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Unforced variations: Dec 2014

Filed under: — group @ 3 December 2014

This month’s open thread. Think history, Lima, and upcoming additions of a single data point to timeseries based on arbitrary calendrical boundaries.

265 Responses to “Unforced variations: Dec 2014”

  1. 201
    Pete Dunkelberg says:

    Chuck @ 196:
    1. Don’t bank too much on reforestation. Each ecosystem has its approximate natural fire frequency. More semi-permanent underground biomass might be produced by grassland, and the grass might be usable for fuel.

    2. “…we’re gonna hit 500ppm this century no matter what we do?” As stated, makes no sense. For instance if carbon is phased out by 450 ppm we will not get to 500.

    If too many people fall for “We are the Borg. Resistance is futile” it may become a self fulfilling prophecy. Don’t fall for it.
    To read: http://www.juancole.com/2014/12/reasons-prices-electric.html

  2. 202
    Hank Roberts says:

    > how much reforestation

    I can tell you from personal experience that numbers on CO2 fixed by forests are hard to come by as estimates and awfully expensive to actually research site by site — and the numbers would be very site specific. And probably need a baseline of decades before you could feel comfortable saying you’d detected a trend.

    A forestry professional reminded me, when I took on one such restoration as a hobby project, that I’d never know whether what I do makes a difference either way — but if I left a good enough baseline, then after fifty or sixty years, someone could figure that out.

    I haven’t found a review or summary; lots written: http://scholar.google.com/scholar?as_vis=1&q=forestry+credits+by+the+California+Air+Resources+Board,+which+regulates+the+carbon+market.&hl=en&as_sdt=1,5&as_ylo=2014

  3. 203
    Chris Dudley says:

    Hank (#199),

    They are using regular carbon dioxide bands so they may just mean that with their instrument there are no labels. There is an isotopic signature for fossil fuel use though not for biofuel use or for cropland burning. Examples of using molecular transitions that I’ve seen tend to be laser pumped so I’m not sure how far you can go with remote sensing using natural light.

  4. 204
    Hank Roberts says:

    > grassland …. might be usable as fuel

    I agree on building soil; the studies on that are that grassland can do that rather quickly if left in natural condition (not overgrazed or plowed).

    But, cautionary on biofuel from grassland — dry grass and dry harvested grass make one hell of a lot more of a fire problem than timberland does.

    ‘Greenpa’ saw that coming and warned about it years ago.

  5. 205
    wili says:

    PD @ #201 wrote: “For instance if carbon is phased out by 450 ppm we will not get to 500”
    1) Do you think it likely that all carbon sources of fuels will be phased out before we get to 450? The current rate of increase is about two and a half ppm per year, and that rate has been increasing every decade. So at current rates we would blow past your figure in about 40 years. With likely increases in that rate, we hit it far earlier.

    Do you really think we will have completely stopped using all fossil fuels within 20-40 years?

    2) And please note that even a complete and immediate halt of any more carbon emissions today would not necessarily stop the increase in atmospheric levels of CO2. MacDougal et al. (2013) and other studies that include carbon feedbacks show that we now will see inevitable continued rise in atmospheric CO2 levels, not matter how quickly or drastically we cut emissions. The likelihood and magnitude of such feedbacks will only increase as we continue to add more forcings. So by the time we get to 450 ppm we very well might have committed ourselves to 500 or more, even if we did by some miracle completely halt any further emissions at that point.

    All that doesn’t exactly mean ‘resistance is futile’ exactly. We all can and must fight to decrease the levels of further damage that will come with each added ton of CO2 and other ghg’s to the atmosphere. But let’s try to be a bit clear eyed about what we’re facing, and about the fact that climate is a complex system which will not necessarily just roll gently back to where it was once we stop pushing in toward a hotter state.

  6. 206
    wili says:

    PD: Nice point about grasslands, though.

