The very first sentence of the Marcott et al (which is getting heavy press) abstract says:
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time.
Okay, let’s have a look at the claim. First this graph from the publication:
![marcott-A-1000[1]](http://wattsupwiththat.files.wordpress.com/2013/03/marcott-a-10001.jpg?quality=83)
Seems reasonable when you look at that data, right? But let us examine a well known reconstruction from GISP2 ice core data in Greenland. Here’s a section from Dr. Richard Alley’s reconstruction:
Now here is a simple scaling of the Marcott et al graph to get an approximate match for the temperature and time scales:
Note that this is just a simple visual comparison, with a rough match of the data for time and temperature scales – it isn’t intended to be anything else.
The full un-cropped Alley GISP2 plot can be seen below:
In my overlay above, the Marcott et al graph full time scale on the x axis is 2000 years, and its temperature full scale on the y axis is two degrees C. The scaled overlay to the Alley GISP2 plot is a reasonably close match to the GISP2 plot scale units. The centerlines don’t match, but they can’t with this sort of comparison.
The idea here is simply to compare magnitudes of the data on the same time scale.
Clearly, the GISP2 data has greater magnitudes in the past 1500 years, and at longer time scales, the GISP2 temperature reconstruction dwarfs the magnitude of the Marcott et al temperature reconstruction. Dr. Don Easterbrook has a good synopsis of GISP 2 temperature reconstruction magnitude on WUWT here.
This simple visual comparison suggests that their “unprecedented” claim for the 1500 years BP is unlikely to hold up when examined against other reconstructions. As they say in the big leagues, more study is needed.
Marcott et al alludes to the warmer temperatures of the past in this paragraph:
Our results indicate that global mean temperature for the decade 2000–2009 (34) has not yet exceeded the warmest temperatures of the early Holocene (5000 to 10,000 yr B.P.). These temperatures are, however, warmer than 82% of the Holocene distribution as represented by the Standard5×5 stack, or 72% after making plausible corrections for inherent smoothing of the high frequencies in the stack (6) (Fig. 3). In contrast, the decadal mean global temperature of the early 20th century (1900–1909) was cooler than >95% of the Holocene distribution under both the Standard5×5 and high-frequency corrected scenarios.
Perhaps this weekend when I have more time, either I can do a proper plot of the data in a similar fashion to see how well they match when plotted side-by-side in the 1500 year time frame. Unfortunately I have other work to do today, so I can’t at the moment, and I’m traveling again tomorrow. Posting will be light.
Thanks for doing the heavy lifting NiV.
The modern anomaly is more likely due to the low resolution and dating uncertainty in the proxy data than unprecedented warming. There’s a reason why we don’t correlate well logs based on radiometric dating or even on paleontology. We correlate them based on log characteristics (kind of like wiggle matching).
Leif: “When is ‘present’? The acronym BP [before present] normally means before 1950 so that the time axis stays fixed.”
That’s a common criticism of Easterbrook graphics (which these appear to be; they’re not from Alley’s 2000 QSR article — although that’s somewhat implied). The first datapoint appears to be 95 BP, which is 1845 — “hiding the rise” during the past 150 years.
Is this correct? If so, there should a large note in the article text.
Also, it would be nice to have a citation (or link) to the source of these graphics.
Past warming won’t show up in this study if it wasn’t “sustained for at least 100 years” according to Marcott:
“The resolution of the reconstruction is averaged into 100-year segments, which means yearly or every-decade variability fails to show up in the new study. There could have been a period sometime in the past 11,000 years that was warmer than today, but if so it wasn’t sustained for at least 100 years.
‘That is a drawback,’ Marcott acknowledged, though he said the resolution is sufficient to show the rapid change between 1900 and 2000 and the change projected by climate models between 2000 and 2100.”
What do climate model projections have to do with it? Does their new and improved hockey stick include model projections?
“That was done for a reason, so that the Y axis scales would both be visible”
Ah yes Anthony, I see what you have done there.
Richard
Dear Anthony,
One need to be cautious by using the GISP2 data: that is one point on the map that reflects the temperature on the summit of the Greenland ice core, nothing else. It may reflect more or less the whole Greenland and beyond area, but in general temperature fluctuations of Greenland and NW Europe follow opposite swings, together with changes in the NAO.
More interesting would be the d18O/dD data from the same ice core, as that reflects the temperature of a large part of the North Atlantic Ocean, where most of the precipitation on the Greenland summit originates. That says more about the past temperatures over a larger area…
A “reconstruction” that misses the Minoan Warming Period 3x longer than the claimed resolution is not in need of fine tuning, it is in need of scraping.
