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Unforced Variations: March 2013

Filed under: — group @ 4 March 2013

A new open thread – hopefully for some new climate science topics…

350 Responses to “Unforced Variations: March 2013”

  1. 1
    BillS says:

    Interesting Letter in Nature GeoScience & available on-line for the moment at least:

    From the abstract:

    “Global temperatures have risen over the past few decades. The water vapour content of the atmosphere has increased as a result, strengthening the global hydrological cycle. This, in turn, has led to wet regions getting wetter, and dry regions drier. Climate model simulations suggest that a similar intensification of existing patterns may also apply to the seasonal cycle of rainfall. Here, we analyse regional and global trends in seasonal precipitation extremes over the past three decades, using a number of global and land-alone observational data sets.”

  2. 2
  3. 3
    James says:

    This is likely a dumb question, however it came up while reading recently about advancements in hydrogen fueled cars. Is it problematic that their (hydrogen fueled cars) emissions are water vapor (ie strong greenhouse gas)? Or would the level of emissions be insignificant compared to natural sources?

  4. 4
    Vincent van der Goes says:

    Thanks to everybody who offered feedback at the end of the previous open thread, in response to my question (see here). My source for 5-6m SLR in the 25th century is this article, although as a layman I am unable to judge how much confidence I should have in this single article and how well it represents general scientific understanding.

    In general I think it is a shame that so many studies seem to have a cut-off point at the year 2100. My feeling is that the true magnitude of the problem only shows if you look at the longer term. In Holland (where I live), for example, SLR may become painfully expensive by 2100 but we’ll probably manage. But over the course of centuries, the picture becomes ever more bleak and eventually, unless a green revolution happens, massive floodstorms and evacuations will become inevitable. Few people living here realise this. The cut-off point of 2100 in many reports might partially be responsible for the lack of understanding. But I’m digressing.

    Killian, thanks for the interesting input. Short answer, in my story I’m assuming a dystopian regime and a drastically reduced population (not only due to global warming and its side effects, but also due to various shortages and a nuclear war).

    Lawrence Coleman, I have heard about the possibility of a runaway greenhouse effect and I know what it did to Venus, but I don’t think the scientific consensus is that this is a likely scenario in the geologically near future. Of course it depends on how exactly you define “BAU” and I do know that James Hansen spoke about it and that he is someone to take seriously. However, as far as I know this is still a bit speculative. Please feel free to point me to correct me, or to point me to additional sources.

  5. 5
    Brennan says:

    Is it just me or is that a flagrantly cherry-picked data point in 2004 for his flat line?

  6. 6
    Chris Dudley says:

    Lawrence (#420 Feb.),

    You might be interested in reading James Hansen’s “Storms of my Grandchildren.” In Chapter 10, “The Venus Syndrome” he looks at what models can say about very large increases in carbon dioxide concentration. They hint that water vapor may become the main constituent of the atmosphere. In that case, sea level would fall I guess.

  7. 7
    Dan H. says:

    I think it is just you. The Argo data shown, has four years of flat-lining, followed by six years of rise, and another nine years of flat-lining. Looks more like a step functioning, but then again, the data length is rather short.

  8. 8
    L Hamilton says:

    Effects of daily temperature on public beliefs about anthopogenic climate change (the “Zorro” graph and link to new paper in AMS journal Weather, Climate, and Society).

  9. 9
    MARodger says:

    nuclear_is_good @2
    You link to a very strange piece of analysis. Watts (giving a hat-tip to old man Pielke, so it may be Watts is just repeating what he has been told) seems first to accept that OHC is a valid part of AGW and presumably if OHC is on the rise then there is no pause in AGW. But then Watts asserts he has a 0-700m OHC graph that contains “more up-to-date data from the ARGO bouy system,” – that is more up-to-date than the ScepticalScience graph.
    Watts seems pleased by his ‘discovery’ yet he is wrong in what he says. The “new data” in the graph (that comes from the NOAA) results from a reanalysis of old XBT data. The 2003-12 data that takes Watts interest in the NOAA graph is not new at all. It is the same old ARGO data as seen in that SkepticalScience graph which Watts is trying to belittle, the SkepticalScience graph that includes both 0-700m OHC and 700-2000m OHC, the latter being where OHC has been doing its stuff over recent years. (We’ll ignore the OHC rise below 2000m.)

