13 August 2009

Evidence that Global Temperature Trends Have Been Overstated

UPDATE: My father discuss the underlying scientific issues in further depth here.

I am a co-author on a paper that has just been accepted by the Journal of Geophysical Research-Atmospheres and is now in press (PDF here, I will add a link to a version on my personal page as soon as it is up). The paper originated in a “dinner table debate” between me and my father. It subsequently turned into a research paper involving a collaboration with Phil Klotzbach of CSU and John Christy and Dick McNider at the University of Alabama-Huntsville.

The paper is important for two reasons. First, it provides confirmatory evidence that the globe has indeed been warming over the period of the satellite records. Indeed the argument that we make in the paper depends upon the presence of a warming trend, Second, it provides a parsimonious and logical explanation for a discrepancy observed in the temperature record that has been often highlighted but which to date been unsatisfactorily explained.

For several years my father has been talking about the possibility of a “warm bias” in the surface temperature record. It took me a while to understand his argument, which involves insights from a range of scientific areas of study including basic processes of boundary-layer meteorology in the context of long-term changes in climate, land-surface processes, and land-atmospheric interactions, as they are related to the manner in which surface and satellite temperatures are actually monitored and how surface temperature trends are calculated (I should add that the interdisciplinary expertise required to intergrate these areas of knowledge is well-represented in our author team). I was skeptical so I proposed an empirical test that we might apply to prove or disprove his claim. It turns out that the suggestion of a warm bias in the surface temperature record not only passes the tests that we apply, but they provide further evidence in support of of my father's arguments. Score (another) one for Dad.

We begin our paper by noting a well-documented and puzzling discrepancy in global atmospheric temperature measurements:
Since 1979, when satellite observations of global atmospheric temperature became available, trends in thermometer-estimated surface warming have been larger than trends in the lower troposphere estimated from satellites and radiosondes as discussed in a recent Climate Change Science Program (CCSP) report [Karl et al., 2006]. Santer et al. [2005] presented three possible explanations for this divergence: i) an artifact resulting from the data quality of the surface, satellite and/or radiosonde observations; ii) a real difference due to natural internal variability and/or external forcings; or iii) a portion of the difference is due to the spatial coverage differences between the satellite and surface temperature data. Santer et al. [2005] focused on the second and third explanations, finding them insufficient to fully explain the divergence. They suggest in conclusion that, among other possible explanations, “A nonsignificant trend differential would also occur if the surface warming had been overestimated by 0.05°C per decade in the IPCC data.”
We call the discrepancy between trends observed at the surface and those in the lower troposphere a “divergence” meaning that they are behaving differently. In 2006 the Climate Change Science Program discussed this divergence and found the issue to be “still open.” Our paper conducts an investigation of the neglected first hypothesis proposed by Santer et al. (2005) as follows:
[W]e consider the possible existence of a warm bias in the surface temperature trend analyses using the following two hypotheses related to the divergence between the surface and lower tropospheric temperature records since 1979:

1. If there is no warm bias in the surface temperature trends, then there should not be an increasing divergence with time between the tropospheric and surface temperature anomalies [Karl et al., 2006]. The difference between lower troposphere and surface anomalies should not be greater over land areas.

2. If there is no warm bias in the surface temperature trends, then the divergence should not be larger for both maximum and minimum temperatures at high latitude land locations in the winter.

We conclude that the first explanation offered by Santer et al. [2005] provides the most parsimonious explanation for the divergence between surface and lower troposphere temperature trends, based on recent research suggestive of biases in the surface temperature record. Our findings suggest that the supposed reconciliation of differences between surface and satellite datasets [Karl et al., 2006] has not occurred.
What do we find?

First, we explain why it is that there is evidence of a “warm bias” in the global temperature record. It has to do with how surface temperatures used to calculate long-term trends are constructed – by averaging daily maximum and minimum temperatures combined with the effects of what are called “atmospheric boundary layer processes” on minimum temperatures. In the paper we provide a review of this well-understood area of meteorology. This discussion is somewhat complex and technical, but it is also well-supported and should be non-controversial.

We argue that:
Because the land surface temperature record does in fact combine temperature minimum and maximum temperature measurements, where there has been a reduction in nighttime cooling due to this disruption, the long-term temperature record will have a warm bias. The warm bias will represent an increase in measured temperature due to a local redistribution of heat, however it will not represent an increase in the accumulation of heat in the deep atmosphere. The reduction in nighttime cooling that leads to this bias may indeed be the result of human interference in the climate system (i.e., local effects of increasing greenhouse gases, surface conditions, aerosols or human effects on cloud cover), but through a causal mechanism distinct from the large-scale radiative effects of greenhouse gases.
It is important to underscore that our hypothesis depends upon (a) the presence of a real warming trend, and (b) (to some extent) an increase in greenhouse gases. So if you accept our arguments, then you necessarily are accepting the presence of a warming trend and corresponding increases in greenhouse gases. This too should be non-controversial, but I want to be clear to avoid any possible misinterpretations.

So then let’s look at the data. We use surface data from the Hadley Center in the UK and NOAA in the US, and for satellite data we use the UAH and the RSS datasets. We analyze the data over land and ocean. The figures below show the differences between the surface temperature records and the satellite records for the period 1979 to 2008. Also shown is the difference that would be expected based on the results of a number of climate model runs as presented by the CCSP (i.e., the values from the models are from the CCSP). Clearly there is a visual divergence represented as a increase in the differences over time as well as a visual difference between what has been observed and what the models suggest should be expected.
Figure 1. NCDC minus UAH lower troposphere (blue line) and NCDC minus RSS lower troposphere (green line) annual land temperature differences over the period from 1979-2008. The expected anomaly difference given the model amplification lapse rate factor of 1.2 is also provided. All differences are normalized so that the difference in 1979 is zero.

Figure 2. CRUTEM3v minus UAH lower troposphere (blue line) and CRUTEM3v minus RSS lower troposphere (green line) annual land temperature differences over the period from 1979-2008. The expected anomaly difference given the model amplification lapse rate factor of 1.2 is also provided. All differences are normalized so that the difference in 1979 is zero.
What is really interesting is that the divergence that we observe is statistically significant in 3 of 4 cases over land (that is, NCDC minus UAH, NCDC minus RSS, Hadley minus UAH) but not in any of the cases over the ocean, which is exactly what we’d expect in the presence of a warm bias in the land surface temperature measurements. We think as well that we can explain why there is not a statistically significant difference over land between Hadley and RSS, and this is discussed in the paper.

