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New study refutes CO2 as significant driver

  1. Jul 24, 2009 #1
    McLean, J. D., C. R. de Freitas, and R. M. Carter (2009), Influence of the Southern Oscillation on tropospheric temperature, J. Geophys. Res., 114, D14104, doi:10.1029/2008JD011637.

    http://www.agu.org/pubs/crossref/2009/2008JD011637.shtml

    From the abstract:

    Change in SOI accounts for 72% of the variance in Global Tropospheric Temperature Anomalies (GTTA) for the 29-year-long MSU record and 68% of the variance in GTTA for the longer 50-year RATPAC record.

    The results showed that SOI accounted for 81% of the variance in tropospheric temperature anomalies in the tropics. Overall the results suggest that the Southern Oscillation exercises a consistently dominant influence on mean global temperature, with a maximum effect in the tropics, except for periods when equatorial volcanism causes ad hoc cooling.

    That mean global tropospheric temperature has for the last 50 years fallen and risen in close accord with the SOI of 5–7 months earlier shows the potential of natural forcing mechanisms to account for most of the temperature variation.
     
  2. jcsd
  3. Jul 24, 2009 #2

    sylas

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    The heading of this thread is false.

    What the study actually shows is that ENSO (the el Nino la Nina cycle) is a significant source of variance. That is what the quoted abstract here is saying. This is not big news, and I have talked about it before in these threads myself.

    Here's a fact of life which is obvious when you look at any temperature record, and is a source of endless confusion from people who want to deny a warming trend... there's a lot of variation, year to year. The underlying trend of increasing temperatures, which is the basis for speaking of global warming, is quite definite; but it is not the same thing as "variation". The trend is not a smooth steady increase. What you have is a system with lots of influences and factors that gives you big changes from year to year, so that you can't even be sure of measuring a trend at all over less than fifteen or twenty years. The short term swings are "variation", and THIS is what ENSO explains... quite effectively. Variation is is also the dominant effect over the short term, of around a decade or less.

    This paper identifies the ENSO oscillation as the major source of this variation in global temperature records in the troposphere. That does nothing whatsoever to refute the warming trend, which ENSO does not explain; and it most certainly does nothing to "refute" CO2 as a significant driver.

    The paper does include some comments about the trend of warming, as well as the variance, but there's pretty much no empirical support for that. It appears to be a kind of random addon to the paper, well beyond what is actually supported by the evidence they present.

    The critical importance of ENSO for variation is already front and center in the last two IPCC reports. See, for example, this extract from Chapter 3 of the WG1 scientific basis report, page 246:
    Interannual variations in the heat fluxes to the atmosphere can exceed 100 W m-2 locally in individual months, but the main prolonged variations occur with the El Niño-Southern Oscillation (ENSO), where changes in the central tropical Pacific exceed ±50 W m-2 for many months during major ENSO events (Trenberth et al., 2002a).

    There's plenty more on this topic in the IPCC reports and in the scientific literature; the idea that ENSO is a major source of variation or even the major source of variation is just not new or surprising. The paper does have some potentially useful new ideas about the time delays or lags between the SO index and temperature (7 months), but as a refutation of the importance of CO2 for the long term trends, there's literally nothing there at all.

    It is effectively a sleight of hand to present an explanation of variation as a refutation of drivers for a long term trend. There's nothing in the paper to back up claims that CO2 is "refuted", and there's no physical basis for the notion that ENSO would be even capable of extended trends, although they are pretty much a physical inevitability as a result of an extended trend of increasing greenhouse gas concentrations.

    Sorting out the physical basis for ENSO and developing the capacity to model it accurately is an important unsolved problem for modeling the complexities of climate; but that has nothing to do at all with replacing greenhouse gases, or with finding an alternative way to get a long term trend.

    Cheers -- sylas
     
  4. Jul 24, 2009 #3

    Xnn

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    Unfortunately, we are not allowed to post charts made from actual data.
    However, we can post about the data.

    Here's a link to monthly global temperatures since 1880:

    ftp://ftp.ncdc.noaa.gov/pub/data/anomalies/monthly.land_and_ocean.90S.90N.df_1901-2000mean.dat[/URL]

    If you graph this data, what becomes obvious are 2 things:

    First, there is a long term warming trend of about 0.017C/year.
    Second, there are periodic warming/cooling episodes of about 0.3C

    What the study is saying is that those warming/cooling episodes line up with volcanic eruptions and ENSO events. However, the study does not dispute the 0.017C/year warming trend. They are just not calling the warming a variation, since it is a trend.
     
    Last edited by a moderator: Apr 24, 2017
  5. Jul 28, 2009 #4
    @ sylas In the words of the study's authors:

    “The surge in global temperatures since 1977 can be attributed to a 1976 climate shift in the Pacific Ocean that made warming El Niño conditions more likely than they were over the previous 30 years and cooling La Niña conditions less likely” says corresponding author de Freitas.

    “We have shown that internal global climate-system variability accounts for at least 80% of the observed global climate variation over the past half-century. It may even be more if the period of influence of major volcanoes can be more clearly identified and the corresponding data excluded from the analysis.”


    “The close relationship between ENSO and global temperature, as described in the paper, leaves little room for any warming driven by human carbon dioxide emissions. The available data indicate that future global temperatures will continue to change primarily in response to ENSO cycling, volcanic activity and solar changes.”

    “Our paper confirms what many scientists already know: which is that no scientific justification exists for emissions regulation, and that, irrespective of the severity of the cuts proposed, ETS (emission trading scheme) will exert no measurable effect on future climate.”
     
  6. Jul 28, 2009 #5

    sylas

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    This bit in particular is nonsense... and it is not in the paper. The methods used in the paper deliberately remove trend by a use of rather poorly chosen filters. It's a mess... the kind of paper which can be used to demonstrate that peer review isn't perfect. No surprise there, poor quality papers get published from time to time, and that's okay.

    Be that as it may, the notion that "little room is left" for carbon dioxide is flatly false. The paper uses "derivative" (subtracting values separated by 12 months) to highlight the variance and remove all long term trend from the data.

    This kind of thing makes one despair. There's no way in the world this research does a thing to back up these remarks. I'm profoundly cynical, and suspect that the paper was published mainly in order to give a platform for this kind of secondary unpublished comment. If we were to stick with the paper itself it would not be so bad. The remarks above are definitely not in the paper, and are most certainly not a sensible implication of the technique.

    Cheers -- sylas
     
  7. Jul 28, 2009 #6
    Where did he claim that the quotes were from the paper? He clearly attributed it to the authors words.
     
  8. Jul 28, 2009 #7

    sylas

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    Of course. I am not making any suggestion that Wagmc quoted incorrectly.

    I am just pointing out that the author's words are not backed up in the paper. Normally, a scientist commenting on their paper will explain implications of their work. But sometimes they don't... and in this case de Freitas is making a physically nonsensical statement which cannot possibly be backed up by his paper. The technique used in the paper specifically applies two filters to the data, one of which removes all long term trend. Therefore it is flatly false that the paper "leaves no room" for the effect of factors that drive long term trends.

    The claims in the abstract of the paper, on the other hand, are sensible, and not particularly surprising. The paper does support its abstract. Those conclusions have been part of conventional climate science, and the IPCC reports, for some time. Variation in temperature records are due mostly to short term factors that vary from year to year, and the ENSO cycle in particular is well known to be one of the most important such sources of variance. But it is not a source of trend.

    Cheers -- sylas
     
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