    And there is perhaps another rod for Watts’s back in his post – 2003 to 2012 doesn’t constitute his 17 years of paused AGW.
    No. Steady now. Perhaps on Wattsupia 12 – 3 = 17.

  10. 10
    t_p_hamilton says:

    Re 2: Tamino has some thoughts about John Coleman’s analysis.

  11. 11
  12. 12
    Russell says:

    Evidence of the basic biogeochemical cycle that drives the climate wars has been discovered in Australia.

  13. 13
    Icarus62 says:

    Significant contribution to climate warming from the permafrost carbon feedback – Andrew H. MacDougall, Christopher A. Avis & Andrew J. Weaver.

    In figure 3, the paper suggests that even with a hypothetical complete cessation of anthropogenic CO2 and sulphate emissions in the year 2013, atmospheric CO2 would not fall by more than about 10ppm for hundreds of years, if climate sensitivity is ~3C per doubling. That seems very worrying if true – doesn’t it mean that they expect permafrost carbon release to have offset all natural carbon sinks within the next decade or two? The usual scenario is that land and ocean sinks would quickly start to draw down atmospheric CO2 if we stopped emitting it (e.g. in the ‘Climate change commitments’ RealClimate article from 2010).

  14. 14
    nuclear_is_good says:

    @3 (and as an extension @2)
    It also was suggested somewhere else that the data comes from a place that claims to use methodology from Lyman 2010 but the graphs from Lyman 2010 had 2004 and 2007 looking quite very different than this graph (and much more like Levitus 2012).

  15. 15
    MalcolmT says:

    Brennan @ #3: It’s not just you.

  16. 16
    Hank Roberts says:

    nuc’ and Brennan — Tamino covered it:

    “Problem: That trend line suggesting “the last 15 years have seen a cooling in the United States” isn’t statistically significant. Not even close.

    “Other problem: That’s not the last 15 years.
    Here’s all the data ….”

    Lesson – check _every_ claim — what the data is, where it’s from — as well as the arithmetic. Not that it’ll convince anyone over at WTF.
    Have you been watching Doonesbury lately?

  17. 17

    #3–No, Brennan, it’s not just you. Was that even supposed to be convincing?

  18. 18
    John Mashey says:

    See Climate Change series @ USA Today, of which one is
    Dan Vergano’s article on Ruddiman’s latest,

    and another is Wendy Koch’s Why you should sweat climate change.

    USA Today has surprised me more than once, as when in 2011 and editorial had
    “Taken together, these developments ought to leave the deniers in the same position as the “birthers,” who continue to challenge President Obama’s American citizenship — a vocal minority that refuses to accept overwhelming evidence.”

    Anyway, if people like what they are doing, tell them so … I’m sure they’re getting plenty of negative email.

  19. 19
    wili says:

    The good folks at Neven’s Arctic Sea Ice blog are tracking extensive cracks throughout the sea ice far beyond what any of those seasoned veterans of sea ice observation have seen before. Here is just the latest in a series of increasingly apocalyptic sounding exclamations from those otherwise rather stayed observers of all things Arctic and icy, this from A-Team:

    “Things fell apart out there this afternoon. This new pair of 550 km long fractures represents a significant eastward extension of the crack system through the core of the thickest, oldest, coldest, hardest ice of the CAA.

    It happened rather fast: nothing at 14:36 UTC, hairline cracks on the 16:16, both visible but barely at 17:51, both well-developed by 19:31. They’ll be a several kilometers wide by the next satellite pass. I will catch it with an animation these evening in the off-chance that it will be seen in a few months as a historic tipping point.”

  20. 20
    Killian says:

    19 Wili:

    Here’s the current image. Current Arctic Break-up, March 5, 2013

    (Hope this link works.)

  21. 21
  22. 22
    Chris Colose says:


    See this NAS Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia (particularly Chapter 6) for a comprehensive review of long-term climate change impacts.

  23. 23
    Susan Anderson says:

    re Arctic breakup broken link, this might point towards the line of country though probably not the precise item:

    scary monsters!

    new topic

    Hate to go off science, but a disgusting Nocera article about Hansen just appeared in the NYTimes. Have at it before comments close:

  24. 24
    Chris Dudley says:

    James (#3),

    Not a dumb question. Water vapor is a greenhouse gas. But it is a condensable gas. It’s concentration in the atmosphere is thus limited by the temperature of the atmosphere. If there is too much water vapor, it rains or snows and the atmosphere dries out somewhat. Water vapor provides a dominant feedback for noncondensable greenhouse gases. But it is a little like running on a treadmill if you were to use it directly.

