How Scientific Debate Should Be Conducted [With John Nielsen-Gammon]

John Neilsen-Gammon and I have had a constructive exchange of viewpoints on his weblog Climate Abyss under his post Roger Pielke Jr.’s Inkblot. John is an outstanding scientific colleague and I value such interactions with him.

I have reproduced it below

    • Hi John

      I have issues with several of your conclusions with respect to how the climate system is behaving. For example, you write

      “satellite temperature measurements show similar warming”

      However, as we report in

      Klotzbach, P.J., R.A. Pielke Sr., R.A. Pielke Jr., J.R. Christy, and R.T. McNider, 2009: An alternative explanation for differential temperature trends at the surface and in the lower troposphere. J. Geophys. Res., 114, D21102, doi:10.1029/2009JD011841. http://pielkeclimatesci.files.wordpress.com/2009/11/r-345.pdf

      the surface temperature and lower tropospheric global average temperature anomalies are actually diverging in recent years.

      This can be seen quite clearly in the RSS MSU LT anaylsis (see Figure 7)-http://www.ssmi.com/msu/msu_data_description.html, where there has not been an increase a a number of years.

      With respect to the issue “Tyndall gas climate signal to emerge from the other signals in a manner clear enough to convince a non-scientist”

      the documentation of the increase of CO2 from human emissions is already obvious. We do not need to wait to see a radiative forcing signal to discern this human influence on the climate.

      The fundamntal issue, however, in my view, is the relative role of this added CO2 with respect to othe human (and natural) climate forcings. You seem to accept that the radiative effect of the added CO2 will emerge as the dominant climate change forcing, yet other human forcings, such as due to land use/land cover change are emerging as possibly larger effects.

      We overview this perspective in our article

      Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell, W. Rossow, J. Schaake, J. Smith, S. Sorooshian, and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union.
      http://pielkeclimatesci.files.wordpress.com/2009/12/r-354.pdf

      Roger

       
      • john n-g says:

        Roger – You challenge my statement “satellite temperature measurements show similar warming” with the statement “the surface temperature and lower tropospheric global average temperature anomalies are actually diverging in recent years”. So we both agree they differ to some extent. The question, for the purpose of hypothesis testing, is whether the satellite measurements indicate that no substantial warming has taken place over the past several decades.

        The RSS Fig. 7 doesn’t address the issue because it doesn’t compare the different data sets, but the Klotzbach et al. (2009) paper does. The global surface temperature trends from NCDC and HadCRU from 1979 to 2008 are 0.16 C/decade. The global lower tropospheric temperature trends from UAH and RSS are 0.13 C/decade and 0.17 C/decade, respectively. Seems pretty similar.

        Klotzbach et al. (2009) point out that the surface and lower temperature trends shouldn’t be expected to match exactly, because none of the forcings are expected to produce temperature trends that are uniform with height. They assume a model-derived expected lower tropospheric amplification factor of 1.2, which I agree with. This means the lower tropospheric trend would need to be 0.19 C/decade to perfectly match the surface temperature trend.

        I computed updated trends through July 2011 using woodfortrees.org. HadCRUT3 trend = 0.152, GISTEMP trend = 0.164. Amplified for the lower troposphere, these are 0.182 and 0.197. Actual satellite values are 0.137 for UAH and 0.143 for RSS. So estimated lower troposphere warming (from surface measurements) is about 0.19 C/decade, and actual satellite-based lower troposphere warming is about 0.14 C/decade. Is this difference worth investigating? Absolutely. Is this difference so large that it calls into question whether the Earth is warming? Absolutely not!

        You don’t have to convince me that surface temperature measurements have biases and errors, but they’re more than good enough to get the sign right.

        The other issue you raise, the relative importance of other anthropogenic effects, does not argue against the hypothesis I stated, and neither does the Pielke et al. (2009) Eos article.

         
  • Hi John – Thank you for your reply. In terms of agreement between the surface and lower tropospheric temperature trends, in my view we need to examine shorter time periods as well. In recent years, the annual global average tropospheric temperature trends have been flat, as has the annual global average upper ocean heat content trends since about 2003.

    The difference in recent years between the surface and lower tropospheric trends raises questions on mechanisms for these temperature trends, since, if these difference are real it indicates the lower tropospheric vertical temperature lapse rate has changed.

