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Climate Hustle

How we know global warming is still happening

Posted on 28 September 2009 by John Cook

Skeptics proclaim that global warming stopped in 1998. That we're now experiencing global cooling. However, these arguments overlook one simple physical reality - the land and atmosphere are only one small fraction of the Earth's climate (albeit the part we inhabit). Global warming is by definition global. The entire planet is accumulating heat due to an energy imbalance. The atmosphere is warming. Oceans are accumulating energy. Land absorbs energy and ice absorbs heat to melt. To get the full picture on global warming, you need to view the Earth's entire heat content.

This analysis is performed in An observationally based energy balance for the Earth since 1950 (Murphy 2009) which adds up heat content from the ocean, atmosphere, land and ice. To calculate the Earth's total heat content, the authors used data of ocean heat content from the upper 700 metres. They included heat content from deeper waters down to 3000 metres depth. They computed atmospheric heat content using the surface temperature record and the heat capacity of the troposphere. Land and ice heat content (eg - the energy required to melt ice) were also included.


Figure 1: Total Earth Heat Content from 1950 (Murphy 2009). Ocean data taken from Domingues et al 2008.

A look at the Earth's total heat content clearly shows global warming has continued past 1998. So why do surface temperature records show 1998 as the hottest year on record? Figure 1 shows the heat capacity of the land and atmosphere are small compared to the ocean (the tiny brown sliver of "land + atmosphere" also includes the heat absorbed to melt ice). Hence, relatively small exchanges of heat between the atmosphere and ocean can cause significant changes in surface temperature.

In 1998, an abnormally strong El Nino caused heat transfer from the Pacific Ocean to the atmosphere. Consequently, we experienced above average surface temperatures. Conversely, the last few years have seen moderate La Nina conditions which had a cooling effect on global temperatures. And the last few months have swung back to warmer El Nino conditions. This has coincided with the warmest June-August sea surface temperatures on record. This internal variation where heat is shuffled around our climate is the reason why surface temperature is such a noisy signal.

Figure 1 also underscores just how much global warming the planet is experiencing. Since 1970, the Earth's heat content has been rising at a rate of 6 x 1021 Joules per year. In more meaningful terms, the planet has been accumulating energy at a rate of 190,260 GigaWatts. Considering a typical nuclear power plant has an output of 1 GigaWatt, imagine 190,000 nuclear power plants pouring their energy output directly into our oceans.

Figure 1 only goes as far as 2003 as the ocean heat data used (Domingues 2008) only goes that far. What has global warming been doing since then? Since 2003, ocean heat data has been measured by the newly deployed Argo network. However, there have been teething problems with the Argo buoys experiencing pressure sensor issues that impose a cooling bias on the data. Consequently there have been several data analyses on ocean heat since 2003. One reconstruction of ocean heat show  cooling since 2003 (Willis 2008). Other analyses of the Argo data show ocean warming (Levitus 2009, Leuliette 2009, Cazenave 2009).

How do we determine which analyses are more accurate? Ocean heat data can also be independently determined through other empirical means. Cazenave 2009 uses satellite gravity measurements to create two independent estimates of ocean heat - both find warming. Sea level has been inexorably rising since 2003. As a large portion of sea level rise is due to thermal expansion from ocean warming, this is an indirect confirmation of warming.

Lastly, the planet's energy imbalance is confirmed by satellite measurements of incoming and outgoing radiation. Earth's Global Energy Budget (Trenberth 2009) examines satellite measurements for the Mar 2000 to May 2004 period and finds the planet is accumulating energy at a rate of 0.9 ± 0.15 W m?2. This is consistent with the amount of heat accumulating in the ocean. Preliminary analysis on the latest CERES satellite data shows an increasing energy imbalance from 2004 to the end of 2008 (although this data is yet to be published, more on this later).

So the point to remember when considering short term cooling trends in surface temperature records is that the atmosphere is only one small part of a planet which is in energy imbalance. Empirical measurements show the planet continues to accumulate heat. More energy is coming in than is radiating back out to space. Global warming continued past 1998 and is still happening.