    Now, there are very serious problems with hydrogen as a fuel when it comes to warming. The stratosphere is very dry and adding water vapor there can have a strong warming effect. Fugitive hydrogen from fuel production and use could enter the stratosphere and become water vapor through oxidation. (Fugitive methane can do the same.) Under those conditions, the water vapor has a chance to accumulate and behave like a noncondesable gas for a while. But it is not the water vapor tailpipe emissions that would be the problem but rather hydrogen fuel leaks.

  25. 25
    Edward Greisch says:

    20 Killian: “You don’t have permission to open this page”

  26. 26
    Paraquat says:

    This is likely a dumb question, however it came up while reading recently about advancements in hydrogen fueled cars. Is it problematic that their (hydrogen fueled cars) emissions are water vapor (ie strong greenhouse gas)? Or would the level of emissions be insignificant compared to natural sources? – Comment by James

    Of course, we are a rather long way from having hydrogen-powered cars, but assuming it comes to pass, what would be the likely effect of expelling water vapor out the tailpipe?

    My guess is: not much effect. Water vapor rises, condenses, forms clouds (which actually reflect the sun’s heat) and eventually falls to earth as rain or snow. That’s why I moan every time I hear the idiotic argument from the WTFUWT folks that “water vapor, not CO2, is causing 90% of the greenhouse effect.” Fact is, water vapor is plentiful on earth (fortunately, otherwise we’d live in a frozen world) but water vapor reaches a saturation point and then condenses into a liquid. CO2 cannot exist as a liquid on earth (it could if the earth’s atmosphere was about 5 times denser than it is today, and if the planet was much cooler).

    But back to cars – I don’t think there is much hope of powering them purely on hydrogen. A stronger possibility would be to use ammonia. Burning ammonia gives you free nitrogen plus water vapor. The technology to do it was developed during WWII and was actually used in Belgium. There are some downsides (ammonia is poisonous, so you’ve got to handle it carefully), and of course you first need some sort of non-fossil fuel electricity (solar, wind, nuclear?) to produce the ammonia if the goal is prevent AGW. But it’s an interesting possibility. I’m not sure if anyone is seriously working on making it happen though.


  27. 27
    Hasis says:

    Is there any chance of putting Neven’s Artic Sea Ice blog on the blogroll guys?

  28. 28
    Lawrence Coleman says:

    4: Vincent. As you are aware the signs of Climate change are not hard to miss in most parts of the globe and that’s only with around 400ppm of atmospheric CO2 and that’s reaally only begun to hit within the last 30 years as conditions in the 1980’s were pretty much as many below av. temps as there were high. Now in 2013 the subjective and measurable effects climate change is getting increasingly obvious. A BAU up to 2500 hypothetically speaking assumes that we will still be using harmful hydrocarbons which will (assuming the world’s pop. will probably stabilize at around to 10-12 billion mark within the next 100 years thus the demand for fossil fuel and hydrocarbons) will potentially double. We will have to find alternative sources of energy when our oil reserves and coal and gas end and they will be in all liklihood be climate friendly..but this is all academic because the world would have been pushed to beyond breaking point some argue very validly already. By the time the climate gets too wild and woolly and world governments en-masse agreee that CC mitigation methods must be immediately implemented it is already way way too late to do anything about it. I am guessing this will happen before 2050. Arctic ice is melting at an unprecedented pace right now and will in all likelihood be ice free in summer within the next 8 years. As the ocean warms it releases the frozen methane stored in the arctic ocean sediment around 1700GT. Methane is 20-25 times more potent a greenhouse gas than CO2. Simutaneously the methane and CO2 stored in the permafrost tundra regions also thaw..incidentally this is already well under additional 1500-2000GT of CH4(methane)and CO2. The rate at which this gas gets released depends on the ocean and land surface 1.5C additional warming than today all the methane and C02 in the permafrost will get liberated into the atmosphere. However the ocean floor is hovering just above freezing now and any additional warming will cause progressive and unstoppable methane release over the coming get the picture. I’m half dutch as well and I believe the dutch are very good at seeing things as they are, so I hope your book leads you to explore the rich and fascinating and very sobering field of Climate science. I am not a scientist per se, but a very interested Climate Change researcher. Good luck!

