RealClimate logo

Runaway tipping points of no return

Filed under: — gavin @ 5 July 2006 - (Slovenčina)

I wonder if any else has noticed that we appear to have crossed a threshold in the usage of the phrase ‘tipping point’ in discussions of climate? We went from a time when it was never used, to a point (of no return?) where it is used in almost 100% of articles on the subject. Someone should come up with a name for this phenomenon….

Regardless of the recent linguistic trends, the concept has been around for a long time. The idea is that in many non-linear systems (of which the climate is certainly one), a small push away from one state only has small effects at first but at some ‘tipping point’ the system can flip and go rapidly into another state. This is fundamentally tied to the existence of positive feedbacks and is sometimes related to the concept of multiple ‘attractors’ (i.e. at any time two different ‘states’ could be possible and near a transition the system can flip very quickly from one to another). Another ‘tipping point’ in non-linear systems occurs when as some parameter varies, the current attractor changes character or disappears. However it is currently being used interchangeably a number of potentially confusing ways and so I thought I’d try and make it a little clearer.

Positive feedback

A positive feedback occurs when a change in one component of the climate occurs, leading to other changes that eventually “feeds back” on the original change to amplify it. The classic ones in climate are the ice-albedo feedback (melting ice reduces the reflectivity of the surface, leading to more solar absorption, more warming and hence more melting) and the water vapour feedback (as air temperatures rise, water vapour amounts increase, and due to the greenhouse effect of the vapour, this leads to more warming), but there are lots of other examples. Of course, there are plenty of negative feedbacks as well (the increase in long wave radiation as temperatures rise or the reduction in atmospheric poleward heat flux as the equator-to-pole gradient decreases) and these (in the end) are dominant (having kept Earth’s climate somewhere between boiling and freezing for about 4.5 billion years and counting). But it is the postive feedbacks that make weather chaotic and climate interesting.

People often conclude that the existence of positive feedbacks must imply ‘runaway’ effects i.e. the system spiralling out of control. However, while positive feedbacks are obviously necessary for such an effect, they do not by any means force that to happen. Even in simple systems, small positive feedbacks can lead to stable situations as long as the ‘gain’ factor is less than one (i.e. for every initial change in the quantity, the feedback change is less than the original one). A simple example leads to a geometric series for instance; i.e. if an initial change to a parameter is D, and the feedback results in an additional rD then the final change will be the sum of D+rD+r2D…etc. ). This series converges if |r|<1, and diverges (‘runs away’) otherwise. You can think of the Earth’s climate (unlike Venus’) as having an ‘r‘ less than one, i.e. no ‘runaway’ effects, but plenty of positive feedbacks.

Tipping points

So are there ‘tipping points’ in climate? One way to assess that is by looking for elements of the physical system where we think that there is a threshold behaviour. Two frequently discussed examples are the overturning circulation in the North Atlantic and the summer sea ice in the Arctic. In both of these cases, the existence of these phenomena can be disrupted in models (and there is evidence of similar behaviour in the real world) by small changes in freshwater and increasing polar amplification, respectively. At some point, both could simply cease to be viable. But we are not very confident of where these points are or how sensitive the threshold is. These are examples of ‘known unknowns’.

There is also the existence of ‘unknown unknowns’ – tipping points that we are as yet unaware of. An example of this kind of surprise happened in relation to the Antarctic ozone hole, where unexpected chemistry on surfaces of ice particles lead to much more efficient destruction of ozone in the polar vortex than had been expected, making an existing concern into a serious problem. By their nature, we are not able to assess how important any such surprises might be, but it is impossible to rule them out entirely.

By far the most common examples of tipping points though are in relation to ecosystems. The extremely complex web of interdependencies that keep ecosystems dynamic and healthy give rise to plenty of potential thresholds and it is extremely difficult to predict consequences of external changes. The myriad influences on the health of ecosystems (habitat loss, logging, urbanization, species introduction etc. as well as climate change) means that it is most likely here that the tipping point concept will be most applicable. Examples such as a rise in minimum winter temperatures that allow a new insect species to gain a foothold in a new ecosystem (pine bark beetles in Alaska), or warming that leads to movement upward in altitude of ecosystem zones that end up reducing the area of existing alpine biomes. As the planet warms, it is easy to imagine an increasing number of ‘tipping points’ being passed, each related to some different sub-system of the climate or biosphere.

Points of no return

Are ‘tipping points’ the same as the ‘points of no return’ oft used in the media? For a species that becomes extinct as a result of crossing a threshold, the answer is obviously yes. But in the physical climate system, are there genii that can’t be put back in the bottle? This is really a question of time scale. Changes to aerosol concentrations can be reversed in a few weeks after an emission change. CO2 levels however are much slower to change and are already very unlikely to revert to pre-industrial values in any scenario over the next few hundred years. In this minimal sense the climate is already past the point of no return compared to pre-industrial climate.

The ‘known’ physical tipping points described above have natural timescales that determine whether ‘returns’ are possible. The Arctic sea ice, for instance, has timescales of around 5 years to a decade, and so a collapse of summer ice cover could conceivably be reversed in a ‘cooling world’ after only a decade or so (interactions with the Arctic ocean stratification may make that take a little longer though). Model simulations of the thermohaline circulation indicate that for small perturbations, recovery can occur in a few decades. For larger perturbations (i.e. complete collapses) intermediate-complexity models suggest that in some regimes these changes can be quasi-permanent, although this behaviour has not yet been fully explored in current state-of-the-art GCMs. The clues from the paleo-record indicate that there is likely a bi-modal spectrum of overturning states in glacial climates, but there is no evidence of such multiple steady states in the Holocene. Thus there is no strong reason to think either of these ‘tipping points’ are really irreversible – though that is not to imply that the process of loss and recovery wouldn’t have significant impacts.

