What Are the “Unknown Unknowns” of Global Warming

Year after year the worriers and fretters would come to me with awful predictions of the outbreak of war. I denied it each time. I was only wrong twice.

— Senior British intelligence official, retiring in 1950 after 47 years of service weekend’s question is:  What are the “Unknown Unknown” climate impacts?

In 2002, Former Defense Secretary Donald Rumsfeld infamously popularized the term “unknown unknowns” – “the ones we don’t know we don’t know.” See video below.

As my illustrated review of 50 recent studies on climate impacts made clear, what we know with confidence is coming on our current emissions path is  more than enough reason to act.

If we go to 7°F — let alone 9°F or higher — we are far outside the bounds of simple linear projection. Some of the worst impacts may not be obvious — and there may be unexpected negative synergies. The best evidence that will happen with the staggering warming we face if we keep doing nothing is that it already happened with even the 1°F or so warming we have seen to date.

As quantified in the journal Nature, “Mountain pine beetle and forest carbon feedback to climate change,” (subs. req’d), which just looks at the current and future impact from the beetle’s warming-driven devastation in British Columbia:  “The cumulative impact of the beetle … converted the forest from a small net carbon sink to a large net carbon source.

No wonder the carbon sinks are saturating faster than we thought (see here) — unmodeled impacts of climate change are destroying them:

Insect outbreaks such as this represent an important mechanism by which climate change may undermine the ability of northern forests to take up and store atmospheric carbon, and such impacts should be accounted for in large-scale modelling analyses.

And the bark beetle is slamming the Western U.S. and Alaska, too.

The key point is this catastrophic climate change impact and its carbon-cycle feedback were not foreseen even a decade ago — which suggests future climate impacts will bring other equally unpleasant surprises, especially as we continue on our path of no resistance.

Note I am not talking about the many “known unknowns” — the stuff we know could happen but we have no idea how fast and fierce:

I’m talking about stuff that is not really explored in the scientific literature.

I’m talking the real black swans — an “extreme event” that is “an outlier, as it lies outside the realm of regular expectations, because nothing in the past can convincingly point to its possibility” (see “Is global warming a black swan“).

What are the “Unknown Unknown” climate impacts?

83 Responses to What Are the “Unknown Unknowns” of Global Warming

  1. The advances of pests — insects, animals, and diseases — has always been part of the deal. Warmth expands the number of niches that things can live in. What the specific ones might turn out to be — like the pine bark beetle or the crabs moving into the Arctic oceans — can’t really be predicted, but pests were going to spread.

  2. Ummm, once the responses have been identified, even if only speculatively, they are no longer “unknown” unknowns.

    Like much of Rumsfeld’s thinking, this always struck me as totally confused.

  3. catman306 says:

    I don’t know what kind of unknowns will be revealed during the next few decades, but I’m pretty sure that they will graph exponentially. We’ve crossed the threshold, stumbled over the tipping point, and have left linear effects behind, it’s mostly exponential from here on out.

  4. Joe Romm says:

    Well, yes, but that doesn’t mean they don’t exist at this point.

  5. James Newberry says:

    Perhaps unknown to 99.9% of the public is the prospect that human oxidization of Lithosphere carbon materials is melting polar ice caps (some seven million cubic miles of ice) thereby uncapping volcanic and other tectonic forces which will cause earthquakes of a “not natural” origin.

    Western economics will be unable to account for a rise of earthquake damage from this trend as fossil fuel related.

  6. publius2012 says:

    “the main dangers lie in the “unknown knowns” – the disavowed beliefs, suppositions and obscene practices we pretend not to know about, even though they form the background of our public values.” Slavoj Žižek

    . . . Unkown unknowns? Effects of dark energy, parallel universes, and extraterrestrial life?

  7. Ernest says:

    I don’t know. Maybe an emergence of a new form of life adapted to warm and hot climates? (bacterial, archaeal, “extermeophiles”), that would wipe out current forms of higher mammalian life? …

    (If you take the Ray Kurzweil scenario of human machine convergence, the disappearance of human life, but the emergence machine life housing both machine and human intelligence, but in this case to survive in an inhospitable planet? Kind of the “singularity meets climate change” …)

  8. Rabid Doomsayer says:

    There is the inevitability of war over scarce resources particularly water.

    The rate of sea level rise will continue to accelerate after 2100.

    There is Peter Ward’s “Under a Green Sky” scenario where the oceans become hypoxic and produce vast amounts of hydrogen sulfide. He estimates when CO2 reaches 1,000 ppm it becomes possible. The older literature calls this a Canfield State.

    The paleo comparisons of where we are headed are scary. But there is no paleo comparison on how fast we are changing the forcing. We are already at an unprecedented rate of change and continuing to accelerate.

    Nature will throw us curve balls and the evisceration of science will ensure these curve balls catch us utterly unaware. Just consider how weird the weather is already.

    And as James Newberry points out, we refuse to deal with the known. We have rejected mitigation and adatation so now comes the suffering.

  9. Jan says:

    Human behavior – in reaction to sudden awareness of the reality of climate change, or, if still in denial, to its manifestations.

    This could range, in my opinion, from some short-notice, all-out, world-wide effort to mitigate, to large-scale international or civil wars to defend business as usual (which I personally consider more likely). Not to mention possible reactions that are, as of yet, unknown ;-)

  10. prokaryotes says:

    What happens with Methane spikes, could this create ground hovering, ignitable clouds. Or Co2 clouds which kill everything.