We then take the analysis a step further:
The warm bias in the temperature data would most likely be in evidence over land areas where larger vertical temperature stratification occurs near the ground along with a reduction of the atmospheric cooling rate. This effect will be largest in the higher latitudes, especially in minimum temperatures during the winter months, since any reduction in the cooling rate of the of the atmosphere will result in a particularly large temperature increase near the ground surface in this strongly stably stratified boundary layer.
So we look at the higher latitudes and find that:
… the northern polar areas have received considerably more warming in the boreal winter with regards to minimum temperatures than with regards to maximum temperatures. The reader should be careful in interpreting these results, however, since the 95% confidence intervals for maximum and minimum temperatures in the polar areas during the winter months is quite large. The trend in minimum temperatures in northern polar areas is statistically significantly greater than the trend in maximum temperature at the 95% level during the winter months. This is consistent with the findings reported in Pielke and Matsui [2005], Pielke et al. [2007] and Lin et al. [2007] of a warm bias in the global analysis of surface temperature trends. This is also consistent with the view that column climate sensitivity is dependent on the depth of the boundary layer [Esau, 2008]. At higher latitudes, boundary layer depths are in general lower and more stable and thus heat is distributed over a shallower layer making the proportional response greater. This leads to more warming at the surface than aloft and thus is not indicative of heat accumulation in the deep atmosphere.
So we believe that we have demonstrated compelling evidence for the presence of a warm bias in global temperature trends that may indeed be reflective of a human influence on the climate system, but is not due to the accumulation of heat in the system. The obvious conclusion from this result, should it be correct and hold up, is that the effects of carbon dioxide on global temperature trends may have been overstated in past assessments by some amount.

Again, this does not mean that increasing carbon dioxide is not a problem, nor does it mean that efforts to decarbonize the economy do not make sense. Our paper has not led me to alter the climate mitigation and adaptation policies that I advocate one bit. It does mean that there remains plenty of questions to ask and answers to find – some perhaps surprising – about the relationship of human activities and the global earth system.

Here is how we conclude our paper:
We find that there have, in general, been larger linear trends in surface temperature datasets such as the NCDC and HadCRUTv3 surface datasets when compared with the UAH and RSS lower tropospheric datasets, especially over land areas. This variation in trends is also confirmed by the larger temperature anomalies that have been reported for near surface air temperatures (e.g., Zorita et al., 2008; Chase et al., 2006; 2008, Connolley, 2008). The differences between surface and satellite datasets tend to be largest over land areas, indicating that there may still be some contamination due to various aspects of land surface change, atmospheric aerosols and the tendency of shallow boundary layers to warm at a greater rate [Lin et al., 2007; Esau, 2008; Christy et al., 2009]. Trends in minimum temperatures in northern polar areas are statistically significantly greater than the trends in maximum temperatures over northern polar areas during the boreal winter months.

We conclude that the fact that trends in thermometer-estimated surface warming over land areas have been larger than trends in the lower troposphere estimated from satellites and radiosondes is most parsimoniously explained by the first possible explanation offered by Santer et al. [2005]. Specifically, the characteristics of the divergence across the datasets are strongly suggestive that it is an artifact resulting from the data quality of the surface, satellite and/or radiosonde observations. These findings indicate that the reconciliation of differences between surface and satellite datasets [Karl et al., 2006] has not yet occurred, and we have offered a suggested reason for the continuing lack of reconciliation.

57 comments:

  1. Doesn't this analysis draw attention to a problem distinct from "global" warming -- that is, "local" warming?

    It seems to me that local warming could be every bit as risky as global warming, and that the better models and better risk mitigation policies for which global warming activists argue are just as needed in this area.

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  2. It appears that CRU's loss of original raw data, and S. McIntyre and you have reported, has given some cover to (resulting in more time to determine whether) the "warm-bias" is attribtable to the "value-added" by CRU to its available data. Is that where focus is heading - less on equipment and more on those in charge?

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  3. Roger sez:

    “First, it provides confirmatory evidence that the globe has indeed been warming over the period of the satellite records.”

    Okay, there is a very slight warming trend from 1979 to the present (the period of the satellite records).

    Even if we ignore the fact that -- per NOAA data -- 1979 was the low point of a cooling trend which began in 1934, I say so what?

    1) Vostok data suggest the globe has been warming for the last 2,000 years. And, it appears to me, there is general consensus on that.

    2) Vostok data further suggest there is nothing even remotely unusual about current temperatures OR current trends. Click here for the full post.

    Tell me Roger, which should I be worried about?

    A) The current cooling trend?

    B) The 2,000 year warming trend?

    C) The (still on going) 10,000 year cooling trend?

    D) The 20,000 year warming trend?

    E) The 30 million year cooling trend?

    F) None of the above - they are ALL primarily driven by natural cycles.

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  4. This is interesting, thanks. I'm not an expert on these matters, but could your findings not also be a source of concern? I can see people using them to suggest that the seriousness of climate change has been overstated. However, if we accept the independent evidence for a response to warming, such as retreating glaciers, then this response has occurred as a consequence of a smaller warming trend. Therefore, is it not possible that we have underestimated the sensitivity of the earth system to climate change?

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  5. Roger,

    Glad the hear this. Now I can change my (many) citations of this from "Klotzbach et al., 2009, in review", to "Klotzbach et al., 2009, in press"! Much better!!

    -Chip

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  6. -4-SteveF

    You ask:

    "could your findings not also be a source of concern? I can see people using them to suggest that the seriousness of climate change has been overstated . . ."

    If "seriousness of climate change" depends upon our results being incorrect, then I suppose these results would be inconvenient. However, I have two responses.

    1. We think that our analysis is solid. Maybe future data or research will show it not to be.

    2. I think a compelling case can be made that climate change is serious, even if historical trends due to radiative forcing from CO2 is somewhat less than previously thought.

    Science proceeds, politics and policy must be able to adapt to new knowledge.

    As readers here are surely aware, I'm not a big fan of evaluating research according to its political expediency (and to be clear, I'm not accusing you of doing so, however your question implies that some will).

