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  1. A central point here: even if the surface temperature stagnates our planet continues to take up heat. The increasing greenhouse effect leads to a radiation imbalance: we absorb more heat from the sun than we emit back into space.

    There’s one piece to that jigsaw which is not often discussed: the primary feedbacks (water vapour, clouds), which ultimately determine the magnitude of the imbalance, are mainly dependent on surface temperature change rather than the mere presence of GHGs or related energy fluxes. That means a period of stagnant surface temperatures, due to ENSO/PDO/IPO, would presumably be expected to correspond with a small reduction in the rate of energy accumulation.

    Regarding the Otto et al. 2013 paper, IIRC their results were largely insensitive to the “hiatus” in the HadCRUT4 data because their method used decadal averages, much like the lower panel of Figure 1 above.

    Comment by Paul S — 17 Dec 2013 @ 9:21 AM

  2. “The IPCC has therefore never tried to predict the climate evolution over 15 years, because that’s just too much influenced by random internal variability (such as ENSO), which we cannot predict (at least as yet).”


    As we all remember, the IPCC said in AR4 explicitly: “For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected. {10.3, 10.7}. – Since 2000, the concentration of CO2 has increased at BAU speed, but warming has been insignificant. RSS now shows a 207 month period with 0.0 trend. Sadly, Rahmstorf does not offer any falsification criteria for his promise/prediction/projection/guess that warming will resume.

    [Response: That AR4 quote does not make a specific forecast for a 15-year period. It is from one of those yellow boxes in the Summary for Policy Makers which highlight key findings in extremely condensed form, as can be seen by the imprecise phrasing (e.g. “about 0.2°C”, without specific error bars) – its intention is to give you a rough indication of how much warming the models project on average in the early part of the 21st Century. But the SPM also very clearly shows the error bars: in Fig. SPM.6 probability distributions are shown for the warming by the year 2020-2029, which even include a small probability of cooling. Unless you quote-mine out of context, you have to say that the IPCC AR4 already very clearly communicated the fact that short-term trends can vary widely due to natural variability. -Stefan]

    Comment by Matti Virtanen — 17 Dec 2013 @ 10:07 AM

  3. Re the Arctic data gap

    Polar amplification of warming arises because the initial baseline simulations underrepresent the warmth of ancient greenhouse climates. Because this issue continues to affect all coupled ocean-atmosphere models (e.g., 22–24), the warming (Fig. 3) represents the expression of positive biotic feedback mechanisms missing from earlier simulations of these climates obtained with prescribed PI concentrations of trace GHGs. Link

    Does the interpolation of the data gap account for the underrepresented initial baseline, according to Beerling et al 2011?

    Comment by prokaryotes — 17 Dec 2013 @ 10:44 AM

  4. Judith Lean’s Bjerknes Lecture at the AGU last week gave a very nice perspective on these issues as well.

    Comment by Jonathan Gilligan — 17 Dec 2013 @ 11:29 AM

  5. Is anybody aware of any papers that demonstrate that there is statistically significant evidence for the existence of a change in the underlying rate of warming?

    It seems to me that the onus should be on those who are confidently claiming that there has been a genuine hiatus in surface temperatures to demonstrate that the apparent flattening is not explainable by the natural variability in the data. I’ve not seen this done, and my initial experiments on breakpoint detection seem to suggest that there is insufficient evidence to suggest that there has been a change in the underlying rate of warming.

    Comment by Dikran Marsupial — 17 Dec 2013 @ 11:33 AM

  6. Paul S (#1) – Since the Planck Response dominates over positive feedback responses to temperature, wouldn’t a La Nina-like failure of surface temperature to rise lead to an increase rather than a reduction in energy accumulation compared with accumulation during a surface warming – presumably a small increase, so that the observed rise in ocean heat content would still be substantial?

    Comment by Fred Moolten — 17 Dec 2013 @ 1:05 PM

  7. To clarify my above comment, I was suggesting that the observed rise in ocean heat content would be substantial with or without the La Nina effect, representing primarily the persistence of a long term warming trend.

    Comment by Fred Moolten — 17 Dec 2013 @ 1:11 PM

  8. The Otto study’s TCR estimates for the 2000s would be unaffected by whether Levitus or ORAS-4 is used for OHC estimates, is it not?

    But regarding ECS, what are your thoughts on this post implying that satellites don’t confirm the change in OHC circa 2005 (thus arguing that ORAS-4 pre-2005 estimates are high due to data errors)?

    Comment by RB — 17 Dec 2013 @ 1:49 PM

  9. Dikran Marsupial

    Is anybody aware of any papers that demonstrate that there is statistically significant evidence for the existence of a change in the underlying rate of warming?

    A couple of months ago Tamino said “By at least one calculation, the difference is “statistically significant”, but doesn’t cite the source. As always, his piece is well worth reading anyway.

    Comment by Mal Adapted — 17 Dec 2013 @ 2:41 PM

  10. See Tamino’s

    Comment by Hank Roberts — 17 Dec 2013 @ 3:10 PM

  11. Why hasn’t the ‘pause’ been debunked just by noting that it starts at a point nearly a decade’s worth of warming above the trend in 1997? And if we include the ‘pause’ in the long term trend, the trend actually goes up. These seem like powerful points, but I’ve only seen Gavin note them, not the IPCC, or Met Office.

    Comment by Chuck Carlson — 17 Dec 2013 @ 3:22 PM

  12. The major physics at play here is that as long as there is less outgoing radiated energy than incoming, temperatures must increase until we are back at equilibrium. ENSO and deep ocean heating are blips in the bigger scheme of things. If the oceans release energy to the atmosphere, that doesn’t fix the long-term imbalance. If we are in a lower than normal solar cycle, that is also a blip. Increasing GHG concentrations slows outgoing radiation.

    This stuff is all interesting and useful but we should not forget the big picture when looking at what influences the blips.

    Comment by Philip Machanick — 17 Dec 2013 @ 3:34 PM

  13. see also:

    CO2 is rising faster now that it was just a few decades ago. We can even estimate how the rate of increase is changing, by calculating the difference between CO2 concentration each month, and its value 12 months previously, to figure its annual change

    Comment by Hank Roberts — 17 Dec 2013 @ 3:35 PM

  14. Stefan: the intro says “various ingredients are small and not simply additive” while further down you say “ all these factors indeed contributed to a slowing of the warming, and they are also additive” – but nothing explicitly links these two statements together. Maybe you could clarify?

