Runaway tipping points of no return
) 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.
5 July 2006 at 12:48 PM
Great summary. My favorite use of “tipping points” thusfar was by Al Gore in a recent interview on PBS. He stated that he (I am paraphrasing here) “understands less about climate than many climatologists have forgotten, but he understands politics, and in politics there are tipping points, too.” He then continues to say that great things can happen almost suddenly when enough people get on board. This is the justification he gives for his new movie and his desire to train more people to give his slide show. Does anyone know where he is going to recruit the 1000 people from? I’d love to be trained to give his slideshow. The graphics are far better than those of my own slide show that I give fairly often.
5 July 2006 at 1:20 PM
I’m not sure about Al Gore’s “presentation training” plans, but it may be a large part of the nonprofit Alliance for Climate Protection that he is organizing.
Another source for presentation training is the nonprofit Green House Network (http://www.greenhousenet.org), which since 2000 has organized low-cost speaker training workshops in many parts of the country, including climate scientists, resource scientists, activitsts, and communicators among its trainers. These workshops have trained hundreds of presenters from many walks of life, who collectively have given thousands of presentations on campuses, to community and business groups, etc. The next workshop, billed as a “Global Warming Solutions Weekend Retreat,” is scheduled for Spring Green, Wisconsin on July 14-16. See the Green House Network’s Website for details.
5 July 2006 at 1:25 PM
fabulous posting! i have long wished for a blog entry or article that described this clearly. i had it on a list of things to do myself, but never got to it. i alluded to this idea frequently in discussions, the “tunneling” phenomena in some non-linear systems, but had nowhere to send people except things like Hirsch, Smale, Differential Equations, Dynamical Systems, and Linear Algebra, ISBN 0-12-349550-4, 1974.
thanks very much!
5 July 2006 at 1:42 PM
“Eemian/Stage 5e period (about 120,000 years ago) when temperatures may have been a degree or so warmer than now ”
Just curious, since the CO2 levels are much higher now than they were back then, why was it hotter back then?
Also, CO2 and temperatures seem to line up very well in this graph:
http://www.logicalscience.com/images/vostok-ice-core.jpg
They also seem to line up here:
http://www.realclimate.org/index.php/archives/2005/11/650000-years-of-greenhouse-gas-concentrations/
So if CO2 levels are so much higher now (26% higher than any point since 420K years before the industrial era), why aren’t temperatures lining up?
[Response: The orbital configuration was different, with warmer NH summers than today (or even the early Holocene). That seasonal change may have been crucial for the ice sheets. See the recent Overpeck et al and Otto-Bliesner et al papers in Science for what climate differences one would expect. With respect to today’s CO2, that is not being changed by anything like the same mechanism, and so simply correlations with past data are not going to help. -gavin]
5 July 2006 at 2:15 PM
Excellent discussion, Gavin. Realclimate readers might also be interested in Gabrielle Walker’s discussion of this topic in the 15 June Nature:
http://www.nature.com/nature/journal/v441/n7095/full/441802a.html
5 July 2006 at 2:21 PM
Link for abstracts of the two papers Gavin refers to:
http://www.sciencemag.org/cgi/gca?gca=311%2F5768%2F1747&gca=311%2F5768%2F1751&sendit.x=42&sendit.y=10&sendit=Get+all+checked+abstract%28s%29
5 July 2006 at 2:22 PM
Re glacial cycle CO2 and temp correlation, it is useful to remember that the timescale of that record is 100’s of thousands of years, where as the CO2 rise today has occurred over ~100. The temporal resolution of the ice core records is also very coarse, millenia between samples, so one would have to wait maybe 10K yrs and look back to see if we have the same T and CO2 correlation (assuming there is ice left to core at that time). We may still see very good correlation on the one or two century scale but don’t forget that thermal inertia, mostly in the oceans, causes a long delay before T can catch up to CO2.
Gavin’s point about the physical mechanisms being totally different now still stands.
5 July 2006 at 2:29 PM
I think that this record also shows a significant tipping point scenario at ~12, ~22 and ~34 Myr bp with the formation and disintegration of the Antarctic ice sheet.
I suppose that one is still pretty far off, but I would not be surprise if a few hundred thousand years from now, or less, there was no ice left anywhere. If Greenland “tips”, the WAIS may follow then temperatures would go high enough to eventually melt the EAIS to the bedrock.
5 July 2006 at 2:33 PM
It is not for nothing that Al married Tipper.
5 July 2006 at 3:08 PM
Regarding Hansen’s advice about 10 years, it seems like you are softening his statement. In his recent article in the New York Review of Books (see http://www.nybooks.com/articles/19131) he states “…we have at most ten years — not ten years to decide to decide upon action, but ten years to alter fundamentally the trajectory of greenhouse gas emissions.” So I take him to mean that we have to “start” seroiusly to reduce emissions somewhere between now and 10 years, not by 10 years from the present. Obviously Hansen’s is one very informed scientist’s opinion, so maybe 10 years is overly conservative. But given your description of tipping points and points of no return, a conservative approach seems to be in order.
5 July 2006 at 3:12 PM
A few hundred thousand years?
You are several orders of magnitude off with that comment. Current rates of carbon dioxide increase indicate total global deglaciation in the order of ~1000 years.
5 July 2006 at 3:13 PM
A name for the phenomenon?
widespread panic
cower tipping
defrost on the punkin’
5 July 2006 at 3:43 PM
Excellent post.Take that factor down by 10 to complete deglaciation and loss of all ice at poles within 100 years. Long before that thermohaline shutdown and superstorms and 20 foot sea rise. If co2 emmissions not reduced by 80 % NOW there is very little hope of bypassing the tipping point. Good post, good comments. Hope the Republicans(who hold all the power in all three branches) are listening.Some disappointment on lack of support for AB32 here in CA by certain “Democratic” state legislators.
Thankyou to all the posts and comments from your site. You guys are cool, and should be mandatory reading at Senate briefings.
5 July 2006 at 4:26 PM
“You guys are cool, and should be mandatory reading at Senate briefings.”
Senator Inhofe has already made Crichton’s “State of Fear” mandatory reading for Senators. I’m being dead serious btw.
5 July 2006 at 4:38 PM
Gavin,
“The orbital configuration was different”
Do you have any suggested reading on this? How exactly do they know what the orbital configuration was like 120K years ago?
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.
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Hank Roberts,
Thankyou very much for the direct links.
5 July 2006 at 5:40 PM
This discussion of tipping points is very timely, as you point out, the press seems to be quite keen on it as people seem to be able to relate particularly well to this concept compared with some others such as “dangerous anthropogenic influence” or “catastrophic change”. Some other analogies:
“The horse has left the barn”
“Crossing the Rubicon” From Wikipedia — “The use of crossing the Rubicon derives from the crossing of the river Rubicon by Julius Caesar in 49 BC, who thereby violated Roman law and rendered armed conflict inevitable. As Caesar said at the time: “alea iacta est” (”the die is cast”).”
Or, related to having passed that tipping point, more figuratively, “he who mounts the wild elephant goes where the wild elephant goes” — I apologize for not knowing the proper credit for this.
I think that Figure 1 in [Falkowski, P. G. and others. 2000. The global carbon cycle: A test of our knowledge of the Earth as a system. Science 290: 291-294.] is useful in making this point. It shows the correlation between atmospheric partial pressure of CO2 for the last 420,000 years and the deuterium-based air temperature anomaly. I think it is appropriate that the figure is a little dated in that ‘modern’ atmospheric pCO2 (plotted on the figure) is now literally off the graph and if you mentally plot a reasonable assumption for an atmospheric pCO2 stabilization in the future it is hard to imagine how we will return to a climate experienced in the last 420,000 years, much less a ‘pre-industrial’ climate in the foreseeable future.
As intriguing a concept as it is, a ‘tipping point’ is less useful if poorly defined quantitatively or largely unknown, as apparently is the case with two key examples that you cite: thermohaline circulation and substantial melting of ice sheets leading to ‘dangerous’ sea level rise.
I agree that it is important to point out that there can be many tipping points depending on your frame of reference. For islanders that have already been forced to relocate 20th century sea-level rise has already passed a tipping point of no return.
5 July 2006 at 6:04 PM
A name for the phenomenon?