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  7. SteveF,

    I get really annoyed with the “retreating glaciers” argument.

    The glaciers have been “retreating” for the last 18-20 thousand years -- ever since the last glacial maximum.

    Click here for more of my observations on ice melt.

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  8. I believe that one could argue that siting issues play a significant role in the surface station record as per the work of Anthony Watts and crew. However with regards to the northern latitudes, I believe the drastic reduction of "rural" stations in both Canada and Siberia in the last 20 years plays a significant role in padding minimum temperature trends due to UHI type effects with the remaining stations. Please note that one can view how many (or more accurately, how few) stations in the northern areas are actually used by surface station datasets such as HADCRUT, GISTEMP and NOAA.

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  9. Roger,

    Thanks for the reply. My feeling is that there remain some unresolved issues with the temperature records in question. I therefore wouldn't be surprised if your latest paper is accurate, or at least is along the right lines.

    I'm prepared to accept that there may have been an overstatement of global temperature trends - my ultimate question isn't so much concerned with how this might be interpreted by certain people who are generally sceptical of the IPCC type consensus (though I did mention it). Rather I'm interested in whether a lesser warming trend could actually be interpreted as a greater cause for concern. Irrespective of the historical temperature trends, the response of the earth system (such as melting glaciers etc etc) has been the same. If the trends have been less, then smaller changes in temperature have lead to the observed responses. In which case, could this not imply that the system is more unstable (or perhaps variable would be a more appropriate term) than has been previously thought? Rather than a 1 degree change required to bring about a large cyrospheric (for example) response, it only requires a 0.5 degree change (figures illustrative, not accurate). I'm just thinking aloud really, but wondering if this is a valid inference.

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  10. Roger you said

    'As readers here are surely aware, I'm not a big fan of evaluating research according to its political expediency '.

    In that case, why did you say

    'Again, this does not mean that increasing carbon dioxide is not a problem, nor does it mean that efforts to decarbonize the economy do not make sense. '

    I have zero faith in the IPCC political process precisely because of the self defence required by significant individuals commenting in this field. The circus at the APS around Jeffrey Marque was extremely instructive.

    thanks

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  11. -10-Eric

    There is a big difference between evaluating science according to criteria of political expediency, and evaluating policy options in the context of scientific findings.

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  12. Nice paper. Let me say as a "denier" that I do not disagree with the proposition that CO2 has increased or temperature has risen slightly. Although I am less sure about, say, water vapor, and certain that Methane is flatlining and several other greenhouse gases have declined...but the net should be warming.

    But please clarify. Is your assumption that ALL the warming in the satellites is Greenhouse warming? Or just that there is some warming and some greenhouse warming? The latter is of course non controversial. The former is even controversial among those of us who think that the IPCC's statement about most of the warming since 1950 (not all and not since 1900 or 1850 you notice!) being greenhouse warming might well be correct. At least some of it is probably due to natural or other anthropogenic effects, like soot, in our view. I assume that your assumptions are that CO2 is contributing to warming and some is happening. Correct me if I'm wrong.

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  13. Yes Roger there is a difference, but I wonder why you have to provide a pre-emptive defence against one kind of evaluation ?

    Have you or your colleagues ever warned against your research being used for alarmist purposes ?

    My opinion is that scientific neutrality is suffering enormously through this blatant politically biased process.

    This is what Mike Hulme said.

    'One is even quite sure what sort of knowledge it is that the IPCC, as a “boundary organisation” – part science, part politics - actually produces. Nor how the world at large interprets that hybrid knowledge'.

    best wishes

    Eric

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  14. Dr. Pielke,

    1) I have a high degree of respect for your integrity on these issues -- even where we disagree.

    2) Would you say the IPCC has a very long history of “evaluating science according to criteria of political expediency”?

    3) To what extent do you base your own assumptions that CO2 mitigation is advisable upon the purely political evaluations of the IPCC?

    I suspect you’re very tired of my continual reminders, but I am still waiting for you to honor your commitment to explain what led you -- personally -- to conclude that it is advisable to perpetuate the current CO2 famine.

    In my opinion, reevaluating your personal assumptions can only increase your personal integrity -- even if your conclusions remain the same. If you can reevaluate your conclusions by relying exclusively and directly upon peer reviewed science (as opposed to the purely political IPCC interpretations of that science) you might see things in a different light.

    Case in point, in this post, I directly quote both the science cited by the IPCC and the purely political CO2 centric spin which the IPCC applied in their OBVIOUSLY one-sided interpretation.

    Respectfully,
    SBVOR

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  15. -13-Eric

    "Have you or your colleagues ever warned against your research being used for alarmist purposes?"

    Sure, see my disaster work, I've been making exactly such warnings for about 15 years.

    -14-SBVOR

    You are persistent, I'll give you that. but I am afraid that I am going to make you wait a good while longer for your answer, but hopefully it will be worth the wait.

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  16. -15-Roger,

    Respectfully, why the wait?

    I would think you could rattle this off the top of your head.

    Aren't these assumptions the driving force behind your life's work?

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  17. -16-SBVOR

    I've addressed this many times, but you are right that a thoughtful explication is not unwarranted. However, it will take some time, and that is in short order at the moment.

    Don't worry, the issue is not going away. Neither am I. All on this for now.

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  18. > statistically significant in 3 of 4 cases

    Can you explain how this test works for us non-experts? Do you predict in advance what proportion of the cases will be significant, then evaluate that prediction?

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  19. Hank-

    Thanks for the question.

    The short answer to your question is that we take a well-known and unsatisfactorily-explained feature of the temperature record -- a growing divergence between surface and satellite tropospheric temps -- and explore whether it is consistent with a previously alleged bias in the surface temperature record.

    We offer up two hypotheses that follow directly from this line of thinking and then look at what the data show. What you are asking about is part of the answer to one of these hypotheses.

    Santer et al. 2005 tried to explain the observed divergence and pointed to but ignored the option that we are exploring here. We think that it makes physical sense and is supported by the data.

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  20. "Because the land surface temperature record does in fact combine temperature minimum and maximum temperature measurements, where there has been a reduction in nighttime cooling due to this disruption, the long-term temperature record will have a warm bias. The warm bias will represent an increase in measured temperature due to a local redistribution of heat, however it will not represent an increase in the accumulation of heat in the deep atmosphere."

