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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.


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. 201
    Mark says:

    “But manacker’s trend is (so far) empirically observed.

    Comment by simon abingdon ”

    And max decries the IPCC reports and climate models as merely curve fitting.

    Where is his science?

    “He assumes nothing.”

    Yup, he certainly does THAT all right.

    And he isn’t extrapolating a trend. He’s drawing a line between two points and continuing the line. He’s not even fitting all the data, he’s fitting two points of the data.

  2. 202
    Mark says:

    “On what basis do you claim that warming will resume in 20 years?”

    Because the underlying forces have not changed.


    There was a man who fell from a high storey building. His descent was halted by an updraft and he was thrown through a window and survived. (he may have jumped, can’t remember).

    Yet if that window hadn’t been there, even though his descent was halted by an updraft, he would have resumed his plummet groundward.


    Because gravity still exists.

  3. 203
    Mark says:

    “and an absolute renewed refusal to recognise any changes in ice cover, ecology, ocean chemistry etc”

    Although their faith in these proxies are astounding when they can be stated to “disprove” AGW…

  4. 204
    pete best says:

    PETM (55 million years ago) is for some reason being related to todays climate change (CO2 emissions I am presuming) only it happened over 10,000 years then (relatively quick in geological terms I am presuming) with CO2 emission 70% then pre industrial cannot explain the entire warming which seems to be major news on this peer reviewed paper.

    Antatrica was not iced over during this time and other conditions may have been very different to today so it not being CO2 but something else seems to be giving the deniers ammunition against the GCM which seems silly and daft. James Hansen has already alluded to earth sensitivity being double originally thought but these scenarios are omitted from the IPCC 2007 FAR due to nt ebough being known about longer time feedbacks which may make up the difference and only paint a blacker picture for us?

  5. 205
    simon abingdon says:

    dhogaza (#199) and Mark (#203) Well, Mauna Loa CO2 increase looks linear to me, so we can extrapolate that pretty confidently. The rest: clouds, oceans, albedo etc is all noisy, so we’ll have to wait 30 years to see whether there really is cooling now or that the observed gentle warming trend has continued.

  6. 206

    Most of this won’t be news to regulars, but re the “pause” in warming, here’s what I wrote elsewhere this morning on the topic of “cooling since 1998”:

    As to the “it’s been cooling since 1998” hooha repeated several time on this thread, here is the list of the ten warmest years in the instrumental record (STR ’05 dataset) from warmest to coolest:


    Oh, and it’s a virtual certainty that this year will come in significantly warmer than last, which will mean that there will be no years prior to 1998 in the top ten list, since ’97 will be bumped to 11th. . .

    But perhaps you don’t trust surface thermometers? Well, how about the UAH satellite data, beloved by denialists because it always shows the lowest warming trend of any common metric? A while back I downloaded their data and averaged ’89-’98 and ’99-’08 separately:

    90s: .04367 C above baseline temp
    00s: .20025 C above baseline temp

    So the decadal average for the 00s was .15 C warmer than the 90’s. As I said earlier, love that “cooling”. . .

    Check my work if you like:

  7. 207
    Mark says:

    “PETM (55 million years ago) is for some reason being related to todays climate change (CO2 emissions I am presuming) ”

    The reason why it is being used is because it counters the “proof” against AGW of the 800 year lag.

    That “proof” is only true if CO2 is never the cause, only the result of warming.

    PETM shows that CO2 can precede warming, removing even the vaguest appearance of validity (which the argument of the cores never had anyway, since the heating AFTER CO2 would be caused BY that CO2 and therefore, unless you have a tachyonic CO2 molecule, would cause warming AFTER its increase).

    But when dealing with the morbidly credulous, you need to knock down even the vaguest appearance of relevance if that relevance doesn’t in reality exist.

  8. 208
    Mark says:

    “and that since atmospheric CO2 is steadily increasing, we should expect to see the slope of the warming trend steadily increasing too.”

    No more than the knowledge that gravity is a constant on the earth should mean that a feather will fall steadily if dropped…

  9. 209
    stevec says:

    pete, a high long term climate sensitivity would indicate that some significant portion of the warming of the last half of the 20th century would be from the long term climate sensitivity of the first half of the 20th century.

  10. 210
    Hank Roberts says:

    BobFJ, first look up the paper.
    Are you talking about this one?

    Klyashtorin L.B.1; Lyubushin A.A.2
    Energy & Environment
    Volume 14, Number 6, 1 November 2003 , pp. 773-782(10)

    Look it up; look for citing papers. Has anyone published anything relying on it?

