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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

Figure 1:  Global average radiative forcing in 2005 (best estimates and 5 to 95% uncertainty ranges) with respect to 1750.  Source (IPCC AR4).

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):

"Regional variations in radiative forcing may have important regional and global climatic implications that are not resolved by the concept of global mean radiative forcing."

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:

"Despite the vigor with which you criticize Roy Spencer, he actually has been instrumental in elevating our awareness that natural variations in cloud cover, as a result of temporal variations in atmospheric circulation features, as causing long term variations in the TOA radiative imbalance."

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:

"In the meantime, we need to be cautious. If anything, the models are underestimating change, compared with the geological record. According to the evidence from the past, the Earth's climate is sensitive to small changes, whereas the climate models seem to require a much bigger disturbance to produce abrupt change. Simulations of the coming century with the current generation of complex models may be giving us a false sense of security." (Valdes 2011)

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.

"I do not find the glacial and interglacial periods as useful comparisons with the current climate since when we study them with models, they have large differences in imposed terrain (e.g. massive continetal glaciers over the northern hemisphere which will alter jet stream features, for example).

In any case, I find the discussion of the so-called “climate sensitivity” by all sides of this issue as an almost meaningless activity."

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:

"they did not recognize that the global average temperature trend in the lower troposphere has been nearly flat  as shown, for example, in the figure below from the RSS MSU data...There has been NO long-term trend since the large El Niño in 1998.  That’s 13 years."

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

In another blog post, Dr. Pielke said that the upper 700 meters of ocean have accumulated no heat since 2003.  However, we examined the data from several studies on the subject (provided by NOAA), and found that between 2003 and 2009, the upper 700 meters accumulated between 1.1 x 1021 Joules (Levitus - though this reference may be slightly out of date), and 5.6 x 1022 Joules (Palmer), with Willis et al. falling in between at 5.1 x 1021 Joules. 

And of course there's nothing special about the upper 700 meters; von Shuckmann and Le Traon (2011) estimate an increase of 5.9 x 1022 Joules between 2005 and 2010 for 10 to 1,500 meters, and heat is accumulating in the deep oceans as well (i.e. see here and here and here).

While the trends listed above are not statistically significant due to the short timeframe, they are nevertheless most likely positive, and we certainly can't be confident that they are zero, particularly given the order of magnitude discrepancy between the various estimates.  Given this data we wonder, will Dr. Pielke agree that his previous assessment of zero Joules accumulated during this period was incorrect, and that the timeframe (since 2003) and depth (700 meters) is insufficient for a suitable assessment of the climatological trend?

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Comments 1 to 50 out of 120:

  1. One quick comment (still digesting this) - SkS and Pielke Sr may be talking past each other on the CO2 thing. I suspect he's thinking of CO2 vs. water vapor, while you're not.
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  2. Angliss #1, IDK, but it is possible, I can't speak for any contributors to the exchange. In any case, water does not spontaneously decide to become vapor, or delay precipitating once thresholds are reached, and there is already plenty of it exposed to air; therefore, it is not a primary driver. It can only respond to and enhance warming or cooling around it. So, if Pielke is comparing water vapor with CO2, he is comparing a feedback with a forcing, and the discussion has been around primary forcings. CO2 can also be a feedback because a temperature change can alter the carbon cycle, but in this case we know we have added lots of gigatons to the biosphere; so, we know we have created a causative agent, and we can only hope that our cause does not trigger a strong feedback of itself. Dana, thanks for completing the flip-side of what you came to an agreement on. It's kind of anti-climactic for me, but not completing it would have been a gaping hole in the series. It strikes me that many in the denier camp cling to the proposition that AGW is only based on models because the models are complicated and never 100% right; so, they are easy to argue against. Whereas, the paleoclimate record is simple to understand, and it is hard to argue against the idea that, this is what the earth has done in the past, we can expect it to do something similar now.
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  3. Forgot to finish that line of thought: The what-about-the-paleoclimate response to low sensitivity estimates has almost become a meme on the AGW side, but then, I've been seeing it for years, and I have yet to see a comprehensive response. IIRCR, Lindzen made an attempt, but it fell short of being globally applicable.
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  4. Water vapor is a feedback while we're discussing forcings, so that's not the issue. I think it's mostly that Dr. Pielke thinks the black carbon forcing is underestimated, and possibly methane as well. I discussed this in 'CO2 contribution' section.
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  5. It looks to me like Pielke Sr. has simply taken the 26%-for-CO2 number from the paper of Kiehl & Trenberth 1997, which concluded that CO2 is responsible for 26% of the greenhouse effect. That's a long way from 26% of the warming, however.
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  6. I have a problem with the assertion that …. “Based on the NRC definition, the increase in global temperature is a subset of climate change.” In my view, all aspects of climate change have one thing in common – change in temperature. How then can it be seen as anything other than the driving force rather than a sub-set of climate change?
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  7. Agnostic, I'll have a go at answering your question. It really isn't all about change in temperature. Rather, it is about change in energy. Changes in energy can cause phase state changes, like between water and vapor, and water and ice. Difference balance points between where energy is absorbed and where it is transferred somewhere else can affect wind patterns, and also currents. Temperature makes a nice proxy for energy levels, but climate change is more than just temperature because different energy levels change more than just temperature.
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  8. Agnostic Chris G has a point. I'll add that even without temperature changes, increasing CO2 has an effect on ocean acidification and C3/C4 plant responses - climate change as well. That said, global temperatures are a really important indicator, and I feel Dr. Pielke is inappropriately dismissing it.
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  9. Keith, Nice pickup on the distinction between contribution to radiative forcing and contribution to warming. I followed Dr. Peilke's comments to where he mentions that figure, and then to the slide that he referenced, and I'm struggling a bit with understanding his claim that, "The CO2 contribution to the radiative warming decreases to 26.5%" Granted, there are other changes that are forcings, for instance an increase in black aerosols, and if CO2 were to stay the same and they were to increase, then, percentage-wise, there could be a decrease in the relative forcing of CO2. But, CO2 has increased by ~40%, and even given the logarithmic nature of its effect, I have a hard time believing that the effect of the other constituents has increased so much as to cause a relative decrease in the effect of CO2. If that were the case, then I suspect there would be a lot more missing heat to account for. Because, if we can calculate the expected increase in warming from just CO2 at around 0.9 K, there would have to be more forced warming from other sources in order for there to be a percentage decrease in CO2's contribution. In any case, you are right, the question was, how much of the warming, and what he answered was how much of the radiative forcing, and they are not the same.
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  10. KR, thanks for adding those. I was tunneled in on energy and forgot about the chemical changes.
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  11. Dana, May I ask how transient is "transient climate response"? Because, I don't know how you ever avoid obfuscation issues with lag. Why the temp might be under the best estimate could be because, a) the best estimate is a little off, b) there are some small cooling effects being introduced as well, or c) there is a bit more lag in the system than was estimated. I'm not entirely clear on this, but it might be premature to say that (b) is the answer. Hmm, I'm wondering if the answer doesn't hinge on the outcome of the debate whether there is missing heat, possibly in the ocean depths where it is difficult to measure, or there is no missing heat, possibly because of an increase in aerosols from China and India (mostly).