    Matti Virtanen #2: Check out Figure 1. Decadal averages are moving up pretty consistently with prediction. Do you have a source for your RSS “analysis”? Not anti-science blog I hope …

    [Response: Sure: what I called additive (at least to good approximation) are the radiative forcings. Not additive are ENSO and ocean heat uptake, since they are two ways at looking at the same thing (again to reasonable approximation). -Stefan]

    Comment by Philip Machanick — 17 Dec 2013 @ 3:48 PM

  15. Re Paul S at #1 and Fred Moolten at #6:

    Prolonged suppression of Planck feedback; I tried to explain this here:

    Thought experiment

    It looks as if there would be a greater sea level rise for a given amount of added greenhouse gas.

    Comment by deconvoluter — 17 Dec 2013 @ 4:07 PM

  16. RB (#8) – ORAS-4 may have overestimated OHC uptake, but perhaps not as much as implied in the link you cited – see, e.g.,OHC data. Regarding ECS (“equilibrium climate sensitivity”), I think there are difficulties estimating anything truly resembling a Charney-type ECS from data involving OHC uptake and forcing estimates, because these estimates are fraught with so many uncertainties, and because the values that are calculated, even if accurate, bear an uncertain relationship to how the climate would behave at equilibrium. My preference would be to refer to these as estimates of “effective climate sensitivity” rather than ECS. Even the conventional notion of ECS involving the short-term (Charney) feedbacks doesn’t represent an equilibrium result, which is better represented by “Earth System Sensitivity” estimates. Maybe the word “equilibrium” should be omitted from all climate sensitivity estimates, from the shortest term values (TCR) to the longest and most comprehensive (Earth System), since all the different forms of sensitivity estimation seem, in my view, to be looking at somewhat different phenomena and should not necessarily yield the same values.

    Comment by Fred Moolten — 17 Dec 2013 @ 4:13 PM

  17. Mal Adapted:
    Tamino’s reference to “statistically significant” refers to the warm period that ran from 1992 to 2006, not the current “hiatus”.

    Comment by michael sweet — 17 Dec 2013 @ 4:36 PM

  18. Matti Virtanen,
    Ever hear of physics? Try it sometime. It’s great!

    Comment by Ray Ladbury — 17 Dec 2013 @ 5:32 PM

  19. As always, a fine, clear, well written piece, Stefan. But, err, apropos of nothing much … would “hiatus” be one of those big words for ordinary things?

    Comment by GlenFergus — 17 Dec 2013 @ 5:53 PM

  20. Fred at #6:

    That is what Kosaka and Xie found in their elegant little model experiment — see their supplementary Figure 3. I hope all you modellers out there are busy replicating / extending…

    Comment by GlenFergus — 17 Dec 2013 @ 6:12 PM

  21. I’m wondering if anyone has collected the model runs with long hiatus periods in them and looked for commonalities…for example extended periods of La Ninas or anything else. It would be fascinating if there was only a small group of associations- could lead to targets for further research. Apologies if this has already been done. If not, anyone looking for a slightly pre-retirement Chemist to take on as a visiting scientist on a project like this?

    Comment by Dave123 — 17 Dec 2013 @ 8:32 PM

  22. I think Matti Vertanen (#2) probably got his claim about the RSS data from Monckton on WUWT, and while Monckton is not a particularly credible source in my opinion, I think the RSS data are probably as claimed. I also agree that model predictions of 0.2 C surface warming per decade were clearly inaccurate, but on the larger question of climate trends, they were probably not very far off. What has happened over recent decades is that planetary warming has continued unabated, as evidenced by ocean heat content (OHC) increases, while surface warming has slowed, and tropospheric warming as measured by RSS has halted. The reasons clearly lie in the shift in the distribution of the accumulating heat in the ocean to greater depths with less remaining on the surface. Models are still not skillful enough to anticipate the timing of these shifts, but they are not too bad at getting the planetary trends right, or at least keeping their estimates within reasonable proximity to observed trends, even if on the high side of observations.

    The OHC data are critical to any analysis of surface temperature change. In particular, as discussed above, internal climate oscillations warm the surface by losing OHC, while external forcing by CO2 or other modalities warms the surface by increasing OHC. This permits us to apportion surface temperature change over long intervals on the basis of OHC change. An important quantitative consideration of this principle has been discussed by Isaac Held at Heat Uptake and Internal Variability. It indicates that the current combination of post-1950 warming, OHC rise, and the geographical distribution of temperature change renders a substantial contribution to the warming from internal variability highly unlikely, and the role of greenhouse gas forcing accordingly the likely contributor to a very large fraction of the observed warming.

    Comment by Fred Moolten — 17 Dec 2013 @ 9:27 PM

  23. Stefan:

    //”They argue that an explanation for the “pause” in global warming would have to explain this particular pattern. But this is not compelling: there could be two independent mechanisms superimposed.”//

    I don’t understand how your objection to the Cohen recommendation follows from the fact that multiple mechanisms may be important. Isn’t this whole problem one of trying to tease out the small contributions from external forcing, internal variability, instrumentation uncertainty, or mis-specified forcing (in the case of model world)? The relevance of the underlying spatial pattern may be tied very much to the contributing terms. I’d agree if the hiatus is simply a product of external forcing and we’re comparing the internal variability of observations vs. a model (since the variability is very high in Eurasian winter), but if we’re interested in things like the ocean state, prevailing modes of variability, etc then this may project onto the Eurasian DJF signal seen in the obs.

    [Response: Just saying that “the explanation for the pause” need not have anything to do with the pattern of winter cooling over Eurasia. It might have an ENSO/PDO style spatial pattern as shown by Trenberth. And the Eurasian winter cooling could be a separate, superimposed effect, with no impact on global mean temperature and hence nothing to do with the “pause”. I think it is important to be clear about this. -Stefan]

    Comment by Chris Colose — 17 Dec 2013 @ 10:16 PM

  24. Who is Monckton? Let the numbers do the talking – the RSS data is here:

    Comment by Matti Virtanen — 18 Dec 2013 @ 12:48 AM

  25. Mal, Hank & Michael, many thanks for the response, Taminos article is on a slightly different topic (although the point he makes is spot-on as usual).

    Tamino also had an excellent set of three articles on step changes, which is the sort of thing I am interested in, but he didin’t look at the hiatus.

    Comment by Dikran Marsupial — 18 Dec 2013 @ 5:15 AM

  26. Here’s an interesting item from the CryoSat people. Oct 2013 ice volume is about 9000 km3, up from 6000, in 2012.

    Watching the 2010-2013 Oct. data, it look like it’s the highest in the 4 years of taking data.

    Also definitely higher then the PIOMAS model predicts.