    We both agree that CO2 is being added due to human activity (e.g. see my post today – http://pielkeclimatesci.wordpress.com/2011/08/25/an-independent-way-to-assess-the-fossil-fuel-input-of-gases-including-co2-into-the-atmosphere/. However, the changes in the heat content of the climate system in response clearly appears more complex than suggested by a more-or-less montonic global warming produced by the IPCC models.

    There is also conflicting information on the other climate metrics that you present, such as glacial retreat. It is more complicated as there are quite a few glaciers that are advancing. This variabibility illustrates why we need to examine regional atmospheric and ocean circulations as the more important metric to assess climate. The never-ending drought and heat you have had to endure this summer is due to a regional circulation feature, not a global average surface temperature anomaly. Parts of western Europe are reported as having their coolest summer in 50 years for example.

    I look forward to continuing our dialog!

    Roger

     
    • john n-g says:

      Roger –

      You said:

      In terms of agreement between the surface and lower tropospheric temperature trends, in my view we need to examine shorter time periods as well. In recent years, the annual global average tropospheric temperature trends have been flat, as has the annual global average upper ocean heat content trends since about 2003. 

      Shorter-period trends tell us more about all the other things that affect climate than they do about Tyndall gas buildup, since Tyndall gas concentrations have relatively little short-term variability. Since we do care about all the other things that affect climate, I agree that short-term trends need to be examined too. But that’s a separate issue.

      To isolate the effect of Tyndall gases on shorter-term variability, it’s necessary to account for the causes of the short-term trends. Several people have done this; a handy example is Tamino. When you account for the effects of just three such causes (ENSO, solar variability, and volcanic eruptions), the long-term warming trend emerges even on the sub-decade scale.

      You said:

      The difference in recent years between the surface and lower tropospheric trends raises questions on mechanisms for these temperature trends, since, if these difference are real it indicates the lower tropospheric vertical temperature lapse rate has changed. 

      Klotzbach et al. (2009) concluded that the differences were not real: “The characteristics of the divergence across the data sets are strongly suggestive that it is an artifact resulting from the data quality of the surface, satellite and/or radiosonde observations.” I agree. You did too, at one time, since you’re second author.

      You said:

      We both agree that CO2 is being added due to human activity (e.g. see my post today – http://pielkeclimatesci.wordpress.com/2011/08/25/an-independent-way-to-assess-the-fossil-fuel-input-of-gases-including-co2-into-the-atmosphere/. However, the changes in the heat content of the climate system in response clearly appears more complex than suggested by a more-or-less monotonic global warming produced by the IPCC models. 

      As one might gather from earlier portions of the response, I am of the view that the climate system is responding to a variety of forcings and also changes due to natural variability. It’s not surprising that when all factors are active, there’s more variation than when only Tyndall gases are used as a forcing agent (though even some models’ natural variability is sufficient to produce a flat decade of surface temperatures or a flat decade of ocean heat content). Again, in the context of the hypothesis I put forth, the issue is the magnitude of the response due to Tyndall gases, and the most telling evidence of that response comes when shorter-term factors have evened out over the long haul.

      You said:

      There is also conflicting information on the other climate metrics that you present, such as glacial retreat. It is more complicated as there are quite a few glaciers that are advancing. This variabibility illustrates why we need to examine regional atmospheric and ocean circulations as the more important metric to assess climate. The never-ending drought and heat you have had to endure this summer is due to a regional circulation feature, not a global average surface temperature anomaly. Parts of western Europe are reported as having their coolest summer in 50 years for example. 

      Yes, your regional mileage may vary. As I said before, this is a separate issue than what’s happening on the global average. Saying my hypothesis is not the most important one does not go very far in disproving it.

      And since you’ve brought up the Texas drought and heat:

      The circulation anomaly is not all that unusual. More important is the lack of preexisting soil moisture, which alters the Bowen ratio in favor of hotter temperatures while at the same time making the atmosphere less susceptible to locally-generated convection and prolonging the drought conditions in a positive feedback.

      Texas is running about 5.5F warmer than normal so far in August. Most of that is due to the dry soil feedback, but the degree or so add-on caused by global warming doesn’t help. (If this were a cold spell, it would help.)