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  12. Chris G - TCR represents what we expect in terms of the immediate climate response to a radiative forcing. It seems like your a and c are basically saying the TCR value may be off, which is certainly true, and why I specified "best estimate". However, if the best estimate is correct, then b is correct.
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  13. I expect this might be a minor point, but the NRC link doesn't appear to have a definition for climate change. The definition quote on Dr Pielke's blog appears to be the defintion for "climate system". Have wires got crossed somewhere, or am I missing something?
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  14. "The" preferred climate change indicator for 'skeptics' is whatever one that has more uncertainty as they tend to have more room for denial. Tricky stitching together of different sensors is also something to look for: - tropospheric hotspot (even 'skeptics' who don't have a clue what it is love it) - short-term noisy temp data - short-term noisy OHC - cloud feedback
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  15. You say '"...Dr. Pielke responded: "~26% of the positive radiative forcing was from CO2"' This may be an overestimate, not an underestimate. Schmidt et al. 2010. Attribution of the present-day total greenhouse effect finds just 20% of it due to CO2. See also NASA, Real Climate. Dr Schmidt says at RC
    One amusing aspect of the process was that one of the referees initially suggested that our paper wasn’t necessary because it was common knowledge that the attribution to CO2 was between 9 and 26% (sound familiar?). As it turns out, they were reading a page from UCAR which was quoting (without attribution!) from my original blog post.
    The chart you show at the top of the post is talking about something else. Evidently the chart folds the water vapor feedback into CO2. It looks like a chart of climate forcings, not radiative forcings, so that you and Dr Pielke Sr. are talking about different things.
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  16. I think I may have gotten caught up in this a bit myself, but I think the distinction between a forcing and a total effect is being blurred. There was a pre-industrial (and pre-agricultural) balance of total radiative energy effects. A change in any of the contributing factors is a forcing. So, saying that the total attribution of CO2 is x is not the same as saying that the forcing is x; the forcing will be some other number determined by how much it has changed and how much that change affects the balance. If CO2 had not changed, its percentage of any positive forcing would be 0%. Let us pretend that you could double CO2 and hold everything else constant. The forcing would be on the order of ln(2) * x, where x was whatever its total contribution was before. But from a percentage standpoint, 100% of the positive forcing would be from CO2. If you account for an increase in water vapor, then the attribution of the positive forcing would be something less than 100%, and so on. Water vapor is a feedback, not an initial forcing, but, it does change the radiative energy balance, and sticking by the definition at the NRC link above, that makes it a forcing. Dr. Pielke is saying that CO2 is only about 1/4 of the positive forcing, which means that the other positive forcings are three times larger in effect than the ~40% change in CO2. At this point, I don't know; maybe that number is not that far off if water vapor contributes a large portion of the remaining 74%. However, that would mean that Dr. Pielke is making a fairly serious omission by not mentioning that it is our CO2 that is driving the increase in water vapor.
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  17. The chart in the post may be based on out of date and inadequate data on black carbon. Compare for instance Jacobson_2010_Fossil_and_Biofuel_Soot_Climate_Effects.pdf (5.5 MB pdf). Mark Z. Jacobson is a man who knows his soot. Whether he is equally sharp on climate forcing I don't know. Other reports that I don't have a link for just now indicate that black carbon in the atmosphere, over the Arctic in particular, may have been significantly underestimated.
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  18. Pete @15 - you're talking about percentage of the greenhouse effect, not percentage of positive radiative forcing. Water vapor is the largest contributor to the greenhouse effect, but not a forcing. Pete @17 - I noted in the post that the black carbon forcing may be underestimated. So may the aerosol negative forcing.
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  19. Dana,I know water vapor is not a climate forcing. So does Gavin Schmidt. That said, is not the disagreement between you and Dr Pielke Sr. based on talking about different things?
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  20. Pete @19, Dr. Pielke was asked a very specific question "what fraction of the observed global warming is due to CO2 and other anthropogenic effects". In that context his answer makes no sense at all. Perhaps he misunderstood the question, but us arguing in circles is not going to shed much light on this. Dr. Pielke really now has two things to answer/explain 1) The original question and 2) explain how he arrived at 26% for radiative forcing for CO2. His numbers do not gel with the body of science on this issue. I hope that people do not get too focussed on this radiative forcing issue (at least not until we have more information from his side), because some of the other issues where Dr. Pielke is at odds with the body of knowledge are equally as critical.
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  21. What we all understand is that the increase in water vapor in response to the temperature increase caused by CO2 is a climate feedback. Trust Gavin: radiative forcing is a separate and important concept. Abstract of Schimdt et al. linked above:
    The relative contributions of atmospheric long-wave absorbers to the present-day global greenhouse effect are among the most misquoted statistics in public discussions of climate change. Much of the interest in these values is however due to an implicit assumption that these contributions are directly relevant for the question of climate sensitivity. Motivated by the need for a clear reference for this issue, we review the existing literature and use the Goddard Institute for Space Studies ModelE radiation module to provide an overview of the role of each absorber at the present-day and under doubled CO2. With a straightforward scheme for allocating overlaps, we find that water vapor is the dominant contributor (~50% of the effect), followed by clouds (~25%) and then CO2 with ~20%. All other absorbers play only minor roles. In a doubled CO2 scenario, this allocation is essentially unchanged, even though the magnitude of the total greenhouse effect is significantly larger than the initial radiative forcing, underscoring the importance of feedbacks from water vapor and clouds to climate sensitivity.
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  22. How might RP Sr have arrived at 26% radiative forcing for CO2? see # 15. It has gone into "common knowledge". Thus the linked paper by Schmidt et al. is needed.
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  23. So, if someone disagrees with the definition with the definition of "forcing" as I am using it, I'd be happier if you would just say so. We are all capable of rational disagreements here. I don't think it matters a great deal though, just different words applied to the same physical processes. In any event, I was thinking about the math some more. If you use the definition, "Climate forcing An energy imbalance imposed on the climate system either externally or by human activities." you would therefore include an increase in water vapor as contributing to the radiative imbalance. Then, if you use a 1.2 K estimate of no-feedback warming that could be attributed to a doubling of CO2, and you combine that with Dr. Pielke's estimate that the positive radiative forcing of CO2 is only 26% of the total forcing, then you end up with something like a warming sensitivity to a doubling of CO2 in the 4.5 K ballpark (1.2/0.26 ~= 4.5), minus negative forcings. Obviously a back-of-the-napkin estimate, and I have slightly abused the 26% number because it was provided in the context of forcing so far rather than forcing for 2x, but that is pretty close to a mainstream estimate. It may be that Dr. Pielke, Sr. has not arrived at estimates that differ by much from the mainstream, but the way he frames his statements makes it seem that way.
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  24. I am coming around to the conclusion that the disagreement is mostly related to Dr. Pielke's not acknowledging the positive forcing feedbacks, dominated by water vapor, but I suspect methane should be included (thawing permafrost and clathrates), that are a direct result of the initial driving force of the increase in CO2. Looking around for statements made by him on the subject of water vapor, his seems to be an argument of uncertainty.
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  25. My problem with Dr.Pielke's analysis is that it undercuts the "moral hazard" arguments discussed on other threads. If CO2 is only responsible for about a quarter of climate change, and land use is the determining factor for regional effects, the industrialized world has far less responsibility for catastrophes in tropical regions, since by his logic, they will be their own fault. Tropical rain forests are the lungs of the planet, and essential for everyone on it ... but they have no economic value unless logged or cleared for agricultural use. This is probably the most extreme market failure in the history of capitalism.
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  26. Old Mole, That is the rub, you can claim that the increase in CO2 is only a quarter of the forcing, and you might be technically correct (or at least in the right ballpark for driving forcing), but your estimate would suffer an error of omission by not acknowledging the feedback forcings that come with any increase in energy content (temperature). It is almost like an accounting game where you show that CO2 has less effect by comparing it to the total effect which includes water vapor, but you don't give CO2 credit for causing the increase in water vapor. I suspect Pielke is avoiding the feedbacks that CO2 is responsible for because he cites work that he published in 2008 that did not find an increase over North America and makes no mention, nor sites the work that Trenberth did earlier, in 2005, which did. Both authors acknowledge that the data is (was?) problematic, but if you post a quote that says, "‘there are no sufficient data sets on hand with a long enough period of record from any source to make a conclusive scientific statement about global water vapor trends’." (attributed to Vonder Haar), why turn around and cite anything at all, unless you really want to believe that there is little water vapor feedback. Meanwhile, there is no reason to believe that warmer air and water does not lead to more water vapor in the air. Kind of speculating here on Pielke's rationale; anyone have more solid information?
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  27. Chris G - The basis of the statement was uncovered in the comments of the 'Pielke Sr. Agrees' post. His calculation is unrelated to feedbacks. RealClimate put up an article about it at the time: 'Recently, Roger Pielke Sr. came up with a (rather improbably precise) value of 26.5% for the CO2 contribution. This was predicated on the enhanced methane forcing mentioned above (though he didn’t remove the ozone effect, which was inconsistent), an unjustified downgrading of the CO2 forcing (from 1.4 to 1.1 W/m2), the addition of an estimated albedo change from remote sensing (but there is no way to assess whether that was either already included (due to aerosol effects), or is a feedback rather than a forcing). A more appropriate re-calculation would give numbers more like those discussed above (i.e. around 30 to 40%).'