Gladwellian
5 July 2006 at 6:16 PM
Re #15: Here is one link on orbital parameters
http://www.ncdc.noaa.gov/paleo/milankovitch.html
One of the major reasons that the ice ages are potentially such a useful test of our understanding of climate sensitivity is that we know, from celestial mechanics, with remarkable precision, exactly how the Earth’s orbit has evolved in time, at least for the past few million years
5 July 2006 at 6:47 PM
With respect to the complete collapse of the Atlantic thermohaline circulation will you kindly clearify the following for me.
It is my understanding that a fluid initially at rest on a rotating mostly sphere-like surface which in turn is revolving around a sun cannot remain at rest. If this is not correct let me know. Otherwise will you summarize the patterns of the induced motions for fluid bounded by the same boundries that now bound the ATC. That is, for fluid between North-Central-South America on the Western edge and Europe-Africa on the Easten edge.
Additionally, what are the expected consequences of a “complete collapse”? This article (http://www.americanscientist.org/template/AssetDetail/assetid/51963?fulltext=true&print=yes) seems to indicate that significant changes in weather/climate are not expected. Let me know if I have not correctly understood the article.
Thanks
5 July 2006 at 6:50 PM
This is a bit surprising — I wonder if this is why the Russian astronomer predicts a drastic change in climate in the next few decades? The change illustrated is over a far longer time span, but it’s striking in the graphic. I have no idea if this is one individual’s work or a consensus among astronomers.
Gavin, Ray, worth at least a glance I suggest, I just stumbled on it:
http://www.edpsciences.org/journal/index.cfm?edpsname=aa&niv1=others&niv2=press_release&niv3=PRaa200410
5 July 2006 at 7:41 PM
In the IPCC TAR, the report of Working Group II suggested that it is unlikely that we would reach any global scale tipping points (they used the terms “singularities” and “discontinuities”) before temperatures rose at least 2-3 C about 1990 levels. In the middle of the road projections, this corresponds to sometime in the latter third of this century.
I realize Hansen is talking about the head long plunge of human and climate commitment, rather than the transition itself, but are there new results since the TAR to suggest that a tipping point might come earlier than previously expected? It seems rather severe to think a catastrophe is 60 or 100 years in the future, but we only have 10 years to ensure that it won’t happen. (Of course one does want to stay on the careful side in case the model results are too conservative.)
I guess I am also surprised by how much press is devoted to tipping points, if, as the IPCC suggest, most of us may not actually live long enough to see such events. Not that I want my grandchildren to have to worry about it either, but it would seem more natural to spend more time on the problems we will already have before we get to the IPCC’s reported tipping threshold.
5 July 2006 at 7:48 PM
Re: #15. I’d suggest Wikipedia is a good place to start: Milankovitch cycles.
Orbital mechanics is very precise, and we can reliable describe the changes in the Earth orbit going back more than 10 million years. The present interglacial occurs during a period of low orbital eccentricity, and consequently the scale of the orbital forcing is lower now than during the last several interglacials.
5 July 2006 at 9:38 PM
Re: #19 That is a very interesting article, and I certainly learned quite a bit from it. However, I don’t think you can read it to say that “significant changes in weather/climate are not expected”. What he points out is that the differences between London’s and New York’s climate are not caused by the heat transfer via the Atlantic current. As I read the article *both* New York and London would be somewhat (not hugely) colder if the current were turned off. Plus the equator would be warmer, and one could therefore assume that there would be more storms in the equatorial region and perhaps fewer in the mid-Atlantic.
Not that I’m an expert or anything, but that seems to me what he’s saying.
5 July 2006 at 10:11 PM
Aloha all. This is my first post here and actually my first visit here. I followed a link from ThinkProgress.org to a list of the recently ranked Top 5 science blogs and this was one of them. After a good read, I can see why.
I run a blog that is almost entirely political in nature but recently I decided to expand its horizons to include personal exeriences as someone who has spent so much time on and under the ocean.
It’s titled: “The Canary is Dead!. The title of a movie put together by the PCRF.
I am NOT a scientist by any stretch of the imagination. I’m a Navy vet who never graduated from college. But I have spent more time underwater by age 34 than most people will spend on or near the water in their lifetimes. So I would love to hear feed back from some of you smart folks. And possibly either encouragement to continue or suggestions to stop because it’s not my intention to put out any bad information.
Thanks in advance everyone!
5 July 2006 at 10:50 PM
Nate:
Professional divers with the ability to operate underwater machinery are in demand by some, if not all paleoclimate labs. When I was a grad student, my officemate was an ex-diver who had come back to school to do a PhD. But because he was one of the few people at the school with the requisite hours to operate underwater drill corers, he went on every other reseacher’s field trips as a technician. I have no idea who, if anyone, is currently doing paleoclimate research in Hawaii. But if you are interested in getting involved and volunterring, they could probably use your know-how.
5 July 2006 at 11:50 PM
cwmagee… Thanks for the follow up comment. For the past several years I have been building websites and media/marketing consulting to help companies improve their image and increase their bottom line and its been killing my soul a little bit each day. About a month ago I started selling off many of my “things” and wrapping up my yuppie condo lifestyle and I was planning on sending my resume’ out far and wide to organizations doing ocean and paleo-climate research.
I don’t even mean to suggest that’s all I want to do. PCRF, research organizations of any kind. All I know is I want to use my talents to do something that won’t make me ashamed of what I’m doing with my life. Something I can actually do that would make me proud of myself again.
5 July 2006 at 11:50 PM
#18, Nat’l Climate Data Center, includes a link to the same site I noted in #20 among many others, as a good recent calculation. Apparently the dating of geological epochs is now accurate to approximately 40,000 years (plus or minus, I think?), based on the best calculations of Earth’s orbit and the changes tied to that. Past 100k years chaos takes its toll.
6 July 2006 at 1:12 AM
“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 phenomena….”
[Someone should hire an editor to check someone’s grammar.]
Do you think that the fact that Malcolm Gladwell wrote a recent best-seller named ” The Tipping Point” might account for the increased usage of the phrase? I do. You might as well simply acknowledge the obvious. Add that to “An Inconvenient Truth,” and, well…duh.
[Response: Possibly you might want to check your humour detection algorithms… -gavin]
6 July 2006 at 1:40 AM
I’m not sure I agree with CO2 levels .. are .. very unlikely to revert to pre-industrial values ..in ..the next few hundred years . Actually I mean flows not levels. Oil depletion could have a dramatic slowing effect on economic activity taking coal burning with it. This seems to introduce the case of a flow variable (industrial CO2) perhaps passing a ‘tipping point’ but then slowing.
6 July 2006 at 2:47 AM
The progenitor of nonlinear dynamics was the -equally celebrated and at the conclusion disappointing, but nevertheless enlightening- concept of Catastrophe Theory, back in the ’70s. The name itself is appropriate and revealing, identifying “tipping” points as “catastrophe” points, whose configuration depends on specific multi-dimensional geometric structures that best describe the phenomenon of interest according to the number of relevant parameters.
Nevertheless, the concept underlines the fact that these catastrophe points are not, actually, points of no return; they are rather points of not-feasible return, where the energy and time (or any other crucial governing factor) required to revert the system (like a planetary climate system) to a previous state is by far greater than the energy (or time, or…) that initially served as a feedback to drive it to the beyond-catastrophe state.
In other words, whatever scope we look at the climate problem, it is at least uneconomical to expect to remedy the system after the damage is done.
This is not doom-seering. A system of this magnitude, with this huge number of identified and unidentified governing factors, corresponds to a multi-dimensional geometric structure with proportionally numerous catastrophe points… When one of them is reached and crossed over, a new system state is reached, which rapidly leads to the next catastrophe point in line. And then to the next… and so on…
My point is: if the debate really stalls at the question whether it is viable to act now or not, simply think: we may not be able to prevent the first wave of catastrophe events that will upset the system initially. But, we have to start considering what we can do about the next set of catastrophe points, which will probably be much more drastic than expected. Change may be abrupt, but it also happens gradually, one could say quantumly.
Think about it. I am open to suggestions.
6 July 2006 at 5:37 AM
Thankyou for those that responded with the Milankovitch cycle links. I am aware of the fact that planets wobble, earths tilt effects seasons, mars caps are melting via topographic forcing, etc.
