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Saturday, June 15, 2013

Shhh - there's too much noise and I can't hear the signal - or Ben Santer's 17 years

Sou | 10:53 PM Go to the first of 8 comments. Add a comment

There's an eccentric English chap called Christopher Monckton of Brenchley who has Anthony Watts of WUWT in thrall. Barry Bickmore can fill you in on this vexatious Viscount.

Monckton is claiming that there 'hasn't been any significant warming for seventeen years and four months'.

That's right.  I kid you not!  He has done his sums and it's seventeen years and four months. Oh and I guess its seventeen years, four months, one day, 13 hours and 25 seconds by now.

It's good to know that he's finally settled on a number.  His previous lucky dips were for 16, 17, 18, 19 and 23 years (all in the one letter); then he went for "approaching two decades"; then just last month it was 18 years.

Apparently Monckton is trying to put one over the 8% Dismissives over at WUWT, an anti-science blog.  I don't know why he bothers.  The clowns over there already have their heads stuffed full of insects, underwater volcanoes, exploding vegetation, ice ages peeping around corners, lack of ENSOs, leaping El Ninos and scientific dogs.  I doubt there is room in their heads for another denier meme.  Still, I suppose Anthony has to fill up that white space with nonsense several times a day to keep his crowd entertained.

The way I see it, Anthony Watts had a whole heap more than usual of Friday Funnies on WUWT this week.  This article by Monckton was just one of many.  Anthony chose to make Monckton's article a "sticky".  When you're down on your luck you take what you can get.  And Anthony hasn't been having much luck at all lately.

The basis of Monckton's article was ostensibly Santer et al (2011), so I thought I'd write some of what that research found.


Ben Santer and colleagues, the signal and seventeen years of noise and counting


The Santer paper is titled: Separating signal and noise in atmospheric temperature changes: The importance of timescale.

First up they let us know that they are comparing satellite estimates of lower troposphere with CMIP3 model simulations.  What they find, unsurprisingly, is that the signal to noise ratio increases the longer the time period.  From the abstract:
...Because of the pronounced effect of interannual noise on decadal trends, a multi-model ensemble of anthropogenically-forced simulations displays many 10-year periods with little warming. A single decade of observational TLT data (temperature of the lower troposphere) is therefore inadequate for identifying a slowly evolving anthropogenic warming signal. Our results show that temperature records of at least 17 years in length are required for identifying human effects on global-mean tropospheric temperature.
In the Discussion and Conclusions section, the authors elaborate further.  Here are some excerpts (my bold):
Efforts to apply rigorous statistical methods to the problem of identifying human effects on climate commenced over 30 years ago [Hasselmann, 1979]. At the inception of this endeavor, it was recognized that any human-caused climate change signal is embedded in the noise of natural climate variability, and that separation of human and natural influences requires information on signal and noise properties over a range of timescales....
...Our estimated signal-to-noise (S/N) ratios for global-scale TLT changes were less than 1.0 on the 10-year timescale (Figure 6c). On the 32-year timescale, however, S/N exceeded 3.9 in all three observational TLT data sets. The latter result shows that natural internal variability, as simulated by current climate models, is a highly unlikely explanation for the observed lower tropospheric warming over the satellite era (Figure 6d). Comparisons between simulated and observed low-frequency TLT variability suggest that our estimates of S/N ratios on 5–20 year timescales are conservative (Figures 9 and 10). The strong timescale dependence of S/N ratios arises primarily because of the large decrease in noise amplitude as the period used for trend fitting increases (Figure 6b)....
... In summary, because of the effects of natural internal climate variability, we do not expect each year to be inexorably warmer than the preceding year, or each decade to be warmer than the last decade, even in the presence of strong anthropogenic forcing of the climate system. The clear message from our signal-to-noise analysis is that multi-decadal records are required for identifying human effects on tropospheric temperature. Minimal warming over a single decade does not disprove the existence of a slowly-evolving anthropogenic warming signal.

What I understand from that research is that:
  • the longer the time period the more the signal emerges from the noise
  • multi-decadal records are needed, the more the better
  • it's important to not introduce noise unnecessarily.

How did Monckton fare against these findings?  First, Monckton misrepresented what Santer said.  Santer et al wrote that at least seventeen years and the longer the better to extract the signal from the noise:
Our results show that temperature records of at least 17 years in length are required for identifying human effects on global-mean tropospheric temperature....

...The clear message from our signal-to-noise analysis is that multi-decadal records are required for identifying human effects on tropospheric temperature. Minimal warming over a single decade does not disprove the existence of a slowly-evolving anthropogenic warming signal.

