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Pielke Sr. and SkS Disagreements and Open Questions

Posted on 1 October 2011 by dana1981

Dr. Roger Pielke Sr. has responded to our last set of questions and answers, and we would like to thank him for a civil discourse to this point. Unfortunately, in the meantime Dr. Pielke has taken offense to some challenging, but relatively benign comments (although we think he got in a few licks himself), and decided that his interaction with SkS was over.

To sum up the discussion, there are some points on which we agree, others on which we disagree, and a few others which require further clarification.  We will summarize the disagreements and open questions in the text below, based on our understanding of Dr. Pielke's comments.  Readers are invited to read Dr. Pielke's comments to verify that we are accurately representing them in this summary.

CO2 Contribution to Global Warming

In response to our question regarding what fraction of the observed global warming is due to CO2 and other anthropogenic effects, Dr. Pielke responded:

"~26% of the positive radiative forcing was from CO2"

This is not a complete answer, but the question is a complex one.  However, we believe Dr. Pielke has underestimated the CO2 contribution.  Figure 1 shows the radiative forcing estimates in the 2007 IPCC report.

ipcc forcings


The radiative forcing from CO2 is well-known, and estimated at 1.66 Watts per square meter (W/m2).  The remainder of the positive radiative forcings add up to 1.63 W/m2.  Therefore, CO2 accounts for approximately 50% of the positive radiative forcing - twice Dr. Pielke's estimate.  Dr. Pielke references research which has suggested that, for example, methane plays a larger role than the IPCC estimate.  However, the radiative forcing from methane (which is well-known) is based on its atmospheric concentration, which is also well-known.  Dr. Pielke also clarified his opinion that soot (black carbon) might account for a larger positive radiative forcing than CO2.  However, aerosols have both warming and cooling effects, with the cooling effects likely being larger in magnitude (Ramanathan and Carmichael 2008).

Answering the SkS Question

Our view of this question is that if we use the current CO2 forcing and a transient climate response of approximately 2°C for doubled atmospheric CO2 (IPCC AR4 best estimate), the atmospheric CO2 increase over the past century has caused approximately 0.9°C warming of the average global surface temperature (best estimate).  This best estimate is more than 100% of the observed surface warming (0.8°C), meaning that all other non-CO2 anthropogenic plus natural effects have most likely had a small net cooling effect over this period.

NRC Report

Dr. Pielke cites the 2005 National Research Council (NRC) report on radiative forcing of climate change in arguing that climate models underestimate the effects of land-use change on climate.  The report does note (emphasis added):


However, the NRC report does not share Dr. Pielke's minimization of the role of CO2, or the continued importance of the top the atmosphere (TOA) energy imbalance:

"The strengths of the traditional radiative forcing concept warrant its continued use in scientific investigations, climate change assessments, and policy applications"

"The largest positive forcing (warming) from the increase of well-mixed greenhouse gases (CO2, nitrous oxide [N2O], methane [CH4], and chlorofluorocarbons [CFCs])"

OHC as The Global Warming Diagnostic

Dr. Pielke appears to believe that ocean heat content (OHC) by itself is a sufficient "diagnostic to monitor global warming."  We do agree that most of the global energy imbalance goes into the oceans - we even created a high resolution graphic illustrating this point:

where's GW going

However, as the graphic illustrates, nearly 7% of the energy goes into the rest of the climate system.  Moreover, the degree of accuracy of OHC measurements is still quite uncertain: the ARGO network is relatively new, and doesn't measure the deep oceans, and short-term noise in the data remains a concern (i.e. see Domingues et al. 2008). 

Furthermore, we humans are surface-dwelling creatures, so impacts to the climate on the surface is highly significant to us.  And most fast feedbacks are dominated by surface/atmospheric temperatures; so to rely on OHC as the sole diagnostic would disguise the progression of processes that will affect our experience of climate.

Ultimately we stand behind our answer that we must consider all lines of evidence, and all aspects of the climate.  SkS does not believe there should be a single preferred global warming diagnostic.  However, it's also important to note that a lot of energy has gone into the oceans (more on this below).


Ocean Heat Content anomaly from 0 to 700 metres calculated by various teams (Lyman 2010).

Colleagues' Contributions

Dr. Pielke has yet to acknowledge the frequent climate myth and misinformation propagation of several of his colleagues (most notably Roy Spencer and John Christy).  We do agree that these individuals have done some good scientific research and made valuable contributions, such as the development of the satellite temperature record.  Dr. Pielke says of Roy Spencer:


We question the accuracy of this statement.  Much of Spencer's research related to cloud cover has been fundamentally flawed, due, for example, to his over-reliance on an overly simplistic climate model (i.e. see here and here and here).  And while they have made some valuable contributions, they have also done significant damage by misinforming the public and policymakers on climate issues.