However, I simply don’t see a pattern regarding to orbital configuration vs. global temperature in this image:
http://en.wikipedia.org/wiki/Image:Milankovitch_Variations.png
I’m trying to find proof that those cycles were caused by a changing orbit and I’m having trouble doing so.
[Response: Hays, Imbrie and Shackleton, 1974. (or read The Ice Ages by Imbrie and Imbrie - highly recommended). -gavin]
6 July 2006 at 6:13 AM
The following review by Mark Maslin is worth a read:
http://www.geog.ucl.ac.uk/%7Emmaslin/publications/maslin3.pdf
6 July 2006 at 6:53 AM
I have been an appreciative reader of this site, not having anything useful to add. I have done quite much work on future research and virus marketing and this “Tipping point” -subject now seems a suitable place to try and perhaps contribute something.
It seems to me that the Tipping point -concept would be much more useful when studying how to win converts to join the work. Basically what the world needs is a “phase change” in the attitudes of politicians, voters and bureaucrats. The most efficient conversion method is not through media but through social networks and small world phenomena - you change your opinion when your friends or collagues change their opinions and express their opinions to you directly. This happens one by one and it succeeds, if on the average, each convertee succeeds more than once (within short enough time if we have only ten years). Al Gore’s concept of spreading good slides seems to be very efficient as lecturers always need good material and make many converts.
This site is also supplying very good material for all of us who wish to convince others. Especially important is the cautious avoidance of overextending the facts for a shock effect. This very easily leads to a backslash as happened in Finland with H5N1. (People generally think that the threath is passed as everything did not happen at once and then newspapers stopped reporting on the developments almost totally. And reality is that due to the events in Indonesia and few other places the probability has continuously risen. It may still take years for H5N1 to realize as a pandemic if ever and the popular support for efficient measures against the threath should last equally long as the threath.)
Critical mass is required for efficient action against global warming and some of it has to be gained by other means than direct facts. Professionals can be converted by facts. Amateurs like me are unable to follow all the facts and know that one can be mislead. What convinces us is partially things that we believe to be facts and this kind of open high quality discussion, which one in principle could join. But most laypeople do not follow this kind of discussions. They may instead see one soothing article, which says that there is nothing to worry. And then they cling to this belief as it makes their life so much easier. It may also be that they just do not care what happens after they die. It requires a networked approach - each person needs to be converted by someone they can trust. Social pressure is also important. You do the right thing because your friends expect you to do it. Here the Tipping point -metaphor, Meme theory, Virus marketing and other related approaches may be very useful. Naturally getting converts will become easier when people have seen some major changes but then precious time has been lost.
6 July 2006 at 7:11 AM
The BBC have gathered a panel to consider climate change. The unanimity of agreement in some of their conclusions have surprised me (OK stunned me). See here: http://news.bbc.co.uk/1/hi/sci/tech/5152590.stm Perhaps we could be approaching a tipping point in public acceptance of this as an issue? I’ll put my inate cynicism on hold and cross my fingers.
I suspect RC may have some comment on this to come, but thought posters/readers here might find it as interesting as I have. I do NOT want to spark off comments on this issue under this thread.
Regards
CobblyWorlds, aka Chris Reed.
6 July 2006 at 9:29 AM
It seems rather severe to think a catastrophe is 60 or 100 years in the future, but we only have 10 years to ensure that it won’t happen.
A parachutist insures the soundness of his silk well before getting into the plane.
6 July 2006 at 9:36 AM
To the Editors of RealClimate
Other than studies detailing anthropogenic forcings for present global warming, are there well-document, peer-reviewed, well-accepted studies showing that are other factors at work as well?
[Response: Papers that look at the 20th Century tend to include all forcings - though not just anthropogenic ones (i.e. volcanoes and solar are included) - see Hansen et al for an individual assessment of almost all the forcings we can think of. Prior to that, the natural mechanisms are obviously more prominent. Going back to the mid Holocene and further, orbital forcings figure strongly. Did you have anything specifically in mind? - gavin]
6 July 2006 at 10:53 AM
Thanks for the article! It’s a bit better to read than some of the latest posts, since the technobabble has been reduced. Not that I’m not intested in the details, but it takes me some time when it’s becoming too flux-compensator-warp-core-like. I nevertheless dig through all of the more complex posts, since I can learn a lot from you guys. I usually find helpful references here to papers I can use in building up climate-related articles in the German-language Wikipedia. I don’t know if there are any German-speaking people here, but if you are, it would be great to see more of you working on articles like Globale Erwärmung (global warming) or my newest ambitions on Folgen der globalen Erwärmung (effects of global warming), and whatever climate-related article you can find. Don’t hesitate to get involved, it’s fun (or isn’t it, William!)
6 July 2006 at 11:34 AM
A DANGER IN TALKING ABOUT TIPPING POINTS is shown in Paul Samuelson’s poorly thought-out opinion column (Washington Post 7/5, free registration)
He argues that our knowledge and our political and economic systems make it impossible to “relieve global warming.” So we can do nothing… except pray for a magical deus ex machina (invention of free energy, geoengineering, whatever). Samuelson’s error is that he thinks climate change is an all-or-nothing matter. Talk of a tipping point, a point-of-no-return, etc. is only too likely to encourage this fallacy. It just doesn’t occur to him that there could be a range of policies, with a policy that keeps the temperature in 2100 only five degrees higher better than a policy that lets it get six degrees higher, etc. Hansen & others have shown that there are economically and politically feasible policies with current technology that will reduce the problem. And even if it is already too late to avoid some damage, the sooner we start the better.
6 July 2006 at 12:05 PM
Re 31 - IMHO, the reason that the Eemian was warmer was because the Arctic sea ice had melted, and so the amount of solar radiation absorbed in the northern hemisphere was greatly increased. The fact that the Greenland ice cores can only reach back as far as the Eemian shows that the Greenland ice may also have melted then too.
As Gavin mentioned in his post, the Greenland ice is self sustaining, but so is the Arctic sea ice! When it disappears, we will have to lower global temperatures well below those of today to get it to reform.
Gavin, you do not seem to have resolved the problem of what a tipping point is. Is it when the Arctic sea ice goes and we can’t get it back, or was it when the ice started to melt and made it inevitable that it would go?
6 July 2006 at 12:28 PM
Re: 38
Samuelson’s editorial seems to me to be either a counsel of despair or a stalking horse for the nuclear industry. By dismissing the moral aspects of continuing behavior that may lead to a disaster of global proportions, he minimizes one of our most potent sources of motivation: conscience. And he is simply wrong in saying that people won’t make sacrificies. People have accepted draconian change in the past once their leaders have shown an understanding of the dangers and made a committment to eqalitarian sacrifice. By dismissing the possibility of shared sacrifice, he’s attempting to rhetorically finesse away any objection to a nuclear solution.
6 July 2006 at 12:53 PM
Re: 33: ‘Converting’ people:
I entirely agree with this post. Someone suggested that we need an “environmental Winston Churchill”; someone with credibility who speaks well. Gore has little credibility with many because of US government and industry efforts to attack him (rather than the science) and the general willingness of ‘free’ Americans to reduce everything to a partisan issue. I also entirely believe that the time has come to stop arguing with ‘climate change skeptics’ and start doing things. I think we need a ‘Gandhi for the planet,’ or better, many of them. Climate change skeptics are irresponsible but powerful fools, and need to be treated as such.
Think of it this way: as severe climate events happen and thus the evidence becomes unignorable, the majority of people will realise they’ve been duped. If we also happen to have passed some tipping points and PONR’s along the way, then how will those people react? The BBC article suggests that people may give up and live in the now, or despair and commit suicide. How about anger? Do you think anyone will be just a little upset, and perhaps may want to take out their anger on the world’s largest contributor both to climate change and to suppressing the truth about it?
I find it fascinating that many fields are converging: the hard sciences, ethics, religion, social sciences, and so on. Climate change cannot be considered just a ’science’ problem.
6 July 2006 at 1:03 PM
PS - the BBC article stated that ‘experts convened by the BBC concludes [sic] that climate change is “real and severe”, but maybe not “catastrophic”,’ where Lovelock leaned toward the latter.
What is “severe” climate change?