"At least seventeen years are required", and "multi-decadal records are required". Compare that to this, from Monckton:
However, as Anthony explained yesterday, the stasis goes back farther than that. He says we shall soon be approaching Dr. Ben Santer’s 17-year test: if there is no warming for 17 years, the models are wrong.

No, Christopher, that's not what Dr Santer and his colleagues found.  Santer didn't write about 'models being wrong'.  He was pointing out that the longer the better.  Even in the press reports this is what was written:
In order to separate human-caused global warming from the "noise" of purely natural climate fluctuations, temperature records must be at least 17 years long, according to climate scientists.
Look we're used to Monckton making up stuff.  We don't have to just lay down and take it though.  

Let's move along.  What else did he do wrong?  

For one thing, he plotted temperature by month, not annually.  What he hoped to achieve I don't know.  Nor do I know if his "results" would have been any different.  But what I do know is that a monthly plot exaggerates the noise and hides the multi-decadal signal.  Why do you think Spencer always provides monthly plots?  It's so that every so often he can gig up the crowd by claiming a drop in temperature.  Yes, from the previous month! Even though it's well above the temperatures of the eighties and nineties.

What else did Monckton do wrong?  For another thing, Monckton misrepresented his chart as an IPCC chart, which it most certainly isn't.  Heck, he even put the name of his foundation on the chart.  And the IPCC doesn't do sloppy, not like Monckton.  Here's one of his charts.  I've animated his "brand" and added an arrow:


As if you couldn't tell anyway.  He's presenting the chart as a monthly chart, stuck some lines on it that he claims are IPCC "backcasted projections", added some dodgy numbers in the left hand corner and put a reference to an IPCC AR5 figure, when AR5 hasn't even been released yet.

Monckton describes it as follows - see if you can understand what he writes. It's not easy:
The IPCC’s forthcoming Fifth Assessment Report backcasts the interval of 34 models’ global warming projections to 2005, since when the world should have been warming at a rate equivalent to 2.33 Cº/century. Instead, it has been cooling at a rate equivalent to a statistically-insignificant 0.87 Cº/century:
I suppose he was right about one thing.  Any "cooling" he might have been able to fiddle is not going to be statistically significant.

On the other matters, since the IPCC's "forthcoming" Fifth Assessment Report is still "forthcoming", neither Monckton nor I would be in a position to say whether it will include any charts that hindcast or backcast or project.  He may have access to the previous draft, but that's a long way from a final version.

What is obvious is that Monckton hasn't the slightest clue about models or climate.  I mean in his second chart as shown above, he's looking at only eight years for heavens sake.  Eight years isn't multi-decadal.  Does he expect surface temperature to go in a straight line somewhere?

Let's do multi-decadal using the same temperature series, HadCRUT4.  It doesn't look anything like what Monckton drew.  You can check for yourself here.

Source: HadCRUT4

I've marked both 1995 (seventeen years of data) and 1996 (sixteen years of data) for what it's worth.  But you don't have to stop at 1995 or 1996.  You can see the trend goes back a lot further than that.  The world is getting hotter.


It's not just the land and sea surface that's warming


I didn't see anyone ask Monckton to explain all the other signs that the earth is warming, but there were a lot of comments so I might have missed it.


Recommended reading


For a different takes on global temperature trends, here are some papers and blogs to check out:



In the comments...


The comments at WUWT had a lot of the usual bowing and scraping to the potty peer.  There was some fun to be had though.  There was one guy called rgbatduke (yes, I read ratbag too, then came to realise it's his initials and he teaches at Duke - which leads us to another play on words).  People were calling him Professor Brown but he isn't a climate researcher.  (I don't think he does much research at all.  He teaches physics I believe.)

Anyway the rgbatduke got stuck right into the analysis, with a very strongly worded missive on how you can't do this, that and the other thing and it's all a mess and so on and so forth.  It took up a few screens so I'll only post one bit from somewhere around the middle of his rant.  rgbatduke says:
June 13, 2013 at 7:20 am  ...Note the implicit swindle in this graph — by forming a mean and standard deviation over model projections and then using the mean as a “most likely” projection and the variance as representative of the range of the error, one is treating the differences between the models as if they are uncorrelated random variates causing >deviation around a true mean!.
Say what?

Monckton didn't seem to object to being called a swindler and we'll see why shortly.  Nick popped in quite some time later and recognised rgbatduke had made an erroneous assumption.  Nick figured out that rgbatduke had the wrong end of the stick and thought the graph was one of the IPCC's.  rgbatduke is obviously not au fait with IPCC reports or he would have twigged at once that the charts were inventions of the potty peer himself.

