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:
OK.
How about:
Over the past 11,300 Years, 20% to 30% of the time it was warmer than today.
There. that’s not so scary, is it?
from the paper–
Although our temperature stack does not fully
resolve variability at periods shorter than 2000 years,
such high-frequency changes would only modestly
broaden the statistical distribution of Holocene
temperatures (Fig. 3 and fig. S22).Moreover,
we suggest that accounting for any spatial or seasonal
biases in the stack would tend to reduce its
variability because of the cancellation of noise in
a large-scale mean and the opposing nature of
seasonal insolation forcing over the Holocene, causing
the Holocene temperature distribution to contract.
Just another sad case of grant addiction..
So 20-30% of the last 10,000 years has been warmer than today without any EVIL SUVs spewing out BABY-KILLING CO2.
What are we supposed to be worried about again?
It gets better.
http://www.sciencemag.org/content/suppl/2013/03/07/339.6124.1198.DC1/Marcott.SM.pdf
So, from 73 records (not databases, but “n”) and 1000 Monte Carlo simulations you interpolate and get your error bars for 12,000 years of data. All I can say is WOW. Talk about Pure F’in Magic. Do climate scientist work at all these days?
“beesaman says:
March 7, 2013 at 2:54 pm
I predict more and more nonsense of this sort, right up to the moment it starts costing governments money.”
Ohoh. Not good, beesaman. I don’t know about the EU, OZ, etc, but in the good old USSA, they never run out, as long as there is a tree for them to make into paper to print money with.
Another hockey stick – this one billed as ‘scarier’ than Mann’s
Here is the real hockey stick=> the solar activity of the last 100 years:
http://www.woodfortrees.org/plot/sidc-ssn/mean:1056/normalise
Okay, so that was worded different than further down,
I will wait for the cliffnotes 😉
Try to fight against the tide of misinformation out there about AGW is akin to being a zoo keeper giving an enema to an elephant that has been constipated for 3 months. !
It’s scary all right. In the same way that horror movies are scary. Nothing to do with reality though. I doubt it will fool many.
love how stable temps were before the deep fall in the little ice age. maybe that fall is the cause for the rebound warmth. After all the scientists have proven temps used to be stable.
‘projections of global temperature for the year 2100,’
when none of us will be around to be reminded of this BS , which is really ‘useful’
I knew it was hotter than I always feared, and now I have a graph by some scientists to prove it! When will Marcott get his Nobel?
(Read with total lack of interest) Oh wow, I am sooooo fearful, now I want to give up all my freedoms and money to a bunch of mindless bureaucrats. (Come on alarmists, you can do better than that.)
Something crooked this way comes….
Anthony add an update with the GWPF’s excellent headline,
EARTH COOLER TODAY THAN 28% OF THE PAST 11,300 YEARS
Who would like to bet which way the distinguished Prof Mann tweets about this study?
Will he proclaim it as a major breakthrough and justification for his own reconstructions?
Or will he tweet abuse because they have upstaged him with an 11000 year reconstruction?
This is another excellent one from Reason,
Earth’s Average Temperature Lower Now Than It Was 5,000 Years Ago
Which strip barks did they use? Or was is sediments? Archived data? Methodology? Can’t wait for Steve to completely disassemble this one. Will be fun….
Better question, did they as Steve McIntyre to be a reviewer?
The big problem with this particular hockey stick appears to be the temporal resolution of the proxies – which is about 120 years average for the historic temps, but is only 1 year for the 20th century data they have tagged on the end.
This is effectively like using a large span running average and automaticatly smears out and removes peaks or hollows in temperature from the past – like the minoan, roman and medieval warm periods that were quite short in duration (1-200 years) but saw large 2°C rises in temperature .
To make this graph more honest you would have to run the same 120 year moving average over the modern temp record – in which case you wouldn’t have anything news-worthy as it would remove the modern peak and fill in part of the little ice age. Alternatively you have to use proxies with high temporal resolution (like ice cores such as Gisp2)
Just horrible pretensions to science. If the paleo part of the chart has a granularity of 120 years, and the present temps are the annual instrumental record (tortured to bend upwards), then it is clear that the medieval warm period (error bars) still make it stick up above the most stretched out hockey stick to date. Lets see what happens if we average the temp of the last 120 years to make an apples to apples comparison. This must be against some law or another or should be.
Just look at the first 500 years of the graph. Less then .01C variation for 500 years!!! Simply Amazing!!!
Borenstein gets into the act:
http://www.usnews.com/science/news/articles/2013/03/07/recent-heat-spike-unlike-anything-in-11000-years
That “Mann et al reconstruction” in the figure is certainly not the original hockey stick in the 2001 IPCC report. Among other things, the original only went back 1000 years.