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New paper shows Medieval Warm Period was global (Read 4135 times)
Ajax
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New paper shows Medieval Warm Period was global
Nov 3rd, 2013 at 11:49am
 
Quote:
New paper shows Medieval Warm Period was global in scope
Andrew Revkin writes:


Michael Mann can’t be happy about this work.

Here’s a chat with two authors of an important new Science paper examining 10,000 years of layered fossil plankton in the western Pacific Ocean. The paper finds that several significant past climate ups and downs — including the medieval warm period and little ice age — were global in scope, challenging some previous conclusions that these were fairly limited Northern Hemisphere phenomena.

(video follows, an interview with authors)



The study finds that the rise in ocean temperatures in recent decades is far faster than anything seen earlier in the Holocene, the period since the end of the last ice age. But the researchers say that this rise is from a relatively cool baseline. Between 10,000 and 8,000 years ago, at depths between 500 and 1,000 meters, the Pacific Ocean was 2 degrees Celsius (3.6 degrees Fahrenheit) warmer than today. (text from the video description)

The paper is here:

http://www.sciencemag.org/content/342/6158/617

http://wattsupwiththat.com/2013/10/31/new-paper-shows-medieval-warm-period-was-g...


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ImSpartacus2
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Re: New paper shows Medieval Warm Period was global
Reply #1 - Nov 3rd, 2013 at 12:08pm
 
Ohh look its sunday morning and sock puppet Ajax is already hard at work cutting and pasting deceitful propaganda for his fossil fuel corporate masters. Well, you know what they say "No rest for the wicked".
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Re: New paper shows Medieval Warm Period was global
Reply #2 - Nov 3rd, 2013 at 12:39pm
 
Not a credible source, but adds detail.
Rosenthal et al 2013

Steve McIntyre, posted on Nov 2, 2013 at 4:15 PM

There has been considerable recent attention to Rosenthal et al 2013: WUWT here, Judy Curry here, Andy Revkin here.

The article itself presents a Holocene temperature reconstruction that is very much at odds both with Marcott et al 2013 and Mann et al 2008. And, only a few weeks after IPCC expressed great confidence in the non-worldwideness of the Medieval Warm Period, Rosenthal et al 2013 argued that the Little Ice Age, Medieval Warm Period and Holocene Optimum were all global events.

Although (or perhaps because) the article apparently contradicts heroes of the revolution, Rosenthal et al 2013 included a single sentence of genuflection to CAGW:

Quote:
    The modern rate of Pacific OHC change is, however, the highest in the past 10,000 years (Fig. 4 and table S3).


In the press release accompanying the article, this claim was ratcheted up into the much more grandiose assertion that modern warming is “15 times faster” than in previous warming cycles over the past 10,000 years (though the term “15 times faster” is not actually made in the peer reviewed article):

Quote:
    In a reconstruction of Pacific Ocean temperatures in the last 10,000 years, researchers have found that its middle depths have warmed 15 times faster in the last 60 years than they did during apparent natural warming cycles in the previous 10,000.


Rather than quoting the article itself, Michael Mann, an academic activist at Penn State University, repeated the claim from the press release in an article at Huffington Post entitled “Pacific Ocean Warming at Fastest Rate in 10,000 Years”.

However, both the claim in the press release and the somewhat weaker claim in the article appear to be unsupported by the actual data.

In the past, we’ve often observed that great care needs to be taken in the interpretation of spaghetti graphs containing both instrumental and proxy data. In the present case, none of the graphics in Rosenthal et al 2013 contain both instrumental and proxy data, a deficiency that I’ve attempted to remedy in today’s post.

First, here is Rosenthal’s figure (3B) showing their reconstruction of IWT (Intermediate Water Temperature) for the past two millennia, which shows a sharp decline in temperature from the medieval period to the Little Ice Age (which, as at Baffin Island also in the news lately, was the coldest period in the past 10,000 years), with a recovery in the 20th century, but to levels lower than those of the medieval and earlier periods.

On the far right, I’ve plotted Pacific ocean heat content, converted to deg C anomaly (red), together with its trend line. The two solid yellow lines show trend lines for 1100-1700 AD and 1600-1950 AD, two of the three periods considered in Rosenthal Table S4. It is true that the rate of change over the past 55 years is somewhat higher than the trend over 1600-1950, but it is not “15 times higher”. While I don’t think that one can safely reify the fluctuations in Rosenthal’s IWT reconstructions, on the other hand, these fluctuations appear to me to preclude any strong conclusions that the relatively modest increase is unprecedented.