  7. 207
    Steve Fish says:

    Re- Comment by Hank Roberts — 28 Dec 2014 @ 11:30 AM, ~#204

    An addition to the “Fuelish Fantasies” you link is the often ignored fact that if you harvest a crop repeatedly the soil becomes rapidly depleted of necessary nutrients. This is true of my garden and any other crop, including switchgrass, and the standard big agriculture solution is artificial fertilizers. Production of fertilizer releases a lot of N2O (a very potent greenhouse gas) and CO2, requires a lot of fossil fuel heat and more fuel to spread the fertilizer and collect the crop. 30% to 70% of this type of fertilizer application runs off and causes problems in both fresh and salt water ecologies. For grasslands to sequester carbon requires leaving the land alone and promoting grazers and browsers to spread their fertilizer where they eat.

    Steve

  8. 208

    #206–Not sure how to answer the very pertinent question “Do you think it likely that all carbon sources of fuels will be phased out before we get to 450?”

    On the one hand, emissions are adding about 2 ppm per year, and that’s accelerating.

    On the other hand, there seems to be a lot more happening with non-carbon energy than I (or just about anyone) could have imagined just a few years ago. Energy economics might just be tipping in a favorable direction (despite the current low price of oil.) There’s also a more favorable political climate than I’d looked for. And 20-40 years is a long time in terms of technological and economic innovation; consider that the Internet age is only a couple of decades old.

    So I think there is a realistic possibility that we *could* indeed phase out fossil fuels fairly completely before we hit 450. How probable that is, I have no idea how to estimate.

  9. 209
    Chuck Hughes says:

    Somebody explain this insanity to me. Where do these idiots get the money to buy all this stuff and throw away that much wealth on a location that is doomed? Sunny day flooding on a regular basis with sea water coming up through the streets and they’re building multimillion dollar estates as fast as they can. How much time before it’s all underwater?

    http://www.washingtonpost.com/news/storyline/wp/2014/12/22/miamis-climate-catch-22-building-luxury-condos-to-pay-for-protection-against-the-rising-sea/

  10. 210
  11. 211
    wili says:

    KM @ #208 wrote: “a more favorable political climate” Could you elaborate on what you mean by this. Last I looked, the US senate went Republican as did many state congresses. Perhaps you meant a political climate favorable to stonewalling any progress on addressing climate change??

  12. 212
    Hank Roberts says:

    > judicious scattering of finished compost

    Yeah, Steve, I know about the idea. Problem is, I gather, that a whole lot of compost has been produced from stuff collected by cities trying to reduce landfill; some of it comes from sewage treatment products as well.

    That may contain variously animal and plant viruses (from food and garden waste), heavy metals and antibiotics and other persistent organic chemicals (from human and animal waste), and other stuff washed in from roof and street rainwater).

    The devil, as they say, is in details of the assays, if you can get assays.

    There’s long been a big problem finding some place to put all that stuff.

    Spreading the stuff on public rangeland is a no-brainer. In several and varied senses of that term.

    It has to go somewhere.

  13. 213
  14. 214
    Jan Hollan says:

    A bit off-topic but actual: There is a Poll of Climate Scientists, at Vision Prize, closing today Dec 30, asking if global temperature anomaly is “the metrics” (and then on the role of natural gas). It includes the October theme of ocean enhtalpy anomaly. To take part in the poll go to: visionprize.com/session/new.
    Past findings of polls are at poll.visionprize.com. The start of such polls was mentioned on RealClimate in 2012.

  15. 215

    #211–wili, luckily the American Congress has no direct bearing on international climate negotiations. I was referring to the fact that the two largest national emitters brought into the recent COP an agreement to limit emissions (in the case of China, a first.) Moreover, there does (despite the rancor and what I would view as ‘underachievement’ which *still* characterized the Lima session) seem to be wider and wider acceptance of, and willingness to engage in, national action. For example:

    http://www.reuters.com/article/2014/08/31/china-carbontrading-idUSL3N0R107420140831

    The national market will start in 2016, although some provinces would be allowed to start later if they lacked the technical infrastructure to participate from the outset, she said.