6 July 2006 at 2:04 PM
If Al Gore’s movie, which was quite favourably reviewed here, is a possible ‘tipping point of no return’ on public awareness of climate change, perhaps someone with knowledge and credentials can comment on the inevitable negative feedback loop in public debate, e.g.,
http://www.cei.org/utils/printer.cfm?AID=5394
DG
6 July 2006 at 2:38 PM
“Someone should come up with a name for this phenomena (sic)….”
Its called ‘climbing on the bandwaggon’. The biggest threat to the case for AGW is ‘crying wolf’.
6 July 2006 at 3:01 PM
Re: T. Elifritz
Due to the thermal inertia of the Greenaland and Antarctic ice sheets won’t it be several millenia before they could completly melt away even under conditions much hotter than now?
[Response: Dynamics are as important as thermodynamics here. Recent evidence (e.g. as reviewed by us a few months back) suggests that the demise of large parts of the major ice sheets could potentially take place far faster–on timescales of perhaps several centuries–due to the influence of ice sheet dynamics. For example, crevices at the surface of the ice sheet are now known to sometimes penetrate all the way down to the bottom of the ice sheet forming channels (”moulins”) that allow surface meltwater to reach the bottom of the ice sheet, where it lubricates the ice, allowing it to stream into the ocean at velocities potentially far greater than once envisioned. These processes are still far from perfectly understood, because they require a representation of the fairly complicated rheology involved in ice sheet dynamics. But it appears far more likely that a better understanding of these processes will act to revised our estimates of ice sheet collapse timescales downward, rather than upward. - mike]
6 July 2006 at 3:14 PM
re: #38 I take heart in the Samuelson piece’s two concluding statements:
“The trouble with the global warming debate is that it has become a moral crusade when it’s really an engineering problem. The inconvenient truth is that if we don’t solve the engineering problem, we’re helpless.”
In his (lame) attempt to redefine the term “inconvenient truth” and dispossess Al Gore of it, he endorses the Gore stance that the issue is not partisan, but moral. And he steps up to the need to fix the threats to our climate or be lost–for Mr. Samualson at least, the “debate” is over. And finally, no publicity is bad publicity.
6 July 2006 at 4:16 PM
So this is now where the climate debate is headed, towards the non linear dynamics of the earth system and whether they can magnify climate change to make it suddenly flip to a new state. these sub systems being
The Amazon and other rainforests drying out
The Siberian bogs (the size of germany, france and the UK combined) start to release methane in accelerating annual volumes
Ice Albedo decreasing
Ocean conveyor (thermohaline systems to some)weakening due to freshening of the seas
And there are probably more sub systems that can feedback and potentially acelerate warming which accelerates the disturbance of the subsystem which accelerates overall warming.
I would imagne that climate has been treated as a linear system since the early days of climate modelling until recently when observed changes are not being picked up by the simulations as much as was hoped and hence the real climate might be taking on a suprisingly rapid (non linear) warming that is yet to be accounted for in the models.
Non linear dynamics and far from equilibrium thermodynamics of which the climate is one such system is a relatively young science and hence maybe as the parameters are pushed from the equilibium to the far from we may see what dynamicists call more interesting system behaviour Doom as people like Lovelock are predicting.
6 July 2006 at 4:56 PM
What are the chances of natural, negative feedbacks kicking in at some point? An example of a positive feedback is Arctic sea ice melting, which exposes the ocean, which absorbs far more energy than the snow and ice did, causing the ocean to heat (or the air to cool?). Do similar negative feedbacks occur that tend to keep the climate in its current state?
6 July 2006 at 4:56 PM
The phrase “tipping point of no return” has now been used twice in this discussion, once in the title and again in comment 16. I sincerely hope this phrase never escapes into the wild and propagates, You wouldn’t want that on your conscience, now would you Gavin?
6 July 2006 at 6:24 PM
>similar negative feedbacks
That was the question that started Lovelock on his research decades ago. There’s a whole lot out there; one simple model is here: http://www.carleton.edu/departments/geol/DaveSTELLA/Daisyworld/gaia.htm
But if acidity goes too high in the oceans, the organisms that produce the sulfates that produce the clouds that cool the ocean could die off, and we’d lose a major feedback loop when most needed, one that’s been observed from space when it blooms:
http://news.bbc.co.uk/2/hi/science/nature/4226917.stm1 February, 2005, 16:31 GMT
…
“Complex climate
–
Dr Carol Turley, from Plymouth Marine Laboratories told this week’s Met Office and UK government-organised climate conference in Exeter she was very worried.
Countless species, she said, depend on a relatively stable pH to extract calcium to build their shells or skeleton. These include shellfish, snails, starfish, sea urchins and some sea worms that play an important part in cycling minerals in the ocean mud.
Tiny coccolithophorids form vast populations
She is particularly concerned about the effects of acidification on plankton at the bottom of the fisheries food chain called coccolithophorids.
These precipitate calcium to make tiny shells called liths. Each lith is only about 2.5 micrometres (millionths of a metre) across but when the algae bloom en masse the effects can be seen from space.
Unpublished research from Norway suggests that increasing acidity harms the coccolithophorids. This might have consequences for fisheries. Scientists think coccolithophorids will probably be replaced if they drop out of the food chain but they cannot be sure.
Coccolithophorids also play a role in climate change. The algae give off CO2 when they bloom and thus contribute to climate change. But they also produce dimethyl sulphide when they bloom which helps the formation of clouds which reflect back heat from the Sun. The science here is still in its early stages….
—–End quote—-
6 July 2006 at 6:41 PM
Related to the runaway tipping point of no return is the magic number of 2 degrees. It has been suggested that this is the limit of warming that we should aim for, in order to rein in the tippy runaways. What is the precision on this number, and where does it come from?
6 July 2006 at 7:06 PM
>50
By typing “two degree” into the Search box at the top of the home page, I found this quickly:
http://www.realclimate.org/index.php?p=115
In the main entry there you’ll find: “… Setting a limit to global warming at 2ºC above pre-industrial temperature is the official policy target of the European Union, and is probably a sensible limit in this sense. But, just like speed limits, it may be difficult to adhere to….”
If you read a bit more you’ll find why; see the links in that thread.
6 July 2006 at 7:14 PM
Re 50 and the magic number of 2 degrees…
As I understand it, this number is due to James Hansen and appears in a New York Review of Books article at
http://www.nybooks.com/articles/19131
Note that this is two degress *Fahrenheit*.
Hansen justifies the figure there. He srgues out that the warmest interglacials in the last million years or so were about 2 degF warmer than today and that a larger warming, of around 5 degF, would lead eventually lead to the disnitegration of the ice sheets. But read it for yourself.
I sincerely hope that the full phrase “runaway tipping point of no return” will never be used again. Doh, I’ve just done it!
[Response: Hansen is talking about the change from today. The 2 deg C number comes from the Eurpoean Union and refers to the change from the pre-industrial. -gavin]
6 July 2006 at 8:12 PM
These thresholds are becoming confusing. Hansen’s use of 2 deg Fahrenheit is particularly unfortunate when a threshold of 2 deg Celsius has already been promulgated to the public.
Re the 2 degC number, I have just been reading the Steering Committee Report from the Conference on Avoiding Dangerous Climate Change, Exeter Feb 2005:
http://www.stabilisation2005.com/Steering_Commitee_Report.pdf
Here I read:
“…a regional increase above present levels of 2.7 degC may be a threshold that triggers melting of the Greenland ice-cap”
with the footnote that
“This [regional 2.7 degC increase] would be associated with a global temperature rise of about 1.5 degC above present or about 2 degC above pre-industrial temperature”
and then
“In general, surveys of the literature suggest increasing damage if the globe warms about 1 to 3 degC above current levels. Serious risk of large scale, irreversible system disruption, such as reversal of the land carbon sink and possible destabilisation of the Antarctic ice sheets is more likely above 3 degC. Such levels are well within the range of climate change projections for the century.”
Later they talk about options for “limiting climate change to 2 C above pre-industrial”.
OK so they seem to have settled on 2 degC above pre-industrial as a useful policy target and they’re saying that 3 degC above present would be really bad.
Is this the source of the 2 degC threshold or has it appeared elsewhere?