    To bad we don’t have a longer record.

    Comment by J. Bob — 18 Dec 2013 @ 10:19 AM

  27. Matti Virtanen #24: thanks for pointing to the numbers. If you try to find a trend over that period, it is close to zero, but so is the correlation. In other words, the period is too short for the trend to break out of the noise. If you are not familiar with the concept of statistical significance, look it up.

    Comment by Philip Machanick — 18 Dec 2013 @ 10:41 AM

  28. Matti Virtanen, Now why would you pick 1996 and why RSS? I mean you have a plethora of choices of start date and date series. Why that combination? Could it be because RSS seems to be much more strongly affected by ENSO than the terrestrial data sets or even UAH?

    Tamino has also looked at this, and found that RSS was odd man out. Cherrypickers cherrypick. Film at 11:00.

    Comment by Ray Ladbury — 18 Dec 2013 @ 10:43 AM

  29. At least
    he’s consistent
    , always turning in the same direction.

    Comment by Hank Roberts — 18 Dec 2013 @ 11:39 AM

  30. ‘oogle: “Matti Virtanen” climate

    Comment by Hank Roberts — 18 Dec 2013 @ 11:40 AM

  31. Fred Moolton #6 – The Planck response (or lack of) is the counter-balance which would make any effect small. My reasoning for expecting a reduction in energy accumulation is based on the observation that models with greater sensitivity tend to transiently develop greater imbalances, given equivalent forcing time series. This means the rate of energy accumulation is dependent on feedbacks as well as forcing, even though higher sensitivity models trigger larger Planck responses.

    During a period in which surface warming is stifled by internal variability the rate of energy accumulation would be influenced only by the forcing – there would be no difference between a high-sensitivity model and a zero-feedback model (assuming zero-dimensional models; the reality, with regionally varying temperatures and feedbacks, would be more complex). Given that greater sensitivity matters for the magnitude of imbalance a period during which this higher sensitivity is not activated should mean a slower rate of energy accumulation than would be the case during a period of “normal” variability.

    Comment by Paul S — 18 Dec 2013 @ 12:02 PM

  32. Short-term temperature changes can be interesting as to their specific causes. However, we shuold be looking at longer-term trends. Over the past century, both a linear fit and polymeric fit culminate at a similar value for 2013 Even though they diverge by over a tenth of a degree at times. Indeed, the short-term temperature may even dip below the long-term trend (as indicated by the polymeric fit). However, this does not indicate that the long-term trend will deviate significantly from the established trend.

    Comment by Dan H. — 18 Dec 2013 @ 1:10 PM

  33. Paul S (#31 – Paul, I may be misinterpreting your explanation, but the comparison I was making (and has been made previously by others, including Stefan, Trenberth and more, apparently supported by observations) is that a failure of the surface to warm due to a La Nina-like process will increase energy accumulation by reducing OLR relative to the OLR that would have been produced by a warmer surface. Positive feedbacks attenuate Planck Responses but don’t overcome them. In the case of a failure of the surface to warm due to a La Nina-like process, the OLR reduction (and hence the energy gain) will be lessened by the reduction in water vapor and other feedback moieties, but it will still be greater than occurs with a warmed surface. As an example of the level of Planck Response attenuation from positive feedbacks, see Table 1 in Soden and Held 2006.

    On a more frivolous note, Matti Virtanen (#24) asked me, “Who is Monckton?”. Matti – he’s the person referred to near the bottom of this page – Matti Knows Monckton. Aren’t you glad to have your question answered?

    Comment by Fred Moolten — 18 Dec 2013 @ 2:07 PM

  34. Dan H. has achieved the impossible–unifying statistics with chemistry: Behold the polymeric fit!

    Comment by Ray Ladbury — 18 Dec 2013 @ 5:06 PM

  35. Thanks for a good clarifying blog post.

    I think it is a bit strange how twisted analysis perspectives sometimes have become, even IPCC seems rather fond of the ‘hiatus’ concept (e.g, Chapter 9).

    But picking shorter parts of noisy global temperature curves, giving them suggestive names and then try to “explain” them is not what you’d expect from year 2000+ science methodology (neither would sacrificing a goat or two to the ‘hiatus’ solve any real problems…).

    In chapter they conclude:
    “…it is concluded that the hiatus is attributable, in roughly equal measure, to a decline in the rate of increase in effective radiative forcing (ERF
    ) and a cooling contribution from internal variability
    (expert judgment,medium confidence)”.

    So they mean that the ‘hiatus’ stands out because it follows a forced trend with internal variability around?

    Better put the primitive intuition in the back seat and use more advanced formal statistical methods. There is just a number of data series with fuzzy observations which you can test your preferably physics-based models against. And in statistics all intervals are created equal, you don’t pick only one for analysis, your model has to explain all intervals.

    Comment by John L — 18 Dec 2013 @ 5:32 PM

  36. Ray Ladbury suggests that we try physics.
    But our problem is planetary physics: a whole bunch of sometimes coupled not exactly oscillators along with a handful of forcing functions and debates (see above for instance) over which is which. All on a rotating sort of sphere where every thing pushes on every thing else. It gets hard.

    I think many commenters would be helped by an RC article on La Niña as a physical phenomenon. Given a purely statistical discussion, many miss that during La Niña the trade winds blow strongly away from the coast of South America, leading to an upwelling of deep ocean water off the coast. This water happens to be cold. The deep ocean does not develop a hole. Water that comes up is replace by water going down. The water going down is warmer than the water that came up. The strong winds blow water across the Pacific. This water becomes warm and produces heavy rain back onto itself. But across the Pacific water piles up a bit and the rain clouds are blown beyond. The remaining water becomes salty (evaporation caries water away but not salt). This warmed salty dense water is some of the water that sinks to replace the cold water that came up near South America. More heat is stored in the ocean. Due to conservation of energy there is less energy to warm the land.

    But why did the wind blow so hard in the first place? Oh well, I said it gets hard.

    Comment by Pete Dunkelberg — 18 Dec 2013 @ 9:31 PM

  37. The war against the Greenhouse Effect started in December 2004 – Richard L. Mit’s interview in the NY Times – the warming stopped after 1998. It has been revived and refueled by just about every pro-pollutionist individual and group since then. No explanation will end their claims – they win just by getting the science bent out of shape when it curries (no pun intended) to their treatment of the atmosphere as a conventional oven, and the oceans as a bathtub.

    ENSO neutral conditions are in effect, and NOAA reported November as the hottest November in the record. The next El Nino is going to heat the globe into new records territory. It won’t cool back down. There hasn’t been a statistically significant cooling period since the 1890s – and that’s not natural variability or a co-incidence.