      We would be thrilled if this summer’s temperatures were only the warmest in 50 years.

       

       

  • Hi John- Thank you for the further feedback.

    I am not sure where we actually disagree except on the preeminence of the radiative effect of added CO2 and a few other greenhouse gases on the climate system over a long enough time period (decades). This dominance, presumably, would be due to the long residence time of CO2 in the atmosphere. Other human climate forcings are usually dismissed because they have a shorter residence time (i.e. aerosols).

    We agree on this long term accumulation of CO2. Actually, I am more concerned on the (very poorly understood) biogeochemical effect of this added CO2, but, regardless, this is a significant concern. In terms of long term global warming, however, the presence of aerosols (which, despite their relatively short residence time) will continue to be reemitted into the atmosphere indefinitely. A number of these aerosol effects (e.g. sulphates) cause radiative TOA cooling. We present other examples of a diversity of cooling and warming aerosol efects in the NRC 2005 report (e.g. see Table 2-2 – http://www.nap.edu/openbook.php?record_id=11175&page=40).

    Moreover, while land use change has not, apparently, caused a global average change in TOA radiative forcing, it certainly may in the coming decades if low latitude population growth continues. This is has a very long “residence time”.

    Thus, while the added CO2, if that was all that was involved, would produce global warming (of a magnitude that depends on the magnitude of the water vapor/cloud feedback), these other human climate forcings significantly complicate the actual changes in the heat content of the climate system in the coming decades.

    Therefore, I do not have your confidence on whether the coming decades will be warmer than the current or recent decades.

    Roger

    P.S. I still agree with

    Klotzbach et al. (2009) concluded that the differences were not real: “The characteristics of the divergence across the data sets are strongly suggestive that it is an artifact resulting from the data quality of the surface, satellite and/or radiosonde observations.” :-)

    Notice I used the conditional “if” in “if these difference are real it indicates the lower tropospheric vertical temperature lapse rate has changed.”

     
    • john n-g says:

      Roger – Yes, I think we’ve sort of converged. We agree that the evidence confirms hypothesis 1, that the earth has warmed on a multidecade scale. We agree that Tyndall gases are a warming factor, though you haven’t pinned yourself down on whether the size of the effect would be enough to cause about 2 degrees of warming by the middle of this century, all else being equal. Conversely, I haven’t pinned myself down on whether I think other forcings (such as aerosols and land use change) might be enough to cancel this effect.

      I will now do so: No, I don’t think they will be near strong enough to cancel the effect of Tyndall gases on a globally-averaged basis. I believe this because: (a) they haven’t been near strong enough to cancel the effect in recent decades; (b) the influence of CO2 can only increase relative to aerosols (simplified argument: since the same power generation that produces aerosols produces CO2 and CO2 accumulates in the atmosphere, aerosols can never catch up); and (c) I can’t conceive of more land use change in the next 100 years than the past 100 years (we can’t double our arable land, for instance).

        
  • Dr. J says:

    An excellent article, as usual Dr. n-g, I of course fully agree with both Dr.s Pielke. The problem is not whether or not human CO2 is increasing and has some effect on global temps, of course that is true and is theoretically and data based. The problem is the significance and magnitude of the effect vis a vis other myriad climate factors. And further, for the greater unwashed population that activist climatologists are trying to influence, why is that problem of such overwhelming significance that we should undertake drastic policy actions to alter it, or indeed, would those actions really do anything in human time frames we could actually see and benefit from. This is where the whole stack of cards comes down, in my opinion. In fact, I just submitted an abstract for a presentation at the annual AGU meeting in Frisco, I doubt it will be accepted, as we know how careful AGU is not to allow such things (it would upset the clanish Princess of China dining event), but that is the topic of it. 

  • Hi John –

    Thank you again for the additional feedback.

    The radiative forcing of CO2 and the other greenhouse gases is a relatively minor warming effect unless there is a significant positive water vapor/cloud feedback. However, if the other human climate forcings (or natural forcings) prevent a significant ocean warming, this positive feedback will not occur or will be very muted.