...

Figure 1. Annotation of Rosenthal Figure 3B. Original caption: “Compiled IWT anomalies based on Indonesian records spanning the ~500- to 900-m water depth (for individual records, see fig. S7). The shaded band represents +-1 SD. Red- OHC Pacific 0-700m heat content converted to temperature using the 0-700m Pacific mass shown in the Rosenthal SI. The values are consistent with 0-700m temperature anomaly values at NOAA http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/index3.html.

[continued ...]
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« Last Edit: Nov 3rd, 2013 at 12:53pm by # »  
 
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Re: New paper shows Medieval Warm Period was global
Reply #3 - Nov 3rd, 2013 at 12:39pm
 
[... continued]

Rosenthal’s assertion that recent OHC trends are unprecedented are derived from their Table S4, which consists of three panels, the first of which is shown below.

...

In my annotation of their Figure 3B shown above, I’ve shown two trend lines, each of which more or less corresponds to the trends reported on lines 2 and 3 of Table S3: a trend of -0.15 deg C/century from 1100-1700 and a trend of 0.09 deg C/century from 1600-1950. The “money” trend in Table S3 is that shown on the fourth line: the value of 0.032 deg C/century is presumably an error. This is not the only error in the table: in the first column, the observed delta-T in the third line (0.25) is greater than that in the fourth line (0.11), but the delta-HC (5.6) is less than that in the fourth line (8.4) – something that seems to be an error. In passing, I wonder whether the “15 times” claim somehow originates in the seemingly unrelated bolded value of “15″ in the fourth column fourth line. (The derivation of “15 times” is not explained anywhere and is not obviously supported by the data.)


Rosenthal’s Holocene Figure
Rosenthal’s Figure 2 shows their temperature reconstruction over the past 10000 years (the version in their Figure 2C is shown below.) I’ve overlaid my digitization of their two-millennium reconstruction shown above (cyan). (Unfortunately, Rosenthal and coauthors didn’t archive anything: neither reconstruction nor underlying data, though, in response to my email, Rosenthal has undertaken to do so.) Once again, I’ve shown the temperature anomaly (as I’ve calculated it from instrumental ocean heat content) in red. At a Holocene scale, it is a very small squiggle – which I’ve accordingly highlighted by a circle around the squiggle). On the right is a blow-up of the graph in the left panel for the past 500 years.

...

Figure 2. From Rosenthal et al 2013 Figure 2C. Red- temperature anomaly converted from NOAA Pacific Ocean 0-700m ocean heat content. Cyan – Rosenthal Figure 3B reconstruction (my digitization). Orange trend line shows third comparison from Rosenthal SI, taken from first row in Table S3.

As with the two-millennium figure, there are many fluctuations within the reconstruction with much greater rates of change over a century than calculated from the modern instrumental OHC record.

Although spin by Mann and others has focused on the modern portion, Rosenthal and coauthors observe that their reconstruction differs on important points from that of Marcott et al 2013,

Quote:
    To the extent that our reconstruction reflects high-latitude climate conditions in both hemispheres, it differs considerably from the recent surface compilations, which suggest ~2°C MWP to- LIA cooling in the 30°N to 90°N zone, whereas the 30°S to 90°S zone warmed by ~0.6°C during the same interval (24- Marcott et al 2013). In contrast, our composite IWT records of water masses linked to NH and SH water masses imply similar patterns of MWP-to- LIA cooling at the source regions.


They showed the Marcott et al 2013 reconstruction in their Figure 2, apparently unaware that its 20th century uptick is (at best) an artifact. It is regrettable that Marcott and coauthors have not issued a corrigendum conceding that the uptick cannot be relied on.

Although IPCC recently reported much confidence in the non-globalness of the MWP, Rosenthal et al took the opposite view:

Quote:
    The inferred similarity in temperature anomalies at both hemispheres is consistent with recent evidence from Antarctica (30), thereby supporting the idea that the HTM (Holocene Thermal Maximum), MWP, and LIA were global events.