    If you think the pinheads of pollution won’t spin more blarney looking for sticky-stuff, save your energy. They’re already crowing up the record cold reported in East Antarctica (-135.8dF in August 2010 and -135.3dF in July 2013).

    The real number that matters is the heating driver: CO2e. Despite the worst economic shrivel in a century, the CO2 pollution has accelerated – averaging over 2 ppm annually for the last decade ( It sets records just about every month of every year … and has for half a century. The 395.3ppm for November is just another record-breaking November. Get the pro-pollutionists to pause that.

    Comment by owl905 — 19 Dec 2013 @ 1:58 AM

  38. RC & stefan: Thanks. This reference should prove useful.

    Comment by Edward Greisch — 19 Dec 2013 @ 2:02 AM

  39. “First an important point: the global temperature trend over only 15 years is neither robust nor predictive of longer-term climate trends.”

    As an older slower physics guy trying get a handle on all this, can someone tell me how many years equals a robust and predictive interval?

    Comment by C. Town Springer — 19 Dec 2013 @ 3:06 AM

  40. Pete Dunkelberg,
    Focus first on the spherical cow–the basic fact behind climate change is energy conservation. Unless Matti is willing to deny that basic fact, he doesn’t have a leg to stand on. The rest is just how the energy gets distributed, and it merely determines precisely how screwed we are.

    Comment by Ray Ladbury — 19 Dec 2013 @ 5:51 AM

  41. C. Town Springer, see


    Comment by Jim Eager — 19 Dec 2013 @ 12:29 PM

  42. Thanks, Stefan.

    I kind of hate the whole idea, though–the ‘hiatus’ meme is being driven by sheer repetition. Rebunking, squared.

    I usually point to the inconsistency between the denialist claim that ‘we’ ignore everything but CO2 as forcing, and the denialist claim that the ‘hiatus’ disproves CO2 as forcing–that last only makes any sense if CO2 is ‘the only forcing.’ But I have no idea how many times I’ve had to post that line so far, so I’m grateful for something I can link to by way of variety.

    Of course, I could always update this:

    Comment by Kevin McKinney — 19 Dec 2013 @ 3:36 PM

  43. In line with my way of thinking, Judith Lean is putting the jigsaw puzzle together with her NRL statistical climate model. Inspired by that model as well as by Foster & Rahmstorf, Kosaka & Xie, and Cowtan & Way, I have been putting together what I refer to as the CSALT model. This pieces together all the natural variability terms in a way that we are better able to extract the CO2 control knob signature. I will keep leaning on it until it breaks, but so far it is robust as it uses all the factors that skeptics seem to think are important. The latest check is to see how the solar cycle fits in to the multivariate analysis:

    So Stefan, keep pursuing this approach.

    Comment by WebHubTelescope — 19 Dec 2013 @ 3:44 PM

  44. Old physics guy @ 39:
    BPL explains the 30 year approximation here
    Spice it with
    With a constantly changing climate I don’t know how well the 30 year rule holds up.

    As a physics guy you expect causative physical factors behind the observed effects. You can learn about the main forcings (factors that increase or decrease outgoing longwave radiation (OLR)) at Makiko’s page
    But of course, physical and human factors that change the forcings must be considered. The physical factors rapidly stray from physics.

    The chemical equilibrium of CO2 between air and ocean dictates that the seas take in nearly half of the CO2 we create by burning reduced carbon. Ocean CO2 in turn strongly involves sea creatures and their shells.

    The current climate change, unlike the iced age cycles of the last million years or so, started with CO2 forcing instead of orbital forcing. This big CO2 increase running ahead of the likely consequent ocean warming is a strong stimulus to Arctic plant growth. This is one reason why the tundra CO2 bomb scare is premature.

    Sulfate aerosols from coal plants = a major cooling forcing. This forcing may decrease rapidly one of these days. This may leave the 30 year approximation of climate behind. But the climate models, which take forcings as input and calculate from there, are expected to keep up.

    What gives climate scientists confidence that climate science is on the right track? The Big Three are paleoclimatology, modern data and models. Paleoclimatology is #1 according to Gavin Schmidt, one of the scientists in the RC group and someone who would know. Paleoclimatology itself has lots of unclear questions, but whether all details are understood or not earth responds to changes in atmospheric CO2. Bye the way physics guy, increased CO2 warms earth some, leading to more water vapor which has a greater greenhouse effect than the CO2 as such.

    Comment by Pete Dunkelberg — 19 Dec 2013 @ 4:06 PM

  45. > Old physics guy
    More physicists, some names you’ll likely recognize, at:

    Comment by Hank Roberts — 19 Dec 2013 @ 7:02 PM

  46. I think it’s a mistake to refer to changes in global average surface air temperatures as if they were definitive measures of the change to the climate system. Averaged over long enough periods, sure, but year to year, decade to decade they retain the capacity to deceive. Personally I think global heat content better reveals actual, accumulated change.

    Stefan I think you and Grant Foster already answered the “hiatus” question quite well; surely just one or two more la Nina years than el Nino’s over a period as short as 15 years would be sufficient to create the illusion of a “hiatus”. Just as a couple more el Nino’s than la Nina’s would create the illusion of accelerated warming. And surely the fact that having just that circumstance – with strong el Nino at the start of the cherry picked period and la Nina’s at the tail – should see a clear temperature ‘drop’ instead of merely levelling off confirms the existence of an underlying warming trend.

    Tying the short term variability to physical climate phenomena and processes is going to be valuable, and when it comes to fighting to have the climate problem taken seriously we need explanations that are easy to understand. ENSO stands out as perhaps the single most potent phenomena affecting year to year, decade to decade variability in surface air temperatures, with TSI and aerosols adding or subtracting their shares.

    Are there any other physical phenomena that are or can be known well enough to reduce the unknowns and reduce the ‘noise’ in similar fashion, that if adjusted for can allow the underlying trend to be revealed more clearly?

    Comment by Ken Fabian — 19 Dec 2013 @ 11:15 PM

  47. At WUWT where Monckton’s article appears, I tried to post the following:

    A spectacularly zero trend with a spectacularly zero correlation. All this means is the period concerned is too short for the trend to break out of short-term noise. Nothing to see here. Move on.

    When I tried to post, it said the comment could not be posted. WTF’s up with That?

    Comment by Philip Machanick — 20 Dec 2013 @ 4:25 AM

  48. Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends.