    I can't understand the use of the word "bias" here.

    You do claim to propose a physical mechanism to explain the divergence. If correct, that would mean that the divergence is not a data error but a real phenomenon. How could this have any implications for an overestimated warming trend at the surface?

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  21. We mean "bias" in the sense that it is defined in the Oxford English dictionary which is simply to "influence unfairly" (see OED) and we are following the exact same use of this term from the CCSP 2006 report, e.g.:

    "Systematic local biases in surface temperature trends may exist due to changes in
    station exposure and instrumentation over land, or changes in measurement
    techniques by ships and buoys in the ocean."

    "Bias" includes but is not limited to the effects of measurement, but also includes issue "exposure."

    Specifically, we are claiming that the different trends observed in (a) surface datasets and (b) lower tropospheric datasets reflects the influence of boundary layer processes on the surface record. As we write, this "represents a redistribution of heat rather than accumulated heat" and thus "leads to a direct warm bias if interpreted as a heat accumulation."

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  22. Uncorrected changes in instrumentation yield a difference between the expectation of the measurement and the true value of the parameter being measured, i.e. a bias.

    If there is "a redistribution of heat rather than accumulated heat" correctly represented in the temperature record, it is entirely misleading to call it a "bias".

    So apparently the crux of the matter is "if interpreted as a heat accumulation". This means that you are saying the temperature record is correct, but that the total thermal energy of the atmosphere is lower than would otherwise be the case. I am not yet convinced of this, but if so, it might reconcile the lower troposphere record with the surface.

    What it would not do, though, is show that the surface record is wrong.

    When, given your high visibility, you publish an article entitled "Evidence that Global Temperature Trends Have Been Overstated", while referring to a similarly titled article by your father, "Why there is a Warm Bias in the Existing Analyses of the Global Average Surface Temperature", you both eave the impression that so many people want to hear, that the surface is not warming and that the tropospheric records are correct. In fact though, if I understand the above, you make exactly the contrary assertion, that the surface is warming as measured and that you have found a reconciliation with the observations.

    If there is a consequential bias (in the usual quantitative sense of the word) that you have discovered, it is in the models, not in the observations. I suggest, then, that you are writing articles whose titles are seriously misleading.

    Much of Klotzbach et al section 2 is devoted to biases in the ordinary sense. This further leaves the expectation that the meaning of "bias" used is the usual one of "systematic nonzero mean observational error". No transition is offered in the implied definition when Klotzbach et al simply jumps to

    "Monitoring temperature at a single height will produce a significant warm bias when the atmosphere has warmed over time [Pielke and Matsui, 2005]. This effect will occur even for otherwise ideal locations for making spatially representative temperature measurements."

    This switches attention to a physical phenomenon, not an instrumentation bias. In other words, the temperature has not been "overstated" at all in the records at all as a consequence of the proposed result.

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  23. -23-Michael

    Thanks for this comment, however I will respectfully disagree on a couple of your claims.

    1. First, where we seem to agree -- you now seem to understand our central claim, below with my inserts:

    "you are saying the [surface] temperature record is correct, but that the total thermal energy of the atmosphere is lower than would otherwise be the case [as represented by that record]. I am not yet convinced of this, but if so, it might reconcile the lower troposphere record with the surface"

    This seems pretty fair.

    2. You write: "What it would not do, though, is show that the surface record is wrong"

    We show evidence for, as I say in the title of this post, that "global temperature trends have been overstated". How is this?

    The IPCC 2007 states:

    "New analyses of balloon-borne and satellite
    measurements of lower- and mid-tropospheric
    temperature show warming rates that are similar
    to those of the surface temperature record and are consistent within their respective uncertainties, largely reconciling a discrepancy noted in the TAR."

    What we present suggests that this conclusion is incorrect (and to be clear, I am now moving from what our paper presents to its significance). How can you reconcile what our paper shows with this statement?

    3. You write: "you both leave the impression that so many people want to hear, that the surface is not warming and that the tropospheric records are correct"

    This statement could not be more wrong. As I wrote above in this post : "if you accept our arguments, then you necessarily are accepting the presence of a warming trend and corresponding increases in greenhouse gases. This too should be non-controversial, but I want to be clear to avoid any possible misinterpretations."

    I don't think an evaluation of our paper depends upon what people do or don't want to hear, do you?

    It may in fact be the case the the lower tropospheric measurements of atmospheric temperature trends provide a better representation of long-term atmospheric warming than does the surface temperature record. Are you willing to accept this as a scientific possibility?

    4. Also, while our paper has implications for the models, our analysis and conclusions are primarily about observations and how to interpret them.

    Maybe our analysis is incorrect. But it is plausible.

    You have not yet engaged the substance of the paper, but language and how it might be received. You may disagree with the semantics, but hopefully this reply clarifies.

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  24. Roger,

    AIUI, what the paper claims to identify is a real physical process whereby the surface temperature has actually warmed a little more than would be the case in the absence of this process.

    How on earth can you justify calling this a bias in the measurements? Granting your argument for now, the warming is due to a very real physical process that the measurements are accurately representing.

    TO put it another way, what do you think the surface temperature record is supposed to represent, if not the temperature at the surface?

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  25. > add a link to a version on my
    > personal page as soon as it is up

    Say when please.

    It'll be interesting to watch how this spreads and see how it's treated. I tried searching on the first sentence from your conclusion:

    http://www.google.com/search?q=%22We+find+that+there+have%2C+in+general%2C+been+larger+linear+trends+in+surface+temperature+datasets+such+as+the+NCDC%22

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  26. -25-James

    Thanks for your question. I answered this above:

    "As we write, this "represents a redistribution of heat rather than accumulated heat" and thus "leads to a direct warm bias if interpreted as a heat accumulation.""

    M Tobis seems to have understood this when he wrote ([with my clarifications]):

    "you are saying the [surface] temperature record is correct, but that the total thermal energy of the atmosphere is lower than would otherwise be the case [as represented by that record]. I am not yet convinced of this, but if so, it might reconcile the lower troposphere record with the surface"

    Let me ask you the same question that I asked Michael, based on what the IPCC wrote:

    ------------
    "New analyses of balloon-borne and satellite
    measurements of lower- and mid-tropospheric
    temperature show warming rates that are similar
    to those of the surface temperature record and are consistent within their respective uncertainties, largely reconciling a discrepancy noted in the TAR."

