More satellite stuff

The November 17th issue of Science has an interesting exchange of letters between Christy and Spencer; Mears and Wentz; and Sherwood and Lanzante (ref here; subs required for substance). The context of this discussion is the tropospheric temperature record; see Et tu LT and The tropical lapse rate quandary for two RC posts that discuss the issue, and in particular three papers in the August 11th issue of Science.

The first part of the Christy and Spencer letter simply admits the error that Mears et al. found back in August. Nothing new there (so why is it being published in Science?); though they are somewhat coy about the nature of their error: but judging from the rather blunter reply from Mears and Wentz, it was a simple sign error. M+W point out that C+S first introduced their error in 1998, in response to a Wentz and Schnabel paper, which pointed out a previous C+S error, related to orbital decay. Christy has used the erroneous data in testimony to the Senate trying to cast doubt on the quality of climate models; it will be interesting to see if this is now corrected. C+S attempt to argue that their new data has a trend “that is within the +/- 0.05″ error margin of the previous trend. But this is specious: those error bounds are the standard statistical margins for line-fitting; they [See note] aren’t supposed to represent the possibility of errors in the dataset construction.

C+S continue by arguing that (contrary to the Sherwood paper from August) there may be some spurious warming trends in the radiosonde data; and they give one example. They point out a possible problem with the Day-Minus-Night adjusted data showing too large trends for 1958-1997 for the region south of 30N. Sherwood and Lanzante disagree, and call this a “misleading statistic”, on the grounds that while the tropics are well sampled the region south of 30S isn’t, which leads to erratic trends from radiosondes averaged over that region. C+S attempt to argue that data from US radiosonde validates the C+S satellite dataset: S+L retort rather sharply that C+S have claimed this agreement for the previous version of their data, so shouldn’t the new revised data now disagree? (an alternative is that the agreement with the US radiosondes is simply a poor test of trends in the satellite dataset).

S+L conclude with a rather ironic line: “…it is hard to believe that Christy and Spencer would argue that a data set showing the ‘wrong’ amount of warming must therefore be flawed. If that were a valid argument, their own satellite analysis would have been discarded years ago.”

[Update: the US CCS program report Temperature Trends in the Lower Atmosphere is now available as a public draft; its 300+ pages though so we haven’t read it yet!]

[Another update: an anonymous contributor (see comment 8) points out that the 0.05 bounds are supposed to represent structural uncertainty, not line-fitting as I thought – W]

9 comments on this post.
  1. Mauri Pelto:

    The US CCS report along with the other referenced materials provide a complete story of the long troubled MSU ower troposphere records.
    I can only say thanks to the authors noted for performing a Sherlock Homes worthy investigation and getting to the bottom of what was obviously a troubled data set. This is a huge reanalysis and they are due considerable credit. The lack of warming in the dat set has been used to slow concern over GW. Though it should be clear to any climatologist that either the surface record or the MSU lt record was incorrect. And it was further obvious that the simple and relatively numerous and consistent surface records would not be significanlty in error. But until the full explanation of the error in the satellite temperature calculation could be determined, it is hard to put this to rest. If only it could have been right in the first place. From a scientists point of view it is fine it was not, as all becomes clear now. However, misconceptions elsewhere will be tough to straighten out.

    [Response: Its a long report, and I haven’t waded through it yet. However, the preface already disappoints. For example, For example, a recent article cleverly demonstrated a subtle problem in the method used in one of the data sets to correct for satellite orbital drift – this appears to be a somewhat cryptic reference to Mears pointing out a sign error in C+S’s dataset, which hardly counts as a “subtle problem” – William]

  2. nanny_govt_sucks:

    Even the Mears and Wentz RSS data shows a near-flat/slight cooling in global temperatures since 2002 (and, incidentally, back to 1998 with less statistical trend significance) in the lower and middle troposphere. This is in the face of rising CO2 concentrations in the atmosphere and reductions in the atmospheric aerosols and their supposed cooling effects in the USA of late, and lack of evidence of cooling effects of aerosols in other regions (like China) where aerosol emissions have increased.

