Being a secondary reporter mostly for laypeople, ClimateCentral of course provides the original:
    http://www.sciencemag.org/content/341/6149/997

    Though I kind of knew about Greenland’s topography, this one gave me furiously to think.

  48. 148
    Lichanos says:

    Re. #135 from secular animist:

    Would the entire sewer system be flooded? I don’t think so, and the sewers of NYC are something I know a lot about. Don’t you think we could work out a few adaptations in the hundreds or thousands of years the author allows us?

    This is a fine example of the limited value of much scenario planning that passes for science these days. Sure, it would all be better if we could avoid the problem, but let usbe realistic…here at REALclimate.org.

  49. 149
    Hank Roberts says:

    > likely to have influenced basal water flow
    > from the ice sheet interior to the margin.

    I wonder if the canyon’s got a deep opening into the Arctic Ocean.
    Anyone looking for outflowing fresh water deep under the icecap there?

  50. 150
    Ray Ladbury says:

    Dave@133, Population growth is just one of the factors causing increased emissions of CO2. Increasing wealth is another–and increasing wealth winds up correlating with decreasing fertility. What is more, as global population decreases, it raises problems for how so few young workers will support all us old farts in our dotage. Demographics may wind up being a problem that makes solving climate change look trivial by comparison.

    And no, we won’t save the planet merely by cutting consumption. What we may do is buy time–time to come up with a technological solution that saves our bacon. Time is what we have squandered. Time is what we now need most of all.


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