    There is significant research that shows that the model simulation of the water vapor/cloud feedback is overstated (e.g. see

    Sun, De-Zheng, Yongqiang Yu, Tao Zhang, 2009: Tropical Water Vapor and Cloud Feedbacks in Climate Models: A Further Assessment Using Coupled Simulations. J. Climate, 22, 1287–1304

    where they wrote

    “……extended calculation using coupled runs confirms the earlier inference from the AMIP runs that underestimating the negative feedback from cloud albedo and overestimating the positive feedback from the greenhouse effect of water vapor over the tropical Pacific during ENSO is a prevalent problem of climate models.”

    In terms of long term climate system heat changes, I agree with you; the evidence is convincing (based on the most robust metric which is the upper ocean heat content in Joules) that it is warmer now than 50 years ago.

    However, in the last 8 years, this heating has halted (or, at least, is very small). This clearly indicates that the added radiative effect of CO2 and the other added greehouse gases is being countered (by natural and/or human forcings). It does tell, us, however, that the water vapor/cloud feedback will be muted irrespective of the cause as the ocean sea surface temperatures have not increased much, if at all, during this recent time period.

    Regarding the assumption that a reduction in CO2 would also result in a reduction of aerosols; this is certainly true for some aerosols such as sulphates (and I in favor of this just for health reasons!). However, dust from degraded landscapes, biomass burning in the tropics will continue indefinitely.

    In terms of landscape change, it is expected to continue quite vigorously in the coming decades as the 3rd world develops. Moreover, it is not just a question of arable land, but also other landscapes such as the boreal forest that are of concern. There is also tropical forests still at risk.

    My question to you, is how many more years of an absence of significant warming in the upper ocean (e.g.equivalent in Joules to a significant fraction of Hansen’s ~0.6 Watts per meter squared) would have to occur before you rethink your view on the dominance of the added CO2 and the other greenhoue gaes?

    Thank you for the opportunity for this constructive dialog!

     
    • john n-g says:

      And now for the rest of the story from Sun et al: “…There is no significant correlation found between the intermodel variations in the cloud albedo feedback during ENSO and the intermodel variations in the cloud albedo feedback during global warming. The results suggest that the two common biases revealed in the simulated ENSO variability may not necessarily be carried over to the simulated global warming.” I therefore reject your characterization of this paper.

      Biomass burning emits Tyndall gases as well as aerosols, and the gases win out in the long run: Jacobson (2004, J. Climate, http://www.stanford.edu/group/efmh/bioburn/index.html)

      “How many more years”? Do you mean how many more years without understanding OHC variability or how many more years after understanding OHC variability? For example, there’s recent observational evidence (Chu 2011, Ocean Dyn., http://www.springerlink.com/content/776065j782110161/fulltext.html) that interannual upper-level OHC in the Pacific is dominated by El Nino and El Nino Modoki modes. Given that short-term global surface temperature variations are already explained by ENSO, the Sun, and volcanoes, the most likely explanation seems to be that short-term OHC variations are also attributable to ENSO, the Sun, and volcanoes.

      The models analyzed by Katzman and van Oldenborgh (2011, GRL http://www.agu.org/journals/gl/gl1114/2011GL048417/) do not include variable solar and volcanic activity, and those models include an occasional 8-year period of no 0-700 m OHC increases. During such periods, ENSO variability does indeed account for the bulk of the “missing heat”, though a large portion also ends up being transferred to the deep ocean. This is consistent with another recent modeling study that finds that it’s necessary to go down to 4000 m to obtain reliable estimates of the total OHC variability (Palmer et al. 2011 GRL http://www.agu.org/journals/gl/gl1113/2011GL047835/).

      [You’ve noted in your blog comments on the latter two articles that energy lost to space or stored in the deep ocean is permanently (or almost permanently) unavailable for affecting the surface climate. However, those losses are in the context of model simulations of long-term 0-700 m OHC trends that match observed trends, so periods of more rapid losses than normal are offset by periods of more rapid gains than normal to yield the simulated (and perhaps observed) long-term gains.]

      A flat trend over any time period only shows that other forcings or natural processes are canceling the warming effect of Tyndall gases over such a period. There are lots of time-varying forcings and natural processes with a variety of periods: ENSO (2-7 years plus longer-term variations), solar (11 years plus longer-term variations), PDO (50-70 years), for example. Any of those could be strong enough to cancel the Tyndall gas effect during half its phase. We know for certain that ENSO is more than strong enough to do that, but yet, over the long haul, the magnitude of global warming has recently exceeded the magnitude of ENSO variability. So, in addition to a flat trend over some period of years, I’d want evidence that it was not merely a temporary flat trend. In the absence of such evidence, I’d settle for a trend longer than half a PDO cycle, or 35 years or so. With such evidence, the trend could be as short as a year, because I’d be swayed not by the trend but by the evidence. 

