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Warming, interrupted: Much ado about natural variability

Filed under: — raypierre @ 12 July 2009

A guest commentary by Kyle Swanson – University of Wisconsin-Milwaukee

I am quite humbled by the interest that has been generated by our paper “Has the climate recently shifted?” (Swanson and Tsonis, 2009), and would like the thank the RealClimate editors for the opportunity to give my perspective on this piece.

Before delving into the paper itself, a few words about the place of our work in the global warming “debate” are in order. A quote from the early 20th century Viennese polymath Egon Friedell (which I ran across in the wonderful book Cultural Amnesia by Clive James) captures the situation better than any words I could ever weave;

Electricity and magnetism are those forces of nature by which people who know nothing about electricity and magnetism can explain everything.

Substitute the words “modes of natural climate variability” for “electricity and magnetism,” and well…, hopefully the point is made.

It first needs to be emphasized that natural variability and radiatively forced warming are not competing in some no-holds barred scientific smack down as explanations for the behavior of the global mean temperature over the past century. Both certainly played a role in the evolution of the temperature trajectory over the 20th century, and significant issues remain to be resolved about their relative importance. However, the salient point, one that is oftentimes not clear in arguments about variability in the climate system, is that all else being equal, climate variability and climate sensitivity are flip sides of the same coin. (see also the post Natural Variability and Climate Sensitivity)

A climate that is highly sensitive to radiative forcing (i.e., responds very strongly to increasing greenhouse gas forcing) by definition will be unable to quickly dissipate global mean temperature anomalies arising from either purely natural dynamical processes or stochastic radiative forcing, and hence will have significant internal variability. The opposite also holds. It’s painfully easy to paint oneself logically into a corner by arguing that either (i) vigorous natural variability caused 20th century climate change, but the climate is insensitive to radiative forcing by greenhouse gases; or (ii) the climate is very sensitive to greenhouse gases, but we still are able to attribute details of inter-decadal wiggles in the global mean temperature to a specific forcing cause. Of course, both could be wrong if the climate is not behaving as a linear forced (stochastic + GHG) system.

With that in mind, our paper is fundamentally about inter-decadal variability in the climate system and its role in the evolution of the 20th century climate trajectory, as well as in near-future climate change. The climate system has well known modes of variability, such as the El Niño/Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), that are active on inter-annual time scales. We are interested in how this short time-scale (from the climate perspective!) variability impacts climate anomalies over multi-decadal time periods.

What we find is that when interannual modes of variability in the climate system have what I’ll refer to as an “episode,” shifts in the multi-decadal global mean temperature trend appear to occur. I’ll leave the details of these episodes to interested readers (here and here), as things get pretty technical. It’s sufficient to note that we have an objective criteria for what defines an episode; we aren’t just eyeballing curves. The climate system appears to have had three distinct “episodes” during the 20th century (during the 1910’s, 1940’s, and 1970’s), and all three marked shifts in the trend of the global mean temperature, along with changes in the qualitative character of ENSO variability. We have also found similar types of shifts in a number of model simulations (both forced and unforced) that were run in support of the IPCC AR4 report.

The contentious part of our paper is that the climate system appears to have had another “episode” around the turn of the 21st century, coinciding with the much discussed “halt” in global warming. Whether or not such a halt has really occurred is of course controversial (it appears quite marked in the HadCRUT3 data, less so in GISTEMP); only time will tell if it’s real. Regardless, it’s important to note that we are not talking about global cooling, just a pause in warming.

What’s our perspective on how the climate will behave in the near future? The HadCRUT3 global mean temperature to the right shows the post-1980 warming, along with the “plateau” in global mean temperature post-1998. Also shown is a linear trend using temperatures over the period 1979-1997 (no cherry picking here; pick any trend that doesn’t include the period 1998-2008). We hypothesize that the established pre-1998 trend is the true forced warming signal, and that the climate system effectively overshot this signal in response to the 1997/98 El Niño. This overshoot is in the process of radiatively dissipating, and the climate will return to its earlier defined, greenhouse gas-forced warming signal. If this hypothesis is correct, the era of consistent record-breaking global mean temperatures will not resume until roughly 2020. Of course, this contrasts sharply with other forecasts of the climate system; the purple line roughly indicates the model-based forecast of Smith et al. (2007) , suggesting with a warming of roughly 0.3 deg C over the 2005-2015 period.

Why would anyone in their right mind believe what I’ve just outlined? Everything hinges on the idea that something extraordinary happened to the climate system in response to the 1997/98 super-El Niño event (an idea that has its roots in the wavelet analysis by Park and Mann (2000)). The figure to the left shows the spatial mean temperature over all grid boxes in the HadCRUT3 data set that have continuous monthly coverage over the 1901-2008 period. While this provides a skewed view of the global mean, as it is heavily weighted toward North America, Europe and coastal areas, unlike the global mean temperature it has the cardinal virtue of being a consistent record with respect to time. The sole exclusion in the figure is the line connecting the 1997 and 1998 temperatures.

