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Thursday, April 4, 2013

Nancy's Spikes of Fancy (and Anthony's gone and done it again!)

MobyT | 9:04 PM Feel free to comment!
Anthony Watts has posted an 'article' by WUWT reader Nancy Green and added some notes of his own.

Watts: you "really aren’t comparing similar data sets"

First - what has Anthony done again?

He just can't help himself.  Anthony decided to ignore the caution from the scientists and has gone ahead once again comparing local with global temperatures.  This time he used the Vostok ice core from Antarctica, which is only one of the proxies used by Marcott et al in their Holocene reconstruction.  And this time he put in a disclaimer: but this image is solely for entertainment purposes in the context of this article, then blew it by adding: and does make the point visually.

Looks like Anthony decided to ignore the scientists' jibe as well as his very own own caution.


Nancy's Spikes of Fancy

Now let's see what Nancy's flight of fancy is.  She's grabbed hold of the idea that because the Marcott et al's Holocene reconstruction resolves only to a couple of hundred years, it could be missing temperature 'spikes' of shorter duration.

So far so good.  Indeed it could.  The question is, how likely is that?

Nancy bounced off this idea into a real flight of fancy.  First she tried it out with informed readers at RealClimate.org, who were able to help her out - though she ignored their efforts.  Here is an excerpt from one of her excursions into the domain of climate scientists.  

Nancy Green says: 1 Apr 2013 at 10:09 AM
...it must be concluded that what Marcott is showing is only the natural variability in temperature and if any weight is to be given to the uptick, it shows that at higher resolutions there may be significant temperature spikes due to natural causes.
Gavin Schmidt helps her out with an inline comment:
[Response: Of the size and magnitude of the 20th Century - unlikely. Even the 8.2kyr event which is the biggest thing in the Holocene records in the North Atlantic is small comparatively. It would definitely be good to get more high resolution well-dated data included though, and Marcott's work is good basis for that to be built from. - gavin]


What about the Younger Dryas?

Nancy continues on this theme, this time referring to the Younger Dryas (which preceded the Holocene):
Nancy Green says:
1 Apr 2013 at 10:47 AM
...When one looks at long duration events we have the Younger Dryas event, with a temperature change of approximately 15C as compared to 2oth century warming of less than 0.7C....
Now that's a mistake any non-scientist and beginner climate science amateur could make, confusing local temperature fluctuations (Nancy's 15ºC) with global temperature fluctuations.  Gavin Schmidt helped set her straight, with an inline comment:
[Response: This is becoming a habit - the YD change of '15ºC' is a Greenland signal. It is not in phase with (much smaller) changes in the high Southern Latitudes, and in ocean cores, even in the N. Atlantic, it is much smaller. An estimate of the impact of the YD on global mean temperatures is found in the Shakun et al (2012) paper, and is likely less than a degree. Note that the whole glacial to interglacial change is only about 5ºC in total! - gavin]

The Younger Dryas is largely a northern hemisphere phenomenon as any reader of WUWT should know by now (they refer to Richard Alley's work describing the Younger Dryas in Central Greenland often, but no-one at WUWT seems to have read it or understood it).  It had particular effect in parts of the arctic. Nancy pushes the point, again confusing local temperature fluctuations with global temperatures:
Nancy Green says:
1 Apr 2013 at 11:03 AM.....Once cannot conclude from Marcott that there have been no short term events of similar magnitude to the Younger Dryas (approx 15C) within the period covered by Marcott. Such events would be hidden by the lack of resolution so long as they were shorter than 1/2 the sampling rate as per Nyquist.
And once more Gavin Schmidt helps her out, trying again to get the message through another way.  He didn't repeat himself that the global temperature didn't change by 15ºC (he's already told her that but she's ignored it.)  This time he reminds her that the reason we know about the Younger Dryas is because of ice cores.  If there had been a similar event it would show up in the ice cores - and it doesn't:
[Response: These are the same core that show the YD! You can't claim that a YD like event wouldn't be shown in the same cores. Please, you can do better than this. - gavin]