  • Hi John – I will comment more on other parts of your reply, but I want to correct your misinterpretation of the Sun et al paper. In my post

    http://pielkeclimatesci.wordpress.com/2008/05/13/tropical-water-vapor-and-cloud-feedbacks-in-climate-models-a-further-assessment-using-coupled-simulations-by-de-zheng-sun-yongqiang-yu-and-tao-zhang/

    I asked him about that statement in his paper. I e-mailed to him at the time the following

    In order to obtain an answer to the above question, I contacted Dr. Sun with the following:

    “I have set for your paper to be weblogged on in a couple of weeks. However, I have a question on your conclusion that ‘We thereby suggest that the two common biases revealed in the simulated ENSO variability may not be carried over to the simulated global warming, though these biases highlight the continuing difficulty that models have to simulate accurately the feedbacks of water vapor and clouds on a time-scale we have observations’, however it is not clear how such a bias could be removed when the models are applied in longer term model projections. Indeed, what is the data which says that the biases are removed?

    Please clarify and I can add to the weblog.”

    He replied

    REPLY FROM DR. SUN

    “You are right that no data have shown that those biases will not be removed. We are just mentioning the possibility that there could be error cancellation as global warming may involve more processes that those in ENSO, and the errors may cancel in such a way that prediction of global warming by these models that have these errors may actually get the answer right. It is just a possibility worth mentioning.”

    You should have not been so quick to reject my characterization of the paper. :-)

    [Roger – There’s no evidence in the paper that the feedbacks behave in the same way on global warming time scales, and instead there’s actual evidence in the paper itself that they behave differently. I agree with Dr. Sun that his paper doesn’t show that the models are right at global warming time scales, but neither does his paper show that they’re wrong on global warming time scales. So I still reject your characterization, albeit more slowly this time. ;-) – John N-G]

  • Hi John – We can agree to disagree on the interpretation of the Sun et al results. It is, of course, not alone at raising serious questions on the robustness of the global climate models. This includes, as just two examples,

    Stephens, G. L., T. L’Ecuyer, R. Forbes, A. Gettlemen, J.‐C. Golaz, A. Bodas‐Salcedo, K. Suzuki, P. Gabriel, and J. Haynes (2010), Dreary state of precipitation in global models, J. Geophys. Res., 115, D24211, doi:10.1029/2010JD014532. http://europa.agu.org/?view=article&uri=/journals/jd/jd1024/2010JD014532/2010JD014532.xml&t=jd,2010,stephens

    and

    Spencer, R.W.; Braswell, W.D. On the Misdiagnosis of Surface Temperature Feedbacks from Variations in Earth’s Radiant Energy Balance. Remote Sens. 2011, 3, 1603-1613. http://www.mdpi.com/2072-4292/3/8/1603/

    In my view, if they cannot skillfully predict the shorter time scales of the climate system, they will necessarily not be skillful tools on the longer time periods of decades.

    My question on the length of time of upper ocean heating that could occur before you would reject them as robust tools is still there. Jim Hansen, for example, very specifically stated in [http://pielkeclimatesci.files.wordpress.com/2009/09/1116592hansen.pdf

    “Our simulated 1993-2003 heat storage rate was 0.6 W/m2 in the upper
    750 m of the ocean. The decadal mean planetary energy imbalance, 0.75 W/m2, includes heat storage in the deeper ocean and energy used to melt ice and warm the air and land. 0.85 W/m2 is the imbalance at the end of the decade.”

    Thus we can concentrate on the upper ocean heating as the metric to test, irrespective of how much heat goes deeper into the ocean. The advantage of the upper ocean diagnosis is that it is much better sampled than the deeper ocean.