  29. 29
    David Werth says:

    I have a question I’ve been mulling over for a while that maybe someone can answer. We can determine CO2 levels of the past by measuring it from ice cores. This means there is CO2 trapped in the ice sheets. So how much CO2 is actually trapped in the ice sheets? Is it enough to be at all a significant source of CO2 as the ice sheets melt?

  30. 30
    Glenn Tamblyn says:

    nuclear_is_good @2

    This just one of Anthony’s more recent spectacular foot-in-mouth episodes, although none of the faithful seem to spot it. Its a sort of ‘golly gee whiz, this graph doesn’t agree with that one does it’ moment. Without noticing the blindingly obvious fact. The two graphs agree!

    Look at the 1st graph from Glikson. Actually from Nuccitelli et al 2012 which is using data from John Church at CSIRO (one of the authors of the paper)

    2 curves for the ocean. 700-2000 (dark blue) and then 0-700 (light blue) stacked on top of it. So to see what 0-700 looks like, in your minds eye subtract the lower curve from the upper and see what the upper alone looks like. Upward trend that then drops of significantly in the early 2000’s. And don’t forget – Anthony just sorta forgot to mention this – the data from Nuccitelli et al is pentadal (5 year running average). The PMEL graph Anthony shows is annual values.

    So you tell me, ignoring the distraction Anthony add with his ‘catch the eye’ yellow line, what is actually different about the 2 graphs? Nada. So what is the point of his post. Andrew Glikson, if he felt like responding to a minor blog, would simply point out. ‘Yeah, the second graph agrees with the first. Your point?’

    Note how Anthony then blurs things, never clearly spelling what he is referring to – OHC, just 0-700 OHC, 0-2000 OHC? Then leaves his ‘followers to draw the conclusion he hoped they would draw.

    All Anthony is doing here – de-rigeur for him – is throwing chum over the side to see how many sharks and smaller fish he can attract.

  31. 31
    Glenn Tamblyn says:

    “Is there any chance of putting Neven’s Artic Sea Ice blog on the blogroll guys?”

    Second that, strongly! Neven and his regulars are mining a narrow vein, but they are mining it deeply, diligently and knowledgeably.

  32. 32
    Lennart van der Linde says:

    Vincent #4,

    Under BAU 5-6m SLR by 2500 would indeed seem a rather conservative estimate. It’s hard to know what would happen, since the forcing would be unprecedented. From what I’ve read in the scientific literature, being a layman as well, there seems to be a significant risk of about 15-16m of SLR by 2500 under BAU. Your 5-6m may be reality by about 2200, or even sooner with a very (even more) abrupt collapse of WAIS.

    For an impression of the sources and reasoning behind this estimate see this presentation I made in my work for a local Dutch ngo:

    For more on the potential mechanisms for such SLR see some interesting info on particularly the risk of WAIS-collapse here on the Arctic Sea Ice Forum (by an engineer calling himself AbruptSLR):

    Note that we both base our guesses in large parts on arguments by Hansen & Sato, which seem to be shared by some (more and more?) in the relevant scientific community, but are certainly not mainstream (yet?). There seems to be quite some debate currently on the rough likelihood of such a SLR-scenario, but many seem to agree to at least some (serious enough) risk of such fast and large SLR.

    Also note that Foster & Rohling (PNAS 2013) estimate about a 50% chance of circa 24m of SLR in the long run with CO2-levels stabilizing at around 400 ppm. They estimate about 84% chance of at least 9m of SLR at 400 ppm, in the long run (centuries to millennia).

    Since we’re already almost at 400 ppm today, and since we show no sign of stopping emissions soon, we’ll certainly go much higher than 400 ppm, and even higher still because of positive carbon feedbacks which seem already starting to kick-in today.

  33. 33
    MARodger says:

    Vincent van der Goes @4
    You were saying it is a story you are writing, set in the 25th century, so 2400 -2500AD. Being a story (I scribble stories myself), what you probably need is less how we 21st century folk would view a BAU 25th century but how 25th century folk would view it.

    If we assume the big damage to human welfare occurs 2070-2200AD (be it due directly to AGW or indirectly as folk tussle for the leftover resources, with nuclear weapons, you say!), by the 25th century that would all be a distant memory for human kind. (Imagine the initial shock of the Black Death wiping out half of humanity – yet it doesn’t have much resonance in say the writings of Shakespeare two centuries later.)