  11. 211
    Mark says:

    “dhogaza (#199) and Mark (#203) Well, Mauna Loa CO2 increase looks linear to me, so we can extrapolate that pretty confidently. The rest: clouds, oceans, albedo etc is all noisy, so we’ll have to wait 30 years to see whether there really is cooling now or that the observed gentle warming trend has continued.

    Comment by simon abingdon”

    Why are you assuming that the only effect on temperature is CO2?

    Are YOU the one all the denialists are complaining about when they say that AGW is all about CO2 and ignoring anything else?

  12. 212
    manacker says:

    So far no one has wagered a (scientifically based and possibly even climate model supported) guess on when the current warming interruption will stop and warming will resume.

    My guess was simply based on the long-term trend line.

    The recorded fact is that the period 1910-1944 saw a linear warming of 0.53C (Hadley), 1944-1975 saw a very slight cooling and 1976-2000 (or 2005) saw warming of 0.37C (or 0.43C) (also Hadley). The warming has been interrupted, although the current years are still among the warmest recorded, as has been noted above.

    Prior to that, the short period right after modern measurements started showed a cooling trend (1850-1857). This was followed by a warming period from 1858 to around 1879, which was followed by a cooling trend from 1880-1909.

    And over the entire period with all the multi-decadal warming/cooling cycles there was an underlying warming trend of 0.041C per decade.

    Theories have been presented explaining these multi-decadal warming/cooling cycles with natural variation factors, and the long-term trend has been explained by a combination of natural and anthropogenic factors.

    The 19th century warming and cooling trends have not gotten much attention, as it is unlikely that human emissions played a major role here.

    The 1910-1944 warming trend has been studied, with the conclusion that the climate models were not able to fully explain this warming period.

    The 1944-1975 slight cooling period has been suggested to have been caused by human aerosol emissions that masked the warming from the rapidly increasing human CO2 emissions in the post-war boom years. Very little if any empirical data have been presented to support this rationalization, as far as I have seen, but maybe someone out there has seen something specific along these lines.

    The 1976-2000 (or 2005) period of rapid warming and increased atmospheric CO2 concentrations has gotten most of the attention. This is the period most often cited by IPCC.

    The question raised by stevec (209) is whether or not “some significant portion of the warming of the last half of the 20th century would be from the long term climate sensitivity of the first half of the 20th century” (i.e. early 20th century warming “still in the pipeline” until the late 20th century).

    An even more pertinent question now is:

    When is the warming going to resume, and, when it does, will it follow the long-term trend line or will it follow a new accelerated trend line driven by anthropogenic GHG emissions (primarily CO2) as estimated by the climate models cited by IPCC?


  13. 213
    Martin Vermeer says:

    Mike (response #200):

    The radiative forcing by CO2 is roughly logarithmic. That means that an exponential increase in CO2 leads to a roughly linear (i.e. constant) warming trend.

    Actually Mike, an exponential increase in the CO2 anomaly over pre-industrial (as we are seeing approximately) will lead to an accelerated forcing. Only when getting to 2x CO2 and beyond, will it gradually level off to linear.
    But in the regime discussed this is not yet relevant.

    [Response: True, I should have been more precise here. The typical approximate formula for the radiative forcing is F=-6.3 log (C/C0) where C is the actual Co2 concentration, and C0 is the value (roughly 300 ppm) at the turn of the 20th century. This represents the equilibrium warming, not the transient (observed) warming, which is an important distinction since the warming is not in equilibrium with the forcing on the timescales of decades of interest here. But this notwithstanding, lets consider the equilibrium warming (the warming that would eventually be realized in response to a given increase in CO2 concentrations). Due to the log dependence, the associated increase in radiative forcing (and consequently the ultimate realized warming) goes as the percent increase in CO2. Going from, say, 1968 to 2008 (a 40 year period), the increase in CO2 has been from roughly 322 ppm to 386 ppm, an increase of about 20%. If we continue on the so-called ‘business as usual’ trajectory, we will reach roughly double pre-industrial (280ppm) levels, i.e. somewhere in the range of 550 ppm, over the next 40 years. That represents an increase of roughly 42%, implying nearly twice as much co2-related warming for the increase in CO2 over the next 40 years as for the increase of the past 40 years (though in reality, this is very much complicated by the precise role that sulphate aerosols have played in the past, and will play in the future). On the other hand, if we were to slow the increase in such as way that we hold CO2 levels to 450 ppm by mid-century, then the % increase over the next 40 years would be 16.5%, and there would be slightly less ultimately realized warming than for the previous 40 year, i.e. the rate of warming would actually slow. Note however that the absolute change in CO2 concentrations in this scenario would be identical for both 40 year intervals! (64 ppm), demonstrating that the process is indeed not linear with increase in CO2, i.e. the logarithmic dependence really *does* matter here. -mike]

  14. 214
    Jim Galasyn says:

    Sidd, in 2001, Saltzman published a book that expands on the idea significantly:

    Dynamical Paleoclimatology: Generalized Theory of Global Climate Change

    Great stuff!

