Story submitted by WUWT reader Nancy Green
There is a message in Marcott that I think many have missed. Marcott tells us almost nothing about how the past compares with today, because of the resolution problem. Marcott recognizes this in their FAQ. The probability function is specific to the resolution. Thus, you cannot infer the probability function for a high resolution series from a low resolution series, because you cannot infer a high resolution signal from a low resolution signal. The result is nonsense.
However, what Marcott does tell us is still very important and I hope the authors of Marcott et al will take the time to consider. The easiest way to explain is by analogy:
50 years ago astronomers searched extensively for planets around stars using lower resolution equipment. They found none and concluded that they were unlikely to find any at the existing resolution. However, some scientists and the press generalized this further to say there were unlikely to be planets around stars, because none had been found.
This is the argument that since we haven’t found 20th century equivalent spikes in low resolution paleo proxies, they are unlike to exist. However, this is a circular argument and it is why Marcott et al has gotten into trouble. It didn’t hold for planets and now we have evidence that it doesn’t hold for climate.
What astronomy found instead was that as we increased the resolution we found planets. Not just a few, but almost everywhere we looked. This is completely contrary to what the low resolution data told us and this example shows the problems with today’s thinking. You cannot use a low resolution series to infer anything reliable about a high resolution series.
However, the reverse is not true. What Marcott is showing is that in the high resolution proxies there is a temperature spike. This is equivalent to looking at the first star with high resolution equipment and finding planets. To find a planet on the first star tells us you are likely to find planets around many stars.
Thus, what Marcott is telling us is that we should expect to find a 20th century type spike in many high resolution paleo series. Rather than being an anomaly, the 20th century spike should appear in many places as we improve the resolution of the paleo temperature series. This is the message of Marcott and it is an important message that the researchers need to consider.
Marcott et al: You have just looked at your first star with high resolution equipment and found a planet. Are you then to conclude that since none of the other stars show planets at low resolution, that there are no planets around them? That is nonsense. The only conclusion you can reasonably make is that as you increase the resolution of other paleo proxies, you are more likely to find spikes in them as well.
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As a primer for this, our own “Charles the Moderator” submitted this low resolution Marcott proxy plot with the Jo Nova’s plot of the Vostok ice core proxy overlaid to match the time scale. Yes the vertical scales don’t match (numerically on the scales due to the ticks being different and the offset difference), but this image is solely for entertainment purposes in the context of this article, and does make the point visually.
Spikes anyone? – Anthony
![marcottvostok2[1]](http://wattsupwiththat.files.wordpress.com/2013/04/marcottvostok21.jpg?quality=83)
(Added) Study: Recent heat spike unlike anything in 11,000 years “Rapid” head spike unlike anything in 11,000 years. Research released Thursday in the journal Science uses fossils of tiny marine organisms to reconstruct global temperatures …. It shows how the globe for several thousands of years was cooling until an unprecedented reversal in the 20th century. — Seth Borenstein, The Associated Press, March 7th
Note: If somebody can point me to a comma delimited file of both the Marcott and Vostok datasets, I’d be happy to add a plot on a unified axis, or if you want to do one, leave a link to the finished image in comments using a service like Tinypic, Imageshack or Flickr. – Anthony
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You cannot use a low resolution series to infer anything reliable about a high resolution series.
Yes you can. You can infer the long-term trend among other things. Don’t overstate your case.
I’ll take strong analogies over weak anomalies anytime! Kudos!
Would it be possible then to produce a Marcottian type compilation but in high resolution? Is such data available?
Nancy Green rocks.
That’s everything these days. Willis rocks too, by way of comparison.
What Nancy Green says is true. However, the astronomers looking for planets wanted to find them. Climate ‘scientists’ looking for hockey sticks want a nice straight shaft then a single blade. This was shown in the CG1 emails with the discussion about getting rid of the Medieval Warm Period. I doubt very much that we will see any concerted search for high resolution proxies for paleo climates as ‘The Team’ would see finding a twentieth century type spike several thousand years ago as a threat to their hypothesis (aka funding).
Anthony, the vertical scales DO match. I did by eyeball only but did it carefully. The baseline is shifted with a WAG based on the smoothed lines.
REPLY: Perhaps I wasn’t clear, I’m saying they don’t match numerically on the scales due to the ticks being different and the offset difference, the amplitude of the scales looks like a reasonable match (added clarification to body of story)- Anthony
Oh, come on Anthony, you can convert a tab-delimited file or even fixed width file to CSV. We all know you are much better than you sometimes pretend to be.
Leif: look up the term aliasing.
Mark
“Marcott tells us almost nothing about how the past compares with today, because of the resolution problem. Marcott recognizes this in their FAQ. The probability function is specific to the resolution. Thus, you cannot infer the probability function for a high resolution series from a low resolution series, because you cannot infer a high resolution signal from a low resolution signal. The result is nonsense.”
Perhaps you should reread his the para in the Marcott paper starting with, “Because the relatively low resolution and time-uncertainty of our data sets should generally suppress higher-frequency temperature variability, an important question is whether the Holocene stack adequately represents centennial- or millennial-scale variability.”