    The Chinese market, when fully functional, would dwarf the European emissions trading system, which is currently the world’s biggest.

    It would be the main carbon trading hub in Asia and the Pacific, where Kazakhstan and New Zealand already operate similar markets. South Korea will launch a national scheme on Jan. 1, 2015, while Indonesia, Thailand and Vietnam are drawing up plans for markets of their own.

    Of course the Republican Congress is of concern. For one thing, if the Paris talks should result in an agreement, US ratification would rest with the Senate, which means that we’d really, really want a different upper house in place in 2016. But I’m hopeful that that could happen (and determined to do everything that I can to make sure it does.) The current gang ‘can’t shoot straight’ because their internal divisions are quite severe and they are so well provided with loose cannons. (Somehow, firearm metaphors seem particularly apt here, but I’m sorry to be mixing them a tad.) With luck, this, combined with the ongoing unfavorable demographic trends for the GOP, the fact that 2016 is a Presidential year which tends to bring out more Democratic and independent voters, and the development of climate change awareness and activism will be enough to do the trick. (And yes, I do think that awareness is slowly increasing. Our opponents clearly feel the opposite, but then they thing the planet is cooling, too, so what do they know?)

  16. 216
    Chris Dudley says:

    Paul (#380 November),

    This passage may be useful to you:

    “A global mean temperature of 14øC is also
    obtained by Jones et al. [1999] when they integrate their absolute
    surface air temperature climatology over the globe. Although these
    estimates of absolute global mean temperature are not accurate to
    0.1 øC, for the sake of consistency between the Jones data and the
    GISS data, one can add 13.9øC to our temperature anomalies and
    14øC to the Jones anomalies. The reason for this is that we define
    our anomalies relative to the base period 1951-1980, while Jones
    define his relative to 1961-1990, and the mean temperature for
    1961-1990 is 0.1 øC warmer than for 1951-1980.”

    http://onlinelibrary.wiley.com/doi/10.1029/1999JD900835/pdf

  17. 217
    Chuck Hughes says:

    With luck, this, combined with the ongoing unfavorable demographic trends for the GOP, the fact that 2016 is a Presidential year which tends to bring out more Democratic and independent voters, and the development of climate change awareness and activism will be enough to do the trick. (And yes, I do think that awareness is slowly increasing. Our opponents clearly feel the opposite, but then they think the planet is cooling, too, so what do they know?)

    Comment by Kevin Mckinney — 30 Dec 2014

    Hey Kevin, I think our biggest problem is the time factor and the limits as to how much CO2 we can emit vs. how much CO2 we can remove. If you’re waiting around on the political climate to change, I’ve been doing that since the Reagan Administration. The fanatics have only become more fanatical. I agree that “in time” these ignorant political factions will expire but on an evolutionary time scale.

    I’m really loving this new Pope. He has thus far been an amazing voice and I think he has the potential to change minds that have been mired in religious dogma but once again we’re up against a political situation and TIME. How much time do we really have? We’re talking about needing a Global effort to turn things around. 1.5 billion Catholics doesn’t get us there. Also, there are so many other things like all the plastic in the oceans, mass extinctions. If it took this long for the oceans and atmosphere to respond to human activity turning that process around would have to take even longer. There are reasons to be hopeful but wow!

  18. 218
    wili says:

    Thanks for the clarification, KM. “we’d really, really want a different upper house in place in 2016”
    I’m right there with ya, bro.

  19. 219

    #217–“Hey Kevin, I think our biggest problem is the time factor…”

    I think so, too.

    “If you’re waiting around on the political climate to change…”

    I’m not. As with many on this site, I’m doing my best to educate, organize and agitate, not to mention getting my lifestyle in sync with my values (as best as may be.)