    What we present suggests that this conclusion is incorrect (and to be clear, I am now moving from what our paper presents to its significance). How can you reconcile what our paper shows with this statement?
    -------------

    One way to reconcile the two would be to assert that the uncertainties in the satellite records are so large as to encompass the surface temperature trends. Another hypothesis is to assert, as we have, that the surface temperature record has a bias in in that leads to a divergence between the trends.

    Both explanations are logically possible. We think that our explanation is grounded in a simple, coherent, physically-based set of processes supported by the observational record. This alone does not make it correct, but it does make it well worth examining in more depth, because it could be right.

    Semantics aside, surely you can grant the basic logic here,regardless whether you agree with the analysis itself (which I hope you guys will engage once we get past the sematical points).

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  27. -26-Hank

    The paper up on the JGR-A site is still this one:

    http://www.climatesci.org/publications/pdf/R-345.pdf

    When I have the published version I'll put it up.

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  28. I didn't follow up on what you meant by "exposure". You seem to suggest that "station exposure" and "issue exposure" use the word "exposure" in a way that is related in some other way than a rather remote etymological connection. Are you saying that the temperature trend is "biased and overstated" means that people pay too much attention to it?

    Admittedly I haven't gotten very far into the paper, but it will be difficult to do so if we are talking different languages. You can see my first effort here, where I assumed that by "bias" you meant what published scientific papers usually mean by "bias".

    http://initforthegold.blogspot.com/2009/08/klotzbach-et-al.html

    I will have to start over in the light of the fact that "bias" means, um, well I still don't know exactly. "Unfair influence" and perhaps "inappropriate exposure"? I'm not sure how that helps me with reasoning about measurements and trends.

    Meanwhile, lets jump over all the material to the concluding paragraph. It says: "the characteristics of the divergence across the datasets are strongly suggestive that it is an artifact resulting from the data quality of the surface, satellite and/or radiosonde observations." In other words, Klotzbach concludes that the data are biased in the plain old fashioned sense of having a nonzero-mean error.

    How is this conclusion reconciled with the story you are telling? The idea of your mechanism reconciling the two datasets is consistent with the next-to-last paragraph in the paper but not, insofar as I can tell, the last one.

    Also, it seems to me that neither is consistent with the way you or RP Sr are informally representing the results. Here it becomes a matter of something more ethically fraught than simply value-neutral science would normally be.

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  29. -29-Michael

    Thanks for these further comments, a few replies:

    1. Again, we mean bias in exactly the same way as used in CCSP 2006. So if you have semantic issues, do note that we are following an established convention. "Exposure" of a station refers to its location and other characteristics with respect to the variable being measured. This seems pretty obvious to me.

    2. The sentence that you highlight from the final paragraph is a direct reference back to Santer et al. 2005 (we use the same phrase in the intro), which offered three hypotheses but examined only 2 of them (we could have made this allusion more clear, I agree, it is a long way from p. 1 to p.17;-). We find support for that unexamined hypothesis.

    3. On your reference to issues of ethics, I have absolutely no idea what you are talking about. If anyone reading this post or my comments thinks that I've crossed some ethical boundaries in discussing this paper, I'd be happy to hear it. When thinking about ethics readers might contrast the tone in discussion about this paper here with the example that you've set forth on your own blog:

    http://initforthegold.blogspot.com/2009/08/pielkes-all-way-down.html

    4. Finally, it is obviously difficult to have a conversation with someone who admits "I haven't gotten very far into the paper" yet feels comfortable writing several highly critical blog posts on it, the most recent of which badly mischaracterizes the paper, e.g., by confusing boundary layer processes with climate sensitivity. So I welcome your getting deeper into the paper and continuing a more informed conversation.

    ReplyDelete
  30. As for the posting you link, it definitely is unimpressed with the methodology of Eastman et al, but comes to no final judgment on other work you or your father may be involved in. Since you claim the present result does not depend on Eastman et al by way of Matsui and Pielke Sr., we need not discuss it, though I am willing to do so.

    Anyway.

    K et al's use of the term "bias" is at best unusual. Your claim clarifying my suggested interpretation in #27 amounts to this: "without updating the theory, the surface record may bias expectations of the troposphere trend". Since you further claim to reconcile the two, you are not claiming to elucidate any error in either record.

    Then, abruptly in the concluding paragraph we see concern about data quality. How does an argument reconciling two data records that might otherwise have been seen as inconsistent raise concerns about data quality? Wouldn't it, rather, put them to rest?

    We all know very well that there are people very eager to see temperature sensitivity turn out very small. Many of them follow your blog.

    So when you title your blog posting as you did this one, do you not imply to them that K et al implies that the surface temperature trend is overstated? And does it not, in fact, constitute a reconciliation with the tropospheric record?

    Since delay of emissions mitigation policies will probably turn out to be increasingly costly if mitigation turns out necessary, headlines that can be used in support of delaying such mitigation should be based on fact. So the question of where the headline for this article is supported in the publication is not a value-neutral question.

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  31. -31-Michael

    A quick reply for now, and then we'll have to pick this up tomorrow.

    1. You ask, "So when you title your blog posting as you did this one, do you not imply to them that K et al implies that the surface temperature trend is overstated?"

    Yes. See #2 below.

    2.Yes. "And does it not, in fact, constitute a reconciliation with the tropospheric record?"

    Yes, but at the _lower rate_ of warming found in the tropospheric record. You can connect the dots between "lower" and "overstated."

    3. I am a strong supporter of mitigation policies. I even wrote in this post:

    "Again, this does not mean that increasing carbon dioxide is not a problem, nor does it mean that efforts to decarbonize the economy do not make sense. Our paper has not led me to alter the climate mitigation and adaptation policies that I advocate one bit."

    The headline is accurate, and I stand by the paper. Attacking it for political reasons is spectacularly ironic.

    Thanks again.

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  32. Um, you claim that part of the surface warming is due to a directly and/or indirectly greenhouse-forced boundary layer effect. Stipulated for purpose of argument. And you claim that this accounts for the smaller tropospheric trend. Stipulated for purpose of argument.

    And this means that I can "connect the dots between 'lower' and 'overstated'." Huh? Sorry. Maybe I am a bit out of practice with connect-the-dots, but I really don't get it and I'm not alone.