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  28. Chris G@11: (Sorry, I'm a bit late to this discussion, hope this point is still of interest) The 0.9C figure is indeed an oversimplification because the 'transient response' is not linear over the 70 year period used to obtain the 2C/x2 figure, although it's almost an aside to Dana's argument, so I'm not very worried. Not sure how accurate it is - I suspect not far off. But I can produce a better estimate using my energy balance model trained against either 20thC climate or to reproduce GISS-modelE enesemble results. I'll try and do that this week, but it may take a few days (exams to set).
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  29. PaulS, Kevin C, Thanks, good information. Yeah, I looked at some model runs, from, and decided the definition of transient did not need to be precise. He isn't playing with the numbers quite as I was guessing, but I still think he is playing numbers games. For instance, he does not talk about feedbacks at all, and I would think that if you are talking about how much CO2 forcing has affected a warming change, you would have to include the feedbacks induced by its initial forcing. Obviously, this is easier said than done, but he is still answering the wrong question. He talks a lot about black carbon, and acknowledges that the increase in black carbon is from the burning of fossil fuels. So, how would you reduce black carbon? Reduce the consumption of fossil fuels would be one way. Reducing the consumption of fossil fuels would also be the answer to how would you most effectively reduce the rate of CO2 increase. So, there isn't much to be gained by arguing how much is carbon black versus how much is CO2. When he says: "2. Attempts to significantly influence regional and local-scale climate based on controlling CO2 emissions alone is an inadequate policy for this purpose." IDK, but if any policy that reduced CO2 also reduced black carbon, and you are downplaying CO2 increases because of BC increases, why would that policy be inadequate? It remains interesting from an academic standpoint, but makes no difference to policy. He also talks a lot about methane; what would be causing a change in methane balance? You can't eliminate an increase in global temperature as causing an increase in methane. So, he could well be mixing initial with feedback forcings, but he treats an increase in methane as an initial forcing. I have heard several plausible physical mechanisms by which it could be a feedback to a warming, I have not heard of any mechanisms other than warming which would cause it to increase. Well, then, there are cows, but do cows really produce more methane than an equivalent biomass of other animals? It now strikes me that the question sounds simple, but might be tricky to answer. Do you include best-guesses on induced feedbacks or not? In particular, if you are disinclined to use global average temperature as a metric, and you have a history of downplaying potential feedbacks, your answer is likely to be at odds with the predominant view.
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  30. RealClimate has a post up on Oceanic Heat Content and they discuss Dr. Pielke Snr's comments on same. They do not agree with Dr. Pielke's reasoning. "I understand Dr. Pielke Sr. has for some time now claimed the Argo system has yet to detect an increase in upper ocean heat content or an ocean heat transport to the deep. Do you concur with his claim and, if not, can you explain how and where this transport to the deep is accomplished? Thank you for your time. [Response: Argo measures temperatures, not heat flux. You can calculate a net heat flux into the top 700m of the ocean given the changes in temperature in this region, but Argo cannot measure the heat flux through that region. The latest data from Willis and others indicates that ocean heat content (top 700m) is increasing, although a lower rate than in the last decade, and the (less comprehensive) studies related to below-700m oceans indicate an increase as well. Most heat transport into the deep ocean will occur in the down-welling branches of the overturning circulation, centered in the North Atlantic and the Southern Oceans. Diffusive fluxes in the rest of the ocean will be much smaller. - gavin]" And "He [Pielke] asks: 1) “If heat is being sequested in the deeper ocean, it must transfer through the upper ocean. In the real world, this has not been seen that I am aware of. In the models, this heat clearly must be transferred (upwards and downwards) through this layer. The Argo network is spatially dense enough that this should have been seen.” Do you agree with this? [Response: Obviously heat going below 700m must have passed through the upper ocean. However, the notion that Argo could see this is odd. Argo measures temperature, not flux. The net flux into a layer is calculated by looking at the change in temperature. It cannot tell you how much came in at the top and left at the bottom, only how much remained. - gavin] Interesting how Dr. Pielke's ideas continue to remain at odds to the science, despite him being presented with overwhelming evidence to the contrary. PS: "gavin" above is Dr. Gavin Schmidt, a much respected NASA scientist.
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  31. Sounds like Pielke has some responses in the works. I certainly agree with Gavin's comments with respect to using OHC as the global warming diagnostic. OHC data just isn't extensive enough, aside from the fact that we need to consider all the evidence.
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  32. Here's my calculation of temperature due to CO2 forcing. The data is MLO from 1959, from here from 1832-1958. Forcing calculated as 3.7*log(co2/284)/log(2). Temperature response function calculated from (a) GISS model E forcings vs 20thC temps, (b) GISS model E forcings vs CMIP3 GISS model E ensemble average temperature. The temperature change estimate of 0.9C from CO2 alone in the article looks a touch on the high side. Why the difference? I get a slightly lower transient sensitivity than 2C/x2 for both the empirical and modelE cases. I think that's consistent with Hansen & Sato 2011 - I think the modelE response is slower some models, giving a lower ratio of transient to long term response. However, I haven't checked to see if they report a figure for transient response.
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    Moderator Response:

    [mc] fixed image link

  33. The image is now broken for me, I'm afraid. I've moved it to an image host with which I've got more experience: I've had a quick look into the TCR (transient response) question. The TCR for modelE is 1.5-1.6, which accounts for the difference in results. My empirical value is very similar, but then I use the GISS forcings. This report says "The full range for TCR in the CMIP3 archive is 1.3 to 2.6°C, with a median of 1.6°C and 25 to 75% quartiles of 1.5 to 2.0°C (Randall et al. 2007). Systematic exploration of model input parameters in one Hadley Centre model gives a range of 1.5 to 2.6°C (Collins, M., et al. 2006).". Which is somewhat ambivalent. Dana's method of scaling the TCR happens to give almost exactly the right answer for any given climate sensitivity. Why? Because as it happens the CO2 forcing has increased pretty linearly over the past 40 years (not shown), and the gradient when projected back crosses the zero line about 70 years ago. So we've effectively lived through a TCR experiment scaled down by a factor of 2, and the resultant temperature rise due to CO2 alone is thus also half of TCR. The only question is what is the correct value for TCR: 1.6 or 2.0°C? GISS modelE and most of the CMIP3 models are around the lower end. However more recently Tung at U.Wash has argued for significantly higher values from solar cycle data.
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  34. Kevin @33, Have you seen this new paper by Padilla et al. (2011)? "For uncertainty assumptions best supported by global surface temperature data up to the present time, we find a most-likely present-day estimate of the transient climate sensitivity to be 1.6 K with 90% confidence the response will fall between 1.3–2.6 K, and we estimate that this interval may be 45% smaller by the year 2030. We calculate that emissions levels equivalent to forcing of less than 475 ppmv CO2 concentration are needed to ensure that the transient temperature response will not exceed 2 K with 95% confidence. This is an assessment for the short-to-medium term and not a recommendation for long-term stabilization forcing; the equilibrium temperature response to this level of CO2 may be much greater. The flat temperature trend of the last decade has a detectable but small influence on TCS."
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  35. Thanks, that's very exciting. Obviously they're way ahead of me. I've only just worked through the mathematics for formally determining the uncertainties on the parameters, but not implemented it yet. I'm not familiar with Kalman filters, but I'm guessing they are more sophisticated than my ad-hoc spline basis functions. It's reassuring though that I'm not doing something stupid, and that we get very similar answers. I'll need to get a copy of the full paper, but reading between the lines of the abstract I think they may have left me one wrinkle to work on. :) (Fixed link to abstract)
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  36. Hi Kevin, No worries, sorry about the dud link. Tks for fixing it.
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  37. SkS - Here are answers to several of your questions: 1. Regarding "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).' I disagree. These events occurred with vastly different land distribution, ocean current etc. 2. Regarding "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?" I did not start in 1998 because it was the warmest in the record. I started after that when the MSU LT became ~flat. We can wait 4 more years to see if the LT starts to warm. Then lets revisit. :-) It certainly has to warm up quickly if Santer's signal will be seen. 3. Regarding "will Dr. Pielke agree that his previous assessment of zero Joules accumulated during this period was incorrect, and that the timeframe (since 2003) and depth (700 meters) is insufficient for a suitable assessment of the climatological trend? I agree it is positive from but relatively small. In my Waterloo talk, I used a value of 1/4 of the rate in the early decade. I would, however, like to also convert this to the heating rate in Watts per meter squared and assess how close it is to Jim Hansen's estimate from GISS of o.6 Watts per meter squared [see]. This is a short time period (~7 years). Nonetheless, I hope you will support me in recommending the adoption of this metric as a primary assessment tool to monitor global warming.
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  38. Dr. Pielke - thank you for answering our questions. Our responses follow, here is the first point: 1) We will have to disagree on this subject. Dr. Hansen has looked at the most recent glacial cycles when the land configuration and oceans currents were very similar to those of today, and was able to estimate an equilibrium climate sensitivity of approximately 3°C for doubled CO2. We have yet to see an explanation for the large discrepancy from those arguing for low climate sensitivity (primarily Spencer, Christy, and Lindzen), and believe it represents a glaring flaw in their hypotheses. Ironically, while Christy and Lindzen have touted their low climate sensitivity estimates as being data- rather than model-based, they are ignoring the paleoclimate data which contradicts their conclusions, and dismissing a whole scientific discipline and volume of data that has been essential in understanding our climate system.