    Killer CO2 cloud – the story climate change “skeptics” hope you won’t read

    It’s not even secret. But those propagandists who run advertising claiming that carbon dioxide is natural and, therefore, harmless, hope against hope that you don’t know the true history, that you’ve never heard of Cameroon, that you don’t know about volcanic emissions, and that you forgot the story of the killer CO2 cloud of 1986.

    Read it here, “Cameroon: The Lake of Death.”

    Propable Tsunami threats for europe or noerthern US west coast from underwater landslides or volcanic mega eruptions.

    Connecting the Dots: Climate Change drives Earthquake / Seismic activity

    Because the speed of Co2 emission is unprecedented in earth history, dangerous feedback meachaism might turn out to happen sooner or with a different tipping point temperature.

    Soil carbon and climate change: from the Jenkinson effect to the compost-bomb instability

    ‘compost-bomb instability’ is most likely to occur in drying organic soils with high porosity covered by an insulating lichen or moss layer. However, the instability is also found to be strongly dependent on the rate of global warming. This paper derives the conditions required to trigger the compost-bomb instability, and discusses the relevance of these to the concept of dangerous rates of climate change. On the basis of simple numerical experiments, rates of long-term warming equivalent to 10°C per century could be sufficient to trigger compost-bomb instability in drying organic soils.

    And how will all these climate setting setup changes, affect human growth long term wise? All the greenhouse gases break down in the atmosphere, thus consuming oygen in the process. When oyxgen levels decline, the environment gets less favourable for life – less growth.

  11. Jan says:

    And not to mention individual and small-group madness, e.g. motivations for and methods/targets of new terrorist groups.

  12. Sou says:

    Obviously we don’t know yet what the unknown unknowns are. It’s likely there will be some and we need to make sure we have capability to recognise them when they happen and respond. Making sure there is research capability across a broad spectrum and response capability flexible enough to respond.

    Eg not replacing satellites is not a good idea. Neither is paying too much heed to ‘fashion’ in research – putting all eggs in one basket so to speak. I’ve seen situations where less fashionable research areas are allowed to wither right through from undergrad education through to senior researchers – leaving a state or nation vulnerable (particularly in agricultural research).

  13. Ziyu says:

    The Washington Post recently published a flawed misinformation article about the EPA’s GHG ruling. The headline reads that the IG report says the EPA needed more data and the first paragraph says it didn’t follow proper protocol. It leaves out a key fact until several facts later. The report says the endangerment finding met proper standards and it was only comparing standards to “highly influential scientific assessment” category. Of course the deniers will pick this up and spread it like climate change driven wildfires.

  14. Sou says:

    By the way – the field I had in mind re loss of capability was entomology interestingly – given the pine beetle problem in North America.

  15. Colorado Bob says:

    After recording its all-time driest month in August with just 0.01 inches (0.25 mm) of precipitation, Chattanooga, Tennessee received 9.49 inches (241.0 mm) of rain on September 5th, breaking the previous daily record of 1.59 inches (40.4 mm) set in 1959.

  16. Peter Mizla says:

    One unknown is how much arctic ice will remain in the arctic -though is is becoming more clear.

    Climate shift- thus far most scientific organizations have predicted a slow change. What happens of this proceeds at a more swift pace- especially in food growing regions.

    Drought and heat progress faster then models have been modeled across broader geographic regions.

  17. Colorado Bob says:

    Illusion of Plenty Masking Collapse of Two Key Southern California Fisheries

    As they describe in the most recent edition of the Canadian Journal of Fisheries and Aquatic Sciences, the researchers say the total amount, or biomass, of each bass species decreased 90 percent since 1980. Yet fisheries catch rates have remained stable for a number of years, even as overall population sizes dropped drastically. This is due, the authors say, to a phenomenon known as “hyperstability” in which fishing targets spawning areas at which large numbers of fish congregate, leading to a misleading high catch rate and masking a decline in the overall population.

    “The problem is when fish are aggregating in these huge masses, fishermen can still catch a lot each trip, so everything looks fine-but in reality the true population is declining,” said Erisman, a member of the Scripps Center for Marine Biodiversity and Conservation. “So as the true abundance is declining, the fisheries data used to assess the health of the fisheries are not showing that and give no indication of a collapse-this is referred to as ‘the illusion of plenty.'”

  18. Colorado Bob says:

    LONDON — Britain has experienced the hottest October day on record.

    National weather service the Met Office says Saturday’s temperature reached 85.8 F (29.9 C) at Gravesend in southeast England.

    That is the highest October temperature since records began a century ago, beating the previous high of 84.9 F (29.4 C) reached on Oct. 4, 1985.

    The average maximum temperature for early October is about 59 F (15 C).

    Read more:

  19. Lewis Cleverdon says:

    James – I share your concern at the prospect of “the destabilization of the geosphere” as Dr McGuire put it, but given that he’s been writing papers on its paleo-record and evidence of its present advance – and he runs vulcanism risk research for Munich Re – this looks more like a known unknown.

    Suffice to say that it could not only take down cities here and there, even where there is no record of earthquake probability – it could also trigger the next mega-landslip on the Canary Islands resulting in a 200ft tsunami surging 16 miles inland down the length of the US east coast – And then there is the truly vast caldera under Yellowstone, whose release could not only eradicate America but also cause a global ‘nuclear winter’ to wipe present populations of us and many other species.

    By raising volcanic emissions of sulphates – as well as by hitting society’s fossil emissions capacity, this geosphere destabilization is the first credible ‘negative’ feedback of global warming that I’ve heard of. Surely we should be hearing more of it from the deniers ?