  15. 215
    manacker says:

    Doug Bostrom

    The topic here is the apparent interruption in global warming, when it will likely end and at what rate the warming is likely to resume, not “moon landings”. Get it?


  16. 216
    manacker says:

    Kevin McKinney

    Your analysis (206) of UAH temperature anomalies of the 90s vs. the 00s is interesting, and is no doubt correct.

    Another way of looking at it is the method preferred by IPCC: determine a linear trend line over the period measured.

    Doing it this way shows a linear cooling rate of around 0.1°C per decade on average over the 4 main records: (Hadley, GISS, UAH, RSS) from January 2001 to today (the 21st century, so far).

    How long this trend will continue is anyone’s guess, as is the warming rate that will ensue when the current warming interruption has ended.

    I believe that is in essence what we are all discussing here, starting with the lead article by Kyle Swanson.


  17. 217
    chris says:

    re #205

    dhogaza (#199) and Mark (#203) Well, Mauna Loa CO2 increase looks linear to me, so we can extrapolate that pretty confidently. The rest: clouds, oceans, albedo etc is all noisy, so we’ll have to wait 30 years to see whether there really is cooling now or that the observed gentle warming trend has continued.

    simon, “looks” ain’t the same as “is”! For example the average yearly increase in atmospheric CO2 concentrations during the decade 1990-1999 was around 1.59 ppm/yr (see Mauna Loa site urled below). During the 2000-2009 “nearly” decade, the average yearly increase in atmospheric CO2 is around 1.98 ppm/yr.

    So the increase in atmospheric CO2 isn’t linear whatever it may look like. It’s got a greater than linear increase. It’s likely that the greater than linear increase in atmospheric CO2 will continue for some time, since (a) there is no evidience that emissions will stop increasing during the foreseeable future, and (b) it becomes progressively more “difficult” for the oceans to absorb increasing amounts of CO2 as the surface layers tend towards saturation.

    So extrapolation based on a false presumption of linearity is dubious….

  18. 218
    Hank Roberts says:

    Sorry, Max, you’re doing the same thing again, ignoring the basics to make a statement that appears sensible.

    How long do you need to collect temperature data to say with statistical confidence that there is either an up or down trend, given the variability we know about?

  19. 219

    Well, my analysis–a somewhat pretentious word for a simple operation, I fear–was motivated by the fact that trend lines are very often abused by cherry-picking start and end dates.

    So comparing entire decades clarifies what the alleged “cooling” might mean for those (like me!) who are not particularly sophisticated in math/stats. Or so I hope, at least.

    With all due respect, I would say that the “trend since 2001” is statistically meaningless.

  20. 220
    Rod B says:

    Mike, I have to study it more but I found your explanation (213) of relative forcing helpful. One odd question: when did the log coefficient become 6.3 and what is the significance/meaning of the minus sign?

    [Response: Oops, not sure how those typos got in. The approximate formula for the forcing should be F=5.35 log (C/C0) and there is of course no negative sign! -mike]

    Thanks, Martin for opening the door.

  21. 221
    chris says:

    Re #191

    I would like to add that there is a big long-term experiment ongoing at CERN, that is checking out some initial work by Svensmark, indicating that the climate effects resulting from the sun’s activity are far more complicated than just the simple emission intensity of sunlight. For instance, the low sunspot activity during the “Maunder Minimum”, as mentioned by Alex may well have complex effects other than the purely thermal from sunlight.

    BobFJ, it’s not really a big experiment! The experiment involves filling a chamber with an atmosphere mix containing trace O3 and sulpher dioxide, using UV to convert sulpher dioxide into sulphuric acid and using a gamma ray source to induce nucleation particles that are detected with a particle detector.