    #218– :-)

  20. 220
    Chuck Hughes says:

    I’m not. As with many on this site, I’m doing my best to educate, organize and agitate, not to mention getting my lifestyle in sync with my values (as best as may be.)

    #218– :-)

    Comment by Kevin McKinney — 31 Dec 2014

    I meant “you’re waiting around” more in the general sense. I’m trying to do the same as you. One thing I’m proud of is buying a Chevy Volt last year. We’re making as many lifestyle changes as possible and I’ve agitated just about everyone I know. I did see yesterday where NBC Evening News with Brian Williams featured 2014 as being the hottest year on record and specifically calling it “Climate Change.” Imagine that!

    Anyway, HAPPY NEW YEAR to everyone here at Realclimate! Here’s to hoping we see some real changes in the coming year.

  21. 221

    #220–Happy New Year to you, too, Chuck, and let me add my wish for real change to yours.

    “…buying a Chevy Volt…”

    Our big deal in 2014 was putting energy-efficient windows into our current home. Love ’em already (though we’ll be paying for them for the next year!)

  22. 222
    Neil Gundel says:

    Recently, a paper has been published that claims that temperature response from a single CO2 release reaches a maximum within about 10 years, which then very gradually declines over CO2’s lifetime in the atmosphere.

    “Maximum warming occurs about one decade after a carbon dioxide emission”
    http://iopscience.iop.org/1748-9326/9/12/124002/article
    http://www.climatecentral.org/news/co2-emissions-peak-heat-18394#article-comments

    This paper has not received a lot of attention as far as I can see, but it seems to challenge a lot of ideas – not least of which is the relationship between the Transient Climate Response and Equilibrium Climate Sensitivity. The likely ranges for these are 1.0 – 2.5C (TCR) and 1.5 – 4.5C (ECS).

    Judging by the graphs in this study, it would seem that TCR would have to be at least as high as ECS, if not a bit higher.

    So how do you see the significance of this study – Am I missing something?

    [Response: This study includes carbon cycle modelling and is thus estimating sensitivity to emissions of CO2. In contrast, TCR and ECS are sensitivity to changes in concentrations. There is no contradiction here because the concentrations in the new study start high and then decline, compared to TCR (1%/yr increasing concentration) or ECS (permanent 2xCO2 concentration). – gavin]

  23. 223
    Hank Roberts says:

    Adding* the DOI, Gavin’s inline response above refers to
    Katharine L Ricke and Ken Caldeira 2014 Environ. Res. Lett. 9 124002
    doi:10.1088/1748-9326/9/12/124002

  24. 224
    MARodger says:

    RSS are quick off the mark with December’s global temperature anomaly = 0.284ºC giving an annual ave of 0.255ºC. It suggests that the other temperature records won’t see December temperatures easing back down.
    HadCET still awaits the provisional data for 31/12/14 but excluding that last day, with the anomaly 0.11ºC above the previous record, it’s certain that 2014 will be the hottest on record (since 1772).

  25. 225
    Tony says:

    Please be aware, folks, that what some leaders say and what they actually do (or are able to do) are not always the same thing. There could even be an historic agreement in Paris this year but we won’t be able to begin to judge if it will have an impact until 2020 (if the original schedule is maintained). Then we will see if there is an impact after that. From past words and actions, I don’t expect much change, even if there was a change in the political majority in the US. It’s my understanding that we are already at more than 450 ppm CO2e, so that isn’t going to be avoided by any agreement.

  26. 226
    wili says:

    Happy New Year to all, and special thanks to the folks here at RealClimate for all their great work.

    As a kind of grim New Year’s present, here is one of the most important speeches of the year, imho, putting GW and mass extinction in a larger historical, political and literary context :

    https://www.youtube.com/watch?v=uAo7ky1kq-Q

    Chris Hedges – “The Myth of Human Progress and the Collapse of Complex Societies” – Full Speech

  27. 227
    Chris Dudley says:

    Tony (#255),

    Careful of equivalent CO2 concentration. 450 ppm conventional is the 2 C level, not 450 ppme.