    The unknown unknown megathreat that seems to me really a matter of time – is that of warming affecting some battery chicken CAFO unit, whose occupants are kept alive by the routine spraying of antibiotics. Those drugs’ efficacy is in an arms-race with the most virulent and contageous pathogens’ developing new immunities, thus selecting out the weaker strains week by week, site by site. By advancing the rate of evolution of more radical, contageous and virulent pathogens we are already engaged in a random process of the utmost peril to society – Random warming, and humidity events, and weather-damage power cuts to ventilation, seems likely to raise that risk of a catastrophe.

    This is reason #1 why I’d vote to close CAFOs globally, before that risk increases further.



  20. Steve Bloom says:

    Joe, I’m gratified that you’re finally going to do the big post on the expansion of the tropics (and when you do, don’t forget the consequent increasing Agulhas Current leakage, which AFAICT is the ultimate source of the warm water eating away at the ESS clathrates), but your mention of beetles above reminded me that you seem to have missed covering the recent news that MPBs have become established in the boreal forest jack pine population. (A site search turned up nothing on this, although I know you’ve mentioned it prospectively.) Of course that this has happened should be a surprise to absolutely no one, notwithstanding the prior pathetic denials of the Canadian and Albertan governments, but that it’s now under way is a big deal. Article here, paper here and scientist oral presentation summary here.

  21. Paul Revere says:

    The greatest black swan in the global warming situation is that geoengineering could actually work, an idea which both global warming advocates and global warming deniers attack.

  22. Allan says:

    I don’t think you can contribute the devastation in the British Columbia pine forest to warming alone. We new we had a problem brewing back in the mid 80’s with an out break in one of our provincial parks. The government of the day stopped a proposed plan to log the infected trees or at least try to quarantine the area by cutting a large swath between infected and non infected trees. The beetle, when emerging from an infected tree, flys to the next one but distance can prevent the beetle from hitting its target. Also, a lot of the forrest was nearing the end of its life cycle [100yrs +-]
    which means it was vulnerable to attack. And your are right that temperature played a part but either you get a cold snap when the beetle is emerging, late spring, or when the beetle has not had an opportunity to burrow to far into the tree. The other option is sustained cold weather[-25c for 2-3 weeks]but snow fall can insulate a tree so reduce the effectiveness. The beetles are devious. They secrete an alcohol like substance when in their hibernating state and so have some protection. The only natural event that truly eradicated the pest was fire and we had supressed forest fires since the 50’s. Department of Forests has changed their policy. If the fire dosen’t endanger life or property, they might let it burn. The beetle is in decline and much of the devistated area is starting to recover. With or without the pine beetle, the forest has a natural life cycle and we are now trying understand the implications of a warmer climate. I am not an authority but had land effected by this problem.

  23. Joan Savage says:

    Under-served areas of climate change research for “unknown unknowns” include non-linearities, non-parametric relationships, and shifts in rare event probability in complex systems.
    Humans tend to extrapolate from the familiar into the future and we gamble on frequency distributions. Each is a flawed method in what is a forced and complex system.

    The language of Harley and Paine’s abstract may help.

    “Ecological responses to climate change may occur gradually with changing conditions, or they may occur rapidly once some threshold or “tipping point” has been reached. Here, we use a high-resolution, 30-year data set on the upper vertical limit of a high intertidal alga to demonstrate that distributional shifts in this species do not keep pace with gradual trends in air temperature or sea level, but rather occur in sudden, discrete steps. These steps occur when unusually warm air temperatures are associated with unusually calm seas and are contingent in the sense that neither atmospheric nor sea conditions by themselves were sufficient to generate the underlying physiological challenge. Shifts in the upper limit did not correlate with large environmental perturbations such as El Niños; rather, they appeared to be associated with stochastic departures from otherwise gradual environmental trends. Our results exemplify the view that multiple environmental factors should be considered when attempting to understand ecological responses to climate change. Furthermore, punctuated responses such as those we have identified urge caution when attempting to infer causal mechanisms and project future distributional shifts using data of limited temporal resolution or scope.”

    Harley and Paine (2009) PNAS June 17, 2009.
    “Contingencies and compounded rare perturbations dictate sudden distributional shifts during periods of gradual climate change”

  24. Joan Savage says:

    re “under-served,” I can’t speak to the level of institutional support, it is just rare to see those topics in popular press.

  25. Mike#22 says:

    Warmer world weather patterns.

  26. Merrelyn Emery says:

    Well I dunno. But I would put money on new diseases from totally unexpected sources, like that sweet, healthy moggy your kids are playing with at the moment.

    A nasty little epidemic that has no manifestation until people try to breed, when they painfully become aware that they are all infertile, ME

  27. Mike#22 says:

    Example, Texas. Weather patterns have shifted lately for this state. If they stay shifted, much of the Texas economy is wrecked and Texas becomes an early causality of Global Warming weather patterns. Did anyone expect this would happen so soon, and has anyone imagined what the outcome for Texans will be?

  28. Some European says:

    Many come to mind, most have been mentioned above.

    I didn’t see this one, though.
    Some climate models seem to project a return of monsoons to the Sahel and a greening of the desert. I think it was somewhere around 3ºC of warming. Then, at the next degree of warming, it would go away. If this happens rapidly, somewhere around the middle of the century, it could bring a cruel disaster to the desperate in the space of a few decades. Millions of hungry survivors would scramble to this new area of plenty, only to perish in hellish conditions, when the rains fail.