Spiking to the Stars

Nancy meanders off hither and thither pursuing her fantasy. The tone and content of this contribution, plus the fact that she hasn't learnt anything from the expert help she's been offered, is a great example of the Dunning-Kruger Effect.  Her post was long and even travelled through the galaxy.  This post of Nancy's is pretty much the same as what she wrote at WUWT. I'll just give an excerpt where she tells climate scientists what they 'should' consider:
Nancy Green says:1 Apr 2013 at 10:53 PM
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.
Nancy elicits responses from a few other people.
The_J says: 2 Apr 2013 at 6:40 AM 
You claimed that the Younger Dryas was a 15C swing in temperatures, and that the Younger Dryas isn’t detectable in the proxies. But both of those claims are wildly, absurdly wrong. I think you may have been confused by a statement on Wikipedia that the summit area on Greenland was 15C colder during YD than it is today. But that’s not a global-scale change of 15C! As discussed here, the entirety of the change from last glacial maximum to the Holocene was approximately 5C, and the Younger Dryas was approximately 0.6C. And of course the Younger Dryas is readily detectable in climate proxies … that’s how we know about it.
Ray Ladbury made some points relevant to Nancy's notions, and says: 3 Apr 2013 at 8:57 AM
...Dude, the planet is really, really big. It isn’t easy to pump that much energy in in a decade or two. We’ve only managed to do so by liberating most of the carbon sequestered since the Jurassic! The Paleocene-Eocene Thermal Maximum failed to achieve such rates of growth despite (probably) burning up the Deccan coal field!
dhogaza says2 Apr 2013 at 11:10 PM
:”PhysicsGuy @102 — Follow the links from comment #100 to discover why no such global spikes exist. There are plenty of other proxies in which such spikes would show up; none found.:’
And, of course, arguing that the paper’s analysis can’t capture such excursions is proof that they exist is just …
kinky.
Even without the fact that other proxies don’t show such spikes.

And here are two substantive comments from real climate scientists. I've broken raypierre's response into paragraphs for easier reading, and bolded what I believe to be the crucial points:

[Response: What a lot of this discussion of "spikes" is missing is that the point isn't whether the Holocene had any sudden rises with a cause analogous to the present. As many people have pointed out, that couldn't be, because the present rise is due to CO2, and is hence "durable," as many people have pointed out; it would show up in a record like Marcott's. But also, as others have pointed out, we already know from ice cores that CO2 fluctuated very little in the pre-industrial Holocene, so that isn't in the cards anyway.
What is at issue is whether there are any other mechanisms of centennial-scale variability that could cause a 1C or even a .5C spike. We know that the AMO can go a smallish fraction of that distance, and it's hard to rule out on first principles that some kind of ocean variability might not be able to do something bigger in amplitude if you wait long enough. There's no evidence that it can, and I myself find it hard to see how you could make the ocean do a centenniel scale uptick (a centennial scale downtick is easier, since there's all that cold water you could conceivably bring to the surface). 
But the Marcott analysis has no bearing on that question. I don't think the paper ever claimed it did, but the comparision with the instrumental era rise may have confused some people into thinking so. 
To repeat my earlier comment, it is useful to compare the instrumental era rise and the forecast of further rise to the Marcott record because we know the rise is durable and will last millennia. Thus, we know we are bringing about a durable increase that is huge compared to any long-duration variation over the Holocene. That's a big, big deal. --raypierre ]
[Response: To add to Raypierre: it would have to be ocean variability causing a spike in global-mean temperature without causing a spike in the high-resolution proxies from the ice cores. That is exceedingly unlikely; the ocean's deep-water formation sites near Greenland and Antarctica would surely experience major change during such a spike. 
Think of the 8k-event: the biggest in the Greenland ice cores over the entire Holocene, yet minor impact on global-mean temperature. -Stefan]

From a statistical viewpoint

This has turned out to be quite a long article already. But it would be very remiss of me to leave out an excellent piece of analysis by Tamino on this very topic.  Tamino shows that if a rise in global temperature anything like that of the past century had occurred  it would have shown up in the data.

You can read his analysis in his article "Smearing Climate Data".

A final word

So there you have it.  This current rise in temperature is 'durable' and caused by CO2 and is a big, big deal. It is well known from various sources that throughout the Holocene there has never been a rise in CO2 anything like the magnitude we've seen over the past century.  It is also virtually certain that during the Holocene, since human civilisation, there has never been a short term 'spike' in global surface temperature of the magnitude we are now facing with certainty (2ºC or more).

Nancy's post on WUWT brings up the number of Marcott Protest articles there to at least twenty four. The deniers have tried to argue from lots of different angles: from Nancy's invisible spikes to upticks to dating of core-tops to comparisons with temperatures on a summit high in Central Greenland and in Antarctica and even tacking centuries of temperatures in one single ocean location to a land-based modern instrumental record in another single location, with a gap of about a century from the tail of one to the beginning of the other.

Not one of their 'arguments' has come anywhere close to finding the slightest flaw in the Marcott Holocene reconstruction.  In fact, despite looking for impossible 'spikes' and obviously not understanding the paper itself, Nancy appears to largely support the paper, which will likely cause pandemonium among the DuKE (TM) of deniers.

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