    “but if you take a conventional 450 ppmv CO2_e value (which will lead to a net equilibrium warming of ~ 2 deg C above pre-industrial levels), we are still a number of years from that, and we have (probably) not yet committed ourselves to reaching it.” – See more at: http://www.realclimate.org/index.php/archives/2007/10/co2-equivalents/#sthash.FoTjIIKH.dpuf

  28. 228
    Nick Gotts says:

    Kevin McKinney@215,

    IIRC, ratifying a treaty requires a 2/3 majority in the US Senate. Siven that only 1/3 of the seats are up for election in 2016, I’d say the chances of the USA ratifying anything coming out of Paris are extremely slim.

  29. 229
  30. 230

    #225–

    Absolutely right, Tony, that “what some leaders say and what they actually do (or are able to do) are not always the same thing.”

    To listen to Stephen Harper and his government, you’d think they were doing a wonderful job on emissions mitigation. But their actions say pretty clearly that the real priority is to do all they can to burn as much tarsands oil as possible.

    Right that we won’t avoid 450e:

    In the Advanced Global Atmospheric Gases Experiment (AGAGE), we continuously measure over 40 of these other GHGs in real time over the globe. If you convert these other GHGs into their equivalent amounts of CO2 that will have the same effect on climate, and add them to the NOAA measurements of CO2, you find that we are actually at 478 ppm of CO2 equivalents right now. In fact, we passed the 400 ppm back in about 1985. So, 478 not 400 is the real number to watch. That’s the number people should be talking about when it comes to climate change.

    http://oceans.mit.edu/featured-stories/5-questions-mits-ron-prinn-400-ppm-threshold

    And you are right that any treaty, any time, anywhere, may or may not achieve its intended results. Some succeed spectacularly; some turn out to be completely counterproductive.

    But none of that much changes what you or I can (or should) do, beyond adding yet more sense of urgency.

  31. 231
    EMichael says:

    Trying to keep up with the OCO-2 observations, from a layman’s point of view.

    It seems to me that the observations of the concentration of CO2 will change on a seasonal basis.

    Is that correct?

  32. 232
    DP says:

    Re 230 read somewhere that coincidentally the warming from other greenhouse gases is about the same as the cooling from sulphate aerosols. If the world tackles air pollution we are in for a nasty shock.

  33. 233
    Hank Roberts says:

    > DP, read somewhere

    You probably read that in one of the IPCC Reports, going back to long ago.
    Or in someone’s paraphrase of that research, which the IPCC cites.

    https://www.google.com/search?q=aerosol+cooling+anthropogenic+warming

    The people saying they are “shocked, shocked” will be collecting their winnings, as the game gets closed down

  34. 234
    Chris Dudley says:

    Kevin (#215) and Nick (#228),

    So far as I can tell, Paris will just be further actions in support of the already ratified Framework Convention. There won’t be a need for ratification by the US Senate. Not every COP action gets ratified. The Cancún Agreement, limiting warming to below 2 C, was not sent around for ratification, for example. An agreement that includes all parties, including developing countries, implementing Cancún, would also seem like the normal workings of the existing ratified Convention.

  35. 235
    Chris Dudley says:

    EMichael (#231),

    Yes that is correct. The largest effects will be seasonal. Here is a simulation: http://www.nasa.gov/press/goddard/2014/november/nasa-computer-model-provides-a-new-portrait-of-carbon-dioxide/#.VKdAx53LJcg

    The big sources are leaf mold and decay of seasonal grasses. That gets picked up again in the Spring. Underlying that big swing is a constant build up from fossil fuel emissions.