Acting on the Prudent path

Although we were able to find common ground with Dr. Pielke on the 'prudent path' of reducing human CO2 emissions, we remain concerned that he continues to vigorously defend his colleagues who make statements that undermine this goal, for example Roy Spencer:

"Just as the deepening horse manure crisis was alleviated by the introduction of the automobile over a century ago, I suspect that our current worries over global warming will evaporate in the coming decades"

While we are happy that SkS and Dr. Pielke find common cause when it comes to how humans should deal with mitigating climate change, we are concerned and confused that Dr. Pielke continues to defend his colleagues who are very clearly opposed to taking this critical action, who think that man-made warming is a non-issue, and who communicate that belief to the public and policymakers in an effort to delay action.

Climate Model Accuracy

Dr. Pielke does not believe that climate model projections have been accurate, particularly at the regional level, and that linking policy to climate model results does more harm than good.

As the saying goes, all models are wrong, but some are useful.  Climate models are by no means perfect and several weaknesses are recognized by the modelers themselves.  For example, models tend to slightly overestimate the lower troposphere temperature trend, underestimate the Arctic sea ice decline, and decadal and sub-regional projections aren't yet satisfactory. However, despite their imperfections, climate models are valuable tools which have been used in many attribution studies, and have given the broadscale picture of what has happened over the past half century reasonably well.  There are examples of models making accurate projections on important metrics, for example in drought (Sheffield and Wood 2007), precipitation extremes (Min et al. 2011), and floods (Pall et al. 2011).  It is the over-emphasizing of their (real or purported) weaknesses that does more harm than good.

Finally, we must bear in mind the possibility that models may paint too rosy of a picture, based on data from the geologic record:


Ocean Acidification

Regarding ocean acidification, Dr. Pielke commented: "Regardless of whether we reduce the alkalinity of the oceans..."  We would like to note that this is not a debatable question: human CO2 emissions are making the oceans more acidic.  For details, see the OA not OK series or booklet, or various posts on the subject, including by renowned ocean expert Ove Hoegh-Guldberg.

Unanswered Questions

From Pielke

Dr. Pielke was dissatisfied with our answers to his questions regarding preferred climate change diagnostics, and whether global warming is a subset of or dominates climate change.  We accept the NRC definition of "climate change" provided by Dr. Pielke.  Our answer remains that we do not have preferred diagnostics of climate change; we must take all lines of evidence and data into consideration, and there are many (i.e. sea-level rise, ice melt, species endangerment and migration, crop yields, heat wave frequency and intensity, etc.).  Based on the NRC definition, the increase in global temperature is a subset of climate change.

From SkS

SkS was dissatisfied with Dr. Pielke's answer to our question about reconciling his colleagues' arguments for low climate sensitivity and the paleoclimate record.



We acknowledge Dr. Pielke's position on this issue, but disagree, and would appreciate an answer to this question.  Ultimately, while there are certainly differences between glacial and interglacial periods, the global energy imbalance must be able to explain the change in surface temperature.  There are also some good paleoclimate analogues to the current climate, like during the Pliocene and the Paleocene-Eocene Thermal Maximum (PETM).

If the equilibrium climate sensitivity is ~1°C for double CO2, as Spencer and Christy and Lindzen argue, a radiative forcing of nearly 20 W/m2 is required to explain glacial-interglacial transitions.  This is three times larger than the net forcing identified in the paleoclimate record during these periods.  That's a big discrepancy; can it be reconciled?  Based on the evidence, we don't believe so.

Further Questions

Although Dr. Pielke appears to have terminated his interactions with SkS, we would like to give him the opportunity to clarify or retract some questionable statements he has recently made on his blog.

Troposphere Warming

Of Santer et al. (2011), Dr. Pielke said:


However, Santer et al. concluded that a minimum of 17 years is necessary to identify human effects in the temperature of the lower troposphere (TLT), so why look at the 13-year trend?  Moreover, as Pielke notes, there was a very strong El Niño in 1998, and TLT data is very sensitive to changes in ENSO.  We wonder, will Dr. Pielke will acknowledge that 1998 was a poorly-chosen start date for this analysis?