    Why don’t we see global atmospheric warming over the last 4 years?

    Two major “forcings” (increasing CO2 concentrations and Sulfate aerosols) have seemingly been overridden, and a near-flat or slight cooling trend is in progress. What powerful cooling forcing or combination of forcings could have caused this? Doesn’t this show that CO2 is a minor player in climate forcings at this point?

    [Response: Its easy enough to see that there is a fair degree of interannual variation – see e.g. http://www.grida.no/climate/ipcc_tar/wg1/figspm-1.htm. GW doesn’t mean every year is monotonically warmer than the last. What models and theory predict is a long-term warming trend, which is exactly what we are seeing. If you are serious in believing that there is a long-term cooling trend, then I suggest you head over to Back Seat Driving where you can bet on the issue – William]

  3. Steve Bloom:

    As William points out, it should go without saying that an uneven long-term warming trend will be characterized by periodic new highs, in between which there will be a series of (competely meaningless) short-term “cooling trends.” One can find these cooling trends in any year except the one following a new high. Statistically, it is pure silliness, as anyone would know who (like Nanny) spends a lot of time arguing about statistics relating to the “hockey stick.” One wonders why she keeps bringing it up, when even other skeptics have pointed out that it’s ridiculous.

    Of course, is she’s consistent then in the next year that follows a new record (now very likely to be set this year) we can look forward to Nanny discovering a warming trend. I can’t wait.

  4. nanny_govt_sucks:

    “Its easy enough to see that there is a fair degree of interannual variation – see e.g. http://www.grida.no/climate/ipcc_tar/wg1/figspm-1.htm.”

    William, first, your graph doesn’t include the time period I’m referring to – 2002->present. Second, I don’t see too many other 4 year near flat/slight cooling trends in the recent (since 1980) data. Third, much of the interannual variation can be attributed to major ENSO, and volcanic events of which we haven’t seen much of in the 2002->present period.

    Without the influence of major ENSO/volcanic events we might expect a clearer “signal” from longer term forcings. But the “signal” is near flat/slight cooling so my guess is that we’re beginning to see that something is amiss with the theory.

    [Response: This is all getting a bit weird and, as others have pointed out, rather naive. The reason 1998 was so warm was precisely because of the major ENSO that year – William]

    “GW doesn’t mean every year is monotonically warmer than the last. What models and theory predict is a long-term warming trend, which is exactly what we are seeing.”

    But any long-term warming could also be attributed to observed long-term increases in Solar TSI, and/or water vapor. So what observed long-term evidence makes CO2 a primary culprit?

    [Response: Its all in the IPCC report, and indeed RC posts. Since there is no long-term solar trend, solar can be ruled out. Water vapour (all together now one last time) is a feedback not a forcing – William]

    “If you are serious in believing that there is a long-term cooling trend, then I suggest you head over to Back Seat Driving where you can bet on the issue – William]”

    It’s neither long-term, nor a belief. I’m simply looking at the global atmospheric temperature measurements, both RSS and UAH interpretations.

    [Response: You should probably stick to the RSS version. The UAH version has had so many corrections by now that, were it a palaeo record, you would be howling for its blood. I wonder if anyone has ever seen their code? – William]

  5. Brian S.:

    Nanny, you’ve said you don’t have a belief in a long-term cooling trend, but also said your guess is something’s amiss with the theory of long term forcings from greenhouse gases. If you think there’s a cooling trend that will last 10 years, you might want to consider arranging a bet with me.

    The people I’m really interested in betting with are the ones who draw opposite conclusions from the science when it involves policy as contrasted to when it involves their wallets. Don’t know if that applies to you or not, Nanny.

