I had to chuckle at the cacophony of Twitfests going on today over this new study from Marcott et al. I especially liked the Mother Jones headline being Tweeted: “The Scariest Climate Change Graph Just Got Scarier”.
It rather reminds me of some people being fearful of certain religious icons.
![marcott-A-1000[1]](http://wattsupwiththat.files.wordpress.com/2013/03/marcott-a-10001.jpg?quality=83)
Yes, be afraid, very afraid, of that “unprecedented” (there’s that word again in the abstract) 0.7C temperature rise is the message I suppose. While the MSM will trumpet this I’m sure, we’ll get down to finding out just how good the science is. One potential problem is that the pollen data median sampling of 120 years, which is 4x the 30 year climate normals periods used today. That’s pretty low resolution for a study that is focusing on 2000 years and leaves lots of opportunity to miss data. Further, when they say the last 100 years was the warmest (with higher resolution data) they really aren’t comparing similar data sets when the other data has a 120 year median sampling.
Here’s the press release:
Press Release 13-037
Earth Is Warmer Today Than During 70 to 80 Percent of the Past 11,300 Years
Reconstruction of Earth history shows significance of temperature rise
March 7, 2013
With data from 73 ice and sediment core monitoring sites around the world, scientists have reconstructed Earth’s temperature history back to the end of the last Ice Age.
The analysis reveals that the planet today is warmer than it’s been during 70 to 80 percent of the last 11,300 years.
Results of the study, by researchers at Oregon State University (OSU) and Harvard University, are published this week in a paper in the journal Science.
Lead paper author Shaun Marcott of OSU says that previous research on past global temperature change has largely focused on the last 2,000 years.
Extending the reconstruction of global temperatures back to the end of the last Ice Age puts today’s climate into a larger context.
“We already knew that on a global scale, Earth is warmer today than it was over much of the past 2,000 years,” Marcott says. “Now we know that it is warmer than most of the past 11,300 years.”
“The last century stands out as the anomaly in this record of global temperature since the end of the last ice age,” says Candace Major, program director in the National Science Foundation’s (NSF) Division of Ocean Sciences. The research was funded by the Paleoclimate Program in NSF’s Division of Atmospheric and Geospace Sciences.
“This research shows that we’ve experienced almost the same range of temperature change since the beginning of the industrial revolution,” says Major, “as over the previous 11,000 years of Earth history–but this change happened a lot more quickly.”
Of concern are projections of global temperature for the year 2100, when climate models evaluated by the Intergovernmental Panel on Climate Change show that temperatures will exceed the warmest temperatures during the 11,300-year period known as the Holocene under all plausible greenhouse gas emission scenarios.
Peter Clark, an OSU paleoclimatologist and co-author of the Science paper, says that many previous temperature reconstructions were regional and not placed in a global context.
“When you just look at one part of the world, temperature history can be affected by regional climate processes like El Niño or monsoon variations,” says Clark.
“But when you combine data from sites around the world, you can average out those regional anomalies and get a clear sense of the Earth’s global temperature history.”
What that history shows, the researchers say, is that during the last 5,000 years, the Earth on average cooled about 1.3 degrees Fahrenheit–until the last 100 years, when it warmed about 1.3 degrees F.
The largest changes were in the Northern Hemisphere, where there are more land masses and larger human populations than in the Southern Hemisphere.
Climate models project that global temperature will rise another 2.0 to 11.5 degrees F by the end of this century, largely dependent on the magnitude of carbon emissions.
“What is most troubling,” Clark says, “is that this warming will be significantly greater than at any time during the past 11,300 years.”
Marcott says that one of the natural factors affecting global temperatures during the last 11,300 years is a gradual change in the distribution of solar insolation linked with Earth’s position relative to the sun.
“During the warmest period of the Holocene, the Earth was positioned such that Northern Hemisphere summers warmed more,” Marcott says.
“As the Earth’s orientation changed, Northern Hemisphere summers became cooler, and we should now be near the bottom of this long-term cooling trend–but obviously, we’re not.”
The research team, which included Jeremy Shakun of Harvard and Alan Mix of OSU, primarily used fossils from ocean sediment cores and terrestrial archives to reconstruct the temperature history.
The chemical and physical characteristics of the fossils–including the species as well as their chemical composition and isotopic ratios–provide reliable proxy records for past temperatures by calibrating them to modern temperature records.
Analyses of data from the 73 sites allow a global picture of the Earth’s history and provide a new context for climate change analysis.
“The Earth’s climate is complex and responds to multiple forcings, including carbon dioxide and solar insolation,” Marcott says.
“Both changed very slowly over the past 11,000 years. But in the last 100 years, the increase in carbon dioxide through increased emissions from human activities has been significant.