Ocean Warming




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Comments 101 to 117 out of 117:

  1. Dana @99, "However, there's nothing special about the 700 meter mark, either. And the warming of the upper 1500 doesn't appear to have slowed appreciably." Agreed, I do not know why some people are so fixated with the top 700 m of the ocean, especially when we know the oceans are much deeper than that and when we have data down to 2000 m. Dr. Pielke says "With respect to the reported deeper ocean heating, why would this heating recently have become larger?" Not sure whether or not this answers the question. Peter Hogarth has just posted a very neat image of the OHC data for 700-2000 m for different basins. Those data show a notable warming trend in the 700-2000 m OHC since 2000. The data before 1970 are probably not worth much given the sparse coverage back then. Anyways, looks like yet another Hockey Stick to me, but caveat emptor, these data should probably to be considered preliminary. [Source]
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  2. Doesn't the 700m mark have to do with limitations of the earlier Argo network?
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  3. Dikran Marsupial - Regarding "What exactly is the hypothesis that you seek to support using the post-1998 trends?" I suggest that the hypothesis be that "The lower tropospheric global annual average temperature trend (TLT) from 2002 until now cannot distinguished from a zero trend." using data from Also, "The lower stratospheric (TLS) global annual average temperature trend from 2002 until now cannot distinguished from a zero trend." and the trends during this time period are different than the trends earlier in the time period. I will be interested in what you conclude.
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  4. Dikran Marsupial -Regarding "But heat going into the deep oceans doesn't impact surface temperatures or the ratio of TLT to surface temperatures" if the surface temperature trends are being used as quantifying the magnitude of global warming (and the so-called "clmiate sensitivity"), heat in the deeper ocean is not included in such an assessment. If the heat were at the surface, it would be seen in the temperature trend.
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  5. pielkesr The hypothesis that "The lower tropospheric global annual average temperature trend (TLT) from 2002 until now cannot distinguished from a zero trend." is not a particularly interesting hypothesis for the simple reason that the statistical power of the test of a non-zero trend is very low because the timespan over which the trend is computed is too short. Your hypothesis is effectively the null hypothesis for the usual test for a non-zero trend. The statistical power is the probability that the null hypothesis will be rejected when it is false so if the test has little statistical power, we should not expect to be able to distinguish from a zero trend, even if the underlying trend is the same as the long term trend and global warming has continued unabated, but its effects are being masked by noise (i.e. internal climate variability, e.g. ENSO). Now if you want to suggest there is any scientific interest in this hypothesis, then you need to show that the hypothesis test has meaningful power. So my question is, what is the statistical power of the test?
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  6. pielkesr#103: ""The lower tropospheric global annual average temperature trend (TLT) from 2002 until now cannot distinguished from a zero trend."" The rationale for choosing 2002 as a breakpoint is still unclear. However, if you take what appears to be a natural breakpoint (1998), you see something completely different. Here is UAH from start to the beginning of 1998 with a 6 month running mean. The trend line is shown. Here is UAH from mid-1998 to present, same mean; the trendline has a higher slope than does the prior period. I seem to recall a video interview with Dr. Pachauri in which he clearly stated that warming was not expected to be monotonic (can't find the link to it at the moment). Perhaps the nonlinearity in the system that everyone agrees is present is expressed in these temporary flattenings along the overall rising curve. In view of that characteristic of these data, choosing arbitrarily short periods for analysis seems utterly counterproductive. And given the data have a high frequency noise, short periods are likely to be more contaminated -- and therefore misleading -- than long periods.
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  7. Tristan - You asked "Dr Pielke, [many policy makers] believe that the flat temperatures between 1998 and 2011 are a result of a cessation of anthropogenic warming, [will you acknowledge] that that flatness is [a temporary result] of natural variability[...]? " There is no question that the diversity of human climate forcings, including that from added CO2, has continued even as global warming has flattened. However, this behavior of the climate system illustrates our still incomplete knowledge of the climate. Policymakers, in my view, are being misled into believing that the climate should more-or-less monotonically warm when in reality both natural variability and the diversity of human climate forcings makes the issue of climate system heat content much more complex.
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  8. Dikran Marsupial - I had three hypotheses. I request you complete the test and see what you obtain. It is a starting point for our further discussuions.
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  9. muoncounter - I took 2002 because visibly there appears to be a change in slope. I request you plot that as well.
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  10. Let's please move any discussion of TLT trends to the new blog post on the subject, and move on to the discussion of OHC data here.
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  11. Dr Pielke @107, you say "global warming has flattened". When it is said that a long term trend has "ceased" of "flattened", what is being claimed is that future temperatures are more likely to lie close to current temperatures rather than close to the projection of the long term trend. Is this what you are claiming? More specifically, are you claiming that the RSS MSU Channel TLT anomaly relative to the 1979-1998 mean is more likely to be closer to 0.25 degrees K, or 0.4 degrees K (ie, approximately current values plus the 1 decade trend)? (RSS TLT anomaly as reproduced by Dr Pielke, Sept 7th, 2011). As an aside, I to believe that policy makers are being misled "into believing that the climate should more-or-less monotonically warm". However, that misleading is coming from people like your friends Christopher Monckton and Anthony Watts.