Now, anomalous behavior is always in the eye of the beholder. However, the jump in temperature between 1997 and 1998 in this record certainly appears to pass the “smell test” (better than 3 standard deviations of interannual variability) for something out of the ordinary. Nor is this behavior dependent on the underlying time interval chosen, as the same basic picture emerges for any starting time up until the 1980’s, provided you look at locations that have continuous coverage over your interval. Again, as the temperature anomaly associated with this jump dissipates, we hypothesize that the climate system will return to its signal as defined by its pre-1998 behavior in roughly 2020 and resume warming.

What do our results have to do with Global Warming, i.e., the century-scale response to greenhouse gas emissions? VERY LITTLE, contrary to claims that others have made on our behalf. Nature (with hopefully some constructive input from humans) will decide the global warming question based upon climate sensitivity, net radiative forcing, and oceanic storage of heat, not on the type of multi-decadal time scale variability we are discussing here. However, this apparent impulsive behavior explicitly highlights the fact that humanity is poking a complex, nonlinear system with GHG forcing – and that there are no guarantees to how the climate may respond.


References:

Park, J. and M.E. Mann, 2000: Interannual Temperature Events and Shifts in Global Temperature: A Multiple Wavelet Correlation Approach. Earth Interactions, 4-001, 1-36.

Swanson, K.L. and A.A. Tsonis, 2009: Has the climate recently shifted? Geophysical Research Letters, 36, doi:10.1029/2008GL037022.


388 Responses to “Warming, interrupted: Much ado about natural variability”

  1. 101

    Alex, I’m a musician and sometime academic by trade, innocent of any mathematical background more advanced than Algebra 2.

    However, I find 2 criteria are largely sufficient to decide where the balance of credibility lies in this climate “debate.”

    1) Who is telling a self-consistent story, and who is merely picking nits, wherever they can be found or imagined? (Hint: the idea–a la Monckton–that warming on Mars “proves” Terrestrial warming to be solar in origin is not logically consistent with the idea that all Terrestrial warming is an artifact of UHI.)
    2) Who is responding constructively to opponents’ points, and who is content to cut-and-paste ad nauseam, no matter how many times an argument may have been answered? (Hint: the “saturated gassy” argument was made at the turn of the century–20th century, that is–and has definitely been shown incorrect since the days of Gilbert Plass’s climate research in the 1950’s. Yet it is so distinctly “undead” in the blogosphere that RC has devoted a whole post to it.)

    In short, behavior–tactical behavior, if you will–is enough to reveal who is really investigating and who is just debating.

    On a related topic, I think pessimism about the state of the public perception of the debate is understandable but ultimately unwarranted. We’ve had the survey numbers swinging the wrong way for a bit, but that’s short-term. The numbers swung pretty seriously our way with AIT; there was bound to be some rebound. Then we got the slightly cooler 2008 temps for denialist talking points.

    But the denialosphere are rapidly finding out that you can only claim it is cooling for so long before people start to wonder why we’re at the same historically high anomalies we’ve been experiencing throughout the decade; why the sea ice hasn’t really recovered; why droughts are getting worse; and so on.

  2. 102
    CTG says:

    “As an exercise for the reader calculate what the mean temperature anomaly would need to be for RC to lose the first part of the bet…”

    Ooh! Ooh! I’ll play! I make it -0.67ºC (using GISTEMP), about 1.3ºC cooler than 2008, and lower than any year in the GISTEMP record. I would definitely take the bet.

    [Response: I think you may have miscalculated – it’s not quite that bad. For the HadCRU3Tv data, I calculate that the mean anomaly from Jun 09 to Oct 10, would need to be 0.014 dec C or less. No year has been that cold since the early 1980s and no month that cold since the immediately post-Pinatubo years. – gavin]

  3. 103
    Mike#22 says:

    Swanson publishes (see the first paper in the post above)

    “These (124) shifts were accompanied by breaks in the global mean temperature trend with respect to (125) time, presumably associated with either discontinuities in the global radiative budget due (126) to the global reorganization of clouds and water vapor or dramatic changes in the uptake (127) of heat by the deep ocean.”

    Well, that seems perfectly reasonable. These huge oceans systems, capable of storing immense amounts of heat, wobble a bit and takes up the incoming inbalance for a while and hides it below the waves. Air temps remain steady. Am I missing something?

  4. 104
    Hank Roberts says:

    Jim, I really don’t know — serious question on my part, I don’t know if the tools we have allow measuring the planet’s outgoing heat. I think we don’t have any instruments far enough away, like Triana was meant to be.