    The “initial work” was an observation of a correlation between the solar cycle and low cloud cover (LCC) during solar cycle 22 using the ISCCP-IR product. This correlation starts to fail around the mid-1990’s and there isn’t really a correlation through cycle 23 to present. If the more reliable ISCCP-IR/vis product is used the correlation is poorer still. The idea, anyhow, is that the gamma rays (cosmic ray flux or CRF) result in atmospheric ionization which promotes cloud condensation nuclei (CCN) which nucleate low level clouds which “cool” the earth’s surface. Reduced CRF results in reduced nucleation of LCC with a warming forcing.

    Simples! However, while Svensmark has puffed this initial observation/hypothesis, writing a (dismal IMHO) book and publicising like mad with press releases and such like, it’s been left to a few other groups to address the empirical evidence for such a link (i.e. causal CRF – LCC link). This has been done in detail by two groups (see references below) who have independently come to the same conclusion – there isn’t a detectable causal relationship between the CRF and LCC, and any apparent correlation that might be occasionally apparent with the solar cycle is with the irradiance component of the solar cycle (rather than the CRF which varies in roughly (anti)-phase with the solar irradiance).

    That’s not to say that the solar – climate effects aren’t complex. However there isn’t really much evidence for the Svensmark hypothesis at all, although you wouldn’t know it from the relentless self-publicising from some quarters!

    Kristjánsson, J. E., A. Staple, J. Kristiansen, and E. Kaas, A new look at possible connections between solar activity, clouds and climate, Geophys. Res. Lett., 29(23), 2107, 10.1029/2002GL015646, 2002.

    Kristjansson JE, Kristiansen J, Kaas E (2004)
    Solar activity, cosmic rays, clouds and climate – an update
    Adv. Space Res. 34, 407-415.

    Kristjansson JE, Stjern CW, Stordal F, et al. (2008) Cosmic rays, cloud condensation nuclei and clouds – a reassessment using MODIS data Atmos. Chem. Phys. 8, 7373-7387.

    Sloan T, Wolfendale AW (2008) Testing the proposed causal link between cosmic rays and cloud cover Environ. Res. Lett. 3 art. # 024001

    A.D. Erlykin, T. Sloan, A.W. Wolfendale (2009) The search for cosmic ray effects on clouds J. Atmos. Solar Terrestr. Phys. 71, 955-958

    A.D. Erlykin, G. Gyalai, K. Kudela, T. Sloan, A.W. Wolfendale (2009) Some aspects of ionization and the cloud cover, cosmic ray correlation problem J. Atmos. Solar Terrestr. Phys. 71, 823-829

  22. 222
    stevec says:

    Actually Max when I hear the term “heat in the pipeline” I think of the short term climate sensitivity as affected by the lag from having to warm up the oceans while when I use the term long term climate sensitivity I think of such things as melting ice, trees growing further north, and the release of methane. Perhaps I have my terminology wrong but in my mind I seperate the issues in this manner and my comment was based on this understanding.

  23. 223

    NCDC data for June is out. GISS already told us it was the second-warmest ever. NCDC has the same ranking; what’s striking is that this is the warmest ever June for oceanic temps and also for SH temps.

    Say hello to El Nino. . . or “buenas dias,” if you prefer.

  24. 224
    co2isnotevil says:

    One of the problems with the radiative forcing model is that it applies to either differences in solar forcing or differences in GHG forcing. For example, the difference in the incident radiation from the Sun is about 80 W/m^2 between perihelion (Jan) and aphelion (Jun). At 20 W//^2 average

  25. 225

    #224, Kevin, The big piece of info from NCDC: ocean temps were warmest ever, beating 2005. My case is closed, Hadley Centre needs a revision of methods, there is no “pause”. Either from the sea, nor above land. Note: Present El-Nino had a weaker start than 1997 yet the GT is much warmer than June of 1997. Combined with my own measurements by other refraction means, I am totally convinced that the warming continues despite strong La-Nina episodes.

    In addition; Data from radiosondes, RATPAC were much warmer than MU UAH upper air measurements, telling indeed…

  26. 226
    simon abingdon says:

    Chris (#217) Lucky then that CO2 needs to be logarithmically increasing to have a linear effect on temperature.

  27. 227
    simon abingdon says:

    Mark (#211) “Why are you assuming that the only effect on temperature is CO2?” I’m not. (But the President of the United States seems to think it’s important).

  28. 228
    Doug Bostrom says:

    manacker 16 Jul 2009 at 11:52 am

    “The topic here is the apparent interruption in global warming, when it will likely end and at what rate the warming is likely to resume, not “moon landings”. Get it?”