Acknowledgements: Many thanks to Dan Murphy for graciously sharing his heat content data and John Cross for his comments and advice.

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Comments 51 to 84 out of 84:

  1. RSVP, in addition to the known multiple forcings in addition to CO2, the positive feedbacks are strong contributors. The temperature rise is a consequence of all of that, not just CO2.
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  2. What follows is an excerpt from an article found here

    http://physicsworld.com/cws/article/print/17402

    "The spectroscopic data that are required to model long-wave atmospheric absorptions are generally well characterized. When these data are put into atmospheric models, water turns out to be responsible for about 60% of the greenhouse effect, while the much-reviled carbon-dioxide molecule accounts for just 26%. Ozone accounts for 8%, and methane and nitrous oxide - the atmospheric concentrations of which have been increased by human activity - contribute a further 8% to the greenhouse effect. "

    The article goes on to say that the warmer the Earth gets, the more water vapor and therefore the more clouds that shield incoming Sun. Probably that is why we are still here to talk about this.
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  3. And whence do you infer that this is not well known of climate science, inappropriately modeled and inconsistent with observations?

    The water vapor/clouds feedback is a matter of much debate and, in any case, still a feedback from warming triggered by increased GH effect. Furthermore, increased cloudiness at higher temperature would seem to require a lowered relative humidity and I'm not sure whether we're seeing that. Models appear to argue against it.

    One fellow skeptic recently trumpeted the Trenberth and Fasullo paper suggesting that cloud feedback might actually be much lower than previously modeled, leading to a lot of extra warming from increased solar irradiance reaching the surface. For all the hooplah demonstrated by that fellow skeptic, it's worth pointing that the HADCRU model is in fact fairly close to Trenberth'runs, and HADCRU long term prognostic is not that different from GISS.

    It is also worth reminding that the decreased cloudiness of Trenberth' model runs was still a feedback of increased GH warming. Much a do about nothing.
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  4. It is not a given that there are more clouds in a generally warmer environment. Cloud formation depends very much on relative humidity and also the availability of lift within the atmosphere, warm moist air must rise and cool to near it's dew point. A product of all climate simulations is a near constant relative humidity as the climate warms.

    Look at the tropics and near tropics today. Most cloud formation is convective in nature and where this is the result of daytime heating the clouds dissipate at night. The tropics receive the vast majority of solar radiation but cloudiness does not prevent that region from being the warmest on Earth. If the climate zones and jet streams are shifted poleward in a warming world why would the dynamics be any different in their displaced positions?
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  5. It is curious that "science" promotes the idea of evolution, and yet scientist are wishing to stop it. A changing environment leads to natural selection which implies no control. Is Darwin in charge or not?
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  6. We're talking about promoting evolution among not only animals, but also the current Human population here. All through a weird, uncontrolled experiment. Can't see how that would be a good idea, but it's just me.

    Science does not promote ideas like marketing people promote products. It attempts to understand the world. Nobody is in charge. Not Darwin, not Einstein, not Bohr, not Schroedinger. There is nobody "in charge", only people trying to understand. Looking at it any other way indicates, IMO, a profound misunderstanding of science.
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  7. I was being facetious, however now that you made these remarks, there seem to be two issues here. The idea of science as simply a method for providing useful conceptual models, and science, this thing that has promoted global destruction. Most of what we call science has brought on the global warming via modern medicine (ie resulting in population explosion), and the industrial revolution (resulting in population explosion).

    There is a word that is very rarely used these days. The word is called RESPONSIBILITY. Science can take us anywhere, good or bad. As you imply, it is indifferent, but scientists are people, and people should not be indifferent. So next time you are doing science, try to THINK about what you are really doing.
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  8. WeatherRusty:"It is not a given that there are more clouds in a generally warmer environment. Cloud formation depends very much on relative humidity and also the availability of lift within the atmosphere, warm moist air must rise and cool to near it's dew point. A product of all climate simulations is a near constant relative humidity as the climate warms.