    Correct, but the short term natural variability may provide an insight into origins of natural variability, then extended to many decades even centuries.
    In recent years, number of articles published suggest that solar wind which exerts well known, defined and measured magnetic pressure on the Earth’s magnetosphere, also has some less defined effect on the upper layers of the atmosphere (known as the Mansurov effect).
    It may be obvious that such an effect would vary in step with the sunspot cycle, but that is not the case for a simple but a lesser known reason.
    The Earth’s field is not constant either, it shows similar decadal variability, as shown in the data from and used by number of distinguished geo-magnetic scientists and researchers (Jault Gire, LeMouel, J. Bloxham, D. Gubbins, A.Jackson, R. Hide, D. Boggs, J. Dickey etc,)
    Since changes in either of two fields affect strength of the magnetosphere, it would be expected that the ‘magnetospheric variability’ time function could be produced by combining two sets of available data.
    That is exactly what I did some months ago introducing terms ‘Geo-Solar Oscillation’ and ‘Geo-Solar Cycle’.
    Comparing the GSC to two well known climatic sets of data opens a way into an unexpected and fascinating direction for climatologists’ research
    The above graph when back extrapolated to 1700, gives a favourable comparison to two other well known AMO reconstructions.
    Not that I expect, but if the author of the above article would be tempted to add these data to the ‘hypothesised’ CO2 effect, the GSC data would be available.

    Comment by vukcevic — 20 Dec 2013 @ 2:43 PM

  49. vukcevic, The solar cycle contribution may be there but it is definitely small if one teases the Hale cycle factors out of the temperature time series.

    Letting a multiple linear regression do the work is certainly more robust than your eyeballing estimates. The eyeballing always exaggerates the parts that fit and tries to obscure the parts that don’t. So if you have something, specify the formulation clearly and those of us that can do the numerical fitting can try it out.

    Comment by WebHubTelescope — 21 Dec 2013 @ 6:00 AM

  50. WebHubTelescope: “The eyeballing always exaggerates the parts that fit and tries to obscure the parts that don’t.”

    QFFT! Thank you. This is why economists have predicted 12 of the last 5 recessions! Cyclicity is particularly problematic because any bounded series will appear to cycle when it nears the bounds. Quasi-periodic behavior is a whole lot more common than actual cyclic behavior. Even the Solar Cycle is not a true periodic phenomenon.

    Comment by Ray Ladbury — 21 Dec 2013 @ 12:12 PM

  51. WebHubTelescope
    As I pointed out elsewhere calculating harmonics of Hale cycle (11, 7.3, 5.5, 4.4, and 3.7 years) has no physical meaning. Periodicity of solar activity is a variable, and do remember ‘von Neumann elephant’ !.
    If you wish to employ Hale cycle then you need to look at each sunspot period individually and incorporate it into your model, and that is exactly what I have done here
    This is NO model it is actual data, and since no one knows period of SC24 let alone any future cycles, then it has no predictive capacity.
    However you can back extrapolate since we have data on the sunspot cycles going back to 1700, and that is exactly what is done here:
    Compare with two other AMO, Scottish rainfall and NAO reconstructions.
    In years to come it will become apparent if the AMO is a major player or inconsequential. I do not claim either.

    Ray Ladbury
    “Even the Solar Cycle is not a true periodic phenomenon.”
    I shall use you other quote:
    QFFT! Thank you.
    This is what I said to WHT (whoever he is, why not be brave and put the real name as many other contributors do)

    “Simply because (you) got Hale cycle periodicity wrong, assuming it is constant 22 years, it ain’t, it is continuously variable (changes with periods of actual cycles, since 1900, the HC periods were : 21.67, 20.75, 20.66, 21.42, 22.58 ), hence it doesn’t have fixed harmonics. Further more ‘harmonics’ periodicity you quote (11, 7.3, 5.5, 4.4, and 3.7 years) have no physical meaning in this context and makes nonsense of whole thing.
    If you whish to go down that path then you could consider odd number ‘sub-harmonics’ i.e. 3x @ ~64/65 (the AMO etc) and important one 5x @ ~ 105 years …. (~1705, ~1810, ~1915, ~2020? solar cycle minima)”

    [Response: Numerology is tedious. No more please. – gavin]

    Comment by vukcevic — 21 Dec 2013 @ 2:15 PM

  52. Response: Numerology is tedious. No more please. – gavin

    I agree, numerology is indeed tedious, and I’ve done more than most, but someone has to do it, and I happen to have the time and inclination. Many data sets reminiscent of a string of pearls do sparkle in a ‘polarised’ light, but alas not easy to tell the real one.
    Happy Xmas to you and the readers of your blog.

    Comment by vukcevic — 21 Dec 2013 @ 5:36 PM

  53. Would it be correct to say that a doubling of co2 from 280 to 560ppm means, before feedbacks, 3.7 Watts less IR radiated to space and 3.7 more radiated downwards to the surface? And that this would cause ~1C of warming to restore equilibrium? Thanks.

    Comment by John — 21 Dec 2013 @ 9:23 PM

  54. #2 Matti Virtanen:

    Since 2000, the concentration of CO2 has increased at BAU speed, but warming has been insignificant

    Warming over periods of 13 years has always been statistically insignificant in the instrumental record.

    Nothing unusual about that.

    Comment by Chris O'Neill — 21 Dec 2013 @ 10:25 PM

  55. So, what are we going to do about this? Sit here whining and writing ever more papers while emissions continue to go up, and up and up? Is there a reason scientists haven’t voiced their concerns in an organized public and angry fashion? We know what’s coming, and yet we do not act to at least minimize impacts. How many of you were on the National Mall last February? Or have you even tried to organize an event that can’t be missed by the media? You know, something with Balls for a change.

    If not, that begs the question of whether we deserve to survive.

    Comment by Jackie Heinl — 22 Dec 2013 @ 11:07 AM

  56. #2 Matti Virtanen:

    Since 2000, the concentration of CO2 has increased at BAU speed, but warming has been insignificant

    Only if you deliberately choose to ignore ocean heating. You know, the 70% of earth’s surface that can actually store accumulated heat.

    Comment by Jim Eager — 22 Dec 2013 @ 2:04 PM

  57. Jackie Heinl says:
    22 Dec 2013 at 11:07 AM
    Have you considered that the global warming, which does exist, may be on the turn, and we may have decade or two of stagnation or even cooling. Beside, the CO2 gas is beneficial to biosphere and food production, more vegetation around more diverse and plentiful wild life is.
    It may or may not come to you as a surprise, but radical actions attract small minority of zealots and alienate wider more sedate masses, who are bombarded to saturation from all kind of ‘impending disasters’.
    Credibility of science, which you espouse, would be far better promoted by calm and considerate explanation of the reasons for the current GW ‘hiatus’.
    As I am in minority on these pages, I would like to make it clear that I do not deny existence of climate change. I think that CO2 role is only minor contributor; further rise in the N. Hemisphere temperature in decades to come is unlikely, but if does materialise it could be more beneficial than damaging since the winter fuel consumption would go down + other benefits as mentioned above.