    I appreciate or “get” that you’re naturally quite keen to maintain the persona you adopt when visiting sites such as this one, where your audience is reasonably well informed. Losing the hermetic nature of this persona and having attention called to your other manifestations will degrade your local credibility and thus harm whatever influence you hope to exert here.

    The problem you’ve created for yourself is th persona you adopted in, say, April of 2007, when you carpet bombed numerous less specialized blogs with the following dross, already stale when you repeated it:

    “Forget all the junk science by so-called experts that are all in on the multi-billion dollar ‘climate research scam’.”

    “Let’s hope things will get warmer, rather than colder. We don’t need another ice age.”

    “Forget all the self-righteous calls for action by power-hungry politicians.”

    I’m sure you’d prefer the history of a selective portion of your other writings to be forgotten, here at least, but that history part-and-parcel of what you’re up to here. It’s necessarily involved in judging what you write, something referred to in jurisprudence as “caput”, the whole person. You’ve created a personal history for yourself in one place that is entirely at variance with what you’ve made elsewhere. Yet the two histories you’ve made are linked where you stand now.

    You’re a person who is clearly able to competently express himself with the written word; I’m sure it was no accident when you wrote:

    ‘The politicians and bureaucrats love the idea of “carbon taxes”, higher taxes on fossil fuels, “carbon footprint offset” schemes, etc., because it gives them more money to spread around (and more power).’

    You’ve also demonstrated your ability to make facile use of publications to bolster an argument. So I’m sure that if you have a source document for the assertion I’ve just quoted, you’ll display it here. Just so for:

    ‘It’s [man made climate change research] driven by an estimated 2.5 to 4 billion dollars per year in climate research grants, with the grants going selectively to those scientists who make the most disastrous predictions.’

    Can you say where the evidence is on which you base that claim? It’s rather important, for what you’re saying by extension is that the proprietors of this site are money-grubbing cynics.

  29. 229
    simon abingdon says:

    Kevin McKinney (#206) Why all the numbers? We all know it’s generally warming. Science is trying to find out why. (And how much of a contribution we might be making).

  30. 230
    David B. Benson says:

    Also despite prolonged solar minimum.

  31. 231
    RichardC says:

    192 gp2 says, “It’s just 1 month…but el nino condition are at the begin and NCDC ocean anomaly for june is already the highest of the time series:”

    But UAH says June has a ZERO anomaly. Anybody have an explanation for the difference?

  32. 232
    BobFJ says:

    Chris #221,
    Concerning the CLOUD experiment at CERN, you wrote in part:

    “…BobFJ, it’s not really a big experiment! The experiment involves filling a chamber with an atmosphere mix containing trace O3 and sulpher dioxide, using UV to convert sulpher dioxide into sulphuric acid and using a gamma ray source to induce nucleation particles that are detected with a particle detector…”

    Here is part of a CERN release, dating I think from 2006

    The CLOUD experiment involves an interdisciplinary team of scientists from 18 institutes in 9 countries, comprised of atmospheric physicists, solar physicists, and cosmic-ray and particle physicists. The PS provides an artificial source of ‘cosmic rays’ that simulates natural conditions as closely as possible. A beam of particles is sent into a reaction chamber and its effects on aerosol production are recorded and analysed.
    The initial stage of the experiment uses a prototype detector, but the full CLOUD experiment will include an advanced cloud chamber and a reactor chamber, equipped with a wide range of external instrumentation to monitor and analyse their contents. The temperature and pressure conditions anywhere in the atmosphere can be re-created within the chambers, and all experimental conditions can be controlled and measured, including the ‘cosmic ray’ intensity and the contents of the chambers.

    Since then, the experiment has advanced through various stages, and facilities, and is now called CLOUD-09. Here is an extract (page 43 of 44) from “CERN Colloquium, 4 June 2009” Lots of info there!

    CLOUD plans
    • 2009:
    * commission CLOUD-09
    * study H2SO4-H2O nucleation with and without beam
    * reproducibility of nucleation events
    * PTR-Mass Spect. to measure organics at 10 pptv level
    * new ion-TOF Mass Spect. for ion characterisation
    • 2010:
    * commission thermal system (-90C → +100C)
    * study H2SO4/water + volatile organic compounds with
    and without beam
    * temperature dependence (effect of altitude)
    • 2011-2013:
    * extend studies to other trace vapours, and to cloud
    droplets & ice particles (adiabatic expansions in chamber)

    You also wrote:

    That’s not to say that the solar – climate effects aren’t complex. However there isn’t really much evidence for the Svensmark hypothesis at all, although you wouldn’t know it from the relentless self-publicising from some quarters!