    Look at the tropics and near tropics today. Most cloud formation is convective in nature and where this is the result of daytime heating the clouds dissipate at night. The tropics receive the vast majority of solar radiation but cloudiness does not prevent that region from being the warmest on Earth. If the climate zones and jet streams are shifted poleward in a warming world why would the dynamics be any different in their displaced positions?"

    Cloud formation depends on RH, but also on the specific humidity. The more water in air, the thicker and deeper will be the clouds that form *once that air cools sufficiently*. There will be more water condensed out of air cooling from 16C to 15C (when everything else is equal) than air cooling from 15C to 14C. If everything else were really equal, then this should lead to correspondingly higher amount of clouds.

    The fact that clouds form quickly and easily in the tropics doesn't prevent them form being the hottest place on Earth(on average), but it does help prevent them from getting as hot as land at the same latitude (during the day).

    Further, it is not a given that RH is, in fact, a constant either.

    Cheers, :)
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  9. shawnhet,

    "Cloud formation depends on RH, but also on the specific humidity. The more water in air, the thicker and deeper will be the clouds that form *once that air cools sufficiently*. There will be more water condensed out of air cooling from 16C to 15C (when everything else is equal) than air cooling from 15C to 14C.
    If everything else were really equal, then this should lead to correspondingly higher amount of clouds."

    Why is that? At a given specific humidity the relative humidity will depend upon the saturation vapor pressure and that in turn is dependent on temperature. The higher the temperature the greater the saturation vapor pressure and lower the RH at a given specific humidity. The GCM's indicate that as global average temperature rises so does specific humidity in such a way that RH remains nearly constant (Clausius-Clapeyron relation) or maybe a bit lower. The tendency to form clouds begins at around 70% RH no matter the temperature or specific humidity.

    You are correct that more water can potentially be condensed out at higher specific humidities where clouds do form, but this relates to precipitable water within the column of atmosphere (because the water load is greater), not necessarily to the tendency for cloud formation.
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  10. Re #58 Shawnet.

    The evidence supports the expectation from basic physics encapsulated in models that the atmosphere retains a roughly constant relative humidity as it warms [*]

    Also, the evidence indicates that a warming world doesn’t mean more clouds; in fact observational evidence from the Pacific indicates that cloud cover may decrease in a warming world. That’s the conclusion from a study just published in Science [**]

    [*] Dessler, A. E. et al. (2008), Water-vapor climate feedback inferred from climate fluctuations, 2003–2008 Geophys. Res. Lett., 35, L20704

    Abstract: Between 2003 and 2008, the global-average surface temperature of the Earth varied by 0.6°C. We analyze here the response of tropospheric water vapor to these variations. Height-resolved measurements of specific humidity (q) and relative humidity (RH) are obtained from NASA's satellite-borne Atmospheric Infrared Sounder (AIRS). Over most of the troposphere, q increased with increasing global-average surface temperature, although some regions showed the opposite response. RH increased in some regions and decreased in others, with the global average remaining nearly constant at most altitudes. The water-vapor feedback implied by these observations is strongly positive, with an average magnitude of λ q = 2.04 W/m2/K, similar to that simulated by climate models. The magnitude is similar to that obtained if the atmosphere maintained constant RH everywhere.

    [**] A. C. Clement et al. (2009) Observational and Model Evidence for Positive Low-Level Cloud Feedback Science 325, 460 – 464.

    Abstract: Feedbacks involving low-level clouds remain a primary cause of uncertainty in global climate model projections. This issue was addressed by examining changes in low-level clouds over the Northeast Pacific in observations and climate models. Decadal fluctuations were identified in multiple, independent cloud data sets, and changes in cloud cover appeared to be linked to changes in both local temperature structure and large-scale circulation. This observational analysis further indicated that clouds act as a positive feedback in this region on decadal time scales. The observed relationships between cloud cover and regional meteorological conditions provide a more complete way of testing the realism of the cloud simulation in current-generation climate models. The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback.
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  11. WeatherRusty, I'm confused. Don't you agree that condensing water is a primary constituent of clouds? Doesn't it follow then, that more condensing water makes it easier for clouds to become larger and thicker? Aren't the clouds in the tropics thicker and deeper than clouds in other parts of the world? OTOH, to require that there is positive cloud feedback requires that it becomes *harder* to condense sufficient moisture out of the air to form a cloud of size X as that air becomes more moist.