    [Response: Triana would not have helped. Triana would have given you full-disk albedo, but would have done nothing for the infrared side of the budget. –raypierre]

  5. 105

    #103 Mike, Makes sense except the current oceans look kind of warm:

    http://www.osdpd.noaa.gov/PSB/EPS/SST/climo&hot.html

    So what about this pause? Has there been a warming exchange block at the interface between ocean and air?

  6. 106
    Jim Galasyn says:

    Hank, it’s a very good question, which I’ve often pondered. My thinking has been that these oscillations are part of the atmospheric overturn that gives us a well-mixed atmosphere, which lets us talk about global average surface temperature.

    But I think that the best way to think about the problem is to look at the final equilibrium state. The trajectory to the final state will have lots of wiggles and oscillations, but ultimately the planet must achieve radiative equilibrium with space, and no pauses/episodes will prevent this.

    [Response: No, I don’t think so. The atmosphere has too little mass to give you much thermal memory on time scales of more than a month or two. If you want to find something that persists for a decade or more, and is not a response to an external forcing like increase of CO2, then you need to look to the oceans. –raypierre]

  7. 107
    save gaia says:

    @73 dhgozza
    Wiggle also known as “wobble” by hurrican movement.

    @81 Weather patterns are wrong all over the world, its not just brazil which miss winter, the europeans still wait for the summer.

    Thawing permafrost and released methane clathrates this is what is going to make it worse now, despite any efforts the coming century.
    We have underlying warming of “~2.4C” and the biggest contributions are still in the pipeline.

    We have to act faster!

    @83 The weather is in flux, due to the fact of missing climate balance.

  8. 108
    Jim Galasyn says:

    Ray, thanks for the help. Is my second point about equilibrium correct, i.e., oscillations like ENSO and PDO won’t change the final temperature? Would it also be correct to say that they won’t delay the arrival of the final temperature?

  9. 109
    Alex Harvey says:

    Raypierre in response to Phil. Felton at #46 13 Jul 2009 at 8:59 am:

    …this points up a common misconception about the operation of climate. Though we speak of “thermal inertia,” it’s not really inertia in the sense of Newtonian mechanics. If you start a warming trend by increasing a climate warming forcing and then zeroing it out, it does not (unlike a body in notion) tend to keep on warming unless you do something later to stop it. Warming is a damped response to the current forcing, and the minute you zero out the forcing, the trend will turn the other way. “Committed warming” is only committed because the scenario there is not zeroing out the GHG forcing, but rather freezing its value, giving the climate time to catch up. In this sense, the dynamics of climate change is more Aristotelian than Newtonian.

    I am not sure how common this misconception of climate is, and I obviously can’t speak for Akasofu, but I do know that it’s not a misconception I have myself here.

    In the little ice age, as I understand it, temperatures fell gradually over a number of centuries to correspond in some as yet unexplained way with the “Maunder Minimum,” a period of reduced sunspot activity. It seems fairly reasonable to suppose that had humans emitted no CO2 at all, temperatures would have risen again anyway in the same pattern that they had fallen previously, i.e. gradually and over a number of centuries. Even the IPCC2007 has said somewhere, I believe, that the levels of CO2 were probably not high enough until about 1950 to have had much effect on the global average temperature. So I am having a lot of trouble in understanding how, in the Swanson & Tsonis theory, these authors can genuinely believe in an underlying “true forced warming signal” from GHG emissions that began 1850 and continues today.

  10. 110

    The choice of 1979-1997 might not have been intended as cherry-picking, but it is unfortunate choice nonetheless. This term is too short for an accurate slope, and it makes the regression way too sensitive to the 1992-1993 temperatures, which were influenced by the Pinatubo eruption. If you take 1970-1997 in GISTEMP (I didn’t try HADCRUT), and leave out the outliers 1992 and 1993, and do a linear regression, then there is no need to assume a pause at all. And you get a slope of 0.016 degrees per year, which seems more realistic than the 0.01 or so obtained in the regression above.

    This does not mean that the pause isn’t possible. But unless the authors come up with a more specific mechanism and data as to where the overshot heat is coming from, I have more confidence in my own regression than in the one posted above.