  36. 236
    EMichael says:

    Thanks, Chris

  37. 237
    Neil Gundel says:

    Gavin (re #222)

    Thanks – I finally get it. Few published projections model any scenario more optimistic than leveling of CO2 concentrations (ECS), but were we to stop cold turkey, we would see a significant decline in concentrations that would eventually taper off, corresponding to a leveling of temperature within about ten years.

  38. 238

    Nick (#228) and Chris (#234)–

    Good points, both. But Kyoto was subject to ratification (and was never submitted to the US senate because–IIRC–there was never a time when it would have passed.) Which, I suppose, leaves us with ambiguity.

  39. 239

    #231–“It seems to me that the observations of the concentration of CO2 will change on a seasonal basis.”

    – See more at: http://www.realclimate.org/index.php/archives/2014/12/unforced-variations-dec-2014/comment-page-5/#comment-622348

    Not sure if I get your point. There’s a well-known seasonality to concentrations, easily seen in any of the terrestrial time series. It’s one reason that we can be quite sure that current methodology is superior to historical ones, which are sometimes touted by denialists who’ve read the likes of Georg Beck. For instance, the Mauna Loa record, which I’m guessing you are already familiar with:

    http://scrippsco2.ucsd.edu

  40. 240
    Chris Dudley says:

    The claim that scientists are being too cautious seems to be getting an unclear airing today: http://www.nytimes.com/2015/01/04/opinion/sunday/playing-dumb-on-climate-change.html

  41. 241
    EMichael says:

    Kevin,

    You have known there is a “well-known seasonality to concentrations”, I did not. I had a question, not a point.

  42. 242

    #240–Thanks for the link, Chris. I don’t wish to comment directly on the Oreskes piece, but I was led to this:

    http://cup.columbia.edu/book/the-collapse-of-western-civilization/9780231169547

    …and submitted a library request. It’s available for $8 or $9 (e-book or paperback) here (but I want my local system to have a copy):

    http://cup.columbia.edu/book/the-collapse-of-western-civilization/9780231169547

    More generally, I plan to do a bunch of research on specific impacts of ‘worst case’ warming, of the sort Oreskes and Conway envision. Any hints? I am especially interested in relatively comprehensive studies which cast light on what particular places might end up “looking like” in a 5- or 6-degree world.

    For example, a couple of places I will be looking at include Istanbul and Atlanta. Estimating the raw numbers of climate isn’t that hard, if you are willing to accept that the estimate is highly imperfect. But what does that mean for the landscape? What sort of ecological succession might occur? (Yes, I suspect that that is a really, really tough question–but even knowing what is and is not known so far would be nice.)

    Any pointers? (Bear in mind that I’ve already published a summary of Six Degrees, which I will be going back to, so that needn’t be included.) Obviously, time with the WG III report is in my future, but past time spent with it suggests that the emphasis is more global, in general, and a lot of drilling down will be required. So if anyone’s got some ‘good stuff’, I’d be most appreciative…

    Oh, in case anyone who hasn’t read Six Degrees yet wants to know about it:

    http://doc-snow.hubpages.com/hub/Mark-Lynass-Six-Degrees-A-Summary-Review

  43. 243
    Chris Dudley says:

    Kevin,

    I’m not all that sure where best to attempt that kind of project. I thought that Hansen’s Venus Syndrome was a potentially useful limit but there turned out to be a problem getting a runaway from greenhouse gas forcing. I looked at how far low cost renewable energy would go in bringing otherwise energetically inaccessible fossil fuels out into the atmosphere and managed to kill mammals everywhere but in alpine regions near the poles.

    RCP8.5 might be detailed enough for what you have in mind, which I think uses energetically accessible fossil fuels though perhaps some that are economically impoverishing.

  44. 244
    Hank Roberts says:

    Query for modelers (any grad students looking for a thesis topic?)