Part of how the Marcott graph fudges history is by flattening inconvenient variation in prior centuries to falsely suggest the difference between the peak of the MWP and bottom of the LIA was only around 0.4 degrees Celsius. In contrast, a more honest source, Loehle data at http://www.drroyspencer.com/global-warming-background-articles/2000-years-of-global-temperatures/ , shows such was around 1.2 degrees Celsius difference.
Every warm period in the Holocene (and before) has had more relative temperature change near the arctic than in the tropics (simply because the tropics never change much in temperature), as is so for the Modern Warm Period (“global warming”) as well as all of the others. The general picture of current temperatures not being much compared to past millennia is seen both in the GISP2 data as well as illustrated in as wide reconstructions as Loehle.
There are loads of other examples, including higher global sea levels than now during the Medieval Warm Period and still more so during the Holocene Climate Optimum. As another illustration, http://www.sciencedirect.com/science/article/pii/S0009254199000297 references how near-Arctic Eurasian vegetation was 20% more than now during the Holocene Climate Optimum and 55% more than now during the Eem interglacial optimum (due to those times being much warmer than now, with less frozen ground).
FerdiEgb,
Both hemispheres appear to correlate well.
Mosher: “in both cases the person who cites higher frequency data to counter lower frequency claims is really OFF TOPIC”
How about the person who splice indirect proxies and the measured temperature record and claim unprecedence? How about the person who thinks a heterogeneous global temperature sampling on continents, weighted with statistical methods has a climatic relevance? Ignoring processes is what the AGW crowd loves the most. No need to understand meteorology and climatic evolution, just measure and compute and tada! It’s there.
The money for promoting man-made global warming hoax and global governance is going bye bye.
China Backing Away From Carbon Tax Start in 2013, Official Says
“China will wait until after this year to introduce a tax on carbon, deferring to concern that economic growth might suffer, a government researcher said. ”
“China first said it would implement an environmental tax in 2011, when the country released its 12th Five Year Plan, a list of policies to be carried out by 2015. ”
http://www.bloomberg.com/news/2013-03-06/china-backing-away-from-carbon-tax-start-in-2013-official-says.html
That should be an immediate red flag.
mod/mods
Thanks for not deleteing me per my hot headed request.
Cooling off time over.
Working on another blog just now and it jumped into my strange brain.
Why not attempt to bait and switch aka trick the Democrats in the U.S. Senate to put up some CO2/Climate Change/Global Waming , big spending bill as in a tax on milage on auto/truck use and or some such tax and spend boondogle.
Once it comes to the floor have Ted Cruz and or Rand Paul or some other U.S. Senator well schooled on the facts known.
Have that person up and ready for a 13 to 20 hour filabuster of facts.
Seems to some a nice cheap way to bypass the msm blockade.
apachewhoknows
Looking closely at the plot posted by DayHay, as I like its helpful grid scaling:
http://i.imgur.com/s19MOMd.jpg
That graph is particularly illustrative of how transitions from the warm state of climate to the cold state have occurred with around 10 degrees temperature drop in GISP2 over as little as around 300 to 400 years sometimes (even if not counting at all the Younger Dryas event which included an even faster drop section, just in case it was different from the others by being influenced by a comet impact, though there seems no way that the bulk of the others could be comet impacts). That would be proportionally like every several decades or faster a magnitude of change equivalent to the difference between the Little Ice Age and now, again and again multiple times over, an extremely rapid change in climate terms, vastly beyond the comparatively tiny fraction-of-a-degree changes in modern history. That fits with what I have heard elsewhere from trustworthy sources, whereas in contrast CAGW propagandists saying any transition to an ice age could only be gradual over tens of thousands of years are just lying as usual.
D.B. Stealey says:
March 8, 2013 at 12:42 pm
Both hemispheres appear to correlate well.
Yes, but that are indeed the d18O and dD temperature proxies. Anthony used the GISP2 borehole temperature, which only reflects the temperature of the Greenland summit at the moment of deposit. The d18O and dD proxies reflect a much wider area of the oceans where the water vapour in the ice originates…
Modoki says:
March 8, 2013 at 11:16 am
“if you have a valid criticism, post it, snark helps nobody -mod”
One study compares local temperature response at an acknowledged labile location (Greenland).
The other study compares global temperature response.
Apples and oranges.
Then again (to his credit) Mr. Watts stated:
” Note that this is just a simple visual comparison, with a rough match of the data for time and temperature scales – it isn’t intended to be anything else.”