And Hansen is saying we shouldn’t risk 2 degF (1.1 degC) above present, which is 1.8 degC above pre-industrial (assuming present minus pre-industrial is equal to the 20th Centrury warming of 0.7 degC)
Like I said, these threshold are becoming confusing.
Not that anyone’s going to take any notice of me, but I think it unwise to use pre-industrial global temperature as a baseline when the global-average surface temperature seems to have varied by several tenths of a degC during the half-millenium or so preceding the industrial era. On the other hand, pre-industrial CO2 was relatively stable and is a sensible baseline.
6 July 2006 at 8:45 PM
As I noted way up in #21, the IPCC TAR picked a number of 2-3 C from 1990 as the level at which tipping points start to become a significant risk. However, one can cause significant damage to the environment even without reaching a tipping point, so the threshold at which climate change becomes subjectively dangerous may well be below this.
6 July 2006 at 10:39 PM
As one who has taken Gavin to task on his English usage in the past (Gavin, people are trying to tell you that “phenomena” is plural. Pay attention.), I am obliged to confess admiration for his delightful pleonasm “runaway tipping points of no return” - I fully intend to plagiarize it. I am also charmed by his fanciful plural form “genii”, which is really the plural of “genius”, of course. Full marks.
[Response: A little idiosyncracy in language should be allowed I think…. - gavin]
7 July 2006 at 12:56 AM
Surely at a CO2 rise of 2 to 3 ppm/y, and rising, we will go crashing through every so called ‘tipping’ point like there is no day after tomorrow. At that rate, I would be very surprised to have any of our descendents see any vestige of continental or polar ice in 1000 years. Clearly 1000 years of fossil fuel combustion defines the concept of unsustainability, considering that almost everyone on the planet is already observing the local macroscopic effects of climate change. I’m not real confident of Paul Hearty’s 30 foot line, but I can clearly see the seven foot line, and the 19 foot line (the two meter and six meter fluxes), etched into my back yard. I’ve got 18 feet, most of it is at or just above sea level (mean high tide) that’s all I’ve got, and we’ve been into beach erosion now for almost 10 years, whereas things have been fairly static previously since the 30’s. On the Wisconsin side, well, the change in the snow line is nothing less than stunning. Everything is rapidly shifting north, even the relatively uneducated country folk in my area can easily discern it with just casual observations.
Everything points to a shock associated with the spike. We’ve got one more hurricane seasons until another election, three more until another president. Local observations indicate this is supposed to be an off year for hurricanes, so we shall see. When the house of cards we have constructed for ourselves falls, well, it’s all over.
7 July 2006 at 12:58 AM
From the original:
“… 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.”
But Venus’ climate has stabilized (”converged”, right?) — so really the Earth and Venus are similar (currently) in terms of this discussion because neither is currently running away. Correct?
[Response: Point taken. I was implicitly thinking about the theoretical situation of two similar planets to Earth, one in Venus’s orbit, one here. - gavin]
Re: 49 — I’m not worried about the meme “turning point of no return” — if it was so successful I think the Malaysians would already be saying it. A common Department of Redundancy Department phrase there is “another one more.”
7 July 2006 at 6:35 AM
Re 58 Steve, you are right to say that Venus has stabilised, and so is similar to the Earth.
The stabilistaion of Venus is caused by the surfur dioxide clouds which formed when the surface became hot enough to vaporise the sulfur. The Earth’s climate is also stabilised by its albedo, viz. clouds and ice sheets. When the size of the ice sheets change, the climate becomes unstable until the cloud system has altered to compensate. Continental ice sheets change slowly because of their uneven relief, and their slow retreat due to great thickeness. Sea ice sheets change suddenly because of their even relief, thinness, and the forcing of the ice albedo effect. They cause rapid climate change.
When the Arctic sea ice suddenly disppears the climate will warm until it settles into a new state where there is increased cloud to compensate for the loss of albedo from the sea ice. One would assume that this would be a climate like that of the Eemian, when tropical animals cavorted in London’s river Thames. But what was the climate like in the mid-west of the USA?
7 July 2006 at 6:48 AM
I think a much better phrase is “catastrophic runaway tipping points of no return” which is easily reduced to CRTPNR. Rather elegant I think.
7 July 2006 at 7:34 AM
In the alarmist climate science book called “the last generation” linear climate change is labelled as Type I whilst the non linear type is labelled Type II. Apparantly the IPCC like type I more than Type II so as to not appear to alarmist in order to offend the climate skeptics.
7 July 2006 at 9:18 AM
Mass coral bleaching is a non-linear response to stress; an individual event could be thought of as pushing a coral ecosystem past a “tipping point”. Corals may bleach - a breakdown of the symbiosis between the reef-building animal and the microalgae in its tissue - when the seawater warms past a threshold (e.g. temperatures are ~1-2 deg C warmer than the usual annual maximum for a whole month). Bleaching events, however, are individual episodes. As the oceans warm, the concern is that the frequency of events will surpass the rate at which coral reef ecosystems can either adapt (to warmer temperatures) or recover (from bleaching events).
7 July 2006 at 10:19 AM
Re: #38, the Washington Post columnist in question is the conservative Robert Samuelson, not the great economist Paul Samuelson.
7 July 2006 at 11:46 AM
- In discussing “tipping points”, the THC may be one of the most important. It’s worth noting that this year (2006) the sea-ice cover in the Greenland Sea was reduced considerably compared to that seen in recent decades. The so-called “Odden Ice Tongue” did not appear in January, February or March, as may be seen from these graphics depicting monthly extent derived from satellite images:
http://nsidc.org/cgi-bin/wist/wist_nt.pl?wcf=seaice_index.txt&panel=1
One may select individual months and years for viewing. The purple curve outlines the median extent. The Odden Ice Tongue is the “hook” seen in this curve just to the west of Greenland and north of Iceland. This feature has been associated with deep convective events or “chimneys”, which have been seen in the Greenland Sea in past years. Whether there is a direct link between the deep convection and the Odden Ice Tongue is a question of great interest and study. Previous measurements of the Greenland Sea indicated that there was a near shutdown of deep convection exhibited there during the late 1970’s and early 1980’s. Recent studies have shown variation in this feature and there have been other years in which it did not prominently appear.
J. C. Comiso, P. Wadhams, L. T. Pedersen, R. A. Gersten, Seasonal and interannual variability of the Odden ice tongue and a study of environmental effects JGR. 106, Number C5, 9093-9116, May 15, 2001.
This apparent change in sea-ice may be part of a multi-year oscillation, such as the NAO, or it may be an indication that larger changes are underway. If the disappearance of the Odden Ice Tongue is evidence of a weakening or shutdown of the deep convection, this may be a cause for immediate worry.
7 July 2006 at 12:36 PM
Re: 64 — the Odden ice tongue
I cannot exactly tell from the picture in the link but it appears that the Odden ice hook forms north of the West Jan Mayen Ridge and Jan Mayen Island ? Can someone say if that is the case ? I ask because I notice that there is a hook in the 1000 fathom contour right about there.
sidd
7 July 2006 at 1:24 PM
It’s not tipping points for the climate I’m worried about. (Does weather die or feel pain? Or do ice sheets & other inorganic matter?) It’s people, other biota, and ecosystems & their death/harm & collapse I’m more worried about (which this article does suggest as the more common realm of discussing tipping points).
So, what I’d be intersted in is how many people will die from all effects of GW if the average temp increases 1, 2, 3, 4, 5, or 6 degrees. And I’m more interested in “runaway” in human terms than geological terms — the point at which nature takes over the warming via positive feedbacks, even if people reduce GHGs 50% or 80% or 100%. That is, runaway from any human control — not that we shouldn’t keep reducing so as to reduce the harms even if we do lose our ability to halt and/or reverse the warming.
Then there are social tipping points — when the material world gets really bad, society may devolve into a chaos of each man for himself (skip the women & children), or rachet up to some totalitarian regime, or both. Why would the contrarians want to risk the very things they fear???
As the article rightly points out, contrarians may take “tipping point” as something not to worry about until we get right up to it, or not to worry about because it’s too late & already reached. And since no one really knows when we’ll reach the real tipping points (no matter how you define them), then contrarians would argue that it’s best to continue business as usual, without any concern.