    Chris, THanks for the CLement paper, I'll take a look at it.

    Cheers, :)
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  12. shawnhet,

    Convective cloud formation is a function of humidity, atmospheric instability and uplift. In short, humid air must be forced to rise and continue to rise and cool under unstable atmospheric conditions. These conditions reach to high altitude in the tropics because the warm, expanded troposphere extends to greater height allowing convection to reach to 50-60 thousand feet before encountering the capping stability of the stratosphere.

    This is all about buoyancy and laps rate, the actual temperature doesn't matter much, other than warm air can support a greater water content or mixing ratio and and thus more energy in the form of latent heat.

    You can learn a lot from the following cite:

    http://www.theweatherprediction.com/habyhints/114/
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  13. Regarding Fig. 1, what's the deal with it going to and below zero prior to 1950? It looks kind of as if it is trying to show that there was zero total heat content prior to 1950. Obviously I'm missing something here, can anyone explain?
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  14. bit_pattern, the figure illustrates the change in heat content relative to 1950, not the absolute amount.
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  15. WeatherRusty, I'm not sure what our disagreement is(if any) anymore. Your link appears to agree with my POV that higher levels of specific humidity are associated with higher(sustained) levels of precipitation.

    For instance"(1) No amount of rising air will produce precipitation unless moisture is present. The more **moisture that is present, the higher the potential for precipitation if uplift mechanisms are in place**."

    If atmospheric instability and uplift remain constant and the amount of specific humidity rises, we should expect more cloud formation.

    Cheers, :)
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  16. Shawnhet, you won't see more cloud formation if the temperature/dew-point spread is unchanged, as will likely be the case if relative humidity is conserved. If relative humidity decreases, you'll see less cloud formation, regardless of the absolute humidity.

    And you seem to assume that, as warmer air (i.e. containing a higher absolute humidity) will reach the dew point, all of its moisture content will condense and precipitate. I seriously doubt that it is that simple.

    This hypothesis (which you do not substantiate with science papers) is also very much in contradiction with references you provided on vegetal NPP, especially what has been observed over the Amazon basin: more sun exposure, due to lower cloud cover. Choose which hypothesis you want to defend, but keep in mind that the Amazon drying is based on empirical obervations.
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  17. Philippe, if the temperature dew point spread is unchanged and air cools the same amount (in degrees C) from a warmer maximum, then it will condense more water based on the Clausius-Clapeyron relationship(which is the basis of the assumption of constant RH). More water condensing should lead to more cloud IMO.

    This idea is not in contradiction with the other papers I have posted IMO, for the simple reason that it is hightly likely that other things than the **feedback** process I outline above influence cloudiness(on regional and global scales). This is really no different from allowing that we can have a period of cooler(or falt temperature) years, even while ever stronger CO2 feedback is (supposed to be) heating the climate. Something besides the feedback I have mentioned, may be forcing the clouds and, hence, obscuring the feedback signal.

    As for substantiation, I don't think it is at all difficult to find people supporting the idea that cloud feedback is negative. ROy Spencer is one prominent example. I suppose I can find a specific paper. IAC, RSVP quoted a paper above(which I haven't read yet) and I have just been laying out what I presume to be the theoretical underpinnings of their conclusion(I haven't read the paper yet).

    Cheers, :)
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  18. The physicsworld.comn piece referenced by RSVP is not a research article but rather an opinion piece. Besides reminders that water vapor is the chief GH gas and CO2 the chief cause of recent increased GH effect, it considers water vapor feedback. It postulates that, with increased cloud cover, the WV feedback may not be as strong as current models show.