    Comment by vukcevic — 22 Dec 2013 @ 4:42 PM

  58. John @53.
    Yes, it would be incorrect to say that.
    The 1.1ºC caused by a doubling of atmospheric CO2 will not leave unchanged the climate system. The warmer globe will, for instance, result in more atmospheric H2O which will add to the 3.7 Wm^-2 and so to the 1.1ºC rise. How much the 1.1ºC will be amplified by positive feedbacks of this sort (and diminished by negative ones), that is not known with great accuracy but the way the globe has responded in the past and is responding now suggest the resulting rise will be in the range 1.5ºC to 4.5ºC.

    Comment by MARodger — 22 Dec 2013 @ 6:59 PM

  59. [too far]

    Comment by sidd — 22 Dec 2013 @ 11:36 PM

  60. #55

    So, what are we going to do about this?

    Not much we can do while our political masters are in denial of the problem.

    Comment by Chris O'Neill — 23 Dec 2013 @ 2:57 AM

  61. vukcevic said about AGW:

    ” but if does materialise it could be more beneficial”

    Rationalization is a hallmark of denialism. If you don’t agree with that, you may want to change the Wikipedia entry for Denial. Look at bullet point #2 on minimisation.

    I notice that whenever skeptics start to lose an argument pertaining to the science, they turn to rationalizing/minimizing the outcomes, or to projecting the blame (bullet point #3).

    So if you don’t want the denial peg, don’t do #2 and #3, and stick to the original science.

    Comment by WebHubTelescope — 23 Dec 2013 @ 3:10 AM

  62. Something that is becoming increasingly clear is that there isn’t a simple equation of increased planetary energy = increased surface temperature – in the short term anyway. Big variations in how energy is distributed between the surface and oceans for example can change the apparent trend. A big El Niño year redistributes energy from the oceans to the atmosphere. A big Arctic sea ice melt year like 2012 redistributes ocean energy to latent heat of melting ice.

    Surface temperature is important because the planetary imbalance caused by increased GHG can only be corrected by more radiation to space, which means a higher surface temperature. As long as that imbalance still exists, evidenced by increased ice melt, increased ocean heat content and other measures of increased planetary energy, a slowdown in surface temperature rise has to be temporary, and no cause for complacency, as the energy imbalance, continuing unabated, has to result eventually in surface temperature increase. If we are in a phase where more of that imbalance than usual is going into oceans or melting ice, that does not help at all – the next big El Niño could dwarf 1998, and less ice means lower albedo, increasing the energy imbalance.

    Comment by Philip Machanick — 23 Dec 2013 @ 3:25 AM

  63. For John, you make a short statement in English and ask if it’s correct; without knowing what else you think, it’s not easy to just say yes or no to that question.

    Have you read Spencer Weart yet? If not, the “Start Here” button at the top of the page, or the link to his work in the right sidebar, will be a good start.

    The math is complicated; the system of feedbacks is complicated; the results don’t all happen all at once.

    And some of the answers out there are attempts to explain the math in English; others are bafflegab meant to confuse people.^2+is+the+total+absorbed+or+captured+power+for+a+doubling+of+CO2%2C+correct%3F

    Comment by Hank Roberts — 23 Dec 2013 @ 9:53 AM

  64. I’ve wondered why there hasn’t been some comment on RealClimate regarding the paper by Abe-Ouchi, et al. (Nature, Vol. 500, p. 190, 2013) entitled “Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume” and reviewed in Science (Vol. 341, p. 599, 2013). It seemed to me that the above model (based on Milanković orbital variations and corresponding fluctuations in atmospheric CO2) of Earth’s ice ages over the last million years or so, when considered along with the paper by Marcott et al., (Science, Vol. 339, p. 1198, 2013 and discussed in the RealClimate , p=15665, of 9/16/13) would strongly suggest that we humans have (unknowingly, unwittingly, and to tragic excess) succeeded in geoengineering our climate sufficiently to avoid our next scheduled ice age toward which we clearly had begun to descend about 4,000 years ago, and thence more rapidly beginning about 1,000 years ago. A curious irony, is it not? Now, if we can only stop pumping more CO2 into the atmosphere in time to have the excess CO2 disposed of by the time the next warm period begins some 80,000 years hence.

    Comment by C. W. Dingman — 23 Dec 2013 @ 10:06 AM

  65. for C.W. Dingman: the idea has been around for a decade or more; you’ll find mentions if you search on “next ice age” here

    Comment by Hank Roberts — 23 Dec 2013 @ 10:36 AM

  66. Jackie Heinl,
    What are we actually going to do about this?

    Evidently, this is coming. So it’s people power or nothing much.

    Comment by Pete Dunkelberg — 23 Dec 2013 @ 10:39 AM

  67. Compare with two other AMO, Scottish rainfall and NAO reconstructions. In years to come it will become apparent if the AMO is a major player or inconsequential. I do not claim either.

    I think we can already see the AMO (blue) is having a small effect on anthropogenic warming on a global basis. The pronounced temperature anomaly drop that commenced at around 1940 appears to be ignoring the AMO. It does appear the PDO (green) might have had something to do with it. When the AMO does go negative around 1958, it appears to have minimal effect on the temperature anomaly. The PDO again appears it could be a player in the change in direction of the temperature anomaly around 1958. But when the PDO goes negative around 1954, the temperature anomaly appears to be minimally effected.

    The 15 years commencing in 1980 warmed at a rate fairly close to the rate we have seen over the 21st Century: .07C per decade versus .06C (Von Storch). From 1990 to 1995 the anomaly is actually negative. So 15 years of a rate not at all unlike the 21st Century: slope = 0.00729652 per year versus 0.00624414 per year.

    I’m just a amateur, but I do not see how people like Judith Curry can seriously say things implying natural variation is currently dominating AGW. If anything, the observation appears to be that natural variation is waning in its ability to change the direction of the global temperature anomaly as it has not summoned enough muscle to do so significantly since around 1940. That was the year my father had no idea he was about to become a highly decorated member of The Greatest Generation.