    With respect the “Tyndall gas effect”, you and I are in complete agreement that the addition of greenhouse gases results in a radiative warming effect. The disagreement is in terms of its contribution in terms of altering atmospheric and ocean circulation patterns, which, in my view, is the more important issue in terms of what matters to society than what is the global surface temperature anomaly. The spatial distribution of radiative heating from added CO2 is much more homogeneous than the spatial distribution of diabatic heating from the aerosols and land use/land cover change. We document this in our paper

    Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974. http://pielkeclimatesci.files.wordpress.com/2009/10/r-312.pdf

    The much larger spatial variations in this heating would result in larger changes to weather patterns than from the added CO2.

    Finally, we both agree that the addition of CO2 and the few other greenhouse gases is a warming effect. However, what other skillful (value-added) information have the multi-decadal global models (even with downscaling) provided for the coming decades on changes in regional climatology?

     
    • john n-g says:

      Roger -

      “shorter time scales”: Your position on this matter has the inherent advantage of making sense. You’d think that the ability of a model to simulate current climate ought to be strongly determinitive of its ability to simulate future climate change. Indeed, I’d really like to investigate the ability of models to reproduce all the different seasonal types of precipitation in Texas before I would have much confidence in their Texas projections.

      And yet…when people look for correlations between skill at simulating current climate and projections of future climate, they usually find that they are unrelated. (The recent Mote et al. 2011 Eos article has an example of this.) Likewise, Chu found that the Enso-time-scale cloud feedbacks were apparently uncorrelated with the climate-change-time-scale cloud feedbacks.

      I can think of a couple of possible reasons for this. First, each climate model comes to its own unique climate equilibrium. Certain processes will be more important in some models than others. Yet for climate change, the important characteristic is not the overall importance of a process and whether its importance matches what’s observed, but the sensitivity of the process to climate change and whether that sensitivity matches what’s observed. Second, maybe there really are characteristics of present-day climate simulations that let us predict how well a model will handle climate change and we just haven’t figured out which characteristics those are.

      Bottom line: I agree with you that cloud feedbacks are the most poorly-handled of all important feedbacks and that the uncertainty is so large that even its sign is unknown. They’d have to be quite negative, though, to negate the other (more precisely known) net positive feedbacks, though, and that is unlikely.

      Also, Spencer has recently dropped below my credibility threshold so don’t bother citing him here unless the work is corroborated.

      “length of time”: I guess I wasn’t clear; the last paragraph in my previous response was my answer to your question. To summarize here: 35 years without any explanation; 1 year with convincing explanation. Your Hansen quote gives one data point, which is not useful for establishing the range of uncertainty. My turn to ask a question: what’s your best estimate for climate sensitivity to doubled CO2?

      “the more important issue”: You may be right and you may be wrong. I haven’t seen research persuasive enough to convince me one way or the other, so I’ll not debate you on it.

      “what other skillful information”: The climate record since the projections is not long enough to assess skill. It seems highly likely that skill decreases in proportion to the non-uniformity of the change in question, but beyond that, who knows?

       
  • Hi John – You asked me this question

    “what’s your best estimate for climate sensitivity to doubled CO2?”

    I do not think this is a well-posed concept (even though it is widely used). “Climate sensitivity” is applied by the IPCc and others to mean the change in the global average surface temperature to an imposed radiative forcing.

    Climate, however, is much more than this as we discuss in depth in

    National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp. http://www.nap.edu/openbook/0309095069/html/

    In addition, all of the assessments of this sensitivity are based on model estimates of the radiative forcing and the observed surface temperature trends. Without commenting here on the uncertainties and apparent biases in the surface temperature trends (which you and I are both very well aware of), the use of models (which themselves are hypotheses) necessarily prevents such an assessment of sensitivity from a real world observational validation.

    In terms of what I have urged be used to assess the response of the climate system to TOA radiative forcings, is the changes in the annual global average storage of heat in Joules in the ocean. This is the framework used in the Katzman and van Oldenborgh (2011, GRL http://www.agu.org/journals/gl/gl1114/2011GL048417/) paper you listed above, and which I posted on in http://pielkeclimatesci.wordpress.com/2011/07/29/additional-information-on-the-oceans-missing-heat-by-katsman-and-van-oldenborgh-2011/

    Do you agree that the monitoring of the ocean heat content changes is a more robust way to assess the radiative imbalance of the climate system, than using the global average surface temperature trends in order to determine a so-called “climate sensitivity”? [which is actually just a subset of climate, and is a really the measure of the heat accumulation rate due to the TOA radiative imbalance].