The big ‘point of no return’ though is usually associated with the melting of the ice sheets – in particular, Greenland and the West Antarctic Ice Sheet (WAIS). Currently the ice sheets exist in part because they already exist i.e. the reason it snows on Greenland is in some large part because there is a large ice sheet there. Should the ice sheet start to melt in a serious way (i.e. much more significantly than current indications suggest), then lowering of the elevation of the ice sheet will induce more melting simply because of the effect of the lapse rate (air being warmer closer to sea level due to pressure effects). Thus if Greenland disappeared, it is unlikely that it would grow back even under current climate, let alone in a warmer world. So loss of either of these ice sheets would indeed be an effect with ‘no return’, at least on any reasonable human timescale.

10 years?

Jim Hansen was widely quoted earlier this year stating that there were likely only 10 years left in which serious actions could be taken to prevent ‘dangerous anthropogenic interference’ on climate occurring in the future. He described this as a ‘tipping point’, but it should be clear that he was not using the term in exactly the same way as I defined above. He very specifically was not indicating that some irreversibly large change in climate would happen in 10 years. Instead he was pointing to the trajectory of increasing CO2 emissions that continue to add to atmospheric concentrations. Actual and projected emission levels are already at the high end of Hansen’s ‘alternative scenario’ which was suggested as an achievable outcome (based on significant control efforts) that kept forcings (including Co2, CH4 and black carbon) below a level that Hansen considered would be ‘dangerous’ (specifically a level that would avoid the melting of any significant fraction of the WAIS or Greenland ice sheet). It is the inertia of societal infrastructure, the carbon cycle and the climate that implies that at any point there is a significant warming that is already ‘in the pipeline’ (and thus very difficult to avoid). We have estimated this at about 0.5 C. Hansen’s statement can therefore be read as a comment on a ‘point of no return’ of the human-climate system, rather than the climate system in a purely physical sense.

The ’10 year’ horizon is the point by which serious efforts will need to have started to move the trajectory of concentrations away from business-as-usual towards the alternative scenario if the ultimate warming is to stay below ‘dangerous levels’. Is it realistic timescale? That is very difficult to judge. Wrapped up in the ’10 year’ horizon are considerations of continued emission growth, climate sensitivity, assumptions about future volcanic eruptions and solar activity etc. What is clear is that uncontrolled emissions will very soon put us in range of temperatures that have been unseen since the Eemian/Stage 5e period (about 120,000 years ago) when temperatures may have been a degree or so warmer than now but where sea level was 4 to 6m higher (see this recent discussion the possible sensitivities of the ice sheets to warming and the large uncertainties involved). In 10 years time CO2 levels will likely be greater than 400 ppm and the additional forcing combined with the inertia of the system will be make it increasingly unlikely that we will avoid a further 1 deg C or more warming. While the ’10 years’ shouldn’t be read as an exact timetable, it is surely in the right ballpark. 30 more years of business-as-usual will make it impossible to keep temperatures from rising beyond Eemian levels (see here for some discussion of stabilisation scenarios), and decisions (on infrastructure, power stations, R&D, etc.) that are being made now will determine the emissions for decades to come.

One point or many?

Much of the discussion about tipping points, like the discussion about ‘dangerous interference’ with climate often implicitly assumes that there is just ‘a’ point at which things tip and become ‘dangerous’. This can lead to two seemingly opposite, and erroneous, conclusions – that nothing will happen until we reach the ‘point’ and conversely, that once we’ve reached it, there will be nothing that can be done about it. i.e. it promotes both a cavalier and fatalistic outlook. However, it seems more appropriate to view the system as having multiple tipping points and thresholds that range in importance and scale from the smallest ecosystem to the size of the planet. As the system is forced into new configurations more and more of those points are likely to be passed, but some of those points are more globally serious than others. An appreciation of that subtlety may be useful when reading some of the worst coverage on the topic.

207 Responses to “Runaway tipping points of no return”

  1. 151
    lars says:

    More on ‘Frozen out’ and global warming
    There is also little dispute regarding natural climate change. Climate has never been static. Over the last few million years the climate has changed particularly dramatically and rapidly. Ice caps have developed in North America and Europe, melted, and then grown again 15 to 20 times. The ice takes about 90,000 years to grow, and 5,000 years or so to melt. The warm periods between glaciations last about 10,000 years. Ours has already lasted for this long. If the natural cycles of the past prevail, the climate should soon quite suddenly cool (over a few years or decades, although the climate switch may initially flicker). The North American ice cap will then expand to cover Canada, and reach Ithaca in about 50,000 years. Less dramatic cycles (the Holocene climate optimum, the little ice age, and the current warming) have affected humanity within our interglacial period. Natural climate change is real, rapid, and significant.

    Prompted by Scarborough, Stossel attacked Gore with Myths, Lies, and Downright Stupidity
    NAS report “said we can’t rule out that this [climate change] is just natural.” He claimed that the report’s authors “said we think” global warming is “man-made,” but that “we don’t know” and “[w]e can’t rule out that these are all natural influences.”