  11. 111
    Johnno says:

    Link to the ‘cooling’ graph Al Gore has been asked to explain while visiting Australia
    http://www.news.com.au/story/0,27574,25780407-5019059,00.html

    [Response: That’s funny. The implicit transient climate sensitivity in that graph is over 6 deg C for a doubling of CO2 (i.e. that is what would have to be the case for the two scales in CO2 and temperature to be commensurate). Given that IPCC estimates TCR (this is not at equilibrium of course) are around 2 deg C, this is at least a factor of three misleading. Not likely to convince anyone who knows anything about it. – gavin]

  12. 112
    llewelly says:

    Alex says: 13 July 2009 at 2:44 PM

    Well, to this simple observer of the AGW scene, all of the AGW predictions, viewed as monotonically climbing graphs, show exactly the opposite of what dhogaza claims. And skeptic friends tell me that the inability of the models to predict anything other than monotonically climbing temperatures is why there’s been a rebranding of AGW as “climate change”. It seems a pity that the models seem unable to take into account significant ocean cycles, solar cycles, etc. To the simple observer it seems either that the models are inadequate or that there’s been a failure to communicate the realities of AGW

    This is an excellent example of why averaging together dozens of differently perturbed model runs(1) is an explanatory disaster, even though it yields superior predictions over the long haul. Such averaging smooths out the ‘weather’ which the climate models do simulate.
    To get an idea of how big a difference this can make – see the first figure in this post, and compare any individual colored line with the smooth black line which is the average of the 55 realizations.
    RC has been showing this sort of thing from time to time, but the vast majority of less technical sources of climate news seldom or never show graphs like that.
    Smoothing is very powerful, but there’s a kind of information it always destroys; it makes the viewer ignorant of how much noise the signal must compete with.
    (1) This is roughly true whether the multiple runs are made with the same model, or different models, or if each of many models is run with many different perturbations and then all are averaged together, or if each ensemble is averaged separately, before being averaged to achieve the final result..

  13. 113
    Mark says:

    Jim, #96, that’s my reading of this too.

  14. 114
    Mark says:

    “But the common perception out in my community is that the world is certainly not warming, hasn’t been for some time, and that’s at variance with the models.”

    Then you’re being trolled by your community.

    This could be selection bias. Since they don’t like the idea of AGW (for various emotional reasons) and they see themselves being bombarded with “Global Warming” from the left-wing news (though the right-wing news tells them the *real* truth…) they remember each winter day there was snow, just like they had in the past (forgetting that there were more snow days in the past) and they remember each summer day that turns out miserable (forgetting that there have been days hotter than before too).

    Is your community in a coal-mining area?

  15. 115
    Mark says:

    “In fact, perhaps Al Gore did a better job of it than the scientific community. But much of his efforts are negated by the mean-spiritied, dishonest, but effective character assassination aimed at him. Despicable, yes — but also effective propaganda.”

    I believe only effective propaganda for those predisposed to accept it. Or for those who are surrounded by those who believe it and, in an effort to conform (odd, given how many like to pose as maverick “skeptics”) agree at that time with the propaganda.

  16. 116
    Mark says:

    andy #80, 35000 europeans died one summer of heatstroke.

    If you take that as your definition of “cooking” us, then it’s happening.

  17. 117
    pete best says:

    Dea RC, is the warming linear in nature over just a decade or two or over a century or more. Our present age of AGW has a large cooling part (probably local as opposed to being global) but its having a masking effect. Is this effect keeping present decadal warming trends linear but if we clean up our pollution but fail to drop our CO2 emissions by much mean an increased linear warming trend or a more non linear one ?

  18. 118
    John Finn says:

    Re: #5

    [Response: Wayne, please note that this is Kyle’s article not mine, though I did encourage him to write it for us. I think the interesting question raised (though not definitively answered) by this line of work is the extent to which some of the pause in warming mid-century might have been more due to decadal ocean variability rather than aerosols than is commonly thought. If that is the case, then a pause or temporary reduction in warming rate could recur even if aerosols are unchanged. Learning how to detect and interpret such things is important, lest a temporary pause be confused with evidence for low climate sensitivity. –raypierre]

    By George, I think they’ve got it. Quite how it’s managed to escape so many for so long that ocean variablility rather than aerosols is the likely cause of mid-20th century cooling (or lack of warming) is totally beyond me.

    I hope Hank Roberts and Tamino are reading this as I’ve taken considerable flak from them over my continued assertion that there is no way that aerosols could have been responsible and that ocean circulation was the place to start looking.

    Of course it does mean that the IPCC “detection and attribution studies” are based on flawed assumptions. It’s also the case that if ocean variability caused the cooling, then it’s likely that it caused (or amplified) the 1910-1940 warming of ~0.13 deg per decade and similarly amplified the post-1975 warming. The implication being that the CO2 signal is much reduced.

    Ray – Just one question, though. If there is a pause. What happens to all the “heat in the pipeline”?

  19. 119

    Alex Harvey writes:

    Dr. Shunichi Akasofu has made exactly the same point, except that the latter has attributed the same trend to recovery from the Little Ice Age rather than GHG forcing.