    Everything is consistent so something is overstated?

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  33. -33-Michael

    Sorry for the connect-the-dots comment, things that I think are obvious obviously are not;-)

    My father provides an example of how our paper implies a smaller warming atmospheric trend at his blog, and I excerpt here:

    ". . . a conservative estimate of the warm bias resulting from measuring the temperature near the ground is around 0.21 C per decade (with the nightime T(min) contributing a large part of this bias) . Since land covers about 29% of the Earth’s surface (see), the warm bias due to this influence explains about 30% of the IPCC estimate of global warming. In other words, consideration of the bias in temperature would reduce the IPCC trend to about 0.14 degrees C per decade, still a warming, but not as large as indicated by the IPCC."

    http://climatesci.org/2009/08/13/new-paper-documents-a-warm-bias-in-the-calculation-of-a-multi-decadal-global-average-surface-temperature-trend-klotzbach-et-al-2009/

    Once again, part of the overall trend we explain as a _redistribution in heat_ not as an increase, so if we want to understand how much the atmosphere has actually warmed this redistribution needs to be factored out.

    It may well have consequences for we are to understand the actual warming of the atmosphere due to the GHG-driven changes in radiative forcing. This goes beyond my expertise, however, so let me put how I understand it in another way. The IPCC says that "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations".

    The processes that we describe in our paper are not considered in the IPCC. So if, for purposes of argument, these processes do account for 30% of the observed trend, this would seem important to know, right?

    Surely it you can accept the logical point that if what we are measuring represents a redistribution of heat rather than an increase, account for that redistribution would necessarily lead to a reduced estimate of the increase.

    ReplyDelete
  34. "leads to a direct warm bias if interpreted as a heat accumulation."

    So just to clarify, you don't have any support whatsoever for your claim that the surface temperature trend is overstated? Rather, you are claiming that the surface temperature trend is greater than expected, in terms of its relationship to the tropospheric temperature trend.

    Indeed your theory (if true) would actually increase support for the accuracy of the surface temperature record, as with this reinterpretation of the surface/troposphere relationship the surface trend now agrees with the satellite record more precisely than before.

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  35. -35-James

    1. You ask:

    "So just to clarify, you don't have any support whatsoever for your claim that the surface temperature trend is overstated?"

    Nope. Please have a look at this thread again, in the previous comment I state:

    "Surely it you can accept the logical point that if what we are measuring represents a redistribution of heat rather than an increase, account for that redistribution would necessarily lead to a reduced estimate of the increase."

    2. You write: "with this reinterpretation of the surface/troposphere relationship the surface trend now agrees with the satellite record more precisely than before"

    You're getting closer. But if you accept this argument then you also wind up with the consequences described in #34 above.

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  36. Roger Pielke Sr. reads along and sends this in:

    "I have been following the discussion and am unclear why there is any confusion with respect to our paper. What we show is that sampling the temperature near the ground, as a means to estimate temperature trends through a deeper layer of the atmosphere introduces a bias in that context. The use of a global average surface temperature trend that includes that surface data overstates the magnitude of climate system heat changes."

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  37. Roger,

    You are still wriggling.

    The topic of your post is the "temperature trend" and specifically you claim that the surface temperature trend has been overstated.

    However all the paper actually claims is that the temperature trend at the surface is greater than at altitude (or at least greater than the 1:1.2 proportion that models generally indicate) so that the depth-averaged warming is less, for a given surface trend, than was previously thought. Alternatively, the surface trend is greater, for a given depth-averaged warming, than was previously thought.

    Nowhere in this work is there any basis for the claim you had made that the surface temperature trend is overstated in any way. The surface temperature trend is, by definition, the amount by which the surface temperature has increased. Yes, part of this is (according to your paper) due to heat distribution. So what? Let's accept that is true for now. The surface has still warmed by the amount indicated by the measurements.

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  38. -38-James

    It is fun to play semantic games, especially on blogs. You write:

    "The topic of your post is the "temperature trend" and specifically you claim that the surface temperature trend has been overstated."

    No. The title of the post is "Evidence that Global Temperature Trends Have Been Overstated". It might have been more accurate to write "global atmospheric temperature trends" but it clearly does not say "surface temperature trend" as you allege. So enogh with the word games, OK?

    Now that you have found the "pea under the thimble" (very classy on your part, by the way), maybe we can move one to more productive discussions?

    More productive might be for you to explain if this result -- whatever you want to call it -- is significant (or not) in your own climate modeling work. Does it matter? Does it matter that climate models (as far as I know) don't account for this effect? What would happen if they did? Our paper suggests an alternative explanation to the surface/LT divergence than that presented in Santer et al., does that matter? And so on.

    Ultimately, I suspect that we'll learn that climate model realizations already produce results "consistent with" this finding ;-)

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  39. James - As Roger communicated in comment #39, the issue is the interpretation of what an increase in the surface (e.g. 2m) land temperatures mean. What we have shown is that the temperature trends at this level, particularly for stably stratified boundary layers, are not quantitatively representative of temperatures above this level

    We have confirmed this with real world observations; see

    Lin, X., R.A. Pielke Sr., K.G. Hubbard, K.C. Crawford, M. A. Shafer, and T. Matsui, 2007: An examination of 1997-2007 surface layer temperature trends at two heights in Oklahoma. Geophys. Res. Letts., 34, L24705, doi:10.1029/2007GL031652.
    http://www.climatesci.org/publications/pdf/R-333.pdf

    where we wrote

    "Our results also indicate that the 1.5 or 2 m minimum long term temperature trends over land are not the same as the minimum long term temperatures at other heights within the surface boundary layer (e.g. 9 m), even over relatively
    flat landscapes such as Oklahoma. For landscapes with more terrain relief, this difference is expected to be even larger. Therefore, the use of minimum temperatures at 1.5 or 2 m for interpreting climate system heat change is not appropriate. This means that the 1.5 to 2 m observations of minimum temperatures that are used as part of the analysis to assess climate system heat changes (e.g., such as used to construct Figure SPM-3 of Intergovernmental Panel on Climate Change [2007] and of Parker [2004, 2006] study) lead to a greater long term temperature trend than would be found if higher heights within the surface boundary layer were used.