    A similar situation could happen in Siberia. It could become the irresistible garden of Eden of the Asian continent. Attractive to its immediate neighbour, China. We’ve all thought of the possibility of nuclear war between India and Pakistan over the Himalayan water supplies. What would happen if Russia were to compete with China over one of the rare comfortably habitable areas left on Earth? (Also, I think it’s unlikely there will still be a united China in 30 years.)

    Other speculative consequences include:
    – geo-engineering wars
    – carbon terrorism (to mitigate or to aggravate/blackmail)
    – tsunamis from methane bubbles, landslides and calving ice shelves
    – seismic activity from isostatic rebound
    – the rise of fascism and a large nation increasing its emissions threefold (USA, anyone? – I’ve downgraded that likelihood lately, due to positive signs – Canada??)

    Sometimes I wonder: If I were a psychopath whose dream was to exterminate all life on Earth, how would I do it? Nuclear, viruses, diverting asteroids, none would work. The most effective ways seem: burn/agent orange the Amazon, burn/melt the permafrost, produce and store several millions of tons of sulphur hexafluoride and release it simultaneously and, last but not least, set up a PR campaign to politicize global warming and discredit the science in strategic countries. Okay, the last one has been done. Do we know any individuals who might fall under the definition of life exterminating psychopath? (English speaking but not American, rather old, charismatic, …)

    Just as with terrorism, one crazy person is enough to hold the planet hostage (“give me a lollypop or I’ll open the SF6 tank”).

  29. Mike Roddy says:

    There is a free way to help the forests restore themselves: leave them the hell alone. Unfortunately, there is no money in this alternative, which is why we hear all the talk about biomass power, cutting them down to “save” them from burning, etc.

    When a forest is logged, 80% or more of the carbon goes into the atmosphere. When it burns, 80% is retained. Yet we still hear from reporters such as Gillis in the New York Times that we need to cut them down.

    The other issue is that logging even in increments affects precipitation patterns and forest health in general. Species are eliminated or kept from migrating. This is what causes forests to become deserted scrublands, starting in the Aegean (especialy Turkey) 3,000 years ago.

    For the 100th time, Joe- you need a top quality forest carbon scientist on this blog. Please.

  30. Joan Savage says:

    Genetic selection pressures on life forms, due to the compounded factors of climate change.

  31. Steve Bloom says:

    Speaking of mountain pine beetles, I happened to see a copy of the print edition of the NYT just now and was utterly gobsmacked. They have a gigantic front-page story on global forest problems related to climate change, starting with a large color photo of Montana MPB damage at the top of the page and jumping to a full 2-page spread. Re the MPB jump to the boreal forest, the article (by Justin Gillis) says “fear are rising” of it, which based on the research I linked above is something of an understatement. Anyway, it’s very much worth a full read. There’s a link to the graphics and some other material.

    The article’s focus on the global implications of forest problems, mainly the decline of a major CO2 sink, is good to see since it’s gotten so little media attention, but that raises the question of when that will happen again? What’s the effect on readers when they see prominent treatment of a problem and then not again for a long time? IMO it sends the opposite message, since the issues that are really important get continuing coverage. If one doesn’t, it must not be really important, right?

  32. Steve Bloom says:

    Of course warming alone would be doing them serious damage.

    Zero cutting in all forests is a hard argument to make, but it’s not as if there is no middle ground between that and massive clear-cutting.

  33. john atcheson says:

    I’d suggest another category: “known” but ignored.

    One of the interesting feedbacks in this category I saw outlined was the simple role of krill in sequestering mass amounts of carbon in deep cold oceans. They currently have a feeding cycle and a death cycle that sequesters a great deal of carbon — but there are now 70% less krill than there used to be due largely to warming. Big deal, but never really addressed.

    The other interesting issue is what are the potential cumulative effects of all such feedbacks? It’s one thing to look at one feedback at a time, but it is likely quite another to contemplate their potential combined effect in terms of rate and extent.

    Can we be precise about such things? No. But that doesn’t mean we should ignore them.

    To do so would be like not jamming on the brakes as you hurtle towards a concrete wall because you can’t say exactly where you’ll stop.

  34. Mike Roddy says:

    Not really an unknown unknown, but more of an ignored and lied about:

    Over half of the boreal forest, which contains 2/3 of the earth’s terrestrial forest carbon stores, is likely to be gone in 50 years, releasing billions of tons of carbon, with tree recolonization an unknown unknown. Driving factors are doubling of CO2 and industrial logging, which is especially rampant in Canada, our Tar Sands buddies.

  35. Mike Roddy says:

    Here’s the true unknown unknown: military outcomes. Habitable land will become scarce faster than humans can reduce populations. This means slaughter over resources, since people tend to not quietly starve. By the time this is happening, people will have realized that prayer is not effective, and corrupt central governments will be discredited.

    It will take the form of small arms infantry with portable artillery, which will be capable of taking out choppers and any building. But the real unknown unknown is this: states will disintegrate, leading to plunder of nuclear weapons and power plant fissile material stocks. Use your nightmare imagination for these events, and have a stiff drink handy. It will be Afghanistan without the religion- incessant fighting, shifting alliances, and no rules whatsoever.

  36. Kooiti Masuda says:

    Locking-in of the Southern Oscillation. Whether it is at the El Nino phase or at the La Nina phase, it will bring permanent drought to some tropical regions around the Pacific. This issue is “known” in a sense, since some paleoclimatologists have suggested that there were few occurrence of El Nino cycles in the early Holocene. But there is no known causal link yet about whether, and if yes, how, global warming would stop the oscillation.