  2. 152
    Matt Pease says:

    I just wanted to point out that in regards to the Pine Bark Beetle infestation of Alaska… I hope that you all are aware that most of British Columbia’s forests are currently being decimated by the Mountain Bark Beetle. Canadian officials fear that it will spread over the rockies and head east… making its way through the Boreal Forest (1/3 of the world’s forest) clear to the East coast of Canada.

    I read here that the current toll stands at 8.5 million hectares of effected forest. I read somewhere else that this number represents BILLIONS of trees. (4th paragraph talks about fear of spread to eastern canada)

    Somewhere I read that BC expects to lose 90% of their forest. I’m not sure where I read that… I didn’t understand if this was 90% of all forest, or 90% of the lodgepole pine (the beetle effected tree)

    It seems to me that we are witnessing the changes unfolding before our eyes. This event must be causing Canadians to want to move to renewable energy ASAP.

    Unfortunately… no such event has hit the US of A. And so people remain unaware of the growing urgent need for action.

  3. 153
    John McCormick says:

    Fires also produce enough carbon dioxide that the recent (2002-2003?) increase of atmospehric CO2 concentration has been attributed, in part, to the massive fires in Borneo.

  4. 154
    John McCormick says:

    Re #147

    Brian, you are getting geoengineering crossed up with bioengineering.

    I too am hesitant about the long term consequences of altering genetic structure of the foods upon which we depend. However, the nigh may be neared than we think or the models project.

    The concern about altering surivial food crops is, to me, a concern similar to the fear that disposal of nuclear waste will threaten humans for ten thousand years, at the least. Wish we had that much time on our side.

  5. 155
    Eric says:

    My information is from studies using a model: (e.g. 9927482)

    [Response: Thanks! It doesn’t appear to include the ozone or CO2 effects, but it does show that the sulphates (+indirect effects) outweigh the soot effects. I stand (partially) corrected, but it may be one of those things that are quite model dependent. I’ll ask around…. – gavin]

  6. 156
    Lynn Vincentnathan says:

    RE the positive feedbacks, any comments on the recent article to appear in the journal SCIENCE re how scientists may have seriouly underestimated the amount of carbon frozen in Arctic permafrost. Which could really spell disaster if it were released due to warming/melting….

    I guess what scientists don’t know (but perhaps discover later) could actually hurt us.

    I read reference to it at ClimateArk, an LA Times story, so of course it may have been sensationalized (or maybe not):

  7. 157
    Sean D says:

    Hi folks, I guess this should really wait until a posting on clouds, but I started a new blog called “Head in A Cloud”, focused on current research in cloud physics and in particular cirrus (my research) and upper troposphere / lower stratosphere topics. Please feel free to swing by and say hi!

  8. 158
    pete best says:

    This report brings together the material from the UK climate meeting in Exeter in 2005 and is headed by Tony Blair who personally believes that climate change is unsustainable and hence the major U turn on nuclear power as well as increased renewable energy commitments.

    This conference appears to have been mainly about type II – abrupt climate change and the speakers and attendeed certainly appear to believe in an worse than predicted warming world.

  9. 159
    Doug Percival says:

    John McCormick in #146 wrote: “Stronger drought, pest and heat resistent crops and silviculture may be our means to buying a little, precious time …”

    Research by the Rodale Institute and others has found that organic agriculture produces higher yields during droughts than “conventional” petrochemical (fertilizer & pesticides) agriculture.

    A large-scale transition to locally produced, organic, vegetarian diets would be helpful in reducing both CO2 and methane emissions from food production and transport.

    For example a recent study by researchers at the University of Chicago found that the difference in CO2 emissions generated by producing the typical American diet and those associated with a vegan diet was comparable to the difference between driving an SUV and driving a compact sedan.

    And eating locally produced food eliminates the CO2 emissions associated with transporting produce such as lettuce and tomatoes (which are 90% water) thousands of miles in refrigerated diesel trucks, which is simply insane.

    Probably the smallest global-warming food-production footprint comes from growing your own food in a backyard garden. Victory Gardens, anyone? In the WWII era, Victory Gardens produced vast amounts of food and really helped feed the country during wartime shortages. Imagine the impact on energy consumption and CO2 emissions by agriculture if typical American suburbanites devoted the time and energy that they presently spend on maintaining lawns and various other decorative landscape plantings to organic food gardens instead.

  10. 160
    Dano says:

    RE 148 (Sadlov):

    “Tipping point” has a more ambiguous meaning…if such a state is a likely outcome, is it “bad,” “good,” or neither?

    To restate, you say a tipping point is ambiguous. This is incorrect. The ecological literature is clear on this point.

    Your following questions:

    what is that state? usually is understood to be ‘a different stable state’ or ‘a less stable state’ than prior to the flip (depending upon the species or system being considered).

    Has the earth been there before, if so, when The five great extinction events (to use your implied global-wide scale. There have been many tipping points at smaller scales, such as desertification or Mayan-era drought.)

    if such a state is a likely outcome, is it “bad,” “good,” or neither? We must consider that our economies and social networks are predicated on THIS stable state. We have no experience or precedent for undergoing such a change to a different state on large scales. None.

    We see contemporary events unfold and read accounts of societal change in past events, and we make our judgements on how they turn out; our predilection for assessing ‘good’ or ‘bad’ from events colors our solutioning and judgement for how the solution turned out. That is: we are wont to assess moral outcomes to events according to our natures. Answering your question as it is framed is highly charged, at best.