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  40. "Surely it you can accept the logical point that if what we are measuring represents a redistribution of heat rather than an increase, account for that redistribution would necessarily lead to a reduced estimate of the increase."

    Are we speaking of the heat content of the atmosphere? The thermal inertia of the atmosphere is small. It makes sense to speak of the heat content of the ocean, but for practical purposes the heat content of the atmosphere is really not very important; it has an adjustment time of a few weeks.

    Let me stipulate that if one rearranges heat rather than increasing it, it does not increase. But nobody cares about the heat content of the atmosphere.

    People care about the temperature profile of the atmosphere. Which you claim is overstated. Now you are apparently NOT claiming that the surface trend is overstated. Are you claiming that the troposphere trend is overstated? It's difficult to see where anything you say supports that, since all this talk is about the surface.

    So the title of this article is not about temeprature, it is about heat "redistribution". So at best your title should be "evidence that trends in the heat energy of the atmosphere have been overstated". Yet, as you emphasize, climate models do not resolve this effect. Hence its contribution to the energy content of the whole atmosphere would be tiny. This leaves the following title: "If anyone had cared about the trend in heat energy content of the atmosphere, we provide evidence that they would have very slightly overstated it".

    Now, this isn't to minimize the actual work here. You purport to reconcile the surface and tropospheric records. That is quite an achievement. Why not use the title "Reconciliation of Surface and Tropospheric Records" then?

    One suspects that it is because that is exactly the opposite of what your political audience wants to hear, while "Overstated Temperature Trend" is what they like to hear best.

    It is very tedious to find papers quoted in political sources as saying things they don't do, but the new trend appears to be authors of papers cutting out the middleman. I can't understand it really. Reconciliation of the tropospheric and surface records is a big deal, and you can't point to any temperature record that is called into question by your result. So why not talk about the substantial result you actually claimed, rather than throw a completely new claim in after the fact?

    As for climate models, whether or not they replicate the phenomenon at hand depends on what it is. So we need to go back to the evidence for the hypothesis. If it is real, there is no fundamental reason models could not be tweaked to obtain it. The odd thing, though, is that the quantitative evidence I have seen so far comes from a dynamic computational model in the first place.

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  41. Roger

    I had missed this thread. It's like you're taking a Turing test. ;-)

    ReplyDelete
  42. -41-Michael

    Let's start with your claim that we have reconciled the surface and tropospheric temperatures in a manner differently than was done by the CCSP and reported in the IPCC. We provide a physically based explanation, the CCSP relied on overlapping error bars.

    If you accept this, then you must also accept that the IPCC failed to account for a mechanism responsible for a large part of the surface temperature trend? You mus see this logical conclusion to concluding that our paper reconciling surface and tropospheric temps.

    Also, who is my "political audience"? The fact that you evaluate papers based on who quotes them in a political debate is a remarkable admission from a climate scientist. I suppose that you don't like my disaster work either.

    Finally, you write, "there is no fundamental reason models could not be tweaked to obtain it" -- I certainly agree.

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  43. -41-Michael

    Let me also point out that you requested on your blog that I and other discuss this paper here, at which point you disallowed my response over there.

    http://initforthegold.blogspot.com/2009/08/pielkes-all-way-down.html

    You now have reopened your thread to discussions, and the sustance is gone leaving only insults and ad homs.

    Here I keep the substance and ask the ad homs to be taken elsewhere. I see that you use the opposite approach. Ethical behavior starts at home, no?

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  44. Hi Roger,

    I shouldn't even be commenting at all on this. The posts on Richard Tol's work and Thomas Schelling's comments are far more interesting to me.

    However, I do a fair amount of QA work. I agree that your paper's use of the word "bias" is non-standard, and tends to cause confusion. The standard use of "bias" would be that another temperature measurement device would not show the same temperature increase if it were more properly located or more accurate. I don't think your paper is claiming that. Instead, I think your paper is claiming that even completely accurate (zero bias) surface temperature measurements will show higher warming trends than completely accurate (zero bias) lower tropospheric temperature trends.

    But this is (merely ;-)) science. You keep trying to get your critics to address policy issues. I'm not sure they ever will, but I'm happy to take a shot. In #14, you quote IPCC 2007:

    "New analyses of balloon-borne and satellite measurements of lower- and mid-tropospheric temperature show warming rates that are similar to those of the surface temperature record and are consistent within their respective uncertainties, largely reconciling a discrepancy noted in the TAR."

    You then write, "What we present suggests that this conclusion is incorrect (and to be clear, I am now moving from what our paper presents to its significance). How can you reconcile what our paper shows with this statement?"

    My answer would be to simply quote your father at his blog, as you do in #34:

    ". . . a conservative estimate of the warm bias resulting from measuring the temperature near the ground is around 0.21 C per decade (with the nightime T(min) contributing a large part of this bias) . Since land covers about 29% of the Earth’s surface (see), the warm bias due to this influence explains about 30% of the IPCC estimate of global warming. In other words, consideration of the bias in temperature would reduce the IPCC trend to about 0.14 degrees C per decade, still a warming, but not as large as indicated by the IPCC."

    As of IPCC 2007 (as far as I know) surface temperature trends were slightly above satellite lower tropospheric temperature trends. They were close enough that they could be stated to be, "consistent within their respective uncertainties." But the surface temperature trend was still slightly higher. Your paper essentially explains why the surface temperature trend was still slightly higher.

    Mark

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  45. -45-Mark

    Thanks. Maybe its only certain climate scientists who can't understand this;-)

    Again on "bias" we were just following CCSP 2006, and I don't recall any criticisms of the term there.

    If the mechanisms in our paper explains 30% (or whatever) of observed surface warming that would seem worth discussing, even if issues of language and politics are more fun ;-)

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  46. Roger (Pielke Sr.?) #40 writes:

    "As Roger communicated in comment #39, the issue is the interpretation of what an increase in the surface (e.g. 2m) land temperatures mean. What we have shown is that the temperature trends at this level, particularly for stably stratified boundary layers, are not quantitatively representative of temperatures above this level..."

    Yes, I think what is causing the main problem is the word, "bias." Just because the temperatures "are not quantitatively representative of temperatures above this level" does not mean they would be identified as "biased" (in the environmental measurement instrumentation QA sense with which I am familiar).