    However, let's not forget the information provided by your fellow skeptic Robbo. Both the Clements paper and the Trenberth and Fasullo paper that he trumpeted with great fanfare suggest decreased lower cloud cover as a feedback to enhanced GH effect. Your own reference to increased NPP in the Amazon due to increased insolation seems to agree.

    As I said, it may not be all that simple.
    Cheers.
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  19. Yes, Philippe I agree that **if** on assumes that all changes in overall cloudiness are a result of a feedback on temperature change, then recent history would tend to argue for positive cloud feedback. However, there is no reason that all recent changes in clouds are a result of feedbacks on temperature(and this seems unlikely).

    There are, OTOH, some pretty good basic physical reasons for assuming that cloud cover will increase or at least stay the same in a warming climate(more condensing water available to form clouds).

    Cheers, :)
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  20. The "unlikely" part is entirely your opinion. Scientists studying the question, such as Trenberth and Fasullo don't find it so unlikely. The only physical reason to expect increased nebulosity is a constant relative humidity and even that is not entirely certain. If relative humidity shows a slight decrease, who knows?
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  21. I don't think it is accurate to say I am the only one who thinks it unlikely that all changes in cloudiness in recent years are a product of feedback from teperature changes. You can try a Google search of Earthshine and albedo if you like.

    Cheers, :)
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  22. Even if cloud amount is sensitive to other factors other than temperature variation, what is the point? What matters is if cloud amount is sensitive to a warming climate or changes in temperature since that is the factor humans are altering.

    Are there studies linking long term changes in cloud amount, both high and low cloudiness, to the warming trend of the past century? If GCR's impact on low cloud amount, we can do nothing about it. If we stick to the physics we know, there is no reason to expect a change in average relative humidity and there are already more than enough nucleation particles in the atmosphere upon which to condense water vapor to form clouds.

    If low cloud amount does increase due to a warmer more moist atmosphere so will the greenhouse effect of water vapor be increased. The increased water vapor must be in place first, so at best increased low cloudiness can reduce warming not negate it.
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  23. WeatherRusty:"If low cloud amount does increase due to a warmer more moist atmosphere so will the greenhouse effect of water vapor be increased. The increased water vapor must be in place first, so at best increased low cloudiness can reduce warming not negate it."

    The point is how much warming will we end up with? If cloud feedback canceled out other forms of feedback we might end up with only ~0.5C of anthropogenic warming over the next century, OTOH, if cloud feedback is strongly positive, then we might end up with as much as 2C in the next century.

    Cheers, :)
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  24. shawnhet,

    Temperatures will gradually rise in general at a rate of approximately 0.2C/decade, although that growth rate will not be linear just as it has never before been. This expectation DOES NOT include the effects of unleashing a positive feedback with carbon in the form of melting permafrost and methane clathrates which would exacerbate the situation considerably.

    So we can expect that by the time CO2 has doubled from 280ppm to 560ppm in the atmosphere, world average temperature will have risen by 2C-4.5C over pre-industrial times with the threat of even greater warming if frozen carbon is unleashed.
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  25. re #73

    That doesn't accord with the evidence Shawnwt, in at least four different ways:

    (i) Remember that most of the estimates of climate sensitivity are empirical, based on phenomenological analysis of climate responses in the past (e.g. during ice age cycles or from paleoCO2/climate responses duing the deeper past). Thus any cloud response is implicitly included in the analysis. The best estimate of a climate sensitivity near 3 oC (plus/minus a bit) incorporates all feedbacks/amplifications (except very slow ice sheet responses and methane release feedbacks).

    R. Knutti and G. C. Hegerl The equilibrium sensitivity of the Earth's temperature to radiation changes Nature Geoscience 1, 735-743

    (ii) The evidence is reasonably good that the direct resonse to a doubling of CO2 (around 1 oC) is amplified to around 2 oC by the water vapour feedback, and therefore the "neutral" situation without extra amplifications would give us more than 2 oC of warming over preindistrial levels during the next century at current rates of CO2 emissions. With albedo feedbacks that will be larger still (let alone any large feedbacks from greatly accelerated release of methane from clathrates or tundra).