    Before J-NG wrote his post about the possibility of record hottest year with 12 months of ENSO neutral, I was thinking we are on the verge of that happening. 2013 is all La Nina leaning ENSO so far, and it is currently a top-5 year. This is just another sign natural variation is waning in its ability to change the direct of the temperature anomaly in a significant negative direction for a prolonged length of time.

    I don’t know what numerology is, and I understand these graphs are simplistic, but I ask of natural variation, where’s the beef?

    Comment by JCH — 23 Dec 2013 @ 11:11 AM

  68. JCH hi
    Pythagoras is considered father of numerology, science of numbers, as astrology was science of stars. However, both terms have lost the original meaning and are now used as derogatory terms.
    I am not bothered by either attribute or for that matter being referred to as denialist (see WHT’s post above).
    There are solar and terrestrial data which contain similar or identical past trends as those found in the global temperature data. Since no solid physical mechanism is clear to provide the ‘missing’ link, those who are convinced that they know everything that needs to be known, refer to those types of calculations as numerology, and that is fine by me.
    As far as 2013 is concerned, most of the ordinary people and that includes myself, are selfishly only seriously concerned by climate change in their own back yard. Due to past circumstances, I happen to live in London UK, here we have longest and most studied local temperature record referred to as the CET.
    2013 for the CET area was for the most of the year noticeably colder than the past 20 year average (only the summer was warmer than the average to everyone’s delight )
    so it is far from being warmest on the record.
    Where is the beef in the natural variability?
    Difficult to tell, we just have to wait and see. If my calculations prove to be correct then ‘the beef’ will show itself, in which case most of the currently promoted climate models may prove to be closer to numerology than their authors would care to admit.
    On personal note, something in common, in 1943 my dad escaped Nazi’s firing squad, but alas didn’t get a medal for his 4 years resistance activities, since didn’t much care for the victorious forces regime either, fortunately he lived long enough to see its demise.
    Happy Xmas & n.y.

    Comment by vukcevic — 23 Dec 2013 @ 3:48 PM

  69. Another piece of the jigsaw puzzle is van Loon and Meehl’s analysis

    H. van Loon and G. A. Meehl, “Interactions between externally-forced climate signals from sunspot peaks and the internally-generated Pacific Decadal and North Atlantic Oscillations,” Geophys. Res. Lett., p. 2013GL058670, Dec. 2013.

    Small pieces will help solve the puzzle at the expense of information complexity.

    Comment by WebHubTelescope — 23 Dec 2013 @ 6:26 PM

  70. “However, the temperatures (at least according to the data of Cowtan & Way) are within the range which is spanned by 90% of the models. So there is no evidence for model errors here.”

    No, they are not. Cowtan and Way is not measured data. The recent HadCrut4 values lie below the 5-95% model range. Therefore greater than 95% of CMIP models are now overpredicting temperatures, a mere handful of years into their projections, no less. To make this claim directly in front of a figure (6) that clearly contradicts it is bizarrely inaccurate, to phrase it politely.

    [Response: Please read this. – gavin]

    Comment by Alex — 24 Dec 2013 @ 12:08 PM

  71. In addition to the underestimate in HadCRUT4 indicated by Cowtan & Way, when examining some of its use in reports and papers, I find some students seem to misunderstand the degree and manner to which HadCRUT4 ensembles represent surface temperature variability. To really get at that variability, the covariance estimates published by HadCRUT4 need to be used. I have seen people expect to find such variability in the ensemble ranges themselves, even to the point of resampling from them and expecting to capture the underlying variation. This cannot work, and, without a significant correction based upon covariance, will understate variability and, so, torpedo credibility of inferences that these temperatures are not consistent with predictions, projections, or models.

    I’m hoping to finish a write-up on a specific case of this for release in the next couple of weeks.

    Comment by Jan Galkowski — 24 Dec 2013 @ 4:54 PM

  72. I am very interested in the Subject. Retired IBM employee Electrical engineering.
    Now at Olli at the University of Arizona. Moderated a class in Energy and Climate Change.

    Want to learn about Oceans – Earth and its processes with History and current understanding of ICE AGE.

    Comment by Rahmat Aziz — 26 Dec 2013 @ 8:44 AM

  73. Are all climate models taking account of the new value for TSI of 1361.5W/sq.m? This is down 4.5W/sq.m from the previously accepted value of 1366W/sq.m. See the SORCE website. (Kopp & Lean, GRL, 38, L01706, 2011)

    This equates to a reduction of solar radiation at TOA of about 1.1W/sq.m from what was previously used in models of warming imbalance. If a constant albedo portion (about 30% reflected) is maintained then the the 70% incoming radiation portion is reduced by about 0.77W/sq.m.

    This is pretty significant when the postulated warming imbalance is anywhere from 0.6 to 0.9W/sq.m.

    How are the latest incoming and outgoing radiation numbers being adjusted to maintain this imbalance with the reduced TSI?

    [Response: This has much less impact than you might think because the models are calibrated with respect to the TSI number. This is a different issue to when the TSI changes after the models have been frozen. See Rind et al (in press) for an exploration of exactly this point. – gavin]

    Comment by Ken Lambert — 27 Dec 2013 @ 8:05 AM

  74. Gavin,

    I had a look at the Rind et al extract thus: quote “The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both the pre-industrial and doubled CO2 climates” endquote

    Am I to assume this to mean that the albedo number has been altered to produce the desired incoming solar radiation?

    If so we are back to the Hansen story where the imbalance number is theorised and not actually measured, and then ‘corrections’ are made to actual observations to preserve the theory.

    [Response: Huh? This has nothing to do with Hansen (though I don’t get your reference in any case). Because models are not perfect calculations from first principles, there are always a number of relatively unconstrained parameters that can be varied as part of the model calibration. One target to get right is the global albedo and the fact that the pre-industrial atmospheric runs need to be in quasi-equilibrium. If you have a model that is calibrated with a TSI at 1365 W/m2, those parameters have been set to give a reasonable albedo and TOA radiative balance. Now, change the TSI to 1361 W?m2 – the model will be now be out of balance by about 0.7 W/m2. This will be fixed via a new calibration (whereby there will be a little more high cloud and a little less low cloud) in order to get a new equilibrium. Once these calibrations have been done, they are fixed for all the perturbation runs (like the 20th Century hindcasts, RCPs and paleo runs etc.). This has nothing to do with the imbalance that you get from increasing GHGs since it is exactly how the climate responds to that that you are trying to understand. Basic point – calibrations come before experiments and once the calibration is fixed it doesn’t change during any experiment. – gavin]

    Comment by Ken Lambert — 27 Dec 2013 @ 9:01 PM

  75. “This has nothing to do with the imbalance that you get from increasing GHGs since it is exactly how the climate responds to that that you are trying to understand.”