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  39. dana1981- In response to #38, the geography at the time, due to vast areas of continental glaciation with substantial altitude, and of larger areas of sea ice, resulted in the polar jet (apparently) being depressed equatorward. This would make for a quite different climate regime that we currently have. I also question that robustness of calculating the land part of a global average surface temperature anomaly when the elevations in these large continental ice sheet regions was so different than today.
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  40. pielkesr at 07:14 AM on 10 October, 2011. Agreed, climate was different during glacial periods, the question being how different was it in interglacial periods. Though there are obviously uncertainties, these do not mean we can not make increasingly robust estimates of climate sensitivity. The past continental configurations are relatively well defined, but clearly we can only infer Ocean circulation from the proxy temperature records and modelling. Models are becoming more consistent with the limited data we have, and the data itself is becoming more consistent as methodologies improve and uncertainties are reduced. Looking at recent re-evaluations of paleo proxy CO2 levels and the accumulating data sets of regional paleo temperatures, there seems to be reasonable consensus emerging amongst the paleo-climate community, driven by weight of evidence. For example see van de Wal 2011, and also Park and Royer 2011. The latter gives an estimated 95% probability that CO2 driven climate sensitivity is > 3.4 degrees C, and that glaciation, if anything, can increases climate sensitivity, with a longer tail on the upper end of probability distribution. On the other hand Hargeaves 2011 suggests constraining the upper end of overall sensitivity to less than 4 degrees C from ongoing modelling work using an ensemble of SST reconstructions, and this (and other work) hints at meridional overturning in the Atlantic being similar to today.
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  41. Since it has hysteresis, the data from glacial to interglacial transition is not just uncertain, but inapplicable. See for a description. Within a stable state such as the present interglacial, the climate sensitivity to a doubling of CO2 bears no relationship to the glacial stable state or the state transition.
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  42. Dr. Pielke, isn't there a logical inconsistency in suggesting that 7 years is sufficient time to determine a long term trend for upper ocean heat content? How can that be true when different 7 year periods show radically different trends? If 2003-2009 is sufficient to establish a trend of only slight warming why wasn't 1997-2003 (or various other earlier periods) sufficient to establish a more pronounced warming trend? Unless you are suggesting that some major climate forcing has recently changed to a new state which will remain stable for a prolonged period the position seems inherently insupportable. There have been significant trend variations for longer than seven years in the heat content estimates before now. Logically that would seem to indicate that a longer period is needed to screen out data fluctuations and determine the long term trend. Would you be arguing that upper ocean heat content had established a clear long term trend and should serve as the primary (sole?) 'measuring stick' for climate change if we were back in 2003 with only the data available up to that point? Obviously that would have pointed to completely different conclusions than focusing on the past several years does... so either the underlying trends have suddenly changed for some reason or the position is not internally consistent.
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  43. Eric (skeptic) @41, Calov and Ganopolski 2005 argues that NH summer insolation alone is not sufficient by itself to explain the transition between glaciated an non-glaciated states. Fairly obviously, nobody disagrees with that. The difference in albedo between glaciated and non-glaciated state makes an important difference. Importantly, nothing Calov and Ganopolski show suggests that anything other than this change in albedo is the cause for the hysteresis. That being the case, the hysteresis they find is not bar to determining the climate sensitivity of CO2 so long as changes in albedo are treated as a forcing, not a feedback. That is what Hansen has done, so no issue arises.