  6. Alastair McDonald:

    Re 4 comment “You should probably stick to the RSS version. The UAH version has had so many corrections by now that, were it a palaeo record, you would be howling for its blood. I wonder if anyone has ever seen their code? – William”

    Wentz and Schabel found a small error in the UAH code and Mears and Wentz found an even smaller error (within the error margin.) How do you imagine that both teams did that without inspecting the UAH code? The UAH code has been gone through with a fine tooth comb and each check finds only smaller and smaller errors. Nanny is correct in his guess that there is something amiss with the theory of long term forcing. It is based on the Schwarzschild’s equation which he wrote to describe radiation within the sun. It was Robert Emden who first applied it to the earth’s atmosphere, before the advent of the quantum mechanics needed for the correct radiation calculations.

    [Response: I think you’re totally wrong here Alistair. Firstly the errors in the UAH data weren’t small, they were large. The recent (5.2 -> 5.1) correction found by M+W increases the trend by about 50%. The *previous* correction was small only because they made two large changes at the same time of the opposite sign: ironically, we now know that the second was of the *wrong* sign. Secondly, its not at all clear than anyone else has C+S’s code. I don’t think M+W have it: the implication of their paper is that they don’t – William]

  7. nanny_govt_sucks:

    “[Response: This is all getting a bit weird and, as others have pointed out, rather naive. The reason 1998 was so warm was precisely because of the major ENSO that year – William]”

    Again, I’m talking about the period 2002->present. Not 1998.

    The short-term climate forcings seem to have dwindled recently (2002->present) and we should be seeing the long-term signal in the global atmospheric temps. Do you or do you not agree?

    [Response: Well I can see why you’d want to restrict yourself to post-2002: its the only way to get a cooling trend: http://www.cru.uea.ac.uk/ftpdata/tavegl2v.dat. Did you fail to understand the obvious: that temperature is not expected to increase monotonically? If you think that temperature *won’t* increase over the next 10 years, then you have a chance to make money: the bets are there on the table: why not pick them up? – William]

    “[Response: Its all in the IPCC report, and indeed RC posts. Since there is no long-term solar trend, solar can be ruled out.”

    That’s only if you ignore the ACRIM TSI data.

    [Response: One of many; naturally you’ll grasp at it. But the trend in that is hard to find; the solar cycle signal is far larger, and not seen in the T record]

    “Water vapour (all together now one last time) is a feedback not a forcing – William]”

    THat’s beside the point. Water vapor HAS INCREASED in the atmosphere over the last 50 years. That increase may show up as a long-term warming signal in global atmospheric temperatures, and could confuse the CO2-AGW issue.

    [Response: Of course it has. And its increased *because* the temperature has increased]

    “[Response: You should probably stick to the RSS version. The UAH version has had so many corrections by now that, were it a palaeo record, you would be howling for its blood. I wonder if anyone has ever seen their code? – William]”

    According to RealClimate http://www.realclimate.org/index.php?p=170:
    “Incidentally, it is a clear sign of ‘cherry-picking’ when people only report their favorite one of the groups’ [UAH or RSS] trends instead of the range.”

    You’re not ‘cherry picking’, are you William?

    [Response: As you’ll notice, we’ve reported both. However, as I’ve pointed out, the C+S version has had several (large) corrections needed, and there may be more – William]

  8. William Connolley:

    [Posted by WMC on behalf of an anonymous contributor]

    Firstly, the quoted +/-0.05 is not the statistical uncertainty (as you argue), it is the UAH estimate of parametric / structural or “construction” uncertainty. The BAMS paper (Thorne, Parker, Christy and Mears) discusses this.

    Secondly, it is disingeneous to diss the CCSP report on the basis solely of the preface. And I expected a more sympathetic stance on this from you guys. This report has been the life of 21 scientists for the past 2 years. The preface has received the least attention and was written by the editorial team. The report should be read and considered as a whole, as only that way can the relevance of, and justification for, a statement like that highlighted be ascertained. The preface is solely an introduction.

    [Response: I accept you’re right that the 0.05 isn’t line fitting; it is structural uncertainty. But that value doesn’t include actual errors, either. On the CCSP report, I was fairly careful to say I was judging it by its preface; once someone has digested the whole thing we may well have a post on it – William]

  9. Ashley Bowers:

    Good point Brian I think people think with there wallet alot more than with there heart.