    But certainly those charged with the stewardship of our societies should be cautious about committing societies to uncharted waters, with no compass, and no way of being sure of securing adequate provisions for the journey. So: having to lead billions forward when having no experience, IMHO, is “bad” in the sense that I wouldn’t want to do it, and I know or can conceive of no one who does.



  11. 161

    “A large-scale transition to locally produced, organic, vegetarian diets would be helpful in reducing both CO2 and methane emissions from food production and transport.”

    Proposals that run counter to cultural norms are not only success-proof, but they make the environmenal movement look, shall we say, not serious.

    Americans will give up hamburgers and go vegan when Mexicans switch from maize to buckwheat kasha.

    Anyway, there’s plenty of dry prairie out West which has always been unsuitable for grain but does perfectly well for stock raising.

  12. 162
    Mark A. York says:

    “Unfortunately… no such event has hit the US of A. And so people remain unaware of the growing urgent need for action.”

    Not true. In central Idaho the bark beetle is on the march; and In the San Bernardino Mountains outside of LA. Great swaths have been cut due to beetle-killed trees under the National Forest Restoration Act and “Healthy Forests.”

  13. 163
  14. 164

    Interesting local climate note here (Washington DC): About two weeks ago we received approx. 30 centimeters of rain in 4-5 days. I believe that the *yearly* average precipitation is approx. 95 centimeters. So we had approx. four months’ rain in 4-5 days.

    Some local home owners suffered appreciable property damage from flooding, and they applied to the regional water authority for compensation for damages – something to do with sewers I suppose. The authority rejected the claim, stating that the area had experienced a ‘200 year’ storm, which amounted in their judgement to ‘an act of God.’

    Which leads me back to the idea that if you want to track the development of climate change awareness in the practical world, keep your eye on the insurance companies.

    Swiss re, anyone?

  15. 165
    Lynn Vincentnathan says:

    There’s been talk of solutions — all the more needed if we are headed toward a runaway tipping point of no return — including geo-engineering.

    And some have raised religion. (Thanks for posting these, since the religious communities seem in general to have fallen quite short on addressing GW — guess some just like it hot.)

    So here’s a solution: Pray to end GW.

    This is sort of scientific. I read about a science fair project in which a girl experimented on 5 marigold plants. One, the control, the others she talked to, played classical music to, rock music to, and one she prayed over. The talked to & classical music ones did better than the control, and the prayed over one did best, and (you got it) the rock music one….died. So even though there’s no empirical/material theory to go along with this, prayer does seem to work.

    For Catholics on this site I recommend dedicating each decade of the daily rosary to “ending GW”; it can be said while waiting in lines, trying to sleep at night, and other odd moments. The cost is nil, and I think it may finally do the trick of pushing the world’s populace to the tipping point of working to end GW, before we reach the tipping point of “GW is now beyond our ability (thru our GHG reductions) to halt or reverse.”

    (If this isn’t posted, I’ll understand.)

  16. 166
    Doug Percival says:

    Pavel Chichikov wrote: Americans will give up hamburgers and go vegan when Mexicans switch from maize to buckwheat kasha.

    I’ve heard the exact same sentiment expressed innumerable times about how Americans will never give up SUVs and drive compact cars.

    What impresses me most about these sort of comments is the apparent underlying notion that the world revolves around “what Americans want”. If Americans want to drive SUVs, then there simply must be an abundant supply of cheap gasoline forever, and anthropogenic global warming must simply not be real. Case closed.

    If Americans want to consume vast quantities of cheap, factory-farmed cow and chicken and pig flesh, then there simply must be an unending supply of cheap factory-farmed grain to feed the animals, and an unending supply of cheap fossil fuels to power industrial agriculture, and the anthropogenic global warming associated with the CO2 and methane emissions from industrial animal agriculture must simply not be real. Case closed.

    This notion that reality must conform itself to whatever Americans want seems to me a sort of national infantile narcissism. And it is so ingrained that whoever brings up the inconvenient truth that reality does not, in fact, conform to whatever Americans want is viewed as, shall we say, “not serious.”

    My own expectation is that the vast majority of Americans will continue to believe that reality revolves around what they want, and will behave accordingly, until the bitter end. And the result will be ever-escalating wars for control of dwindling oil supplies, ever-escalating destruction of ecosystems, and irreversible, runaway catastrophic global warming, until the whole house of cards that constitutes the present-day “American way of life” collapses, in a very painful and ugly fashion.

  17. 167
    Brian Gordon says:

    Re: 154: Confusing bio with geoengineering:
    John – I assumed that, for bioengineering to have sufficient effect, it would have to be carried out on a global scale. To me, this is, effectively, geoengineering.

    Re: 161: local, organic, vegan
    “Proposals that run counter to cultural norms are not only success-proof, but they make the environmenal movement look, shall we say, not serious.”
    I guess we have to find a way to make the US car-based, excessive-consumption culture work, then? I once owned an upscale vegan restaurant, in Sedona, Arizona. It was next to a Holiday Inn, and often we would get customers just before closing, who had just checked in. Not many Holiday Inn customers were vegan. Not many were happy to discover that the only restaurant they could get to before closing was vegan. Pretty nearly every one of them was shocked and awed that vegan food could taste so good, and that one could *feel* so good after eating. Without lots of wine. :-)

    I believe we are culturally biased toward meat because it is a status symbol: an expensive luxury that used to be in short supply, and another way of showing our dominion over nature. That can change. How much meat did we eat pre-industrial farming? We’ve invested a lot of money in making fast food tasty; no reason we can’t do the same with non-meat-based foods.