    I discuss the value in using the ocean heat content changes as the diagnostic metric to monitor global warming (and cooling) in

    Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335. http://pielkeclimatesci.files.wordpress.com/2009/10/r-247.pdf

    Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55. http://pielkeclimatesci.files.wordpress.com/2009/10/r-334.pdf

    See also

    Ellis et al. 1978: The annual variation in the global heat balance of the Earth. J. Geophys. Res., 83, 1958-1962. http://pielkeclimatesci.files.wordpress.com/2010/12/ellis-et-al-jgr-1978.pdf

    On Roy Spencer’s paper, I recommend you read it for the science he presents. It is in the peer reviewed literature. If he is wrong, this needs ot be reported. If he is correct, it certainly should not be ignored.

     
    • john n-g says:

      Roger -
      Would this be a well-posed question: If the Earth in 2060 were to have a CO2 concentration of 540 ppm, increasing steadily from its present value, but with no further changes in land use, volcanic activity, solar insolation, or other climate forcings, how much warmer do you think the global average temperature would be compared to preindustrial values?

      It may be difficult for us to carry out this experiment, given that we can’t control volcanic activity or solar insolation, but we may get lucky and have them remain stable anyway. So this is a physically realizable future climate state, achieved through a physically possible trajectory. What’s your best estimate?

      “all assessments”: Forster and Gregory (2006) made their estimate completely independent of climate model estimates of the radiative forcing. You are free to apply an ad-hoc correction to the magnitude of the surface temperature trend used in their calculation in order to arrive at your own climate sensitivity estimate independent of model or surface temperature biases. (Actually, that’s pretty much how I do it.)

      “Do you agree”: I agree that monitoring of ocean heat content has the potential of being a more robust way of assessing radiative imbalance. Since it’s a fairly new technology, I’d like to give it a few more years for most of the bugs to shake out, but this may be skepticism based on ignorance. On the other hand, weather is affected much more directly by ocean (and land) surface temperatures than by ocean heat content, so I prefer global surface temperature over ocean heat content as a convenient metric for how much the sensible climate has actually changed or is going to change.

      “Spencer’s paper”: It didn’t take my colleague Andrew Dessler long to work out a demonstration that Spencer’s new paper is wrong. Many of his colleagues have counselled against publishing this demonstration, arguing that the time wasted refuting yet another in a series of incorrect papers by the same author would be better spent advancing our knowledge about the climate system and that at some point it’s better just to ignore incorrect papers. I personally agree with you that an incorrect paper should be publicly refuted in the scientific literature, but I can see how it would get annoying to be working on one public refutation after another.

        
  • Hi John

    In answer to your question

    “If the Earth in 2060 were to have a CO2 concentration of 540 ppm, increasing steadily from its present value, but with no further changes in land use, volcanic activity, solar insolation, or other climate forcings, how much warmer do you think the global average temperature would be compared to preindustrial values?”

    I prefer to answer in terms of Joules of added heat that the models are predicting from the radiative imbalance of added CO2 and a few other greenhouse gases. Jim Hansen concludes that there was a radiative imbalance of 0.85 Watts per meter squared at the end of the 1990s which converts to ~1.38 x 10**23 Joules per decade or about 5.5 x 10**23 Joules of accumulation over the next 40 years if we assumed his value is representative of this time period (it actually would be larger presumably as CO2 increases).

    I do not know, however, a unique and accurate way to convert this to a global average surface temperature anomnaly, since it matters whether it is the mean, the maximum or the minimum temperature anomaly (which matters, as you know over land), and also the value of the absolute temperature (through sigma T**4).

    In terms of the robustness of ocean heat content anomalies, since about 2003, it is considered by Josh Willis as quite accurate in the upper 700m as a result of the density of Argo network and the use of satellite measures of sea level. It is also, in my view, more informative regarding weather than sea surface temperature alone since it the sensible and latent fluxes of this heat into and out of the ocean which strongly influences such features as tropical cyclones, ENSO ect. The sea surface temperature is just a sample of this heat.

    We both agree that IF the added greenhouse gases were the only human climate forcing, there would be warming. However, even in this thought experiment, the magnitude is still uncertain since the water vapor/cloud feedback is still incompletely understood, as exemplified by the Stephens paper.