“It’s the only variable that can best explain the rapid increase in global temperatures.”
-NSF-
A Reconstruction of Regional and Global Temperature for the Past 11,300 Years
1College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.
2Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
- *To whom correspondence should be addressed. E-mail: marcotts@science.oregonstate.edu
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.
===============================================================
UPDATE: Andrew Revkin emailed me a link to his piece where the issue is commented on by Mann and Robert Rhode of (BEST). Being a cheerleader, Mann has little useful to add, but Rhode has some useful comments:
The Marcott et al. results may refine our understanding the last 10,000 years; however, the broad picture of Holocene climate does not seem to have been significantly changed by their findings. Previous work had already pointed towards a period of early Holocene warmth somewhat higher than recent centuries.
…
In discussing their result, there is one important limitation that I feel deserves more attention. They rely on proxy data that is widely spaced in time (median sampling interval 120 years) and in many cases may also be subject to significant dating uncertainty. These effects will both tend to blur and obscure high frequency variability. They estimate (page 1, column 3) that only 50% of the variance is preserved at 1,000-year periods. This amount of variance suppression is roughly what you would expect if the underlying annual temperature time series had been smoothed with a 400-year moving average. In essence, their reconstruction appears to tell us about past changes in climate with a resolution of about 400 years. That is more than adequate for gathering insights about millennial scale changes during the last 10,000 years, but it will completely obscure any rapid fluctuations having durations less than a few hundred years. The only time such obscuring might not occur is during the very recent period when dating uncertainty is likely to be low and sample spacing may be very tight.
Because the analysis method and sparse data used in this study will tend to blur out most century-scale changes, we can’t use the analysis of Marcott et al. to draw any firm conclusions about how unique the rapid changes of the twentieth century are compared to the previous 10,000 years. The 20th century may have had uniquely rapid warming, but we would need higher resolution data to draw that conclusion with any certainty. Similarly, one should be careful in comparing recent decades to early parts of their reconstruction, as one can easily fall into the trap of comparing a single year or decade to what is essentially an average of centuries. To their credit Marcott et al. do recognize and address the issue of suppressed high frequency variability at a number of places in their paper.
Ultimately, the Marcott et al. paper is an interesting addition to the study of millennial scale climate variability during the Holocene. Their results are broadly consistent with previous findings, but the details are interesting and likely to be useful in future studies. However, since their methodology suppresses most of the high frequency variability, one needs to be cautious when making comparisons between their reconstruction and relatively rapid events like the global warming of the last century.
Revkin has a video interview with co-author Shakun also, see it here:
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I love the headline.
Earth Is Warmer Today Than During 70 to 80 Percent of the Past 11,300 Years
Not
Earth Is Cooler Today Than During 20 to 30 Percent of the Past 11,300 Years
Alarmism ‘r’ Us …
w.
By ignoring Nyquist’s criterion one can make a fool of one’s self.
I’m sure all the people on the east coast of the US will read this paper and realize the cold white stuff that keeps getting dumped on them isn’t really snow but the ashes from the planet catching on fire.
I’m not too worried about whatever proxies they come up with. As long as the planet continues to thermally flat-line these folks will just look like clientologists.
Mann’s own recons can’t be validated prior to 1500 CE, a measly 500 years. He knows damn well that something going back 11 frickin’ thousand years is a fairy tale.
Yet once again, temperature numbers assigned by way of mere statistical scaling. No physical theory. No science. No material meaning. The article just goes to show how thoroughly paleoclimatology has become an accepted pseudoscience.
Is the graph in the post from the paper? It doesn’t make any sense. I’m assuming that BP means “before present”.
Interesting that the two lead authors are post docs and Shaken not surprisingly comes off cocky with Revkin like a giddy school girl. It is fascinating Revkin gives Mann so much space in some desperate attempt to salvage his farcical hockey sticks while using his NYT honed “journalism” skills to not even bother looking for a critique.
This NYT post demonstrates just how far Revkin is in the tank with them, any facade he tried to create before has been completely obliterated.
“…when you tack on where we are headed in the 21st century …and BOOM! we’re just outside the [reaching really high], outside the elevator you know, its up and out [reaching high again] so I think that is the kind of interesting perspective you get …a super hockey stick”
– Post doc Shaken giving a “scientific” review of his paper.
Key Statement in the abstract of the paper: “Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.”
Temperatures in past decade have not exceeded peak interglacial values! So comments claiming unprecedented warming are wrong and have misinterpreted the paper. Does anyone know if these authors have avoided the statistical problems of Mann’s reconstructions?
In the second video the first person Shakun mentions is “Bill McKibben” …what does that say for Shakun’s ideology?