    Re: 152: Bye bye forests
    “Somewhere I read that BC expects to lose 90% of their forest. I’m not sure where I read that… I didn’t understand if this was 90% of all forest, or 90% of the lodgepole pine (the beetle effected tree)

    It seems to me that we are witnessing the changes unfolding before our eyes. This event must be causing Canadians to want to move to renewable energy ASAP.”
    You would think. However we recently elected a ‘conservative’ as PM, and they have a poor record conserving anything except their money.

  18. 168
    John McCormick says:


    I want to turn your words upon you and in a constructive way because I share your sentiments and not all your ideas of what is possible.

    You said: “This notion that reality must conform itself to whatever Americans want seems to me a sort of national infantile narcissism. And it is so ingrained that whoever brings up the inconvenient truth that reality does not, in fact, conform to whatever Americans want is viewed as, shall we say, “not serious.”

    I could replace the word “Americans” with Doug Percival and I get the same result —– …..whatever Doug Percival wants is viewd as, shall we say, “not serious”.

    From Richmond, VA to north of Boston, about 100 million people have absolutely no opportunity to subsist on “victory gardens” letalone locally produced food….weather and land availability seeming to be the limting factors. Can we agree on that?

    Yes, I am sure the Rodale method can resolve some of the water deficit problems in agriculture but not on a ten thousand acre wheat farm. Though, there are likely experiments on small plots and farms that might give me hope that drought will not be a problem for the world’s grain basket farmers. But, I am pessimistic.

    I could go on with this reply about “serious” and include comments on campaigns to get Americans to walk or bicycle to work and short errands. But, I fear that will open a new channel for an “us” versus “them” food fight.

    Suffice it to say that solutions imposed upon the ignorant and unwilling will not fly at this “moment in time” in America. But, eventually, there will be nowhere to run and nowhere to hide. That is what I’m serious about…..thinking worst case —- even if that includes genetically modified food, trees, fiber; whatever we and our children and grandchildren will need to buy us some more time.

  19. 169
    Steve Sadlov says:

    RE: #160 – You are speculating. You don’t know for sure.

  20. 170
    Gavin says:

    Please remember to keep to the point, this is not the place to argue about ideal political systems or your personal opinions about ‘average Americans’.

  21. 171
    Doug Percival says:

    With regard to possible “tipping points” in public opinion, I have been wondering what sort of event might act as a “global warming 9/11” — a shocking event that would quickly transform public opinion about the urgent need to make and/or accept large-scale lifestyle changes to quickly and drastically reduce GHG emissions? Is there any such event that is a real possibility, scientifically speaking?

    Or is it the case that there have already been such events — e.g. the 2003 European heatwave that reportedly killed tens of thousands of people, or hurricane Katrina — but that since it can always be said that “no individual extreme event can be directly attributed to global warming”, that no event, no matter how extreme, will ever cause the sort of “tipping point” in public consciousness that the 9/11 attacks did?

  22. 172
    John McCormick says:

    Doug, I see the European heat wave, Katrina, the 36 inch rainfall in Delhi, and typhoon Larry that skimmed the Australain coast as snapshots in a “family album” documenting their suffering and projecting our future. If such events are symptomatic of climate change, their short history will make their autopsies difficult and likely irrelevant.

    However, using an American example, a decade of increasingly greater reduction of snowpack in the Rockies will translate into enormous costs to the US Southwest and particularly economies of Las Vegas, Phoenix, Tucson and Southern California. Dr. Lisa Sloan and her colleagues are beginning to report and warn of diminished water availability along the Pacific coast and the vested interests are certain to feel the pressure to accelerate water conservation, sell ag water rights to municipalities and implement water rationing programs. Depleting Colorado River water reservoirs beneath their outtake systems, in my mind, will be a 9/11 scale event.

    Maldives and other very low profile islands will have their own 9/11 scale events to experience and report but that will happen on a much longer time frame than diminished stream flow due to melting glaciers (e.g., Himalayan glaciers) and minimal snowpack with early melt.

  23. 173
    Eric says:

    Doug, I think you are much more likely to see tipping points for energy consumption than for warming, It takes energy to make, deliver and use energy whether it is alternative or conventional. For example “$50” shale oil costs calculations were made when conventional oil cost $30. The energy shortage spiral will be made worse by political manipulation, subsidizing net negative energy sources for example.

  24. 174
    Hank Roberts says:

    >160, 169
    Dano, excellent first link to that Google Scholar search on the usage ‘tipping point’ — good work there I hadn’t known about, some excellent papers in the first few hits. And a reminder that ‘don’t rock the boat’ is folk wisdom.

    >169 “don’t know for sure” — no one here does; this is science — if you want certainty, that is available in the math department, down the hall.

  25. 175
    Dano says:

    RE 175 (Roberts):

    Thank you Hank.

    I took Steve’s comment to mean you are speculating about your assertion regarding the lack of leaders that are willing to lead billions forward after a tipping point [as we have no experience or memory to guide us, it is a daunting task that few will want to undertake]. That, surely, is a wish. Certainly leaders will arise as they always do, but only out of necessity and not a willingness for such an unprecedented challenge with no rule book.