    Well maybe this 7-year experiment will find the evidence to support the hypothesis?

  33. 233
    dhogaza says:

    But UAH says June has a ZERO anomaly. Anybody have an explanation for the difference?

    Remember that they use a different baseline, for one thing.

    But they also have a history of showing a drop in their computation of anomaly every summer.

    It’s not known why, but if you look at the graphs in the article I link, you can see it’s extreme compared to GISS, HADCrut and RSS.

  34. 234
    Alex Harvey says:

    chris @ #132 14 Jul 2009 at 9:32 am:

    That’s not really correct Alex.

    Well, what you’ve written sounds very plausible; I had a look at Moberg. But after a while I realised that, hangon, it is correct what I wrote; I’ve seen Ray Pierrehumbert himself say so here at RealClimate in a discussion with Nir Shaviv that, yes, the little ice age really is still a bit of a mystery.

    This was Ray Pierrehumbert (20 May 2006 @ 1:21 am, ‘Thank you for emitting’ comments thread) in a discussion with Nir Shaviv:

    Nir, there is nothing wrong with thinking about possible impacts of cosmic rays on climate. Who knows, someday, something might come of it. We sure could use some new ideas about the Little Ice Age, since it’s hard to do that with straight solar effects, even allowing for ozone feedbacks and spectral variations.

    Now I’m sorry but says what it says: we haven’t explained the little ice age yet. And it is a fact (no?) that the temperatures really did fall over a number of centuries to correspond in some completely mysterious way with the Maunder Minimum (who knows, maybe it’s just a coincidence?). But surely, if it took a long time for the temperatures to fall, and we don’t know why, who can believe that without the human impact of CO2, they would have just popped back to where they were previously one morning?

    Finally, the main point I raised hasn’t been touched really by anyone.

    Alex De Visscher said #110 14 Jul 2009 at 12:13 am

    The choice of 1979-1997 might not have been intended as cherry-picking, but it is unfortunate choice nonetheless.

    I agree, it’s a most unfortunate choice because that’s the period in the last 150 years where the gradient of the temperature increase has been steepest. Yet this entire global warming debate is precisely about establishing true gradient of the underlying GHG signal. Some have argued (e.g. Douglass, Lindzen) that the gradient of the underlying GHG signal is quite low. Most argue that it is much steeper. I don’t think anyone has argued that its true steepness is coincident with that of the steepest increase of all, viz. 1976-1998.

    Meanwhile, the ‘steepness’ of the underlying GHG signal has been largely established by computer model runs that made assumptions about the radiative properties of aerosols (e.g. Kiehl 2007). The Tsonis & Swanson theory, if true, would suggest that the cooling of the 1970s had little to do with aerosols, and would invalidate those model runs that showed that the models can reproduce the 20th century surface temperature record. None of those models assumed a Swanson & Tsonis theory of synchronisation of multidecadal ocean cycles to explain the the cooling of the 1970s. Rather, they all assumed radiative properties of aerosols to explain this. Thus, this theory would render all of those runs as invalid, and would call into question again the strength of the water vapour feedback, and the true value of climate sensitivity to CO2.


    *Reference: Kiehl, J. T. (2007), Twentieth century climate model response and climate sensitivity, Geophys. Res. Lett., 34, L22710, doi:10.1029/2007GL031383.

  35. 235
    Richard Steckis says:

    Kevin McKinney says:

    “With all due respect, I would say that the “trend since 2001″ is statistically meaningless”

    No. The trend from 2001 is not statistically meaningless. GISS surface data shows a change from a statistically significant warming trend to 2000 and then a reduction to a statistically insignificant warming from 2001 (Using a Generalised Linear Model). For the lower troposhperic data from satellites the trend becomes a statistically significant decline (p<=0.01).

  36. 236
    RichardC says:

    233 dhogza says, “Remember that they use a different baseline, for one thing.”

    Yes, though slope isn’t so relevant when one value is 0 and the other is 1.

    Thank you for the article. It was exactly what I needed. The 0 has significant flaws.

  37. 237

    Simon, if you look at some of the posts above, I think you’ll see that perhaps not all of us do think it is warming. (And others of us know folks who don’t think so–in fact #12 above asks for talking points.)

    I think evidence of a “pause” in warming is still pretty thin, personally. Evidently, Richard Steckis (7/16, 8:23 PM) disagrees.