    (iii) we've had around 0.8-0.9 oC of warming during the last 100 years. That's entirely consistent with a climate sensitivity near 3 oC of warming per doubling of atmospheric CO2, and it's rather difficult to take seriously your notion that we might have "only ~0.5C of anthropogenic warming over the next century" with a negative cloud feedback. After all where has this supposed "negative cloud feedback" been for the last 100 years?

    (iv) We've already seen that we don't need a positive cloud feedback to give us well over 2 oC of warming during rhe next 100 years, and that there isn't any evidence of a negative cloud feedback. Is there evidence of a positive cloud feedback? yes:

    A. C. Clement et al. (2009) Observational and Model Evidence for Positive Low-Level Cloud Feedback Science 325, 460 – 464
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  26. Chris, sure if you only look at things from your POV, then they will appear to line up, the way you have outlined them. However, there are other ways of analyzing the evidence, I don't really like addressing the same points on two different threads so I will leave most of your post there.

    "(iii) we've had around 0.8-0.9 oC of warming during the last 100 years. That's entirely consistent with a climate sensitivity near 3 oC of warming per doubling of atmospheric CO2, and it's rather difficult to take seriously your notion that we might have "only ~0.5C of anthropogenic warming over the next century" with a negative cloud feedback. After all where has this supposed "negative cloud feedback" been for the last 100 years?"

    We may have had 0.8-0.9C of warming over the last 100 years, but some of that has probably been due to natural fluctuations. The increase up to 1940 is pretty close to the increase since 1940. It is therefore pretty reasonable to say that somewhere around 1/2 of the total increase was natural. That brings the amount of anthropogenic increase up around the 0.5C mark which is pretty much consistent with a no net feedback response to CO2 forcing, which is basically my opinion.

    "(iv) We've already seen that we don't need a positive cloud feedback to give us well over 2 oC of warming during rhe next 100 years, and that there isn't any evidence of a negative cloud feedback."

    In fact, I think that if most GCMs included negative cloud feedback the sensitivity to a CO2 doubling would be under the 2.0C mark. see here. (Don't forget that we are already ~ halfway to a forcing from double CO2).

    ftp://eos.atmos.washington.edu/pub/breth/papers/2006/SPGRL.pdf

    For the record, I haven't been able to get past the paywall on the Clements paper. It looks interesting, but I have a suspicion that it treats all variation to clouds as a feedback and doesn't allow for the possibility that cloudiness can be independently forced(which would obviously have temperature effects).

    Cheers, :)
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  27. Not really Shawnhet. You can't just make things up according to your preference. The attribution of natural contributions to 20th century warming has been addressed empirically and analytically and simply doesn't accord with your unattributed assertions. You really need to address the science; we do notice when you try to sneak completely unfounded assertions into your messages!

    So for example the most recent analyses of natural and anthropogenic contributions to 20th century warming indicate that very little was from natural variation.

    J. L. Lean and D. H. Rind (2008) How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006 Geophys. Res. Lett. 35, L18701

    Which indicates that the natural contribution to warming in the period 1889-2006 was around 0.12 oC (0.002oC per decade ENSO; -0.001 pd volcanic; 0.007 pd solar). Nothing like your hopeful guess of 50%!

    A similar conclusion results from the recent analysis of Schmidt and Benestad:


    Benestad RE and Schmidt GA (2009) Solar trends and global warming J. Geophys. Res. 114, D14101

    who determine a solar contribution of 7% for 20th century warming with a slight cooling contribution since 1980, in line with quite a bit of other research on this subject.

    And while natural variations resulted in significant modulation of 20th century warming its nett contribution was near zero (around 0.1 oC or less):

    Swanson KL, Sugihara G, Tsonis AA (2009) Long-term natural variability and 20th century climate change Proc. Natl. Acad. Sci. USA 106, 16120-16123

    And so on. The science simply doesn’t support your assertions shawnhet, and so your arguments about climate sensitivity are based on a false premise (or wishful thinking perhaps).