  26. 176
    Steve Sadlov says:

    RE: #175 – Specifically, you speculated that our future will bring an abnormality that rivals the 5 great extinction events. Without understanding innate variation levels in the system how can you say whether or not the effects of the projected range of abnormality rivals the effects of the abormalities that are believed to be potential root causes of those extinctions? You may notice I am really hammering this theme. Sorry to say it, but when a faction spends energy trying to downplay or discredit certain ranges of past variation (by trying to make the variation simply go away! or by saying it’s only regional!) that may well be within the normal variation of the “process,” it indicates that there is a sort of doctrine at work. The doctrine purports to describe some mythical “stable state” – almost a sort of Eden. Of course, against such a idealized stick like “flat” framework, the range of possible future innate variation or even, bona fide “subcritical” abnormalities, would appear to be disasterous. If, on the other hand, innate variation is in play, and the long term state is oscillatory, or even a quantum, semi chaotic sequence of events, with a myriad of states which we quite normally and expectedly flip between, then, even some of the worst case things being projected by models may fall well within the innate level of variation. Pause on this last bit, this “chaos and quanta” idea. Juxtapose it with Erwin et al and the notions of highly nonlinear evolutionary history – hopeful monsters – etc.

  27. 177
    Paul Duignan says:

    Picking up on Pete’s point in #123 that he is troubled by not knowing exactly what climate scientists are trying to tell us about where we currently stand in regard to tipping points and todays ABC article on the acceleration of climate change which includes the comment: “But many experts confide privately what they aren’t yet ready to announce publicly: Change is accelerating at a dramatic rate” (URL below) I would find it very helpful if someone from Real Climate could tell us the summary message you want to get across to the public regarding tipping points – is it the “alternative version” I set out in #75 above or is it a modified version of this, if so it would be great if you could post the modified version up here – I would love to hear it.

  28. 178
    Hank Roberts says:

    Paul, have you read these? I suggest this is as clear as anyone can be:

  29. 179
    Dano says:

    RE 176 (Sadlov):

    Hmmm. I’ve discussed the contents of #160 with my editor and she agrees that I could have used a few more words to ensure such speculation as yours would be avoided. Ah, well – this happens in comment threads.

    Nonetheless, upon rereading the exchange, you’ll note that I responded to your ‘likely outcome’ question without passing judgement on its likelihood. That is: I merely answered the question you posed.

    If, on the other hand, innate variation is in play, and the long term state is oscillatory, or even a quantum, semi chaotic sequence of events, with a myriad of states which we quite normally and expectedly flip between, then, even some of the worst case things being projected by models may fall well within the innate level of variation.

    No and yes.

    Organisms exist within ranges of stable bounds. In ecological processes, scale is all-important and your oscillatory states must be bounded by some scalar limits for useful discussion. In socioecological processes, especially in today’s globalized, interconnected economy, regional effects can become global (cross-scalar cause/effect).

    However, we must note that ecological states rarely ‘flip’ at scales important to socioecological processes, and state changes at important scales during our agrarian era (the last ~10K yr) have been few but have had important, lasting impacts (viz. Anasazi, Maya, Eastern Med., Easter Is.).

    So, while one can discuss past variation all day, at time scales important to human society our ecological states have been, in effect, stable. We, simply, have no blueprint for leading this society, today, forward after a flip of an ecological state at any relevant scale. That was my point. We don’t know what agriculture will be like if the state flips in, say, central Europe and wheat can’t be grown there.



  30. 180
    William Golove says:

    In my PhD dissertation, “Avant Le Deluge: An Investigation of Some Neglected Dimensions of Electricity Restructuring in California,” I did proposed a name for this rhetorical phenomenon. I refer to it as “High Salience Terminology,” which basically refers to words and phrases used in a political context that tend to be persuasive/influential, either positively or negatively. I also describe a process which I refer to as the “Search for Salience” were participants in a particular debate/discussion use various terms until one or more emerge as high salience, at which point there is a move toward widespread use.

  31. 181
    ms @ cu says:

    Nice post!

    Tipping point:

    -phase change (e.g., “freezing” liquid to solid)
    -bifurcation (e.g., fork in the road)
    -self organized criticality (e.g., see Per Bak, avalanches, sand pile experiments, ecocatastrophes…)
    -cusp (e.g., “cusp catastrophe”, like in ecological situations like the spruce budworm outbreaks as described by Ludwig, et al)

    These things aren’t necessarily irreversible, of course, though “hysteresis”, e.g., might make it a bit of a long road back to where we were or want to be…

    Some authors re nonlinear systems, complexity, “tipping points” (that can keep it manageable for the laypeople that most of us here are, to be honest with ourselves):

    -Barry Saltzman
    -Steve Strogatz
    -Duncan Watts

    Happy reading!

  32. 182
    ms @ cu says:

    Hi Sean D.

    Re your post #157, maybe you have something to say about “tipping points”, being that cloud droplet nucleation, growth, and evaporation are nice manifestations of behavior around a “tipping point”, or struggle of competing “interests” (surface tension, vapor pressure, e.g.) tipping towards a particular outcome (growth, evaporation, or niiice and steady now)…

    You might be interested to take a look at Prigogine’s words in this context, e.g.. Fun fun.

    Thanks for the heads up on your blog.

  33. 183
  34. 184
    Lynn Vincentnathan says:

    RE #176, I agree that nature has been fluctuating greatly on earth over the past billions of years. And it could make the climate warm all on its own (without human help) in the future, or cool to severe ice ages.

    So my idea is that we not add to any warming nature may cause naturally — & who knows when nature might get a fever, so it’s just prudent not to release GHGs, even when nature doesn’t seem to be warming the earth (due to the time lag). On the other hand, we will need to save all our fossil fuels for an “ice age” day, so we can tweak up the climate a bit when that happens.