    Richard, how did you pick the inflection point of 2001?

    You know quite well that a “trend” of eight years duration in a signal this noisy is–well, bubkes, to go back a couple of posts. Or “well within the expected variability,” if you prefer–despite Dr. Swanson’s caution in invoking that term

  38. 238

    223, Dhogaza–The discrepancy between trop & surface isn’t just UAH, though the annual cycle in UAH you note exacerbates it. It’s pretty marked in RSS, too–June was hugging the median of the data, which just dramatizes how paltry the .08 anomaly is.

    The surface/trop discrepancy is not new in June, either–we saw the same pattern, albeit a bit less markedly, in May. It’s a puzzle, to me at least. Why would the troposphere cool as the surface warms?

  39. 239

    I guess I should have noted that what Wayne says is true–the RATPAC data shows a considerably higher anomaly for the mid-trop; I don’t know what to make of that, either.

    (I should probably also clarify that my previous comment was talking about low trop–some of the previous comments referred to mid-trop, so “confusion alert!”)

  40. 240
    tamino says:

    Re: #234 (Alex Harvey)

    Referring to the period 1979-1997, you state:

    I agree, it’s a most unfortunate choice because that’s the period in the last 150 years where the gradient of the temperature increase has been steepest

    This is not correct. There are equally long periods both before and after with considerably higher warming rate. In fact the period 1979-1997 shows one of the lowest warming rates in the modern (post-1975) GISS record; see this.

    Re: #235 (Richard Steckis)

    GISS surface data shows a change from a statistically significant warming trend to 2000 and then a reduction to a statistically insignificant warming from 2001

    Of course the trend since 2001 isn’t statistically significant; if you make the time span short enough statistical significance always disappears. Your statement is meaningless.

    For the lower troposhperic data from satellites the trend becomes a statistically significant decline (p<=0.01).

    No, it doesn’t, neither for RSS nor for UAH data.

  41. 241
    Hank Roberts says:
    “… 0.15C/decade is a more reasonable estimate of the forced trend, there is no evidence for any major change in this post 1998 and I don’t expect to see any such major change….”

  42. 242
    dhogaza says:

    Now I’m sorry but says what it says: we haven’t explained the little ice age yet.

    You do realize, of course, that the comment was made in the context that Real Science doesn’t show a *global* LIA, and he’s talking about our not being able to fully explain the regional LIA that actually doesn’t impact the long-term global record to the degree touted by denialists.

    Right? You understood that, right? Please don’t disillusion me by making it clear that I’m overestimating you.

  43. 243
    dhogaza says:

    Yes, though slope isn’t so relevant when one value is 0 and the other is 1.

    If that bothers you, use Kelvin. Earth ain’t been at 0K ever.

  44. 244
    dhogaza says:

    The trend from 2001 is not statistically meaningless… a reduction to a statistically insignificant warming from 2001

    I see. So statistically insignificant is now statistically significant?


  45. 245
    Alex Harvey says:

    Tamino #240:

    Thank you for the clarification and the article at your blog.

    Do you know if there is a publicly available comparison of all 20 year trends in the 150 temperature record, i.e. 1850-1890, 1851-1891, … 1988-2008?

    I am sure that in some of these 20 year trends we’ve seen periods of cooling (again I am not a scientist but it seems quite obvious just from eye-balling the charts).

    Thus the point would still remain — 20 years is a very short trend. A 20 year period has been chosen that shows warming. If other periods show less warming, or even cooling, how can this particular period not be cherry-picked?

  46. 246
    Laws of Nature says:

    Hi there,
    If Swanson’s hypotised 1997/8 step change is true, figure 1 shows, that the model trend’s are way off (the only fit the measured temperature in the short interval around the jump)
    The “non-cherry picking trend” is about about half the 2K/century.
    Ironically the flat red line might also be wrong, since it seems we are getting another El Nino-jump this year.
    That would mean 2 out of 3 wrong, where the one correcct is the measurement and the two others are the predictions . .
    All the best regards,

  47. 247

    First, I apologize for not reading the thread, I’m pressed for time this week. I just wanted to throw my two cents in and hope it has some relevance.

    While state changes in complex systems can happen, one must consider the capacity of forcing and smaller scale feedbacks. However the overriding forcing (parent system) has greater capacity to bias internal forcing (short term sub system bias).

    If the overall climate system was in or near a neutral state, decadal variations such as oceanic and solar would have greater capacity to influence a state change on a more significant scale (especially when combined).