It is a rough match of data measuring 2 different metrics which would be expected to be different.
But the paper does not say that recent warming in Greenland are unprecedented – it says:
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time.
So your criticism should be leveled at the paper not Anthony
Here one can find the GISP2 d18O data with yearly resolution over the past 1100 years:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/d18o1yr.txt
and a lot more data:
http://www.ncdc.noaa.gov/paleo/icecore/greenland/summit/document/gispdata.htm
Steven Mosher says:
March 8, 2013 at 11:27 am
So today is Labo(u)r day?
DaveE.
“Oh and here is another thing to ponder: Imagine the Holocene was warmer than they suggest.
That would imply a more sensitive climate since the change in forcing between Holocene and LIA isnt particularly big.” or you just think that c02 is important when it might not be. In fact loocking at the long perspective several million years temp and c02 curves are all over the place so it cant be that co2 is as important as you think.
And remember that MOST of the spike at the end was CREATED by man.. ie Hansen et al.
Sorry. As soon as you flatten out the MWP to next to nothing I smell a rat.
Rather than headlines there should be deep suspitions, at best, and scorn if you were not in the mood to be polite. It is as if you came out with a paper that said that George Washington didn’t exist
Steven Mosher says:
March 8, 2013 at 11:27 am
But diffusion of elements in the ice core is also postulated to “smooth” the temperature variations, so your supposition that “ice core has much better resolution” isn’t justified, Steven. The “high frequncy variation” you mention has likely been lost.
But back to the original posting, Marcott should show his temperature graph of the past 10,000 years so we can all see if it’s valid or not. To what does he compare the last 100 years (of which at least half isn’t due to much anthropogenic influence at all)? Inquiring minds want to know.
What may be unprecedented, that which has certainly spiked markedly in the late 20th/early 21st Century, is culpable stupidity overlapping considerably with outright scientific deception. There is no way that this smoothed foraminifera derived proxy data of low resolution should be juxtaposed with very high resolution modern instrument data. The press are having a field day – EPIC global warming screams one particularly nauseatingly uninformed rag. Furthermore, the whole story is conflated with virtual reality IPCC computer predictions of extreme warming which, without any scientific justification, is being touted as a natural consequence of the trend shown by this ‘new’ data. And why did the study stop at 11,300 years. had they gone back further, they would have encountered the Younger Dryas which might have really screwed up their nice smooth pre-industrial revolution temp data, even at low resolution. Could have ended up with a double-ended hockey stick!
Steven Mosher says:
March 8, 2013 at 11:27 am
The ice core has much better resolution. That means it has a better chance of picking up high frequency variation. marcotts proxies are basically “smooths”
Agreed, but that is also the case for the last 150 years. The resolution for that part is yearly (even with a lot of caveats) in Marcott e.a. The current warming even is not sustained over 100 years. With the same resolution as the proxies, this still is one of the coldest periods. And similar warmings of the past may have been hidden in the lower resolution proxies…
Oh and here is another thing to ponder: Imagine the Holocene was warmer than they suggest.
That would imply a more sensitive climate since the change in forcing between Holocene and LIA isnt particularly big.
A common problem in the models: a huge climate sensitivity for natural forcings (solar, volcanoes) means a huge climate sensitivity for all types of forcings (including GHGs and anthro aerosols), according to the models. But that is very questionable. Do you think that 1 W/m2 more IR absorption by CO2 has the same effect as 1 W/m2 more insolation? I don’t. See e.g.:
http://climate.envsci.rutgers.edu/pdf/StottEtAl.pdf
Further, a lot of (mostly European) researchers disagree too:
http://www.sciencedirect.com/science/article/pii/S0277379105001964
(the link to the free copy doesn’t work anymore)
Here the citation:
So, what would it mean, if the reconstructions indicate a larger (Esper et al., 2002; Pollack and Smerdon, 2004; Moberg et al., 2005) or smaller (Jones et al., 1998; Mann et al., 1999) temperature amplitude?
We suggest that the former situation, i.e. enhanced variability during pre-industrial times, would result in a redistribution of weight towards the role of natural factors in forcing temperature changes, thereby relatively devaluing the impact of anthropogenic emissions and affecting future predicted scenarios.
How do you get error bars of of +/- 0.2 deg C from data with a spread of between 2 and 6 deg C?
How can you justify splicing the high resolution air temp data onto an ocean reconstruction?Surely you would need to use ocean temp.
Talk about pseudoscience!