    As I have said many times, Akasofu-san wa bakayaro des’. What is the physical mechanism behind “recovery from the Little Ice Age?” “Recovery from the Little Ice Age” isn’t a process. Does he think the climate is like a spring in simply harmonic motion? It isn’t.

    And given that there wasn’t enough CO2 in the mid-nineteenth century to be causing the same warming as there was in 1975 it seems rather strange to me to be attributing a single linear trend all the way from 1850 until 1997 to GHGs without any mention of the warming trend that already existed in 1850. Has this analysis been simplified?

    No, but a simple analysis shows the intimate connection between the temperature rise and the CO2:

    http://BartonPaulLevenson.com/Correlation.html

  20. 120

    Rob writes:

    “Also shown is a linear trend using temperatures over the period 1979-1997 (no cherry picking here…””

    Unless you’re cherry picking a linear trend ?!

    A linear trend is ALWAYS the default in statistics unless you can show that a more complicated relationship is statistically valid. Occam’s Razor.

  21. 121

    Gareth writes:

    The El Nino is here, and while it’s not impossible that it might fizzle, the current expectation is that it will last into 2010. There are some intriguing possibilities: strong El Nino, new global temp record in 2010 (ie above 2005 GISS, 1998 HadCrut); moderate El Nino, new global temp record; moderate El Nino, no new record, etc etc. If we had a strong El Nino and no new record, that might suggest something along the lines of the “pause” hypothesis – and no doubt the usual suspects would make hay… Forgive me a shudder at the thought.

    I’ll bet you anything you want that as early as 2013 we’ll be hearing the deniers say “Global warming stopped in 2010!”

  22. 122

    A minor nitpick: “an objective criteria” should be “criterion”.

    How real is this “pause” in warming anyway? In response to some inactivist stuff here in Australia, I downloaded the HadCRUT3 data and did a linear regression for 1995-2008 (the period for which they were claiming there was no longer an upward trend) and found they were wrong, though the upward trend is a lot smaller than the long-term trend (your green line). Given that over this period we’ve had (1) a strong El Niño early on, (2) more recently a big La Niña and (3) the solar cycle has recently bottomed out a relatively low point, is it really surprising that the trend appears to have “paused”?

    How much of the slowdown in increase over the last few years can be explained by the solar cycle? To me it seems pretty significant that we are still close to all-time highs despite all 3 of these natural temperature influences that should have been pointing down the last few years.

    If the solar cycle peaks in 2013, isn’t there a good chance that even if this paper is correct in terms of the big picture, we will see a short-term peak crossing your red line around about then?

  23. 123
    Ray Ladbury says:

    Alex @91, I’m afraid that the lesson here is that reality isn’t as simple or as accommodating as people want it to be. And since science is about truth, the science has to reflect the truths that we cannot overconsume with impunity and that we are messing with a very complicated system on which our welfare depends. There’s a limit to how much we can dumb things down. Maybe it’s the public that needs to wise up.

  24. 124
    Theo Hopkins says:

    I’m Irish and a greenie (and by that I don’t mean leprechaun green).
    But I do have that strange logic that the Irish are rumoured to have – as in the often told tale of the Irishman, asked by a tourist, how to get to Killarney, replied “If you want to get there you shouldn’t start from here”.

    And my odd logic is that as I am concerned about AGW, I actually _want_ to see higher temperatures(see below).

    So I’m worried about climate change and global warming. But as the temperatures over the last ten years or so have more-or-less leveled and have not been rocketing smoothly up, and there now may be a decade’s worth of pause in global warming, so I am crossing my fingers that soon the temperatures will start rising again, just to show sceptics that AGW is real. All this, when as a greenie, or anyone else for that matter, what I would like to see is, of course, global cooling. And given global cooling I could then ditch my stupid little 1000cc Fiat runabout and get that vast new 5.7litre Jaguar XJ4 that I secretly covet and burn a bit of rubber, so as to impress my neighbour who has a big BMW, also a 4×4 (for her dog, he says!), a powerboat, two patio heaters and a ride-on grass mower.

    Point is, when the temperatures are not doing “what they are meant to do” it is hard to deal with sceptics who suggest that within climate variability there is a hidden downward trend. And only a rise soon will do that.

  25. 125
    Andy Revkin says:

    There was a reference above to my piece examining whether climate campaigns can survive a cooling test. Here are relevant links (shortcuts)
    http://bit.ly/dotCool2
    http://bit.ly/dotCool

  26. 126
    Mark says:

    “so I am crossing my fingers that soon the temperatures will start rising again, just to show sceptics that AGW is real. ”

    Only if the underlying process is that there isn’t a problem being stored up for us in future.

    False sense of security.

  27. 127
    Mark says:

    Jphn Finn 118: Whut?

    The ocean is a resevuir of heat.

    It doesn’t create any itself.