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  44. Tom, no argument that there is a lot of feedback from several sources needed to create a hysteresis, one of which is CO2. The other large feedback besides albedo, as suggested by Dr. Pielke, is weather. The problem comes when trying to ascertain the warming contribution of albedo feedback, CO2 feedback and weather feedback. Ice albedo being responsible for the hysteresis does not simplify the calcuation. There are, in short, two ways to do it. Extremely crude energy balances that ignore the changes in weather and produce results between 1 and 6C (Knutti 08) or models which must not only have parameterized weather but parameterized paleo weather. Neither method produces anything more than a guesstimate.
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  45. CBDunkerson - I am proposing that now that we have good ocean heat data coverage, we move towards replacing the global annual average surface temperature trend as the primary metric to diagnose global warming. Certainly 7 years is not sufficient but will be as the years pass. Since the models predict (project) how this ocean heat should change, we can track their skill and set up requirements for them to be considered skillful with this metric.
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  46. Dr. Pielke, the large ice sheets during the last glacial maximum formed as a consequence of the low global temperature. Attributing the temperature decrease to the presence of ice sheets and their geographical impact is circular logic. You are effectively arguing that the ice sheets formed due to the presence of the ice sheets. A climate sensitivity of ~3°C for doubled CO2 is a robust feature of the Phanerozoic Eon, across a very large range of continental distributions. Are you suggesting that changes in geographical distribution have mimicked the effect of a high climate sensitivity across all those distinct geographical distributions and time?
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  47. The glacial to interglacial temperature change is around 10C for a 50% increase in CO2, so the primary cause of the change s the ice albedo feedbacks as Tom pointed out above. So indeed it is true that "ice sheets formed due to the presence of ice sheets" and likewise melt due to the melting of ice sheets. Of course geography matters but mostly to the minimum and maximum states. One of the largest changes apart from ice albedo is weather. Here is one example: "Southward movement of the STF was a contributing factor for the large amplitude and rapid rise of temperatures during HS1 and the YDS within the region between 35°S and 45°S" which then caused glacier retreat. There is no way to tease out a 3C per doubling CO2 from a 10C per 50% rise in CO2 without a model and parameterized (i.e. not modeled) weather.
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  48. A reminder from Hansen and Sato 2011:
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  49. Dana @48, You beat me to it. And here is another reminder from another scientist, this time from Dr. Marci Robinson (US Geological Survey): "Yes, uniformitarianism is often defined to mean that the present is the key to the past. But we might be wise to remember another accurate description: The past is a key to understanding the future". Oddly, many "skeptical" scientists continue to ignore or dismiss the paleo record (the past) and seem to have no interest in learning anything from it, unless perhaps it appears to support a low climate sensitivity.
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  50. Eric and Dr Pielke, you're arguing there is a large increase in climate sensitivity as you go from interglacial to glacial conditions. The only suggested mechanism is that the large continental ice sheets, with their ~100m worth of sea level locked up inside them, divert atmospheric pressure systems and oceanic currents due to the change in terrestrial and marine topography. Why and how this change causes a threefold increase in sensitivity (and not a decrease) has not been specified, and is presently speculation. The trouble is, how do you get there from an interglacial world in which there is low climate sensitivity? The interglacial world has not got the large mid-latitude ice sheets, or the lowered sea level to alter ocean currents, and the orbital forcing is too small to initiate glaciation if your climate sensitivity value is low. You need the high climate sensitivity to turn a low insolation around 65N into ice sheets via increased snowcover and drawdown of CO2. Without the high climate sensitivity, the forcing is insufficient and the ice sheets do not form in the first place, and the oceans remain full of water. Do you see the circularity?
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