Where there’s life, there’s hope, and we should never give up efforts to reduce our GHGs, regardless of whatever tipping point or point of no return we reach, or how far away or close those tipping points are, until we reach our own personal tipping point of death. I suggest this be motivated not by a STATE OF FEAR, but by a STATE OF LOVE.
7 July 2006 at 1:31 PM
Have been reading all the above comments with great interest. I am developing a documentary series based around the concept of tipping points in relation to climate change but am finding much of the information confusing/contradictory (no doubt some of this can be put down to lazy journalism but even amongst the climatologists I have been talking to there doesn’t seem to be much consensus).
I have many questions and if any of you could spare the time to correspond with me via email I would be very grateful. In the meantime, could I just throw out one question which may seem a bit basic but which I am having trouble nailing.
If we assume that there is some global tipping point that can be generally agreed on (perhaps 10-20 years in the future?), can we also assume that by bringing down carbon emissions to an agreed level, we can push this tipping point away into the future by a measurable amount (say to 50-60 years for example)? Or is it the case that we will either reach the tipping point, or avoid it?
Vicki
[Response: Interesting point. Essentially you are asking whether any such point might be related to the rate of warming rather than the absolute level of warming. For the ice sheets the answer is probably no (but experts on the subject might have a better idea), but for the overturning circulation or the ecosystem changes, the answer is probably yes - i.e. a slower rate of warming could lead to a different response (allowing time for ocean mixing to mitigate the effects, or adaptation of species to the new conditions). It would need to be a large slow down in the rate of warming though, I think, to make a significant difference (i.e. 20 years versus 10 years isn’t going to do it, but 100 years vs 10 years might). - gavin]
7 July 2006 at 2:25 PM
Its rather further back to the past, comparing present day climate with….:
“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 ”
…… May be good, but should we be well versed with the climate further back in time, when CO2 concentrations were about 400 ppm, several million years ago I take it. When there was sub-tropical forest, still in exixtence today on Axel Heiberg Island 500 nm from the North Pole. It is likely to this climate we are returning towards, a brief world wide climate description of that time would be rather important.
7 July 2006 at 3:02 PM
Re: #65
Here’s some additional information on the Odden Ice Tongue, including some nice graphics.
http://www.frontier.iarc.uaf.edu/~igor/research/convec/index.php
7 July 2006 at 3:34 PM
I want to thank you a lot for this thread. This is going to come up repeatedly; it is really to good to have it all in one place.
7 July 2006 at 3:53 PM
This was a great post on an important topic and I found it very helpful in thinking about these issues. Thanks! Especially for the discussion of ’system return after perturbation’.
Here’s another simple tipping point analogy -
Put a pot of water on the burner, and wait for it to heat up -eventually, it reaches a ‘tipping point’ and starts to boil. It’s impossible to predict exactly where each bubble will form, however. This is somewhat analogous to the hurricane issue - there is a temperature threshold, and the hurricane tracks are chaotic. The ‘boils’ are also a dynamic effect which computer models of heated water pots might have missed - similar to ice sheet dynamics.
Now drop in a fresh egg. It heats up, and at some point the egg proteins reach a ‘tipping point’ and denature(unfold), and you have yourself a hard-boiled egg. Now cool the whole system down. The bubbles disappear and the water returns to its initial state, but the egg proteins remain unfolded - now you have a cool hard-boiled egg. The two tipping points had different long-term effects. I’m unsure, but this seems analogous to the ice sheet issue - for example, under what climate regime would tropical high-altitude glaciers re-form? Are they best viewed as ice age remnants that wouldn’t form today (or yesterday)?
RE#48 and #59: The long-term negative feedbacks are described by gavin in the first section; however the notion that increased water vapor leads to an increase in cloudiness and that this net effect is a negative feedback - this has been a topic of discussion for a very long time now, hasn’t it? However, a warmer atmosphere means less cloudiness even with more water vapor and then there are seasonal effects. I suppose this can only be addressed via high-resolution modelling - I’d hold off on notions of a tropical paradise in Britain. I searched RealClimate for cloud albedo and came up with these posts.
I wish there was a RealEnergy site to go along with this one.
7 July 2006 at 5:56 PM
>wish there was a RealEnergy site … along with this one
Me too. Closest I’ve found, not associated with RC, is this:
http://www.fpif.org/papers/03petropol/alternatives.html
That site was recommended in comments here:
http://www.ecoequity.org/ceo/WhereWeStand.htm
where Tom Athanasiou and Paul Baer wrote:
“… we prefer to stay in the reality-based world of those (the E.U., the Climate Action Network) who draw the line at 2ºC maximum …. the all-important Who Pays? question has to be answered …. We believe that, if climate mitigation is to be adequate, …. the rich in the South have to pay for real development (which is also fundamental to real climate adaptation), even as the rich in the already developed world pay for accelerated decarbonization…. This is, to be sure, not a realistic position, not in the short term, but there is more to this than short-term politics….”
That seems to me the basic energy question, written before ocean acidification was found to be heading us toward a food chain collapse by 2100.
Lovins perhaps would answer that the market pays, because efficient energy is cheaper. Maybe.
Energy questions, economics questions, intertwingled.
7 July 2006 at 6:05 PM
Re: #66
Not very “scientific,” but Lynn, I agree completely. Thanks
7 July 2006 at 6:36 PM
Gavin,
You briefly mention the disappearance of summertime Arctic sea ice as a potential candidate for a “tipping point”. What is the best evidence from GCMs or other kinds of models that there is hysteresis or multiple equilibria at this point? I have heard speculation over the years about the possibility of changes in oceanic statification creating strong nonlinearity, but where does this discussion stand?
In the 1970’s work with very simple diffusive energy balance climate models focused on the “small icecap instability” as well as the “large icecap (snowball earth) instability”. If there is an ice-free climate that consistently produces a temperature at the pole that is greater than freezing, then putting an ice cube at the pole, even if the ice reflects all solar radiation, will not be stable, since the warm air will simply diffuse in from the sides. So ice covers smaller than a critical size are unstable, which produces hysteresis and multiple equilibria. The critical size is dependent on the diffusivity. You can google ’small icecap instability” for some references. But this instability tends to disappear when there is a substantial seasonal cycle in the ice, even in these simple models. Does sea ice in comprehensive climate models produce hystersis at or near the point of zero summertime ice? (I am not implying that I think that the disappearance of summertime ice is not of great concern, nor do I think that the models are necessarily right, I am just curious as to what models are currently telling us about nonlinearity near this point.)
[Response: Isaac, there are a couple of analyses making their way through the process that look at the IPCC AR4 model behaviour and see evidence for rapid transitions in the sea ice cover. I’m not aware of all the details though. - gavin]
7 July 2006 at 6:51 PM
The current dialogue around climate sometimes seems to go like this:
Public: What’s with this climate change, should I be worried?
Climate Scientist: Well there’s a reasonable chance that if we don’t make serious changes that temperatures will rise by between 2-5 degrees late this century.
Public: OK, well I suppose we need to start thinking about it some time soon, and as the temperature starts to track up that will motivate people to do something about it, so thanks for letting us know, keep in touch, I’ll let you know when I get some free time to concentrate on it.
An alternative version fo the dialogue could be:
Public: What’s with this climate change, should I be worried?
Climate Scientist: Well, for a start we know that if we don’t make serious changes soon the chances are that the temperature will rise at least 2-5 degrees. But that’s only the start, we know that there are tipping points which, if triggered would push the temperature way beyond that. We don’t know when these might be triggered, we haven’t factored them into our estimate of a 2-5 degree rise. Worse still, we now have clear evidence that the assumptions in our models are wrong (for example how fast Greenland will melt) and we are seeing things happen much faster than we expected.
Public: So you can’t give me any guarantee that we are not right on track to trigger tipping points within a matter of years?
Climate Scientist: No I can’t, one of the reasons is that we are already committed to a significant temperature rise which is in the pipeline. So even if I told you that I could see a tipping point coming up in the future, there may be no way to stop us crossing it as the temperature rise in the pipeline plays out. Frankly I am extremely worried about this it is a very very dangerous situation for the world.
Public: Right, who should I vote for, what do I turn off, where can I park up my SUV?
7 July 2006 at 6:55 PM
Re RealEnergy, it would also be nice if there were a good introductory book on the subject to complement the recent slew of climate change books (Recommendations, anyone?). There’s a rumor that the estimable Gar Lipow, whose thoughts can be found here, on MaxSpeak.org, and elsewhere, is working on one. I hope there is some truth to the rumor.