Could someone tell me how it is possible to reconstruct paleotemperatures to fractions of a degree using any kind of analysis. How do the proxies compare to actual measured temps since the invention of thermometers? As someone in a comment in an earlier post pointed out, early thermometer records are probably not even accurate to fractions of a degree, so just how can anyone come up with this conclusion regarding heating or cooling?
Weird.
They just concluded that as much as 20-30% of the holocene may have been warmer than today and every savant here attacks a study they didnt read.
1. You think it was cooler?
2. You think it was warmer?
Which is it? If you think it was warmer.. On what basis? a piece of driftwood?
Simple: we have evidence to reconstruct past temperatures. That evidence is all we have.
We have methods for estimating. They are what they are. You take the data. You apply the methods and you get the answer that you do.
The nice thing about the study is that there are no tree rings.
The other nice thing is the methods are known.
So, if you think it was cooler during the holocene, on what basis?
Warmer? on what basis?
Show your work.
Personally, Im with Robert on this ( as we discussed it earlier this week )
Its broadly consistent with other work and they had an interesting aproach to handling the loss of high frequency signals with proxies that have resolutions varying between 20 and 500 years.
They figured all that from just 73 sites. Well, that’s it then.
Mosher, B.A. English who has no scientific papers published is with Robert Rhode his BEST team member …didn’t see that coming.
How would a non-scientist recognize if the work was shown? Would he do a “review” of the grammar?
Mosher;
The problem is that many people don’t trust a single word out of the mouths of people who claim to be claim to be climatologists.
And with good reason as you well know.
Next time you have a chat with Robert please discuss the risible image of climate science held by the savants.
Steven Mosher says: March 7, 2013 at 8:34
“….They just concluded that as much as 20-30% of the Holocene may have been warmer than today ….”
That is the big thing to come out of it. Something oft quoted and oft refuted in discussions. And here we now have some additional evidence.
The only problem is how it gets headlined, and the emphasis on ‘is worse than we thought’ model projections from this point forward.
Every time climate science has another crack at misanthropy the cool headed skeptics in the scientific community become more determined to show the world just how much of a laughingstock they are, in my opinion, the “Man Made Global Warming” alarmists are kicking a sleeping giant!
Am I allowed to say thank god it is warmer than most of the last 10,000 years?
Life is good, enjoy!
The title of the graph says Years (BP). Is that Years (Before Petrol)?
So the claim is that one can reconstruct, to within +/- 0.2C, what the so-called “global average temperature” was 2000 years ago using proxy measurements from only 73 sites?
Such claims not only strain credulity, but toss it in the blender.
“Stephen Singer says:
March 7, 2013 at 4:55 pm
How come the graph in this story does not resemble the one a Andy Revkins site or the story on MSNBC.com which is much less misleading?
http://science.nbcnews.com/_news/2013/03/07/17225440-warming-fastest-since-dawn-of-civilization-study-shows?lite.
”
I agree with Stephen – the graph is totally different. WUWT? Can some bright spark point out why? If not then we should make a big deal of it.
There is so much freely available evidence that temperatures over the last few millennia have not followed any kind of “hockey stick” curve that any paper which claims that they did is ipso facto not credible.
Next?
After reading all the comments I’m finding it hard to figure out whether people come here to find out stuff or if they really prefer the science just all went away.
I probably got this blog all wrong. I’m just learning. People told me it was a really good place to get info from a skeptics viewpoint. I thought it was about questioning science not dismissing any new study. (The reactions here almost makes you wonder if there’s not something to this CAGW after all.)
Steven Mosher says:
March 7, 2013 at 8:34 pm
So, if you think it was cooler during the holocene, on what basis?
Warmer? on what basis?
The obvious answer to that is: It was both much cooler and much warmer. The problem is (probably – I haven’t read it) not the study, but the press releases. Since, as pointed out in Revkin’s article, the resolution is low for most of the Holocene, you can’t really compare it to today’s temperatures at all without doing a ~400 year average – and if we do that, the CWP is smeared together with the LIA. We have evidence from the Greenland ice cores that previous warming spells (Minoan, Roman, Medieval) lasted for a short time, so from that point of view we have all reason to believe that the current warming is also just a short-lived warming spell, and that in the big 400-year-smoothed picture, we’re still on a long trip downwards to the next glaciation.
But it’s nice that the picture confirms what we already knew: That it was much warmer 6000 years ago than in the last couple of hundred years (we’ve known that for a long time, I learned in school decades ago that in Norwegian mountains which are now Arctic tundra, there were huge forests back then – the preserved roots of those trees can still be found in marshes).
Study shows climate changes – it has been hotter and colder in the past.In what way does this add anything to the debate?