    In your future world, however much of civilisation you decide survives (or is rebuilt) to 2400AD, by such a time the population would be well used to retreating before rising seas. Maybe some city of prestige remains behind defenses metres high, although even one or two such cities – do they make sense if the whole of Antarctica is set to melt eventually?
    Beyond sea level, would temperatures have pretty-much stabalised by 2400AD? Would the climate have started to stabalise? Although the catastrophically bad times (2070-2200AD) may be a distant memory, there possibly will still be pulses of refugee populations seeking new homes, although less so as, bar sea level rise, stability is restored.. But I would say that whatever the world you choose to depict, its population would surely be very sensitive to climatic data – global temperatures, atmospheric CO2, methane, extreme weather events & regional climatic change – all this on top of the rate of sea level rise. Remember they (or their forebears) didn’t listen to folk saying AGW was upon them. Would these people now listen to folk saying (bar sea level) its all over?

  34. 34

    OT, really, but @ 26 Paraquat said “I don’t think there is much hope of powering [cars] purely on hydrogen.”

    His comment was a little ill-timed, I fear:

    (Unless, perchance, he’s not counting hydrogen fuel cell technology as ‘purely’ hydrogen?)

  35. 35
    Steve Metzler says:

    Glenn Tamblyn #30:

    2 curves for the ocean. 700-2000 (dark blue) and then 0-700 (light blue) stacked on top of it. So to see what 0-700 looks like, in your minds eye subtract the lower curve from the upper and see what the upper alone looks like.

    Bingo! Interpreting data correctly was never Anthony’s strong point. How many times has he been called out on his hilariously mistaken ideas concerning baselines? He likes the satellite temp data because he thinks it shows less warming, not realising that it has a later baseline period than the land-based data, and that’s the sole reason why the temp anomalies are lower. What a total anti-science farce his site is, and as the evidence mounts for AGW, his posts only become more stridently ‘not even wrong’.

  36. 36

    I had not heard of this technology; I wonder how many others here have?

    Makes a lot of sense, at first blush.

  37. 37
    tamino says:

    Re: #2 (nuclear_is_good)

    Since you brought up the subject, here’s my take on it:

  38. 38
    wili says:

    Icarus62 @ #13: Thanks for reminding us of that crucial MacDougal article on permafrost tipping points. How would you say that the recent article on the sensitivity of permafrost to sunlight affect the graph you pointed to?

  39. 39
    Pete Dunkelberg says:

    What cooled the Arctic? Clouds? High pressure?

    The arctic winds have been too strong for the thinner than before arctic sea ice:

    Storms blowing from the Arctic are bring record snowfall as far south as Kansas and near record snowfall to north Texas:

    But recall the storm of ’93:

  40. 40
    Pete Dunkelberg says:

    Dear Planet Earth,
    You’re so sensitive! But what is the relevant measure of your sensitivity?
    We have:
    Transient sensitivity, equilibrium or Charney sensitivity, and earth system sensitivity, based on how long you wait to see what happens and on what feedbacks are accounted for.

    Transient sensitivity is the temperature change due to, say, a change in CO2 concentration, within twenty years or so. Charney is the change expected if you wait for near equilibrium to recur, but don’t experience very serious feedbacks like the initial change releasing a big slug of permafrost carbon.

    Earth system sensitivity is what you get if you wait for all the feedbacks. In our current experiment we are releasing a large quantity of CO2 from carbon that was reduced long ago and taken out of the active carbon cycle. If our effort then releases a large amount of permafrost carbon on top of what we release on purpose, what will earth system sensitivity turn out to be? How long will it take to find out?

    Estimates anyone?

  41. 41
    Hank Roberts says:

    > electrode-boilers
    “when cheap electricity is available it can be converted to hot water/steam without any polluting consequences at all.”

    That matches what I hear from local energy guys, who tell me that companies are replacing old solar thermal water heaters with solar PV connected directly to resistance heating coils — any excess power from the solar PV gets saved as heat.

  42. 42
    Leonard Evens says:

    Who is Joe Nocera, and why is he going after James hansen about the pipeline issue? This is the second Op Ed column in the NY Times by Nocera attaking Hansen, this time much more personally. I don’t remember Nocera writing any other columns about climate change, but he seems to be lobbying strongly for the pipeline. It makes me wonder just why he is so concerned with this particular issue.