    The sun does that (and a very minor geothermal component). And that is affected by the aerosols.

    False dichotomy on your reading of others postings.

  28. 128
    Phil. Felton says:

    Re #111
    Link to the ‘cooling’ graph Al Gore has been asked to explain while visiting Australia
    http://www.news.com.au/story/0,27574,25780407-5019059,00.html

    [Response: That’s funny. The implicit transient climate sensitivity in that graph is over 6 deg C for a doubling of CO2 (i.e. that is what would have to be the case for the two scales in CO2 and temperature to be commensurate). Given that IPCC estimates TCR (this is not at equilibrium of course) are around 2 deg C, this is at least a factor of three misleading. Not likely to convince anyone who knows anything about it. – gavin]

    Also it would be more appropriate to plot ln(CO2) anyway.

  29. 129
    Tommy says:

    Thanks for the great scientific view on this topic. I would guess the temperatures will again begin to increase. However, maybe some of our efforts to curb global warming are paying off. Time will tell.

  30. 130
    dhogaza says:

    John Finn:

    By George, I think they’ve got it. Quite how it’s managed to escape so many for so long that ocean variablility rather than aerosols is the likely cause of mid-20th century cooling (or lack of warming) is totally beyond me.

    I hope Hank Roberts and Tamino are reading this as I’ve taken considerable flak from them over my continued assertion that there is no way that aerosols could have been responsible and that ocean circulation was the place to start looking.

    This is a total misreading of Raypierre’s comment.

    Sheesh.

    [Response: Quite so. I was only suggesting a reconsidering of the relative roles of aerosols and ocean decadal fluctuations. I wouldn’t presume to know the answer, and even once we do know the answer aerosols are virtually certain to be an important part of the story, given what we know for certain regarding the radiative effect of aerosols, which is indeed something. –raypierre]

  31. 131
    Hank Roberts says:

    Whoah — look at the two captions on Fielding’s image.
    (cut off in the link at the newspaper, oh oopsie, how could they?)

    Here’s the image with the caption showing at Fielding’s page:
    http://www.stevefielding.com.au/images/uploads/The_global_temperature_chart_thumb.jpg

    Right side caption describes the red line is _temperature_anomaly_.
    (Note where the zero level is — the red line is always above it.)

    Black text at bottom claims the red line is _temperature_ change, but — WTF??

  32. 132
    chris says:

    re Alex #109

    In the little ice age, as I understand it, temperatures fell gradually over a number of centuries to correspond in some as yet unexplained way with the “Maunder Minimum,” a period of reduced sunspot activity. It seems fairly reasonable to suppose that had humans emitted no CO2 at all, temperatures would have risen again anyway in the same pattern that they had fallen previously, i.e. gradually and over a number of centuries. Even the IPCC2007 has said somewhere, I believe, that the levels of CO2 were probably not high enough until about 1950 to have had much effect on the global average temperature. So I am having a lot of trouble in understanding how, in the Swanson & Tsonis theory, these authors can genuinely believe in an underlying “true forced warming signal” from GHG emissions that began 1850 and continues today.

    That’s not really correct Alex. The anthropogenic contribution to atmospheric CO2 was a rise from around 280 ppm preindustrial to 310 ppm around 1940 [*]

    It’s very easy to calculate that within a climate sensitivity near 3 oC of warming per doubling of atmospheric CO2 (the median value from a large range of empirical analyses as described by the IPCC), that this should give a warming near 0.45 oC at equilibrium. Since the period of this rise in atmospheric CO2 was long, we can assume it came nearly to equilibrium by your date of 1950. Let’s say that the real warming contribution was 0.35 oC (0.1 in the pipeline that was realised post-1950).

    Pretty much the largest published difference in temperature between the bottom of the LIA and the mid 20th century is in the paleoreconstruction of Moberg et al. [**] This is around 0.6 oC rise in temperature in the Northern hemisphere. It seems likely that the cold of the LIA was predominantly in the N. hemisphere, but let’s say for the sake of argument that the world was globally cooler by 0.6 oC at the bottom of the LIA compared to the mid 20th century.

    In other words 50% or more of the warming since the bottom of the LIA to the mid 20th century is expected to be due to anthropogenic greenhouse forcing. The other contributions to the LIA cold (highish volcanic activity, low solar activity) likely account for the rest (0.25-0.35 oC) of the reduced temperature, and this is the amount that the earth might have warmed following reversal of the negative solar/volcanic forcing. [The N. hemispheric nature of the LIA might also have had a contribution from reduced ocean current heat flow to the high Northern latitudes (evidence for reduced Gulf stream flow during this period)].

    So the Swanson & Tsonis theory “an underlying “true forced warming signal” from GHG emissions that began 1850 and continues today”, is a pretty robust expectation from our understanding of the greenhouse effect and detailed knowledge of the atmospheric CO2 concentrations in pre-1850 to the present.