  35. 185
    Hank Roberts says:

    Relevant to the topic,

    Discussion found (second hand already) mentioned here:

    “Article: “Leverage Points: Places to Intervene in a System”

    “I read this fascinating paper over the weekend by systems analyst Donella H. Meadows, called “Leverage Points: Places to Intervene in a System”. Leverage points are those “places within a complex system (a corporation, an economy, a living body, a city, an ecosystem) where a small shift in one thing can produce big changes in everything.”

    “The central thesis of Leverage Points is to elucidate a theory by MIT professor Jay Forrester that “People know intuitively where leverage points are…[however] everyone is trying very hard to push [them] in the wrong direction!” So Meadows observes that paradoxically “Leverage points are not intuitive. Or if they are, we intuitively use them backward, systematically worsening whatever problems we are trying to solve.””

  36. 186
    bender says:

    Re: #152: warming and beetle outbreaks
    1. 90% loss of trees in BC due to pine beetles is an overestimate. In some localized instances losses will be that high. Averaged over larger areas, the figure drops considerably.
    2. The loss would only apply to the host tree: lodgepole pine, not all forests.
    3. Warming is not the only factor responsible for the unusual severity of this outbreak. Other suspected factors include selective harvest of spruce over pine, fire suppression, and the ever-present unknown.
    4. What makes you say that “no such event has hit the USA”? The pine beetle outbreaks in the US Rockies in the 1960s and 1980s were extreme, and may have been an early warning sign of trends to emerge later at higher elevations and latitudes. Read papers by Jesse Logan. (The spruce beetle in Alaska may turn out to be a present-day example of the same sort of response.)
    5. There is a lot of uncertainty surrounding insect responses to climate change. Don’t be so quick to assert.
    6. Science is the cure for uncertainty. Yet funding for forest, insect & climate science has not increased in proportion to public concern over the issue. If you want more science and less uncertainty, write to your elected representatives.

  37. 187
    George A. Gonzalez says:

    The current heat wave gripping vast areas of the northern hemisphere indicates the vital need to plan a geoengineering approach to counter ever increasing temperatures. Current temperatures point to the very real possibility that we are already past a tipping point.

  38. 188
    Colin says:

    Thank you Hank #185. The link to the paper on Leverage points is a real bonus. I have saved it and will send it on to several of my co-conspirators with whom I am attempting to engineer a Paradigm shift. I recomend it as a reference paper and a prop for those times of despair that we all get every now and then.

  39. 189
    Hank Roberts says:

    >185, 188
    One of the earlier online cites to the Meadows article is here:

    Interestingly they also address social network analysis — it reads as a serious early attempt to look at the tangles that occur when multiple problems interact that affect public health and there’s no easy way to get hold of leverage that works.

    Interestingly Meadows was also writing about climate modeling — from the references at that CDC page:

    Meadows DH. Leverage Points: Places to Intervene in a System. Sustainability Institute, 1999.

    Meadows DH, Meadows DL, Randers J. Beyond the Limits: Confronting Global Collapse, Envisioning a Sustainable Future. Mills, VT.: Chelsea Green Pub., 1992.

    Meadows DH, Richardson J, Bruckmann G. Groping in the Dark: The First Decade of Global Modelling. New York, NY: Wiley, 1982.

    24 years ago, that last one. Anyone got a copy, for reference?

    The CDC page says:

    “The term â��syndemicâ�� refers to the phenomenon of linked afflictions. Scholars and practitioners have long observed interactions among diseases, but it wasnâ��t until the early 1990s that anthropologist Merrill Singer suggested that empirical connections among epidemics might signify the existence of a higher-order phenomenon–a syndemic. ”

    Yeah — linked afflictions. We got’em.

  40. 190
    George A. Gonzalez says:

    This was sent to me today. It is a synopsis of an article in the _Independent_:

    _Maybe I’m Amazoned at the Way I Really Need You:
    Drought could turn Amazon into desert, researchers warn_

    The Amazon rainforest — soon to be called The Artist Formerly Known as the Amazon Rainforest, and then just some weird little symbol — appears to be undergoing a second year of drought, and that has researchers seriously alarmed. Starting in 2002, scientists at the Woods Hole Research Center simulated drought on a small section of the Amazon and found that after two years, the trees began to die, fall, and release more than two-thirds of their lifetime storage of carbon dioxide. Widespread desertification of the rainforest would likely spread drought into the northern hemisphere; the Amazon contains 90 billion tons of CO2, enough to accelerate global warming by 50 percent, spinning it out of control and eventually making the world uninhabitable. Computer models predict that harm to 50 percent of the Amazon would represent a tipping point — after that, the whole thing starts going down the tubes. Today, about 20 percent has been totally razed and 22 percent has been harmed by logging. Oy. It’s only Tuesday and we’re already doomed.

  41. 191
    Greg says:

    RE: …CO2 are already very unlikely to revert to pre-industrial values…

    In reviewing the historic “bubble data” in ice cores: 1) there were several periods of rise and fall of temperature, CO2, and CH4; and 2) there were times when temperature rise precedes the rise in CO2 and CH4.

    From it, I conclude that: 1) the relationship between greenhouse gases and temperature is uncertain; and 2) there is some feedback mechanism that has prevented the earth from passing â??the tipping pointâ?? before.

    I recognize that we have gone beyond the previous CO2 peaks and that there is no existing ice to provide the same information on CO2 concentrations in previous times. But what was it that stabilized the earth before and how are we certain that not enough of it currently exists now? Also, other paleo-data suggests that CO2 was much higher in the times long before the current caps were formed. What mechanism removed the CO2 and initiated the ice formation? And since then, what is the cause for the periodicity of the long cooling periods followed by short warming periods until this point?