    Well this is very interesting because how the climate responds to increasing GHG’s is also a function of clouds and TSI. The TOA altitude will change, changing the effective radiation temperature. Calibration to an imperfect TSI will achieve an imperfect response to GHG perturbation. In at least one way I can think of, a lower TSI would actually lead to higher sensitivity to GHG’s, though I have no idea how the different mechanisms ledger out. I am interested in the answer to Ken’s question: are climate models taking account (calibrated to) the value of 1361.5 W/m2?

    [Response: The CMIP5 models were generally calibrated to 1365 W/m2 or thereabouts. There might be some small variation. I expect that models developed now will use 1361 W/m2. – gavin]

    Comment by Alex — 28 Dec 2013 @ 11:44 AM

  76. Fred #33, just another virtanen to waste your time

    Comment by Martin Vermeer — 28 Dec 2013 @ 4:03 PM

  77. If I take the second plot published, and isolate the period after 2013 to 2100, it looks pretty insignificant. How anyone can add this exponential increase to it is beyond me. They might as well add an exponential decrease – it would be just as valid.

    Comment by R James — 28 Dec 2013 @ 10:32 PM

  78. R. James, Dude, what the hell are you talking about?

    Comment by Ray Ladbury — 29 Dec 2013 @ 7:43 AM

  79. > How anyone can add this exponential increase to it is beyond me

    They don’t show you the amount of fossil fuel being burned in the future; each line reflects a different set of assumptions about that.

    To get the exponential decrease you imagine could be equally possible, you need to provide a scenario with a vast rapid decrease in CO2 in the atmosphere. Other than the science fiction — a massive outbreak of replicating green goo — nobody has that yet.

    Comment by Hank Roberts — 29 Dec 2013 @ 11:34 AM

  80. Gavin, thanks for your responses at 74 and 75.

    I had a look for an updated Trenberth energy balance diagram using a TSI of 1361.5 and could not find.

    Does such a revision exist? Last time I looked we were still not accurately measuring the warming imbalance, so therefore a more accurate albeit reduced TSI measurement must drive adjustments to the assumed albedo reflection and/or OLR.

    Are these adjustments producing Trenberth’s 0.9W/sq.m imbalance or Hansen’s 0.6W/sq.m imbalance?

    [Response: The imbalance is inferred from heat content changes (ocean and elsewhere). It therefore has nothing to do with the measurements of TOA radiation – which are still not accurate enough to constrain it directly. The change in the energy balance diagram is only 0.7W/m2 in the absorbed SW, so it really doesn’t make that much difference. The Stephens et al (2012) picture is a more recent update though. – gavin]

    Comment by Ken Lambert — 31 Dec 2013 @ 8:57 AM

  81. Fred Moolten,

    To belatedly pick up this thread again…

    the comparison I was making (and has been made previously by others, including Stefan, Trenberth and more, apparently supported by observations) is that a failure of the surface to warm due to a La Nina-like process will increase energy accumulation by reducing OLR relative to the OLR that would have been produced by a warmer surface.

    I think what people have said is that La Nina states tend to enhance energy accumulation at depth instead of near the surface. That means a situation where a greater than normal fraction of an extant imbalance will be sequestered in the oceans, reducing the planet’s immediate ability to diminish the imbalance via Planck response, thereby largely sustaining that extant imbalance.

    What I’m saying is that the magnitude of imbalance is heavily dependent on feedbacks to surface warming. Therefore an “external” (in this case I mean unforced variability, somewhat confusingly) cause of surface temperature stagnation can diminish the growth of an imbalance compared to what would happen during “normal” conditions.

    Looking at model outputs (correlating global average thermosteric sea level with global average surface temperature) suggests, as we’ve been saying, that the two factors act against each other but there appears to be a threshold, related to climate sensivitity, where one dominates. With the caveat that I only had a small sample size, a couple of high sensitivity models clearly correlated periods of enhanced (above trend) near-surface warming with enhanced ocean heat accumulation, and vice versa. In a couple of low-end sensitivity models the picture was less clear. Some periods appeared to show anti-correlation, some correlation.

    I think one key factor here is that most models appear to have stronger water vapour and cloud feedbacks over ocean areas (which makes sense) whereas Planck response tends to be largest over land areas, particularly during transient warming. That seems to be why primarily oceanic variability can have a greater effect on water vapour and cloud feedbacks than on the Planck response, at least temporarily.

    Comment by Paul S — 2 Jan 2014 @ 7:22 AM

  82. I have a sincere question. I am told that human CO2 emmissions became high enough to start changing the climate as a result of post war industrialization, so starting in about 1950. I am told that we must keep the total temperature rise, natural and human induced, below 2 degrees C. When I look at the graphs above they show about .45 degrees C warming from 1950 to now, or about .0071 degrees per year. At that rate of warming, which is over a period which I presume is long enough to average out natural fluctuations, it will take over 280 years to get to 2 degrees of warming. What am I missing?

    Comment by gordon johnson — 6 Jan 2014 @ 11:01 AM

  83. gordon johnson – There are a few things you need to take into account.

    The acceleration of industrialisation since 1950 also brought an acceleration of aerosol emissions which have a net cooling influence on climate and have therefore counteracted some of the expected warming due to well-mixed greenhouse gases (primarily CO2, methane, N2O, CFC/HCFC variants).

    In model simulations which incorporate only historical changes in well-mixed greenhouse gases you’ll typically see about twice as much warming from pre-industrial to present as in simulations which include all historical factors, with aerosols being the main factor in that difference.

    It’s anticipated in all future scenarios (I think) that nations will bring in clean air legislation which will reduce aerosol influence. Whereas in the past aerosols have tended to counteract WMGHG warming, this future reduction will enhance warming rates.


    There are also natural buffering effects in Earth’s climate system which delay the full response in terms of surface temperature increase. The energy imbalance which has been discussed here can be thought of as a manifestation of this buffering.

    The year-on-year forcing increase due to WMGHGs is only about 0.05W/m2 whereas the current imbalance appears to be at least 0.5W/m2 so you can see the energy accumulation is not instantly translated to surface temperature increase.

    Idealised model simulations in which CO2 concentration is increased by 1% per year can provide some insight into how this can affect rates of warming over time. The year-on-year CO2 forcing increase is almost exactly constant in this setup but the rate of warming for the final 30 years in a 70-year run is typically about 50% greater than the rate for the first 30 years.

    Comment by Paul S — 7 Jan 2014 @ 7:47 AM

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