    [*]D. M. Etheridge et al (1996) “Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn J. Geophys Res. 101, 4115 -4128

    [**] Moberg, A et al. (2005) Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data Nature 433, 613–618 (2005)

  33. 133
    Paul Biggs says:

    Could we have a guest post from Anastasios Tsonis? – he seems to tell a slightly different story:

    Now the question is how has warming slowed and how much influence does human activity have?
    “But if we don’t understand what is natural, I don’t think we can say much about what the humans are doing. So our interest is to understand — first the natural variability of climate — and then take it from there. So we were very excited when we realized a lot of changes in the past century from warmer to cooler and then back to warmer were all natural,” Tsonis said.
    Tsonis said he thinks the current trend of steady or even cooling earth temps may last a couple of decades or until the next climate shift occurs.

    http://www.wisn.com/weather/18935841/detail.html

    Maybe Tsonis was misquoted :-)

    [Response: Tasos is a good scientist and quite reasonable person. I won’t speak for him, but I sense from conversations I’ve had with him that he feels that many of his comments were taken out of context, or otherwise misrepresented. And perhaps he might have phrased things differently in hindsight. Tasos: if you happy to be reading this, we’d love to hear from you. –mike]

  34. 134
    John Finn says:

    Re: #127

    Mark says:
    14 July 2009 at 8:15 AM

    Jphn Finn 118: Whut?

    The ocean is a resevuir of heat.

    It doesn’t create any itself.

    I know. But that heat can be ‘re-distributed’, so that more heat is released into the atmosphere during some periods than others. A bit like a drawn out ENSO event.

    PS are you trying to set some sort of record for the number of typos?

    The sun does that (and a very minor geothermal component). And that is affected by the aerosols.

    False dichotomy on your reading of others postings.

  35. 135
    Jim Cross says:

    #5 Raypierre response

    If ocean variability caused the cooling, this suggests to me that the ocean can operate somewhat like the Lindzen iris, although on a time frame of decades. Doesn’t this call into question the long-term predictions of temperature rise if the ocean periodically interrupts the rise by dissipating the heat?

  36. 136

    #131 Hank, quite distressing to see that oz people are subjected to this graph.
    Again, Hadley has something wrong in their system, what it is I don’t know. But not including vast swats of Arctic anomalies don’t help…. 2005 was the warmest year in history, this graph seen alone, suggests that the great melt occurred in 1998….

    but

    http://www.metoffice.gov.uk/climatechange/science/monitoring/hadcrut3.html

    Hadley doesn’t look so bad taken completely….

  37. 137
  38. 138
    Mark says:

    Wayne, there’s a very good reason for removing the artic.

    There aren’t many stations up there AT ALL.

    Definitely not enough to properly cover that expanse.

    So HC leave it out.

    GISS leave it in and interpolate.

    Either can look bad if you want to see it that way.

  39. 139
    Mark says:

    jonh finn, the typos aren’t an attempt to get a record. I just don’t care about impressing you.

    PS isn’t that actually an ad-hom? Sort of “you’re spelling is wrong, so your argument is wrong”.

    PPS lots of others say the same thing: you got it completely wrong and you did so by (assuming you aren’t being deliberately malicious, so if you don’t like it, we can go there if you like…) by misreading a statement into saying what you want it to say.

  40. 140
    dhogaza says:

    Roger Pielke Sr doth pontificate on this “weblog”

    As does his son, who apparently doesn’t understand that RC simply gave Swanson a soapbox from which to discuss his controversial paper.

  41. 141
    Hank Roberts says:

    Ray, I’m puzzled why Triana’s instruments wouldn’t help:

    http://www-pm.larc.nasa.gov/triana/documents/Huang_triana_toronto.pdf

    Did they pick the wrong bands to be useful, or what? Since the instrument’s still in the warehouse, what should be in board that isn’t, to track the information relevant to this topic?

    [Response: Among other things, infrared comes out of the nightside, not just the dayside. Triana only looks at the sunlit side of the planet, and may be suitable for process studies, but is not suitable for doing global energy balance. But even if you had satellites in the right orbit, getting long-term instrumental stability to a level where you could detect the relatively small imbalances caused by ocean/atmosphere heat exchange would be difficult. Hansen and others argue that direct in situ monitoring of ocean heat storage, while also difficult, is less so. –raypierre]

  42. 142
    Jim Galasyn says:

    SteveF: Roger Pielke Sr doth pontificate on this “weblog”…

    It’s always amusing to see this at the end of Roger’s posts: “Sorry, the comment form is closed at this time.”