    It appears from this:

    Combustion iron distribution and deposition
    DOI: 10.1029/2007GB002964
    Global Biogeochemical Cycles
    Volume 22, Issue 1, March 2008

    much cited article:
    http://onlinelibrary.wiley.com/doi/10.1029/2007GB002964/citedby

    That combustion is a significant source of iron fertilization, probably including the ocean.

    Is there any correlation with any proxy for mass of plankton (primary production) over time?

    Is there any concern that there may not be sufficient primary production in the oceans to feed recovery of an ocean food chain comparable to the size that was working in the ocean before whaling and industrial fishing removed it?

    And how would that affect recovery of the climate?

    Is it possible that old familiar branch of the various possible futures isn’t going to be available as combustion (especially as, if, and whenever we cut back on and remove coal plants (which still use very high stack ejection velocities to widely distribute ash residue other than the sulfates and stuff collected at the point of origin))?

  45. 245
    Steve Fish says:

    Re- Comment by Chris Dudley — 4 Jan 2015 @ 4:38 PM, ~#243

    You said- “I looked at how far low cost renewable energy would go in bringing otherwise energetically inaccessible fossil fuels out into the atmosphere and managed to kill mammals everywhere but in alpine regions near the poles.” I cannot decipher anything sensible from this statement.

    Steve

  46. 246
    Chris Dudley says:

    Steve (#245),

    Isn’t that a bit of insincere posturing? You’ve demonstrated better (though not perfect) understanding in the past. http://www.realclimate.org/?comments_popup=17292#comment-542728

    You can start reviewing the topic here: http://www.realclimate.org/?comments_popup=17292

  47. 247
    Hank Roberts says:

    Steve, I think Chris Dudley’s point may be that up til now the electric grid has limited the reach of the oil and gas drilling equipment, we have them on a long tether.

    Once the drilling rigs are all independently solar-powered, they’ll be free agents, autonomous, able to wander and drill, without wires to the grid keeping them under human control, so they’ll slurp up and burn everything, driving the mammals to extinction.

    Or he could be saying we’re so utterly stupid that given cheap solar power, we’d burn and frac everything — bringing on ourselves the same result as we’d get from a drilling robot apocalypse.

    I’m sure there’s a soft green path out there somewhere as an alternative. Probably well fertilized in one way or another.

  48. 248
    wili says:

    Neil Gundel at 237: I think you are misinterpreting Gavin’s response. He was talking about what happens within that particular hypothetical in that study.

    Even with immediate total stoppage of all further GHG emissions, CO2 levels would remain at current levels or higher for a couple centuries at least. http://www.skepticalscience.com/Macdougall.html (See especially figure 3)

    I agree that it is a confusing study (to me, at least), and I would love to see further discussion on what the main real-world consequences of it might be.

  49. 249
    Hank Roberts says:

    http://unsdsn.org/what-we-do/deep-decarbonization-pathways/

    Achieving the 2°C limit will require that global net emissions of greenhouse gases (GHG) approach zero by the second half of the century. This will require a profound transformation of energy systems by mid-century through steep declines in carbon intensity in all sectors of the economy, a transition we call “deep decarbonization.”

    Successfully transitioning to a low-carbon economy will require unprecedented global cooperation, including a global cooperative effort to accelerate the development and diffusion of some key low carbon technologies.
    As underscored throughout this report, the results of the DDPP analyses remain preliminary and incomplete. The DDPP proceeds in two phases. This 2014 report describes the DDPP’s approach to deep decarbonization at the country level and presents preliminary findings on technically feasible pathways to deep decarbonization ….

    http://breakingenergy.com/2014/12/12/why-deep-decarbonization-means-breaking-from-legacy-choices/

  50. 250
    Chris Dudley says:

    Wili (#248),

    “Even with immediate total stoppage of all further GHG emissions, CO2 levels would remain at current levels or higher for a couple centuries at least. http://www.skepticalscience.com/Macdougall.html (See especially figure 3)”

    Look closer at the figure. Lower is the case for the bottom two traces.