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  12. Prof Pielke wrote: "Dikran Marsupial - I had three hypotheses. I request you complete the test and see what you obtain." I do not dispute the fact that your first two hypotheses are entirely true, however, as I pointed out neither of these facts are at all surprising because the timescale over which the trends are calculated are too short for us to reasonably expect to be able to reject the null hypothesis even if it is false. Thus the test, and therefore the hypothesis, is essentially meaningless. Statistical power is often neglected by working scientists, however if you want to claim that a failure to reject the null hypothesis is of any interest, you need to show that the statistical power of the test is sufficiently high that the failure to reject a false null hypotheis would be unusual were it false. You have so far failed to do so. So I ask again, what is the statistical power of the test? I will discuss your third hypothesis on the new blog article, as dana requests, you can find my post here.
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  13. peilkesr wrote : "Policymakers, in my view, are being misled into believing that the climate should more-or-less monotonically warm when in reality both natural variability and the diversity of human climate forcings makes the issue of climate system heat content much more complex." Some examples have already been given as to the sort of people who are indeed trying to mislead policymakers (one of whom has recently actually published details for the picketing of a climate scientist; the other of whom has his own myth-making on this topic exposed and rebutted on SkS); and Albatross on another thread has given plenty of examples of SkS trying to make sure policy makers are indeed properly informed - another link here. In fact, the person who hosts the site at the first link I have given, has plenty of posts about cold, snow, everything-but-CO2-affects-the-climate, everything-is-going-to-be-OK-really, etc., but very little about heat records or explanations as to how temperatures do not rise monotonically - in fact, a recent post ("Breaking: A peer reviewed admission that “global surface temperatures did not rise between 1998 and 2008″ – Dr David Whitehouse on the PNAS paper Kaufmann et al. (2011)" - given over to a post by those 'unbiased' chaps at the GWPF) seemed designed specifically to mislead, and none of the commenters there were informed by the blog owner (who does regularly reply to those he believes are misinformed) that their comments were misleading, etc. But who do you (Dr Pielke) believe is doing the misleading ?
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  14. Tom Curtis - If I look at the RSS MSU plot since 2002, it looks flat over the period 2002-2011. I do not know what it will be in 2012 and 2013. What is your expectation for the next, say, 5 years?
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  15. JMurphy - You write "But who do you (Dr Pielke) believe is doing the misleading" I do not subscribe to the thesis that anyone is deliberating misleading. Everyone I know on all sides of this issue are sincere in their views. This, of course, does not make them correct, but I suggest starting with that respect will go along way to determining what is agreed to and what is not agreed. Then find mutually agreed to ways to resolve the disagrements, or at least to clearly articulate them. I know SkS's goal is to do this. However, in my experience on SkS, as one example, you are seeking to refute the use of the shorter term temperature trend data, rather than accepting that to some, this does raise an issue with the claims of the dominance of the radiative effect of CO2 and a few other greenhouse gases in terms of climate change.
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  16. Dr. Pielke:
    Those "some" are wrong, and thus we seek to explain why they are wrong. We are trying to "refute the use of the shorter term temperature trend data" because forming conclusions based on short-term data is inappropriate. Yes, we are trying to refute something that is incorrect, and will continue to do so. However, TLT discussions should move to the TLT thread, and we should be moving on to the OHC point #3 in this thread. See the second link in my comment #110 for the latest on point #3.
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  17. Dr. Pielke, The amount of heat accumulated in the top 700 m varied by the team processing the data, and one is dealing with a very short window of time, so we should be very cautious about drawing sweeping conclusions or making generalizations. You seem to be making the same error with the OHC data as you are with the RSS data--drawing conclusions that are not justified by the data, or more specifically, the shorty time frame involved. For what it is worth, the accumulated heat since 2003 using the data of Palmer et al. is actually slightly higher than what you estimated using Hansen et al.'s (2005) estimate-- time will tell which analysis is more reliable.
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  18. Where is the forcing from dust in the diagram in this post? If the dust is feedback and not forcing, then how is the paleo-derived sensitivity applicable to today's transition from the present climate to the CO2 doubled climate? (since there is no dust involved now)
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  19. "In the LGM, the direct radiative forcing of soil dust aerosols is close to zero at the tropopause and −0.4Wm−2 at the surface." Source: Takemura et al 2008 Surely if aerosol forcing was underestimated at LGM, that would result in sensitivity being underestimated as well?
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  20. scaddenp, you mean if dust cooling was overestimated then the sensitivity to CO2 was underestimated? IOW if increases in dust cool more in LGM then there is less need for cooling from lowering CO2 to arrive at LGM temperatures and if dust cools less then lowering CO2 must cool more. The paper says that the cooling from dust was offset by warmer clouds due to smaller ice crystals. If that is true, it means dust is not a major factor in cooling and CO2 sensitivity is higher. The authors have some uncertainty in their cloud nucleus analysis (could range from negative to positive cooling). Also I'm not sure if they consider all the weather impacts. It is possible that more dust means less cooling from weather due to less concentrated convection (that seems to apply to the present climate). Alternatively more nucleae could mean more precipitation and more cooling.
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