  43. 143
    stroller says:

    “the extent to which some of the pause in warming mid-century might have been more due to decadal ocean variability rather than aerosols than is commonly thought. If that is the case, then a pause or temporary reduction in warming rate could recur even if aerosols are unchanged” – raypierre

    If it is the case, then how much of the warming in the ’80’s and 90’s was due to the positive phases of the AMO and PDO and how much will this reduce the figure for the sensitivity of the climate to co2?

    [Response: Not at all, because climate sensitivity cannot be reliably deduced from the late 20th Century record. This does not change that. – gavin]

    I assume the debate will now be opened to ask just what are the phenomena behind the natural oscillations which can overcome the forcing of climate by co2 – yes?

  44. 144
    G. Karst says:

    This discussion was way past due. I commend RC for objectively posting it, and the reasonable arguments that followed. The pursuit of truth will eventually be rewarded by gestalt.

  45. 145
    Steve says:

    This is purely and simply fitting the data to the story rather than letting the data tell the story. Bad science. Period.

    [Response: You are being quite unfair. Science has many routes to the truth. Ultimately, one needs to have models that proceed from basic physics, and if you look at Kyle’s voluminous work on geophysical fluid dynamics, you’ll see that he has plenty of that. Still, data analysis that attempts to identify cycles in data is a tried-and-true way to scare up suggestions of things to look for in the physical modelling. –raypierre]

  46. 146
    Mark says:

    Steve, 145, how do you test whether your story is correct WITHOUT trying to make it fit the data? And when it doesn’t fit the data, working out how to make it fit shows where other things may be working into the picture.

    E.g. if the graph is generally going up and there’s one peak (1998) and a trough (2007?) high up above the line and low down below it, would one way to work this problem out be to do something like this:

    What is the “shortfall”/”excess”?

    Now what happened at that time?

    Is that enough to cover the shortfall/excess?

    If it is, maybe you have the answer.

  47. 147
    Hank Roberts says:

    Ray, thanks for all the inline comments (and I hope people are going back and reading them).

    And thanks for the mention of Dr. Rickaby’s work.
    This paper for example describes changes in plankton over long climate cycles. This is wonderful stuff.
    http://dx.doi.org/10.1016/j.epsl.2006.10.016

  48. 148
    Colin says:

    What happens if we stretch this pause in global warming out to 2020, then look at the 30 years of real and predicted temperature data ending in 2020 (or 40 or 50 years)? Would that data provide a statistically significant warming trend?

    I know the preference is for much longer trends in temperature data (though I guess not 15,000 year long trends), but a lot of work I’ve read here talks about 30-50 year trends as being significant (e.g. the Antarctic Warming/Cooling debate).

    I’m sure what to make of the idea that we might,at some point in time, have statistically significant evidence of no warming over a reasonably long time frame.

  49. 149
    susan says:

    Chris Colose (if you’re still around):
    Thanks for the response. It appears I didn’t make myself clear. Perhaps I should have used my full name (Susan Anderson); I understand and agree with – if only through a glass darkly due to my educational deficiencies – the points you made. I was trying to say that even taking the false premises of the denialosphere into account, their argument falls down on the obvious. Visually, 1998 sticks out like a sore thumb. And despite some cool temps, there are plenty of hot ones, as well as extreme events. My point was that while I don’t give local weather much weight, in the aggregate even a short-term argument falls down if the viewpoint is slightly expanded to include the whole planet and ups as well as downs. I know that climate is most accurately understood in the context of longish intervals; that too is distorted by the false premisites by selectively using millions of years when it suits their purpose.

    This is not meant to distract from the more learned arguments made here, to which my comment is only a small footnote. I hope noone takes it amiss; I learn all the time.

    Propagandists’ assume the purpose of science is to proselytize because they do so and assume their limitations extend to those with whom they take issue.

  50. 150
    Radge Havers says:

    Ray Ladbury @ 123.

    I’m afraid that the lesson here is that reality isn’t as simple or as accommodating as people want it to be. And since science is about truth, the science has to reflect the truths that we cannot overconsume with impunity and that we are messing with a very complicated system on which our welfare depends. There’s a limit to how much we can dumb things down. Maybe it’s the public that needs to wise up.

    And yet, and yet I can’t help thinking there’s a way of saying exactly that, and saying it in a way that actually penetrates. There probably won’t be sufficient “wising up” until that message gets through. For starters, the sentences probably need to be less sophisticated, very pointed, and easily remembered and repeated. Not easy.

    And there is no doubt some cultural expectation (exemplified in Einstein’s quote: “If you can’t explain it simply, you don’t understand it well enough.”) that if the problem were really significant, the necessary explanations would already be made to all political bases. The problem is that you’d practically need a whole army of sophisticated popularizers working full time to cut through the currrent pandemic of message clutter.


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