  37. Leif says:

    The military comes to its senses and realizes that Climatic Disruption is truly an issue of National Security in the first order. Looks around and notices that the biggest threats are the denier corporations and the denier goon army they finance. Wall street that finances the whole. The Chicken Sh*t Media that carries their water and the bought courts that somehow all appear to side with capitalism when the chips are down. With the Government that does the same. Do they serve the people or the corrupt society killing Capitalistic/Corporate Government? They pick the “We the People,” declare marshal law, restructure themselves into a “Green Machine” and all the finances that go with it. After fifty years of crash efforts mitigating CO2, Society starts to see a light at the end of the tunnel as levels start to trend toward 350 ppm and humanity breaths a sigh of guarded relief. Re-boots with a premises of an economy structured toward long term sustainability rather than short term profits.

  38. Greg Junell says:

    Human Behavior – With #8 Jan and #27 Mike Roddy.

    If cooperation followed from awareness, we might have everyone on earth working on biochar. A mass enlightened behavior toward a common goal.

    Necessity (love?) could make the only sane act to work together. Classic unity through a common enemy.

    And more precedented… panic. Declining cooperation. Abandoned trade and treaties. Selfishness. Hoarding. Slaughter. Populations moving from unlivable areas into vulnerable areas, collapsing the new area and moving on again like locust. Walled cities and states. Treating the poor and starving like zombies. Inhumanity.

    Fear could cause a breakdown well ahead of actual environmental impingement on our survival.

  39. Paul Magnus says:

    Global Warming causes the earth to wobble on its axis or is trajectory, with more chaotic consequences of not.

  40. Colorado Bob says:

    ‘the illusion of plenty’

  41. Colorado Bob says:

    Joe –
    The Nashville Flood , …. add this on :

    After recording its all-time driest month in August with just 0.01 inches (0.25 mm) of precipitation, Chattanooga, Tennessee received 9.49 inches (241.0 mm) of rain on September 5th, breaking the previous daily record of 1.59 inches (40.4 mm) set in 1959.


  42. Colorado Bob says:

    As a system nears it’s tipping point , it moves to the extremes, and these extremes tend to stick, before the system sweeps to the other extreme.

  43. Colorado Bob says:

    One more current example, .. Britain, after the a cold and cloudy summer in the south. Bingo the warmest October numbers ever written down. She didn’t move 20F degrees above average, she went for 30F degrees above average.
    The march to the extremes. At Childress, Texas on April 2 this year, it was 102F degrees.

  44. Paul Magnus says:

    GW triggers more volcanic activity which causes cooling.
    This though is probably not that way out.

  45. David B. Benson says:

    The knowns and known unknowns are scary enough.

  46. colinc says:

    Really, Joe? You dare cite the imbecilic nonsense of a war criminal? Claiming there are “unknown unknowns” is, at best, redundant, bordering on moronic, and a clear signal of manipulation. Anything that is “unknown” is just that… unknown. Everything else falls within the spectrum of probability. Of course, this doesn’t even begin to address the irrationality of “known unknowns.”

    It would seem that too many are completely unfamiliar with Taleb’s writings or absolutely did not understand them. I guess that really isn’t a surprise since our culture is rife with innumerable baseless beliefs due to the incessant, pervasive programming to which we have all been subjected. It is those beliefs that blind the believer and obviate reason and rationality. Alas, that will be the undoing of the bulk, if not all, of our species and most others on this rock. That sudden stop at the bottom is closer than most can imagine.

  47. BA says:

    Unknown, Unknowns: How the biosphere would respond if we simply laid off, stood down, laid low, stopped emitting crud into the atmosphere.

    Everyone knows that if we completely stopped burning CO2 tomorrow the planet would still keep warming well past what it is now.

    Yeah, OK but how else would the biosphere respond. There are a huge number of unknown, unknowns here and I don’t think any model could ever predict the intricacies of how the planet would respond.

    One thing we know is if we suddenly cut all air pollution there would be a spike in temperature as global dimming would be mitigated. But then too black soot would stop accumulating in the arctic and acidifying the oceans.

    If things settled out and CO2 flat-lined would over taxed carbon sinks start to kick in and do their job? My guess is that they would. My bet is a whole bunch of positive feed backs would start to occur if given enough time. Not all the damage would be reversed but there would be some positive surprises at how resilient the planet can be when we simply lay off.

    So suppose it is 2012 and it starts to look like the Mayans were on to something. The arctic starts belching large volumes of methane from the seafloor. Suddenly almost everyone gets it. The planet is cracking open and melting down. No one but no one is going to fly away, go somewhere nice and get out of this one. Suddenly the scene in Washington is like one one of those fifties Si-Fi movies where everyone is united to do everything possible to conquer the giant ants except in this case it is the methane releases. The President in concord with all the other world leaders declares a “global stand down.” Everyone is to stay put. Only non-carbon burning activities are permitted. Food will be broadly distributed and peoples critical needs will be met. Aside from that the only CO2 that will be burned will be to fly C-130s 24/7 over the arctic region to create a man made cloud cover to produce regional cooling.

    Finally, after some months, the methane belches start to subside and small but positive signs appear that the situation in the seafloor is stabilizing—the arctic temps have cooled slightly. Gradually plans are made to go forward with the rapid building of a new green infrastructure and economy the world over. The industrial age ends and a new, ecologically sound, environmental Renaissance begins

  48. jyyh says:

    Yes, now that we see that insects can make an outbreak (not that anyone has ever heard of locusts) having economical effects, should we consider a possibility of a similar sort of outbreak of diseases of bacterial/fungal origin on agricultural lands in general?