    Notice that your comment about where we are with respect to forcing from doubling of CO2 is not relevant without considering the inertias in the climate system that delay the full temperature response to that forcing. The abundant data on climate sensitivity that indicates a sensitivity near 3 oC per doubling is consistent with the major anthropogenic warming of the 20th century, as indicated by attribution studies as I’ve just indicated, and with modelling which has been rather successful in predicting the greenhouse-induced warming since the mid-1980’s. In fact the modelling is actually consistent with a climate sensitivity somewhat higher than 3 oC.

    J. Hansen et al. (2006) Global temperature change Proc. Natl. Acad. Sci. USA 103, 14288-14293

    If the science from a number of different methodologies indicates that the climate sensitivity is near 3 oC, I don’t think one can gainsay this by unattributed assertions and argumentation that is demonstrably incorrect. It’s best to address the science on these issues.

    R. Knutti and G. C. Hegerl (2008) The equilibrium sensitivity of the Earth's temperature to radiation changes Nature Geoscience 1, 735-743
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  28. Chris, are you really unaware that there is substantial debate in how much natural contribution there has been to warming over the last century? What was the temperature increase from 1800-1900?

    IAC, I'll give a very simple argument here. The PDO shift which happens every 30 or so years has been claimed by many people to be able to cancel out the current rate of global warming, which means that the current rate of GW should be approx. equal to the cooling rate of a negative PDO(and, by extension the warming rate of a positive PDO). From that logic, we had two warming PDOs and one cooling one btw 1900-2000, we end up with PDO shift accounting for btw 0.2-0.25 C of your 0.8-0.9C in the last hundred years. If you then add your **separate** heating of 0.1C you reference above, you end up reasonably close to my 0.5C.

    Cheers, :)
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  29. come on shawnet. You've just been demonstrating that one can fabricate the pretence of a "debate" by saying "stuff" for which there isn't any evidence! In fact there actually isn't much scientific debate about the attribution of natural and anthropogenic factors to 20th century and contemporary warming....the scientific evidence from a number of different analyses (see for example my post #76) indicates that the natural contribution is small and the anthropogenic contribution is large. I prefer to follow the science on these issues.

    Your "simple argument" is meaningless, isn't it, without recourse to evidence. There has been significant scientific investigation of the contribution of ocean current regime shifts on the 20th century temperature trend. The evidence indicates that the nett effect is unlikely to have been much above zero, despite the fact that these effects have likely modulated the time course of warming significantly.

    For example Swanson et al, who have addressed this exact question, find that while ocean current effects have modulated the pattern of 20th century temperature, the nett warming contribution has been negligible (well below 0.1 oC). Lean and Rind (cited in my post above) find much the same. These observations are not surprising shawnet; the movement of waters around the world simply cannot “magic” heat generation, even if they can redistribute this due to long term oscillatory shifts in currents.

    Swanson KL, Sugihara G, Tsonis AA (2009) Long-term natural variability and 20th century climate change Proc. Natl. Acad. Sci. USA 106, 16120-16123

    Rather than use a form of Aristotelian syllogism where you choose the conclusion you desire and bind this into a “logical” “argument” based on false premises (the Shaviv chap you keep referring to does this too), it really does help to look at the evidence. Apart from the abundant science that informs us of these issues, I find it rather compelling that even though we’re apparently within a cooling ENSO regime (your PDO shift which your hopeful guess gives “0.2-0.25 oC” of cooling), and the sun is smack at the bottom of a rather extended solar minimum (which according to your mate Shaviv should give a highly amplified cooling!), we’ve had the warmest September on record [*] and the second warmest June-July-August on record [**]. Of course one can’t draw major conclusions from short time periods, but our current global temperatures are well above the 1990’s average [*,**]. So where’s the marked cooling that your (and Shaviv’s) syllogism is attempting to trick us with?