7 July 2006 at 10:57 PM
As far as renewable energy science goes, the real problem is the lack of a scientific base of expertise in this country - ocean science departments, earth science institutes, meteorology departments - these are all very common. However, there are virtually no renewable energy research programs at any of the major research universities (people always seems surprised by this), and that’s because there is so little funding. There are people who do some research on the side, but it tends to be individual efforts, not ‘organized research units’. Then you have all the intellectual property issues to deal with as well - if you do come up with something useful, who ends up owning it? ExxonMobil has a 5-yr monopoly on any patents produced by Stanford’s Climate and Energy Project, for example.
I do have a little personal insight into this issue. I recieved an MS in Ocean Sciences from the University of California, Santa Cruz a few years ago (in the area of marine nitrogen fluxes); at the time I was a recipient of an NSF Graduate Student Fellowship in microbiology - and I transferred into the Biochemistry department hoping to go into renewable energy research, which seemed to be very interesting, important and useful work - I was particularly interested in algal biochemistry (a great oil source) or fungal enzymes (for cellulose digestion) - but when I took these proposals to the Dean of Graduate Studies, he shook his head and said “You will never be able to find funding for this kind of work - can’t you do something else?” - no kidding (he was very nice about it). Compare the number of proprietary pharmaceutical research programs in this country to the number of renewable energy research programs, and you start wondering exactly what is going on. Look through course catalogs for renewable energy classes of any kind - generally, you find nothing. It’s a real travesty, and yet people seem largely unaware of this reality. Little funding means little research and development. If only this government would double NSF’s budget and create a renewable energy funding unit… but don’t hold your breath, they keep cutting the NREL budget while singing the praises of ’switchgrass’ - unreal.
There are a number of good renewable energy textbooks (mostly written by Germans or Australians, apparently) but very few publicly accessible books on renewable energy. One of the best is “From Space to Earth: The Story of Solar Electricity” by John Perlin, a fascinating historical treatment of the development of solar PV. You can also take a look at my personal favorite, www.nrel.gov/docs/legosti/fy98/24190.pdf (warning- 3.5 MB pdf file download) - the NREL Biodiesel from Algae program, killed off in 1997.
(The Gelbspan link from #72 is interesting, (thanks) but it’s not a scientific discussion of renewable energy technologies, by any means).
7 July 2006 at 11:40 PM
The rumor is correct. Actually it is finished, and is a solicited submission to a publisher - so I am in hope of seeing it published.
8 July 2006 at 2:39 AM
Gar -
Hope to see your book soon. Please let us know when it comes out!
8 July 2006 at 8:07 AM
RE 77:
The NREL Biodiesel from Algae program, killed off in 1997
Seems they really must have killed it because when I try to access the link this is what I get.
Not Found
The requested URL /www.nrel.gov/docs/legosti/fy98/24190.pdf was not found on this server.
8 July 2006 at 9:48 AM
Okay, I’ve written a planetary temperature calculator in javascript and uploaded it to my web site. It gives fair approximations of the temperatures of Venus, Earth and Mars (691 K, 288 K and 221 K versus the observed 735 K, 288 K, 214 K), and is a little oversensitive to CO2 and H2O changes (3.4 K increase on Earth with doubled CO2 and 10.2 K increase with doubled CO2 and H2O feedback — way too high compared to GCM results). But it has the basic physics more or less correct, in a qualitative way. I would have to make the model much more complex to get better accuracy, but I think this one illustrates some basic principles.
-BPL
8 July 2006 at 10:12 AM
Gavinâ??
Thanks for the link. I was specifically interested in the Maunder Max/Min, which is one of the latest contra-arguments. The references in the paper were very helpful.
As the general public latches on to each factor, that factor presumably overrides anthropogenic forcings. Not true, of course. Then I have to dig out the facts. Your site is a gold mine.
Suggestion for the editors of RealClimate:
Because economists are central to our dealing with GW and the environment in general, I would suggest dropping in on some of the major economic blogs when GW is an issue. And it is just starting to be an issue, a healthy sign.
The Economic Roundtable gives a brief daily summary of all the major economic blogs. By looking there, you can see if your expertise would be useful. Quickly perusing this site once a week would be sufficient.
http://www.rtable.net/index/rt/economics/recent/
I find your expertise informative and helpful. I would like key economists to have it as well.
8 July 2006 at 11:33 AM
Lomborg returns: http://www.opinionjournal.com/editorial/feature.html?id=110008626
8 July 2006 at 11:53 AM
>77, 80
The NREL study PDF file is
http://www.nrel.gov/docs/legosti/fy98/24190.pdf
The link in 77 that looks the same has actually been mangled.
(Practice SAFE TEXT: “copy link” — paste to a text* editor first, to see what you’re actually getting, instead of clicking. What you see is NOT what you get in HTML; typos and malware can be hidden in any editor that ‘interprets’ HTML. Eschew Microsoft Word for this purpose, use Notepad.)
8 July 2006 at 12:22 PM
Re: #77
Your comments on biomass production, particularly algal production as described in the NREL reference point to some big problems. Working in the lab to pick the best species out of thousands or manipulating selected species to improve production may not result in a workable system in the real world. As mentioned in work discribed on page 147, maintaining the proper culture in open ponds is difficult. Any monoculture is unstable and, given the many native species, keeping an algal system “pure” will be nearly impossible.
Then, there’s the basic engineering problem. Building any pond system as described will require considerable material and effort to construct. If the energy produced is not large, the net return on the capital invested may be small or the production cost of the resulting fuel may be large relative to other energy sources. Economies of scale become difficult to imagine, as the construction of ever larger, gently sloped structures does not seem practical. One should think in terms of building 1,000 square meter parking lots as an example of the difficulty of controlling the flow with these large, shallow ponds. The ground below the ponds is not likely to be completely stable, especially after disturbance due to grading and pond construction. Then, there are the other problems of temperature and salinity maintenance and harvesting to add to the mix. What happens when it rains heavily over a short time period and lots of fresh water is added to the ponds? One implementation (page 162) involved an enclosed system, using a greenhouse type enclosure, which would be very expensive compared to open ponds. One reason what other types of solar systems have had difficulty competing against fossil energy sources is the cost of the material, be it glass, aluminum or plastic, which initially intercepts the solar energy. This becomes especially critical if the overall system has low overall energy conversion in real world operating situations. In sum, I think the engineering difficulties and costs involved would likely kill any large scale operation (see pages 245-247). Smaller scale operations for waste water purification may be a reasonable approach, as there is a secondary benefit to include in the calculations.
8 July 2006 at 1:07 PM
Re 82 on the Economic Roundtable page –
Alternative suggestion — could RC offer an ‘Economists’ link akin to the one you offer journalists? For journalists it’s “embargoed” stories.
For economists — you could host a conversation for them, invited, with climate scientists. RC has the reputation to attract their interest. Doing it by invitation would cut the chaff.
I did just peruse the Roundtable link — it does seem to do a good job of summarizing and linking out. Worth a look.
For example, a link there to discussion of the July 5 Brooks NYT column, here:
http://adamsmithslostlegacy.com/ASLLBlog.htm — discusses how fairness, equity and attachment are important but usually ignored by politicians, for instance. Climate change is one of those equity problems.
8 July 2006 at 1:35 PM
Re #81: Barton, your calculator does not work properly in Firefox. When you press the buttons to pre-set the values, the numbers flash on, then disappear.
8 July 2006 at 2:05 PM
Re #85:
I have just begun to read the study so possibly my opnion will change by the time I finish it. However this excerpt from page 18 seems to contradict your arguments even though your point about the laboratory strains not proving to be optimal in the open pond systems seems to be upheld. It seems that proof of concept was verified nontheless.
“At the conclusion of the smaller scale tests conducted in California and Hawaii, the program engaged in a competitive bidding process to select a system design for scale up of algae mass culture. The HRP design evaluated at UC Berkeley was selected for scale-up. The â��Outdoor Test Facilityâ�� (OTF) was designed and built at the site of an abandoned water treatment plant in Roswell, New Mexico. From 1988 to 1990,1,000 square meter ponds were successfully operated at Roswell. This project demonstrated how to achieve very efficient (>90%) utilization of CO2 in large ponds.