    I am not planning to count on other feedback mechanisms, but want to recognize that those mechanisms we have are not fully understood â??at least not to me yet.

    This site has been extremely educational. Thanks.

  42. 192

    Re 191. The easiest way to reply is to say that you are correct!

    In the Antarctic ice cores (but not the Greenland cores) the temperature rise has nearly always preceded the rise in CO2 and CH4. Your conclusion that the relationship is uncertain is also true. However it is known that greenhouse gases cause warming, and it seems most likely that the increase in sea surface temperture cause the atmospheric CO2 concentration to rise, and that the increase in land surface temperatures causes the CH4 levels to rise. Thus both gases act as positive feedbacks, and global warming will keep the greenhouse gas levels high even if we stop emitting them, so making global warming self perpetuating.

    There is a negative feedback which prevents global temperatures running away until the surface temperature of the Earth matches that of Venus, and it is the same mechanism that prevents Venus getting any warmer. It is clouds. But clouds do not gently increase as tempertures rise. For clouds to increase we need temperatures to rise considerably, so that the climate settles into a new regime where cloud cover is greater. The tipping point will occur when the current cloud system can no longer provide the negative feedback needed, and temperatues rapidly rise until a new cloud system exists.

    Clouds are the least understood part of the climate system, so you are not alone in not understanding the climate, and the consequences of global warming!

  43. 193
    John L. McCormick says:

    When I read your question Greg, I wondered how it could fetch a short and clear answer. Alastair delivered the goods.

    Now, I would add the other postive feedbacks in the form of melting tundra and permafrost yielding CO2 and CH4 while the oceans acidity accelerates. All contributing to a destabilization over a narrow band of time and too short an interval for humans to adapt civily.

  44. 194
    Karl Sanchez says:

    Once again, for the 5th year running, we have a dead zone off the Oregon coast, a zone that’s getting larger every year (here’s a google link to recent news reports about this, ).

    One scientist noted that this behavior is predicted by global warming models for that region of the Pacific. Is this further related to the lack of mixing action between different ocean layers and predicted increases in acidification due to AGW forcing changes to oceanic and atmospheric circulation? Would it be possible to have a Forum thread address the topic of AGW’s assault on terrestial and oceanic food chains?

  45. 195
    Phillip Shaw says:

    Re #194 – Is there any connection between the dead zones off the Oregon and Gulf coasts and the large methane hydrate deposits off those same coasts? Would the release of methane stimulate phytoplankton, which later dies and rots? Or could there be a chemical reaction between dissolved methane and oxygen that depletes the oxygen level below that needed to sustain life? Please excuse me if these are silly questions.

  46. 196
    Karl Sanchez says:

    Re #195 This item provides answers to your questions,

    Methane hydrates aren’t the cause, but the anoxia is caused as dead plankton’s decay.

  47. 197
    Phillip Shaw says:

    Re #196 – Karl, thank you for the link to the interesting article. Much of the information I already knew and I suspect my questions weren’t phrased very clearly. So I’ll try again.

    The 12/12/2005 RC article on methane hydrate (I’m sorry but I don’t know how to provide the url) refers to large hydrate deposits along the Oregon and Gulf coasts. It describes various ways in which a hydrate deposit can become unstable and melt or break up. And it says “Dissolved methane is chemically unstable in the oxic water column of the ocean, but it has a lifetime of decades (shorter in high-flux environments) [Valentine et al., 2001], so if the methane is released shallow enough in the ocean, it has a good chance of escaping to the atmosphere. Bubbles of methane are typically only able to rise a few hundred meters before they dissolve.”

    I’d like to know what the chemical reaction is for the unstable methane. Is there a net reduction in the dissolved oxygen? And I assume from the article that if the methane hydrate deposit is melting then the bottom water will have a high level of dissolved methane. If this methane saturated bottom water upwells what effect does the methane have on the phytoplankton at the surface? Does it serve as a foodsource and promote rapid growth? Does it inhibit phytoplankton growth? Or is it essentially neutral? Has anyone sampled the dead zones for dissolved methane levels?

    The metaphor I’d use is that the ocean dead zones are the ‘canaries in the coalmine’, dead from an overdose of methane. The persistence and growth of the dead zones may indicate the onset of large-scale hydrate melting. Heaven help us if that’s true.

  48. 198
    Karl Sanchez says:

    Your hypothesis and questions I’m unable to answer. However, I will forward them on to the scientist from the Hatfield Marine Center in Newport quoted in the article. An additional note, the lack of upwelling problem stretches from the southcentral Califonia coast to beyond Vancouver Island, see this item:

    I’ll post whatever response I get from Hatfield.

  49. 199
    Hank Roberts says:

    The lack of upwelling itself is enough to explain the methane levels observed, and the change in wind explains the change in upwelling. I know that observations are made of methane bubbling up.

    Note that fossil methane will be detectable because there won’t be much if any carbon-14 in it, while methane from decomposition of recently dead material will have contemporary levels of carbon-14.

    There’s a lot of attention being given to what happens when the plankton production (“primary production” — the first step where photosynthesis occurs). One example:

  50. 200
    Phillip Shaw says:

    Thank you both for helping me understand more about this. I, like many others, am still on the steep part of the learning curve about AGW and I really appreciate the information provided by the scientists such as yourselves.