  43. 43
    Dan H. says:

    Actually Paraquat’s comment was not that ill-timed at all. The press release that Hyundai will manufacture 1000 fuel cell vehicles for fleet use in 2015, does not make much of a dent in the ~15 million vehicles sold annually. Other companies have manufactured fuel cell vehicles for demonstration tests in select markets also.

  44. 44
    Killian says:


    Yup. I have no problem getting there from my browser, but the link doesn’t work for me either when posted here. Go to Neven’s, find you way, then get to the index. Can’t even remember How I did that, but once you get to the index of images you can look at them going back months. I have it bookmarked, so can get there.

    Just go to the appropriate thread on Neven’s. He has a post on it, but also being discussed on the new forums.

  45. 45
    Killian says:

    New Jennifer Francis video on climate effects on weather:

    So glad of the increasing communication and activism on the part of climate scientists, including the allowance of more discussion of impacts and solutions here at RC.

  46. 46
    Ranga Myneni says:


    This is Ranga Myneni, Professor in the Department of Earth and Environment at Boston University. My research focus is on evaluating climate change impacts to vegetation using satellite data. I have been active in this science for over 25 years. A link to my professional web site is below near my signature.

    There is now sufficient evidence that our way of living is causing unnatural changes in climate. Collectively, we own this damage and therefore we need to solve it together. It is YOUR CLIMATE CHANGE also. Twenty five years have passed since the Intergovernmental Panel on Climate Change (IPCC) has been advising the policy makers regarding the hazards of climate change. Yet, there has been little meaningful action to solve this global problem affecting all life on Earth.

    The solution lies in convincing policy makers that this is a priority for all citizens of the World. Therefore, I started an online project to collect one billion signatures by Earth Day 2014 for a petition addressed to the Secretary-General of the United Nations to act judiciously and expeditiously on anthropogenic climate change.

    You can support by:

    (1) reading and signing the petition at

    (2) spreading the word to your (a) family, (b) friends, (c) colleagues and (d) acquaintances through the links on that page, and

    (3) composing an email to your trusted circle of family and friends, with the subject “Your Climate Change:“, add a short sentence at the beginning of this email (e.g. “I think this may be of interest of you.”) and copy-paste the text of my email

    We can easily reach our goal. If I can motivate at least 10 of you to sign the petition, and you in turn can motivate 10 more to sign the petition and they in turn can motivate 10 others … All it takes is 9 such steps, provided that each signee is unique.

    Thank You!
    Prof. Ranga Myneni (

  47. 47
    AndyL says:

    Is Gavin still planning his follow-up about Climate Sensitivity? It was promised two months ago.

    [Response: Life sometimes gets in the way… Sorry. The main holdup is an analysis I wanted to do showing what Ridley+Lewis’s calculation would give for a climate model where you know the right answer. – gavin]

  48. 48
    Icarus62 says:

    wili @ #38: As you know, the authors acknowledge that they still haven’t included all the permafrost feedbacks, so their projections may still be too conservative. I notice from a full copy of the paper it says:

    The PCF transforms the terrestrial land surface from a sink
    for carbon to a source of carbon to the atmosphere. This transition
    occurs in 2053 (2013-2078) for DEP 2.6, 2068 (2026-2104) for
    DEP 4.5, 2091 (2029-2131) for DEP 6.0 and 2065 (2014-2100) for
    DEP 8.5 (Supplementary Fig. S7). In the absence of the PCF, such
    a transition occurs between 2079 and 2198, contingent on climate
    sensitivity and emissions pathway.

    With the cessation of anthropogenic CO2 emissions the CO2
    fertilization of plants also ceases, leaving only the oceans as a fast
    sink for carbon. The strength of this sink is partially determined
    by the quantity of CO2 that has been added to the atmosphere. If
    the rate at which CO2 is being released from the terrestrial land
    surface exceeds the rate at which the oceans can take up CO2, then
    CO2 will continue to build up in the atmosphere, further warming
    the surface and driving a self-sustaining carbon-cycle feedback.
    In experiments where DEP 8.5 is followed up to a given date
    when emissions are instantaneously reduced to zero, all simulations
    with climate sensitivities above 3.0 C produce a self-sustaining
    PCF even if emissions are reduced to zero in 2013 (Fig. 3 and
    Supplementary Fig. S5).