The thread continued with mostly mindless denialist stuff, occasionally interspersed with Nick's astute comments and some general stirring by Mosher.  As usual, Nick was unflappable, remaining calm and polite and sticking to the facts.  Not like Monckton, who was apoplectic flinging wild accusations left, right and centre.  He called Nick a liar (and a Mr instead of Dr, while calling rgbatduke Professor - unsubtle!).  Monckton even wanted Nick to be banned from WUWT.  Then Anthony chimed in to tell Nick, the only cool head in the place, to keep it cool; to behave himself, he was upsetting the potty peer and denier rgbatduke as well as everyone else.  (On WUWT the unwritten policy is that as long as you deny science you can say what you like.  If you write sensible stuff you're under tight watch and banned if enough people flame you.)

It's a madhouse at WUWT.

As a reward for reading through to the end, here's a little bit of CO2 for your exploding plants.


8 comments:

  1. This is the full abstract of the Santer paper:

    "Abstract. We compare global-scale changes in satellite estimates of the temperature of the lower troposphere (TLT) with model simulations of forced and unforced TLT changes. While previous work has focused on a single period of record, we select analysis timescales ranging from 10 to 32 years, and then compare all possible observed TLT trends on each timescale with corresponding multi-model distributions of forced and unforced trends. We use observed estimates of the signal component of TLT changes and model estimates of climate noise to calculate timescale-dependent signal-to-noise ratios (S/N). These ratios are small (less than 1) on the 10-year timescale, increasing to more than 3.9 for 32-year trends. This large change in S/N is primarily due to a decrease in the amplitude of internally generated variability with increasing trend length. Because of the pronounced effect of interannual noise on decadal trends, a multi-model ensemble of anthropogenically-forced simulations displays many 10-year periods with little warming. A single decade of observational TLT data is therefore inadequate for identifying a slowly evolving anthropogenic warming signal. Our results show that temperature records of at least 17 years in length are required for identifying human effects on global-mean tropospheric temperature."

    Read the last three sentences until it sinks in. 10 years of no warming can be chalked up to noise. 17 years can't

    ReplyDelete
    Replies
    1. Huh? Even the abstract says at least 17 years are required for identifying human effects...

      Anyway, why read just the abstract when you can read the entire paper? I posted the link in the article:

      http://onlinelibrary.wiley.com/doi/10.1029/2011JD016263/full

      Is your name Christopher Monckton by any chance?

      Delete
    2. KR

      "...temperature records of at least 17 years in length are required for identifying human effects on global-mean tropospheric temperature"

      Assuming a normal distribution of variation around the trend to be identified, you achieve a chance (not a certainty) of identifying a trend above normal variations at 17 years (for the tropospheric satellite data).

      If, however, you cherry-pick an extrema, such as the 1998 El Nino, you've thrown away much of that normal distribution. Having started from that extrema, more data will be required to positively separate a trend from the null hypothesis of "no warming".

      The range of statistically possible trends for <17 years includes zero. It also includes trends well above the longer term 0.16C/decade - cherry-picking short time spans does not allow 'skeptics' to refute warming. As I've said elsewhere:

      When examining ANY time-span starting in the instrumental record and ending in the present, note that:

      • Over no period is warming statistically excluded.
      • Over no period is the hypothesis of "no warming" statistically supported WRT a null hypothesis of the longer term trends.
      • And over any period with enough data to actually separate the two hypotheses – there is warming.

      Delete
  2. It is incumbent upon those making a claim to support it. 17 years of flat line does not support the man-made theory. When will people get how science works, your theory you support it, it is not for those who do not see the evidence to support not seeing the evidence. Simple really, shame the internet allows people to say such daft things.

    ReplyDelete
  3. According to the rigors of scientific discipline,no theory or hypothesis is worthy of any consideration unless it implies the sort of evidence that would prove it wrong.Predictions based on the theory are tested against the facts.how many anomalous results are necessary to invalidate a proposition?to paraphrase Einstein.... a mere one.Such a one is the 17-year global warming hiatus.Ergo the AGW theory has been discredited.End of story.Game over.The alarmists lose.

    ReplyDelete
    Replies
    1. Anonymous writes hopefully: Ergo the AGW theory has been discredited

      We all wish it were so, but wishing ain't enough :(

      There is no global warming hiatus.

      Delete
    2. So Anonymous agrees that Einstein's theory of relativity is wrong. It must be, as it doesn't predict anything nearly accurate when we go to the subatomic level. Not just "a mere one" anomalous result!

      And thus, per "anonymous", Einstein's theory of relativity is discredited and we shouldn't send any satellites into space anymore, because the theory that has helped us predict their path has been discredited.

      Marco

      Delete

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