    [*] http://www.cru.uea.ac.uk/cru/data/temperature/crutem3vgl.txt

    [**] http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt
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  30. Chris, all of the issues involved are massively complex, so it is easy to find people on different sides of any issue. If you want to assume that anyone who agrees with you must be right and anyone who disagrees with you wrong, that's fine.

    The fact remains that many people feel that PDO shifts have the capacity to accelerate or deccelerate the warming trends. If this is true, then the fact that there are (essentially)two PDO warming periods and one PDO cooling period in the last 100 years must reduce the anthro contribution to warming.

    One does not have to accept that the PDO can change the rate of warming, of course, but this leads to its own problems (like the anomalous jump in temperatures in ~1976). It is widely supported including by Josh Willis(who is no stranger to ideas of OHC).

    There are other comparisons one could make of course, to try and guage the natural component of climate change. Comparing the temperature now to the temperature at the height of MWP or comparison of temp change(or sea level increase) from 1800-1900 and 1900-2000 or of the rate of temp change from 1910-1945(the previous positive PDO period) to the 1976-2000 period).

    "These observations are not surprising shawnet; the movement of waters around the world simply cannot “magic” heat generation, even if they can redistribute this due to long term oscillatory shifts in currents. "

    The movement of water may not be able to generate heat, but it will definitely allow it to be dissipated and radiated more or less efficiently. Think about it.
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  31. It's not about what people think, shawnhet; it's about what the evidence shows.

    And now you're changing the point into vague generalities and allusion. If we can assess in quite a bit of detail the attributions to 20th century warming (see posts 77/79), why shift the argument to other periods where these are less accessible (MWP to now)? That sounds like an attempt to take the argument back into a comfortable uncertainty where misrepresentation and conspiracy theorising thrives.

    As for "anomalous jump in temperature in ~ 1976", that turns out to be an artefact of a set of expendable bathy-thermographs (as identified for example, by the Willis that you mention in your post [*]), and described recently by Domingues et al [**] and subsequently others. It’s got nothing to do with the PDO.

    [*] Wijffels SE, Willis J, Domingues CM (2008) Changing Expendable Bathythermograph Fall Rates and Their Impact on Estimates of Thermosteric Sea Level Rise J. Climate 21,5657-5672

    [**] Domingues, CM et al (2008) Improved estimates of upper-ocean warming and multi-decadal sea-level rise Nature 453, 1090-1094
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  32. Chris, the trouble with these arguments is that they rapidly get much too detailed for me to debate effectively in the time I have available. Your position holds together fairly well for now, but will become tricky if the temperature stasis lasts for too much longer(if it does, then you will be forced to grant more power to natural variations than you have been willing to do so far).

    "These observations are not surprising shawnet; the movement of waters around the world simply cannot “magic” heat generation, even if they can redistribute this due to long term oscillatory shifts in currents. "

    The movement of water may not be able to generate heat, but it will definitely allow it to be dissipated and radiated more or less efficiently. Think about it.
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  33. The truth is out there,

    before drawing conclusions on CERES I suggest you read 2009 G. Matthews, “In-flight Spectral Characterization and Calibration Stability Estimates for the Clouds and the Earth’s Radiant Energy System” Journal of Atmospheric and Oceanic Technology. Vol 26, Issue 9, pp 1685-1716. Be critical, I cannot fault it, and it explains CERES data currently contains significant calibration drifts so no climatologist should base any conclusions on it (plus its solar wavelength calibration is based on a 13 year old ground radiometer which has not been measured itself). In truth the albedo dropped slightly from 2000 to 2007, the outgoing long wave slightly increased. This agrees with models used by Trenberth etc. Read it and assess for yourself.
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  34. All these short term charts don't mean squat. go back a few thousand years at least. We have been in a warm period for about the last 10K. Look at all of them rather than just the last 100 or so. How in the world can you call CO2 the dominant forcing when you know that if Water vapor was cut by 10% we would probably go into and ice age.
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    Moderator Response: In the Search field at the top left of this page, type "Climate's Changed Before." Also "Water Vapor is the Most Powerful Greenhouse Gas."

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