The best results were obtained using native species of algae that naturally took over in the ponds (as opposed to using laboratory cultures). The OTF also demonstrated production of high levels of oil in algae using both nitrogen and silica depletion strategies. While daily productivities did reach program target levels of 50 grams per square per day, overall productivity was much lower (around 10 grams per square meter per day) due to the number of cold temperature days encountered at this site.
Nevertheless, the project established the proof-of-concept for large scale open pond operations. The facility was shut down in 1990, and has not been operated since.”
8 July 2006 at 6:37 PM
Off topic I know, but I’m very curious…
Why have nighttime temperatures warmed faster than daytime temperatures? It seems to me that the effect of greenhouse gases is strongest when *temperatures* are highest — during daytime — so the greenhouse warming would be strongest during the day. But I’ve looked at plenty of data, so I know that in fact nighttime temperatures have gone up faster than daytime temperatures.
And a related question: why have wintertime temperatures warmed faster than summertime?
8 July 2006 at 7:02 PM
In response to question - “why greater warming effects at night and in winter?”
According to the Scientific American Blog:
http://blog.sciam.com/index.php?p=204&more=1&page=2
>”Greenhouse gases also have distinctive effects on the range of temperatures experienced by the surface. At night, the ground cools down by emitting infrared radiation, whereas during the day, the infrared cooling is secondary to solar heating. Because greenhouse gases impede the cooling but not the heating, they exert their greatest influence at night. If they are the cause of global warming, average nighttime temperatures should increase more than daytime ones — reducing the total daily temperature swing. (To be sure, the trend can be offset by changes in cloud cover and soil moisture.)”
>”For the same reason, greenhouse gases affect wintertime temperatures more than summertime ones, reducing the total annual temperature swing, and high-latitude surface temperatures more than low-latitude ones. These effects are magnified by snow and ice: by reducing snow and ice cover, warming reduces the reflectivity of the ground and allows more solar energy to be absorbed, further increasing the warming; conversely for cooling.”
I’ve also heard arguments that as global dimming is lowered this effect will be reduced.
8 July 2006 at 7:33 PM
Re: #90
I had seen the SciAm blog, but frankly, I wasn’t satisfied with that explanation. So I made a very crude computer model of diurnal heating and cooling, and when I increase the greenhouse effect the diurnal temperature range goes up.
Any suggestions?
8 July 2006 at 7:57 PM
Umm - I’d have to see your computer model. You have the words “very crude” bolded, but no link. Anyway your computer model depends on assumptions. I suspect there are some physics or engineering going on that the popularization I linked to does not go into. For that you will have to wait for actual scientists.
I can take a guess - but it probably will not be right.
I’m guessing that heat gets stored during the day. Because you have heat coming in less of it radiates out than at night when the air is cooler. (Smaller temperature differences result in smaller heat losses; the warmer daytime air acts as insulation - reducing additional flow of heat from thermal mass into the air; real engineers and scientists - is there where I start to go wrong?). At night you no longer have heat added. The air is cooler. So the heat stored in various types thermal mass gets radiated out faster. And of course since it is stored heat it is almost all radiated out in wavelengths that reflect back from greenhouse gases.
Wothehell - if I’m wrong the real scientists can use this post as their straight-line when they get around to it.
8 July 2006 at 8:06 PM
Re #60: Let’s go whole hog: “*abrupt* catastrophic runaway tipping points of no return” = ACRTPNR
8 July 2006 at 8:15 PM
I’m thinking of a short form — “lemming points” — the precipices defined by a propensity for rushing blindly toward them, eh?
8 July 2006 at 9:08 PM
RE #89, the (unscientific) way I figure it is the GHG blanket effect. Of course days are usually warming than night because of the sun, but if you keep a blanket on during the night & during winters, it keeps you fairly toasty….
8 July 2006 at 9:27 PM
Re: #89 etc.
Actually, it’s a mathematical model — I just used the computer to solve the differential eq.
Input is solar energy, given by
E(in) = S sin h,
where S is solar constant * (1-albedo), h is solar altitude. This is given by
sin h = cos d cos L cos(wt) + sin d sin L
where d is the sun’s declination, L the observer’s latitude, w the (radian) frequency (= 2*pi /day), and t the time (in days). If the solar altitude is negative, then E(in) is set to zero. Output is blackbody radiation, given by
E(out) = a T^4
where a is a constant (emissivity * Stephan-Boltzman) and T is the temperature. Then I used
dT/dt = const * (E(in) - E(out))
I simulated greenhouse warming simply by lowering the constant “a”.
There are a *lot* of oversimplifications here. Even so, when I lower the constant “a” the daytime peak temperature rises more than the nighttime low.
8 July 2006 at 9:39 PM
>There are a *lot* of oversimplifications here. Even so, when I lower the constant “a” the daytime peak temperature rises more than the nighttime low.
How about more than the nighttime *high* not *low*?
8 July 2006 at 10:49 PM
“#
If Al Gore’s movie, which was quite favourably reviewed here…….
http://www.cei.org/utils/printer.cfm?AID=5394
DG
Comment by David Goforth � 6 Jul 2006 @ 2:04 pm
”
Gavin, you’ve known about this article for a while. You really need to do a piece on this or open up a forum so we can attempt to collectively tear it apart.
9 July 2006 at 12:35 AM
Re #96: A meaningful greenhouse effect model really needs to have both the Earth and the atmosphere. The atmosphere is an enormous reservoir of energy that is maintained in large part by the ability of greenhouse gases to capture thermal radiation. It is so large in fact that averaging over 24 hours at a typical midlatitude site there is significantly more energy transfered from the atmosphere to the ground than there is transferred from the sun to the ground. See: http://www.globalwarmingart.com/wiki/Image:Greenhouse_Effect.png
I suspect that the problem you are having is that without the natural recycling effects of the interactions between the atmosphere and the Earth you are dissipating energy too rapidly during the night and hence cooling too rapidly. Keep in mind that since most of the radiation that makes it into space is emitted from the atmosphere, it is not merely a matter of adjusting the emissivity, but there is also an effective temperature, T_atmosphere, from where those emissions are eminating that can be substantially cooler than the surface.
9 July 2006 at 1:52 AM
Night time:
I searched here:
http://www.aip.org/history/climate/20ctrend.htm
and found this clue, which may lead you to an answer:
“… “fingerprints” were found that pointed directly to greenhouse warming. One measure was the difference of temperature between night and day. Tyndall had pointed out more than a century back that basic physics declared that the greenhouse effect would act most effectively at night, as the gases impeded radiation from escaping into space. Statistics did show that it was especially at night that the world was warmer….”
9 July 2006 at 9:45 AM
“It may also be that they just do not care what happens after they die.”
A theist here, and a Roman Catholic, probably in a very small minority in this dicussion.
I’ve been interested in the problem for years, and especially after having interviewed two scientists for a small Idaho paper on the subject of stratospheric ozone depletion in the arctic - one an atmospheric physicist and the other an atomospheric chemist.
I sense that Rome is coming around to an awareness and concern in these matters, particularly as they affect the poor in the so-called undeveloped countries.
I do know of individual Catholics who are concerned, and I’m thinking now of a field biologist who works in the sub-Arctic and who has done some notable work in insect infestation of sub-boreal forests.
9 July 2006 at 10:25 AM
It seems that changes in the diurnal temperature range (DTR) are not so easy to attribute to a cause. Nor is DTR changing everywhere by the same amount, or even with the same *sign*.
Some googlescholar search turned up very interesting things about DTR. I can’t seem to find the work by Tyndall (or anyone else) giving the reasons “basic physics” indicates greenhouse warming will decrease DTR. But one of the papers discussing the observed trends throughout the 20th century [Karl et al. 1984, J. Climate and Appl. Meteorology, 23, 1489] simply states that
At least part of the change in DTR seems to be due to atmospheric absorption of solar energy, and by latent heat from increased evaporation [Cao et al. 1992, J. Climate, 5, 920]:
Another important factor seems to be changes in cloud cover. This is from [Karl et al. 1993, Bull. Amer. Met. Soc., 74, 1007]
And this from [Dai et al. 1999 J. Climate, 12, 2451]