    I also would not be so quick to dismiss Spencer’s paper. If Andrew Dessler can refute it, that is how science works, but it needs to be shown in the peer reviewed literature.

     
    • john n-g says:

      Roger –

      “in answer”: If you do not know a unique and accurate way to convert 5.5 x 10**23 Joules of accumulation into a global average surface temperature anomaly, would it be fair to say that you do not know how to convert 5.5 x 10** Joules of accumulation into any particular quantitative consequence for surface weather and climate? And if that is so, doesn’t that mean that ocean heat content is not an adequate metric for global climate change?

      [I regard ocean heat content as a useful metric for some things, and global surface temperature anomaly as a useful metric for other things. For the instantaneous state of the atmosphere, global surface temperature anomaly is more useful than ocean heat content.]

      “robustness”: …and the surface temperature network is considered quite accurate by Brohan et al. for global temperature trends, including minimal impact of urbanization. I hear what Josh is saying, but expert testimonials by themselves are of limited usefulness.

      Update:
      P.S. Thank you for the opportunity to show readers what a “robust scientific debate” actually looks like. Each person gets to check the other’s claims, examine the research on the subject, and evaluate the balance of evidence before responding. And neither side knows how the debate will resolve itself, whether one will convince the other, or whether the debate will unearth a third possibility. Here the debate is happening at a very high-speed rate, and even so it’s taking several days. Now, dear reader, consider how impossible this would be in a one-hour debate event. Notice also, dear reader, that unlike in a one-hour debate event, it’s possible to fact-check, and this necessarily keeps both sides honest. (Roger and I are both honest anyway, but that’s not true of all debaters.) Adequate response time also tends to prevent unconstrained Gish-Galloping.

      P.P.S. If you’re trying to keep track of the threads, we’ve wandered fairly far afield of the original issues, so I’ll summarize. Hypothesis 1: we both agree it’s correct. Hypothesis 2: Roger doesn’t necessarily think it’s incorrect, but that it’s not very useful.

       
  • P.S. These two posts on the analysis I asked Norm Woods to complete on the radiative forcing of added CO2 might be informative in our discussions to and in answer to your question:

    Relative Roles of CO2 and Water Vapor in Radiative Forcing
    http://pielkeclimatesci.wordpress.com/2006/05/05/co2h2o/

    Further Analysis Of Radiative Forcing By Norm Woods
    http://pielkeclimatesci.wordpress.com/2007/08/24/further-analysis-of-radiatve-forcing-by-norm-woods/

  • Hi John

    With respect to your text

    “…..If you do not know a unique and accurate way to convert 5.5 x 10**23 Joules of accumulation into a global average surface temperature anomaly, would it be fair to say that you do not know how to convert 5.5 x 10** Joules of accumulation into any particular quantitative consequence for surface weather and climate? And if that is so, doesn’t that mean that ocean heat content is not an adequate metric for global climate change?”

    The use of ocean heat content change is not an adequate metric for climate change, as that issue encompasses a wide variety of issues. However, in my view (and actually that of Jim Hansen as I have heard him say this), the use of ocean heat content is a much more robust metric of global climate system heat changes (i.e. global warming).

    The global average surface temperature, in contrast, is a much more difficult quantity to define. Besides whether the mean, minimum and maximum is what is meant (and it is usually the mean that is used), there is the question as to what height of measurement is used (e.g. surface skin value; 2m, etc). Now that we have improved sampling of actual heat (in the upper ocean), I recommend we move towards that metric to diagnose global warming.

    For climate change more generally, we need to develop new metrics as we recommended in the 2005 National Research Council report. The metric we proposed in

    Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974.
    http://pielkeclimatesci.files.wordpress.com/2009/10/r-312.pdf

    is one example of such a metric.

    I also agree with you that this is an effective way to debate the science issues! Indeed, this is how we have succesfully published several papers together. :-)

     
    • john n-g says:

      Roger – Thank you. I have enjoyed our discussion. In this instance, I don’t think either of us have changed our minds, but it is always useful to think things through.

      Okay, if anybody else is out there, we’re done! You can weigh in now with opinions or other considerations without interrupting a good debate!

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