    "Our results also indicate that the 1.5 or 2 m minimum long term temperature trends over land are not the same as the minimum long term temperatures at other heights within the surface boundary layer (e.g. 9 m), even over relatively flat landscapes such as Oklahoma. For landscapes with more terrain relief, this difference is expected to be even larger. Therefore, the use of minimum temperatures at 1.5 or 2 m for interpreting climate system heat change is not appropriate."

    Again, I think the problem is in the use of the word "bias." It's not that the temperature measurements at 1.5 or 2 m are wrong, it's just that they are not representative of temperatures at other heights even within the surface boundary layer, and that they are not representative of heat changes. (As you yourself have pointed out, if this is RP Sr., heat changes are in Joules, temperatures are in degrees.)

    "This means that the 1.5 to 2 m observations of minimum temperatures that are used as part of the analysis to assess climate system heat changes (e.g., such as used to construct Figure SPM-3 of Intergovernmental Panel on Climate Change [2007] and of Parker [2004, 2006] study) lead to a greater long term temperature trend than would be found if higher heights within the surface boundary layer were used."

    OK. Interesting stuff. Well written. I don't think this will be disputed (other than y'all may be wrong...but that's another story). ;-)

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  47. Mark - You are correct that the proper metric to assess climate system heat changes is Joules. In terms of heat in the surface layer, as we discussed in our papers; e.g. see

    Pielke Sr., R.A., C. Davey, and J. Morgan, 2004: Assessing "global warming" with surface heat content. Eos, 85, No. 21, 210-211
    http://www.climatesci.org/publications/pdf/R-290.pdf

    Davey, C.A., R.A. Pielke Sr., and K.P. Gallo, 2006: Differences between near-surface equivalent temperature and temperature trends for the eastern United States - Equivalent temperature as an alternative measure of heat content. Global and Planetary Change, 54, 19–32.
    http://www.climatesci.org/publications/pdf/R-268.pdf

    and

    Fall, S., N. Diffenbaugh, D. Niyogi, R.A. Pielke Sr., and G. Rochon, 2009: Temperature and equivalent temperature over the United States (1979 – 2005). Int. J. Climatol., submitted.
    http://www.climatesci.org/publications/pdf/R-346.pdf

    water vapor also needs to be included. However, the dry bulb temperature also needs to be representative, and our new paper shows that a value at a single level is not representative of the dry bulb temperature (and thus the moist enthalpy) at higher levels when the surface layer is thermodynamically stably stratified.

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  48. "However, the dry bulb temperature also needs to be representative, and our new paper shows that a value at a single level is not representative of the dry bulb temperature (and thus the moist enthalpy) at higher levels when the surface layer is thermodynamically stably stratified."

    Indeed. In my opinion, if there was a sincere interest in an honest scientific evaluation of the effects of CO2 and other GHGs on atmospheric temperature, surface temperatures would have been dropped for lower tropospheric satellite measurements several years ago.

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  49. I have to agree with markbahner that the term "bias" in this context is imprecise and leads to confusion. The work being done by Anthony Watts may show a bias in the usual sense. While this paper is interesting, warming over land from land use/land cover changes cannot be quantified until the bias from poorly sited stations and unnecessary adjustments to the temperature record are removed. I do think there is a strong possibility you are right are on the right track. We just will not know until Watts is done.

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  50. What have we really learned from what has been demonstrated? As Roger Sr states "What we have shown is that the temperature trends at this level, particularly for stably stratified boundary layers, are not quantitatively representative of temperatures above this level."

    Fine. But what does that mean for the future of the planet? For example, we cannot claim the difference is the result of land use/land cover changes because the issue of bias from poor siting and unnecessary adjustments to the temperature record have not been settled. But that does not mean we learned nothing.

    It seems to me we can, at least, say a percentage of the increase in globally averaged temp record is NOT from CO2. It may be the entire difference is due to poor siting issues, in which case the chance global warming will be catastrophic will be marginally reduced. Or it may be the entire difference is due to land use/land cover changes, and what does that mean regarding the chance global warming will be catastrophic?

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  51. It never ceases to amaze how the simple mention of global warming in a news story sets off a tsunami of rhetoric. It generally comes from a very vocal minority that would go to its grave swearing that the sum total of climate science is a liberal plot to enrich Al Gore. Alternately, we are told the Martian ice caps are melting, proof that solar radiation and sunspot cycles — and not greenhouse gases — are the cause of planetary warmups.

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  52. Many institutions limit access to their online information. Making this information available will be an asset to all.
    Research Paper Writing

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  53. New developments on this story reported here:

    http://julesandjames.blogspot.com/2011/01/pielkes-all-way-down-revisited.html

    Here is Annan's last sentence:

    > Thus the central claim of PM05, which underpinned this entire edifice, is refuted. No doubt this will be spun as a glorious victory, in some quarters...

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  54. -54-willard

    Many thanks for this ... not reported by Annan but in the GRL paper Annan cite to impeach the work of Pielke Sr. (a GRL paper that is co-authored by ... Pielke Sr.!):

    "Finally, we agree with PM05 that additional work is needed to understand SBL responses to both land use change and radiative forcing. Klotzbach et al. [2009], for example, which shows a statistically significant divergence between the long-term trends of the surface air and lower tropospheric temperatures at higher latitudes in the winter, indicate that the changes in the SBL over time remains an important climate change issue that has been not yet completely examined and understood."

    Klotzbach et al. 2009 was an empirical study, which Annan seems to miccharacterize repeatedly.

    But if he is on to something, then perhaps he will take an action that his post is (oddly enough) critical of -- ask a scientific question and then publish the results in the peer reviewed literature. You know climate science has some issues when this act is criticized.

    If history is any guide, I expect that a snarky, misleading blog post is all he's got;-)

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  55. Well, he has your last comment, so. . .

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  56. New developments on the new developments reported there, five hours later than the first new developments were reported:

    http://pielkeclimatesci.wordpress.com/2011/01/28/james-annan-misses-the-point-again/

    The response by Pielke Sr. does not quote this conclusion:

    > Thus our findings appear to support the earlier findings by Parker [2004] who found that the temperature increase from observations (ascribed to greenhouse gases) is rather independent from wind speed."

    We could say that deemphasizing this support of Parker's results might mischaracterize at least a bit of what Annan is trying to say. Perhaps we should wait for some more peer-reviewed lichurchur before concluding anything.

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