    Since the current parent climate forcing is positive, not negative, the parent system can reasonably be expected to override the sub system variations (even when combined, though that is the question at hand – is it or isn’t it?).

    The main question is can, or does, the sub system variations combined have the capacity to override the parent system forcing on a decadal time scale and in a meaningful manner?

    I would tend to believe that it can, but that the parent system forcing of course would win in the end.

    The main question here is are enough of the internal systems considered and are they considered in a meaningful manner to yield reasonable results in the expectations?

    Examining these internal (sub-system forcings) will likely yield better understanding of the state change capacity and increase predictability of influence. This, in my mind, is a bridge of understanding that enables better predictability of climate forcing as it approaches the area of weather (shorter than 30 years), and is a good step towards understanding the major internal systems on decadal scales.

    From a general systems view the sub systems, such as short term ocean and solar, can trigger a state change under certain conditions, unless other sub systems or the parent system override. Arctic exposure combined with solar increase in the next 6 to seven years may have a significant impact on preventing a cooling period lasting till 2020. That combined with the parent system positive forcing bias will likely rule the impacts, in my opinion. Dark ocean in the Arctic increasingly exposed can have a pretty strong effect enhancing the Arctic amplification.

    Will be interesting to learn more about the combined subsystem bias and affects on forcing on these shorter time scales.

    If all this has been discussed I apologize. Will try to catch up soon.

    #235 Richard Steckis

    For perspective on 10 years of warming/cooling take a look at:

  48. 248
    BobFJ says:

    Hank Roberts, Reur 210:

    If you were to read my 183 with more care, you should be able to see that the core of my post was that the current “pause” in warming is remarkably similar to that which occurred around 1940. I notice that you make no comment, (do not disagree), with this observation. Instead you chose to denigrate the K & L 2003 paper that I secondarily put-up as what I know as the earliest reference to an apparent ~60 year cycle, which, by strange fortune they forecasted rather well, from back in 2003, what we are seeing right now .
    OK; let’s do a deal! Forget the L & K 2003 paper and just study the first figure that I posted in 183. If you don’t understand it then try this mark-up of Hadcrut through 2007, that I did for discussion elsewhere, a year ago. Some of it is OT for this issue, but please read the notes highlighted by the green boxes.
    It would be a stronger presentation if updated for the relatively cold year of 2008, but hopefully you will get the idea.
    Regardless of the deal I propose; to ignore K & T, and just let the core issue I raised stand on its own, I concede that the K & T 2003 paper that I cited on the second figure in my 183 is hardly going to set the world on fire. One difficulty with it is that they show a nice clean major sine wave 62-year cycle which can never be proven, partly because of lesser cycles such as PDO superimposed on it. However, that is not to say that their conceptual observation is invalid, (cause unknown), although the fact is that it fits rather well to the current “pause” in warming, and also to that of around 1940. Furthermore, their forecast, fitting what we see today, was made back in 2003 and thus has not been contradicted.


  49. 249
    Ben Kalafut says:

    “I see. So statistically insignificant is now statistically significant?


    If we’re going to be raw empiricists about this, which I very much hate:

    It’s what we call a “changepoint”, where the data go from being well described by one (statistical, not physical) model to another. What would be interesting, and I don’t have time for it tonight, would be to compare one-changepoint to no-changepoint models here. A good starter no changepoint (statistical) model would be ordinarly linear regression for the whole set, and a good one changepoint model would be ordinary linear regression for part of it and a flat line for another part; compare the two using Schwarz Information Criterion or Akaike Information Criterion.

    Yes, I know that the ordinary least squares linear regression is not the correct method for these data, as the noise is probably autoregressive, but this is a ‘blog post. And I don’t really know how to do changepoint analysis using nonparametric methods (e.g. Spearman ranks correlation).

  50. 250
    Mark says:

    “Mark (#211) “Why are you assuming that the only effect on temperature is CO2?” I’m not. (But the President of the United States seems to think it’s important).

    Comment by simon abingdon ”

    No, it is you.

    You stated that a question that is only relevant if you believe CO2 is the only component.

    NOTE: when it comes to mitigation, we can’t all go paddling out in the ocean to unto an El Nino event. Nor can we create sunspots.

    But what we CAN do is stop adding CO2.

    Hence when it comes to MITIGATION, CO2 is the biggest and best item to modify.

    But please tell us where mitigation of temperature change is temperature change.

    The gymnastics in logic to do so should be entertaining…