    I think we can assume that the self-sustaining PCF hasn’t happened yet or we’d be seeing 4ppm increase in atmospheric CO2 per year instead of 2ppm… but the paper isn’t exactly optimistic about how much time we’ve got before this happens. Maybe we have 40 to 60 years, or maybe much less. What do you think?

  49. 49
    Paraquat says:

    34 Kevin McKinney says:
    OT, really, but @ 26 Paraquat said “I don’t think there is much hope of powering [cars] purely on hydrogen.”
    His comment was a little ill-timed, I fear:
    (Unless, perchance, he’s not counting hydrogen fuel cell technology as ‘purely’ hydrogen?)

    Hi Kevin. I stand by what I said. Hydrogen fuel cells have been around for decades. But at a cost of around US$1 million each, there is little chance of widespread adoption in cars. A few showpiece vehicles manufactured for big companies that want to milk the public relations benefits is not going to put a dent in gasoline or diesel fuel consumption.

    Much cheaper than fuel cells is to burn hydrogen directly in a slightly modified internal combustion engine. This too was done decades ago. I remember seeing in the 1970s a prototype by Caltech shown at a press conference. The beaming students drove the car around the university’s parking lot to a chorus of oohs and aahs by the reporters. We were all assured that this was “the car of the future.” That was maybe 40 years ago.

    What they reporters didn’t catch on to was that the hydrogen was supplied by a gas cylinder in the car’s trunk and the vehicle had a range of maybe five miles. Getting enough hydrogen on board to actually travel a reasonable distance means cooling the hyrogen until it becomes a liquid. That occurs at about 20 degrees Kelvin. Keeping it that cool is not easy. Park the vehicle in the sun and it rapidly warms, the hydrogen expands, and if you don’t want an explosion then you need a pressure-release valve, which means that in a short time you’ve got an empty tank. If you park the vehicle in a garage, leaking hydrogen (and it is a notoriously leaky gas) means you’ve the stage for an exploding garage.

    Ammonia, on the other hand, it quite a bit easier to handle, even though it is toxic. Compressed to about 10 atmospheres, it will remain a liquid indefinitely at room temperature. We already have a thriving ammonia industry (it’s used to make fertilizer, among other things). The main issue holding back ammonia-powered cars is that you do need some form of electricity to manufacture it – ammonia doesn’t come out of wells drilled in the ground. Since the goal is to reduce CO2 emissions, you would need a clean source of electricity. This is also an issue for hydrogen-powered cars (though for the reasons mentioned above, I don’t think they will ever be viable for mass production). The clean source of electricity could be wind, solar, nuclear or whatever, but until that infrastructure is in place, we aren’t likely to see many ammonia-powered cars on the road.

  50. 50
    wili says:

    Icarus wrote: “I think we can assume that the self-sustaining PCF hasn’t happened yet or we’d be seeing 4ppm increase in atmospheric CO2 per year instead of 2ppm… but the paper isn’t exactly optimistic about how much time we’ve got before this happens. Maybe we have 40 to 60 years, or maybe much less. What do you think?”

    As you point out, in the paper itself, they say that they have not included all feedbacks, so even their most extreme-sounding claims are likely an understatement of the actual situation.

    So I have to conclude that we are close to if not at/just past the point when feedbacks would sustain CO2 levels at or above current levels for centuries, even if we stopped all further emissions immediately. No one has been able to tell me why this is not so. Note also that comparing weekly averages, we have recently been about 3ppm above last year’s same-time-of-year weekly averages.

    Also, the beginning of feedback does not necessarily equate with a sudden explosion in CO2 rate of increase. It will start as a very small added effect, then build on itself.

    For the record, no matter what is happening with feedbacks, runaways, etc, it is clear to me that our moral imperative at this moment in history is to dramatically reduce our emissions–personally, as a family, in our businesses, schools and institutions, and at the municipal, state, national and international levels–as quickly and completely as possible. I have been working to all so at all these levels, at great disadvantage to many of my closest relationships and to my career. I urgently urge all others to do the same.

    But I still want to know as accurately as possible the true nature of our current condition, however grim. This (sometimes) can be one of the best places to get such insights.

    (reCaptcha: “said no u go f” !)