  49. Martin Palmer says:

    Biological, ecological, and sociological factors might be the most sensitive to climate change, as others have pointed out.

    Well, whenever biology is involved, the possibility of very sensitive dependence on current conditions becomes large.

    The pine beetle infestation is a good example of this, I think. Change winter temperatures by a small amount, and suddenly we’re getting three generations of beetle per year instead of two, and millions of acres of forest end up decimated.

    So biological and ecological unknowns are pretty high on the list, I guess.

    I also wonder about geological instability, especially if we start losing really major amounts of ice from the poles and transferring that mass to the oceans, closer to the equator. By conservation of momentum, that will start to decelerate the oceans relative to the rest of the earth. This could interfere with the geomagnetic field, and over the long term cause first geomagnetic chaos and a geomagnetic reversal.

    As others have pointed out, human behavior can also be very sensitively dependent on existing conditions. Wars and terrorism generated by droughts and floods seem likely.

  50. Steve Bloom says:

    Re unknown unknowns, if they’re guessable here they’re not unknown. But actually, Joe, in the post you mentioned the only thing they can be, which is unanticipated synergies. Unknown circulation changes almost qualify as well, since knowing that they’re circulation changes isn’t really knowing much given the complexity of the ocean-atmosphere circulation.

  51. Rabid Doomsayer says:

    How big would a methane burst have to be to swamp the hydroxyl radicals on a local/regional basis and thus significantly extend the residency time in the atmosphere?

  52. Merrelyn Emery says:

    That question made me think all day and none of it is nice. My first, somewhat flippant response is above. But the question reverberated.

    How long will it take for the bush to reclaim all our inland cities, towns and the coastal areas that have not become citadels for the great god Jellyfish?

    How many will we be able to move to underground towns? – not that we are building any at the moment as we pretend that our silly little targets and carbon trading scheme will solve the problem.

    Will any of our unique and superbly adapted marsupials and monotremes survive or will the future Australia be one where mutated rabbits, cane toads, feral cats, goats, pigs, birds, carp, etc plus imported plants, fight it out for survival?

    Should we care? Or should we accept that any form of life is OK?

    Will any of our Aboriginal people survive to help with their thousands of years of detailed knowledge of this ancient, most beautiful continent?

    Given that we have the continent of extremes – the vernacular about the weather cycle here is that it is “drought, fire, flood” – is that a recipe for some sort of adaptation or a death sentence?

    What will it take to bring people to their senses? Or will a lot of people go to their death being none the wiser?

    Horrible question, horrible thoughts, ME

  53. Spike says:

    The effect on soils is a big unknown to me, at least not one i have seen much discussion of. I guess this is because industrial agriculture has allowed us to ignore the importance of that thin surface layer of the Earth on which all life on land depends. But what will intense droughts and deluges do; what will happen in warmer soils to the bacteria, fungi, nematodes etc..; what will happen to soil carbon and nitrogen; where in the world will the impacts be most severe?

  54. Joe Romm says:

    There are impacts we know with high certainty. Their are impacts whose scale and timing are unknown. And then there’s the stuff that isn’t in the literature at all (real black swans). Seems like a reasonable distinction..

  55. Belgrave says:

    I live in the Canary Islands – in Tenerife, hopefully in the lee of the west side of the island of La Palma (the unstable one.) At the moment it’s quite stable and we’re a long way from any ice caps so I think the main worry would be local earthquake activity as the islands are of volcanic origin – and all except one only dormant. But the islands are festooned with seismographs so there should be a fair period of warning.

    The “unknown unknowns” which worry me more are unpredictable synergistic effects between “knowns” and “Known unknowns” (the latter being phenomena which seem probable but their timing, magnitude and effects are unknown). For example, a limited release of methane from the Siberian ice shelf plus some degree of tropical rainforest wildfires plus some further advance of ocean acidification plus only slight reduction in anthropogenic release of greenhouse gases. None of them singly enough to cause really serious problems (at least in the short term) but all interacting to produce unknown synergies, possibly even taking us over “unknown tipping points”. I’ve done a search for work on this but not come up with much – understandable as I suppose computer models would have so many variables as to be little better than informed guesses.

    But I suspect that “unknown synergistic tipping points” could result in very rapid and disastrous changes.

    And that’s without taking into account human synergies – peak oil, famine, epidemics, war…

  56. Belgrave says:

    Some heartless people might say that that wouldn’t be a problem – quite the contrary!

  57. Mike Roddy says:

    I’m surprised you kept your cool after that bitchy little diatribe, Joe, I would have hollered back. I like Taleb, too- and even corresponded with him briefly- and can say that he would take your side here.

  58. Martin Palmer says:

    I’ve wondered myself if the Japanese tsunami which triggered the Fukushima nuclear disaster might have been one of those unknown unknowns.

    There is no scientific evidence for this that I know of, but I’ve wondered if sea level increases or changing stresses on the bottom of the ocean due to temperature changes in the ocean could trigger release of built up seismic stress.

    The global sea level rise maps show that areas off the coast of Japan have large and chaotic variations in sea level. Could these waves of sea level rise have triggered the earthquake that led to the tsunami?

    NASA JPL video .mpg file

  59. BA says:

    A geologist told me that existing models do not account for the strength of recent seismic activity including Fukashima.

    Also, I have heard that the melting of glaciers may be releasing stress on the earths plates contributing to the strength of earth quakes. And I remember hearing that the sun rose in Greenland minutes earlier or later than predicted last spring I think and they said that may be due to the earths crust rising as the ice melts and releases pressure. I hear this and that. It would be interesting to learn more.