I know the FAQ helps most WU readers, but I don’t think there is anything new there. It’s all in the original paper, including the points make above.
fyi, Tamino has a new post claiming to have tested via “three spikes” to show that any previous increase comparable to the past century would have shown up in the Marcott 11,300 year study period.
Here is an interesting comment in response:
http://climateaudit.org/2013/04/02/april-fools-day-for-marcott-et-al/#comment-409677
It is refreshing to see an analogy that actually fits. I don’t know what it is about climate science, but the number of bogus analogies you find in discussions on the subject is disturbing.
Good analogies are invaluable in making difficult concepts comprehensible to those who lack understanding, which includes me.
Mark T says:
April 3, 2013 at 8:11 pm
Leif: look up the term aliasing.
Won’t make any difference as the data is not sampled but averaged [as far as I can assess]
Strangely enough, the comment I left at RC applies perfectly to this post:
“1- That’s not “spikes”, that’s “noise”. Why do you think the authors performed this Monte-carlo simulation? Because the raw data itself is not interpretable on short timescales.
2- A short “spike” in the past could not be comparable to modern warming, because modern warming is not just fast, it is also *durable*. Even if CO2 emissions completely stop in 2100, the warmth will remain for centuries. If something like *that* had happened in the past, Marcott’s proxies and methods would have detected it.
They didn’t, so it hasn’t. Hence, “unprecedented”.”
Leif Svalgaard,
“Yes you can. You can infer the long-term trend among other things.”
To my eyes it looks like the long term trend in the Marcott series is going the wrong way for the CAGW crowd.
A short “spike” in the past could not be comparable to modern warming, because modern warming is not just fast, it is also *durable*. Even if CO2 emissions completely stop in 2100, the warmth will remain for centuries.
You may believe that. But you can’t believe it based on a low resolution study such as Marcott.
This attempting to defend the “spike” by bringing in material completely external to the study is sadly typical of its defenders.
1) Marcott can’t show whether a spike is precedented or not.
2) Marcott can’t show the cause of anything at all, let alone a spike.
3) Marcott can say nothing of any long term trends (note, the base trend is down).
Your defence is the “look! flying monkeys!” defence. Please stop.
Marcott can say nothing of any long term trends into the future.
Sorry.
toto says:
April 3, 2013 at 8:41 pm
Because the raw data itself is not interpretable on short timescales.
and
A short “spike” in the past could not be comparable to modern warming,
>>>>>>>>>>>>>>>>>>
So you are saying that modern warming is different from the past warming even though you’ve stated that the data can’t be used to interpret the past warming so you don’t actually know what it looked like at all? Yet you are confident that it is different?
toto says: April 3, 2013 at 8:41 pm
“…A short “spike” in the past could not be comparable to modern warming, because modern warming is not just fast, it is also *durable*. Even if CO2 emissions completely stop in 2100, the warmth will remain for centuries…”
And you know this how, exactly? Crystal ball, perhaps? Or simply unquestioning faith in what can only be described as a “plausible theory with several major suppositions”?
Any suggestions as to what may have caused the “temporary short spikes” in the past?
[snip]
OK that’s it you are banned. While I don’t like Mann’s issues either, that was uncalled for, further, you have been abusing your welcome here by shape shifting
Puppet_Master_Blaster_Master
Enter_Sand_Man
Sad-But-True-Its-You
Are all you, plus there’s the fake email addresses. Congratulations. You have a triple policy violation all in one comment.
Get off my blog. – Anthony
Correct. Your conclusions can only be as accurate as your least most accurate data.
toto says (April 3, 2013 at 8:41 pm):
“1- That’s not “spikes”, that’s “noise”.
A variant of weather is not climate.
2- A short “spike” in the past could not be comparable to modern warming, because modern warming is not just fast, it is also *durable*. Even if CO2 emissions completely stop in 2100, the warmth will remain for centuries.
Durable, that’s a good one. Even if I don’t see the evidence for it, I like the idea that the only thing that humans have done which is sustainable is to fix the climate. /sarc
The case is also understated, because the issue is not only the low frequency sampling.
There is further spreading and flattening of maxima and minima due to
1. dating errors (suppose Hadcrut year 2001 temperatures would be computed by averaging 1905 temperatures from location A and 2003 temperatures from location B)
2. non temperature influences on proxies.
The latter appears to be very severe in this reconstruction. McIntyre’s hemispheric reconstructions have very little similarity with instrumental temperature for the whole instrumental record.
The very good think about Marcott et al is it has brought this ‘spike’ issue out into a blazing bright spotlight.
The spike created by grafting high resolution instrumental data onto very low resolution, ‘smoothed by nature and statistics’ proxies, even though that was not the cause of Marcott’s uptick (as Steve McIntyre and others have shown) had CAGW proponents bringing up the defensive argument “well, we already a have an instrument record that shows the same thing”.
I love that Vostok overlay by Anthony, I’ll run that under a few noses. Thanks!
Who? Hah! Who? Hah!
Nancy Green!!!!!
Yea!!!!!
Eugene WR Gallun
One thing I don’t understand. With 11000 years of history indicating the current trend is downwards, wouldn’t you think there might be a problem with a projection that goes straight up? The analysis of the paleo data would indicate CAGW projections are likely wrong. What am I missing?