  60. prokaryotes says:

    A balloon and hosepipe as the answer to climate change? It’s just pie in the sky

    Increasingly bizarre attempts at geo-engineering simply deflect attention from the fact we need to cut greenhouse gases

  61. prokaryotes says:

    The Psychological Impacts of Global Climate Change

    An appreciation of the psychological impacts of global climate change entails recognizing the complexity and multiple meanings associated with climate change; situating impacts within other social, technological, and ecological transitions; and recognizing mediators and moderators of impacts. This article describes three classes of psychological impacts: direct (e.g., acute or traumatic effects of extreme weather events and a changed environment); indirect (e.g., threats to emotional well-being based on observation of impacts and concern or uncertainty about future risks); and psychosocial (e.g., chronic social and community effects of heat, drought, migrations, and climate-related conflicts, and postdisaster adjustment).

  62. BA says:

    “The paleo comparisons of where we are headed are scary. But there is no paleo comparison on how fast we are changing the forcing. We are already at an unprecedented rate of change and continuing to accelerate.”—I agree with that! I read Under a Green Sky and that came to mind when I first thought of Unknowns.

  63. BA says:

    I make an attempt at a “short-notice, all-out, world-wide effort to mitigate” scenario down below. I think we should have those ideas laying around just in case.

  64. BA says:

    I have little faith in Geo-engineering and think it will most likely make things worse although in a post down below I have given a scenario where contrails are used as an emergency cooling measure.

    I sometimes call myself a Luddite and someone always makes a snarky remark but what I mean is that I do not have faith in technology to save us. OK, I think it is part of the answer to the problem of global warming but I also think that we have to scale back—actually take a step back toward the per-industrial era especially where agriculture is concerned. Not only do I think we need to have much more local economies I think a sane response to what we are facing might be to bring back the Clipper Ship for international trade.

  65. BA says:

    In a reply to a post above I mention a return to per-industrial agriculture methods. Our forestry choices right now are between cutting and leaving alone to burn and do what it will without human disruption but in per-industrial times humans had a lively interaction with the forest environment. I read a book by Jack Turner, Abstracted Wild, in which as I remember he points out that many areas we would consider wilderness are inhabited with people: the Himalaya, the Amazon. Also I have read that Smokey Mountains N.P. along the Appalachian trail has been loosing meadow area and biodiversity because it is thought that in the past humans regularly burned these areas to keep them free from trees. In Rebecca Solnit’s wonderful book Savage Dreams she discusses how native peoples lived in Yosemite harvesting acorns and other plants right up into the 1960’s. Our assumption is that nature and wilderness exist without us. So here is the question: could our forest lands be repopulated, sparsely, with low technological in habitation—no CO2 burning technology—to steward, cultivate, and farm natural areas? In the past N. Am. had mind boggling herds of bison, elk, and fish runs through the Colombia water shed. Even the Lake Tahoe area had huge fish runs. If it were possible to restore some of that it would not only provide benefit to the climate it would be a much needed source of protein.

  66. Martin Palmer says:

    Yes, it would be very interesting to know more.

    As mass shifts from the poles toward the equator, conservation of angular momentum will try to slow the rotation of the earth, and of the oceans relative to the rest of the planet.

    Will this lead to new ocean currents, flowing westward? Will this lead to new stresses on the westward boundaries of oceans? It should be noted, maybe, that Japan is on the westward boundary of the Pacific.

    An old paper by Richard Mueller of Berkeley suggests that a large impact event could cause a geomagnetic reversal. He calculates that if a small ice age is triggered by the impact, the shift of mass from the equator toward the poles as icecaps grow could disrupt the rotation of the mantle relative to the core, creating a geomagnetic reversal.

    The effect of global warming would be the opposite, with a shift of mass from the poles toward the equator, rather than the other way around, but the geomagnetic effects could be similar, if the shift of mass is large enough and quick enough:

    Mueller/Morris Geomagnetic Reversals From Impacts on the Earth

    The impact of a large extraterrestrial object on the Earth can produce a geomagnetic reversal through the following mechanism: dust from the impact crater and soot from fires trigger a climate change and the beginning of a little ice age. The redistribution of water near the equator to ice at high latitudes alters the rotation rate of the crust and mantle of the Earth. If the sea‐level change is sufficiently large (>10 meters) and rapid (in a few hundred years), then the velocity shear in the liquid core disrupts the convective cells that drive the dynamo. The new convective cells that subsequently form distort and tangle the previous field, reducing the dipole component near to zero while increasing the energy in multipole components. Eventually a dipole is rebuilt by dynamo action, and the event is seen either as a geomagnetic reversal or as an excursion. Sudden climate changes from other causes such as volcanic eruptions could also trigger reversals. This mechanism may not be the sole cause of geomagnetic reversals, but it can account for the rapid drop of the dipole component preceding a reversal, the predominance of multipole components during a transition, the associations of microtektites, temperature drops and extinctions with reversals, and the possible correlation between peaks in the geomagnetic reversal rate and the times of mass extinctions. The model may also account for the long‐term changes in the average rate of reversals. We make several testable predictions.

    So to add to all the other climate misery we are inflicting upon coming generations, it may be that we will be inflicting a geomagnetic reversal and associated increased cosmic radiation and side effects of that on them.

  67. Florifulgurator says:

    A positive musing: What feedbacks will save the biosphere (not necessarily humans) from runaway heating (a la Venus)?

    A known unknown seems to be artcic phytoplankton: When summer sea ice is gone it could grow substantially more than now. But experts aren’t sure.

  68. Joan Savage says:

    Statistical correlations have been showing up between recent changes in distribution of mass and earthquakes.

    Increased soil erosion from the Himalayas shifts the weight distribution of the Asian continent. Melt of land-based glaciers changes weight distribution. The distribution of mass in the oceans changes with the temperature cycle of the currents, such as the ENSO cycle. These have been correlated to earthquake incidence, but primarily in areas like Chile that are already known for earthquake activity.

    So what might we make of the August 23 Washington DC earthquake in an historically low incidence location? Or the severity of the Tohoku earthquake on March 11? I’m counting on geologists to connect the dots.

  69. Allan says:

    I don’t know what “Your Comment is awaiting moderation” implies but here is a very succinct article from Alison Berry. Forest policy up in Smoke: Fire suppression in the United States. Could be Canada. Because of suppression, we have exasperated the problem of insect infestation, fuel load on the forest floor and densification of the forest.
    With warming temperatures, how the life cycle of the forest will change, needs immediate review.

  70. Cynthia says:

    “Unknowns unknowns?” The following is from a book (don’t remember the name) I read years ago:

    “Rising sea level… brings additional warming…because of lowering of the altitude of continents. New, shallower, heat absorbing coastal seas and freshly created bogs will warm up the atmosphere still further.”

    “As ice dissolved (post-glacial civilizations)… crushing weight of the ice (compressed weight on the earth)… land rose, engendering colossal landslips and volcanic eruptions… as massive crustal upheavals took place…. (resulting in) tsunamis”.

    The following is from another book:

    (On possibilities)… “upheavals in the Arctic and the Antarctic that will make for the eruptions of volcanoes in the Torrid areas, and… the shifting then of the poles– so that where there have been those of a frigid or semi-tropical will become the more tropical, and moss and fern will grow…”

    “Portions of… east coast of New York… disappear. The greater portion of Japan… go into the sea.”

  71. Ken says:

    Maybe a known unknown but with unknown unknowables contained within – Will Gaia wipe out humans before humans wipe out Gaia? This is a corallary to the known Hansen Venus Syndrome unknown. Hansen did not assume the Earth is a living being. But what if it is and fights back. I expect civilization will crumble before Gaia does. With humans crushed will Gaia heal?

  72. Mike Roddy says:

    Agreed. Forests can be the largest store of renewable protein, especially migratory fish.

  73. Raul M. says:

    A day at a time one could start to do the things that will help and work in the expected future. Such as first hand learning of hydroponics. An unknown would be how long till discression becomes the better part of valor. Say in that someone makes the better choose.
    Anyway good luck in helping people to see that the weather is changing and they will need to make changes too.

  74. Martin Palmer says:

    Well, these two “black swans” are in the literature, but need to be more widely known, I think.

    The first black swan is atmospheric chemistry changes due to increasing methane concentrations. Increases in methane start to overwhelm hydroxyl radical concentrations, increasing methane lifetime. Tropospheric ozone and stratospheric water vapor increase, multiplying the greenhouse heating effect of extremely large methane releases several times:

    Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions

    Another black swan is water vapor feedback. This is commonly associated with CO2 increases, but in fact this feedback would multiply the greenhouse forcing from any source, since the link between forcing and feedback is temperature. Any forcing, from any greenhouse gas, will be multiplied by the water vapor feedback.

  75. Joan Savage says:

    A basic category of unknown-unknowns are novel outcomes of interactions among the knowns, particularly if the magnitudes of any of the knowns are underestimated.

    We have an inkling of this with Fukushima, where design engineers had only prepared for separate “reasonable” disasters, not a combination. They underestimated each element: earthquake intensity, tsunami size, shoreline earth sinking in an earthquake, and the volume of fuel rods in storage in operation at 40 years.

  76. Joan Savage says:

    Another basic category of unknown-unknowns are forces external to the atmosphere.
    A solar flare like the 1859 Carrington event might do more than inhibit satellite communications, damage transformers and corrode pipelines.
    In 2004 a flux of solar particles correlated with an intensely spinning Arctic polar vortex and a startling loss of stratospheric ozone.

  77. Mike Roddy says:

    Joan, you’re pretty good. I like your stuff.

  78. Pangolin` says:

    Paint Texas titanium white. (nobody will be using it anyway)
    Convert the automobile plants to producing ATV sized/transportable biochar retorts.
    Employ the one billion underemployed people in the world to convert every twig, branch, pruning, stover and deadfall in the world to biochar. (kill no standing wood if possible)
    Plow said biochar into forest/savanna transition zones and plant replacement forests with whatever will grow with heavy emphasis on food trees.

    Then get really crazy……

  79. Martin Palmer says:

    Yes, I like your stuff, too.

    Another example of unknown synergistic reinforcement of known factors might be methane release, atmospheric chemistry effects including increasing methane lifetime, and then the water vapor feedback multiplying the greenhouse forcing of all greenhouse gases. Add those all together, and we’re getting pretty close to Hansen’s Venus syndrome, I think.

  80. BA says:

    ..and the great plains. Elk are really a plains animal.

  81. Water vapor feedback is just a white swan. As the temperature warms, water evaporates from the ocean, and the water vapor content in the atmosphere will be approximately (though not exactly) proportional to the amount at the saturation, and so enhances the greenhouse effect by a known factor.

    Well, this is about water vapor in the troposphere. Behavior of water vapor in the stratosphere is complicated, and that may be a black swan.