Given all the publicity about the supposed unprecedentedness of the recent increase in Rosenthal et al 2013, the data in the article offers little support for the assertion that the modern rate of increase is 15 times greater than any previous increase – or, indeed, for the weaker proposition that the modern increase is unprecedented. Moreover, it stands against claims that modern temperatures are themselves unprecedented, not only within the Holocene, but within the last two millennia.
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Re: New paper shows Medieval Warm Period was global
Reply #4 - Nov 3rd, 2013 at 12:45pm
 
Quote:
 
In a reconstruction of Pacific Ocean temperatures in the last 10,000 years, researchers have found that its middle depths have warmed 15 times faster in the last 60 years than they did during apparent natural warming cycles in the previous 10,000.


Computer model was it........?????

Take a few proxies adjust them feed them into the computer models and presto we have an outcome.....!!!!!

...
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Re: New paper shows Medieval Warm Period was global
Reply #5 - Nov 3rd, 2013 at 12:49pm
 
liar
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Re: New paper shows Medieval Warm Period was global
Reply #6 - Nov 3rd, 2013 at 12:51pm
 
Chimp_Logic wrote on Nov 3rd, 2013 at 12:49pm:
liar



the truth will set you free

...
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Re: New paper shows Medieval Warm Period was global
Reply #7 - Nov 3rd, 2013 at 12:52pm
 
Hard to believe it's the same study:
Where’s the heat? Warming of Pacific Ocean fastest seen in 10,000 years


Skeptics have made much of the so called 15 year “pause” in warming for land surface temperatures, while conveniently overlooking the warming oceans.

A study just released this week in Science indicates the Pacific Ocean may be warming at a rate faster than it has in the last 10,0000 years [pay wall]:

Quote:
    Observed increases in ocean heat content (OHC) and temperature are robust indicators of global warming during the past several decades. We used high-resolution proxy records from sediment cores to extend these observations in the Pacific 10,000 years beyond the instrumental record. We show that water masses linked to North Pacific and Antarctic intermediate waters were warmer by 2.1 ± 0.4°C and 1.5 ± 0.4°C, respectively, during the middle Holocene Thermal Maximum than over the past century. Both water masses were ~0.9°C warmer during the Medieval Warm period than during the Little Ice Age and ~0.65° warmer than in recent decades. Although documented changes in global surface temperatures during the Holocene and Common era are relatively small, the concomitant changes in OHC are large.

This study was also reported in the LA Times, where some (genuine) climate scientists expressed scepticism about the rate of warming. Still it is very clear the oceans have been acting as a “buffer” in absorbing additional heat. However we can’t bank on the oceans performing this role in future centuries:

Quote:
    “This is much faster than anything we’ve seen in the long term,” said Yair Rosenthal, a professor of earth sciences at Rutgers University and lead author of the study.

    The timing could be fortuitous, because we may be pumping the atmosphere full of carbon after a naturally-occurring cooldown, just when the oceans are most prepared to absorb the heat, Rosenthal said.

    “There may be some hope, “ he said, “because maybe the ocean will be able to store more heat than we were estimating before.”

    It could also spell trouble. While temperatures in the atmosphere go up and down pretty quickly, seawater can absorb a lot of heat before its temperature rises. So even if carbon emissions are reduced, it could take years or even centuries for the ocean to respond, a lag that could have consequences far into the future.
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Re: New paper shows Medieval Warm Period was global
Reply #8 - Nov 3rd, 2013 at 1:06pm
 
liar
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Re: New paper shows Medieval Warm Period was global
Reply #9 - Nov 3rd, 2013 at 1:07pm
 
Still persisting with the crystal ball......!!!!!!!!

So what instruments where used to measure the temperature of the lower layers of the ocean (3000 metres and deeper)........????

How do we know what these temperatures where hundreds, thousands or millions of years and how where they measured................???

The deep ocean that is.............!!!!!!

http://wattsupwiththat.com/2013/07/04/rough-estimate-of-the-annual-changes-in-oc...
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Re: New paper shows Medieval Warm Period was global
Reply #10 - Nov 3rd, 2013 at 1:18pm
 
a liar and pretender

reveal yourself

take off that mask liar
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Re: New paper shows Medieval Warm Period was global
Reply #11 - Nov 3rd, 2013 at 1:22pm
 
Chimp_Logic wrote on Nov 3rd, 2013 at 1:18pm:
a liar and pretender

reveal yourself

take off that mask liar


Tell me how where the temperatures of the deep ocean layers taken hundreds thousands and millions of years ago....????

Then tell me how the temperatures of the deep oceans are acutually taken today................????

I'm all ears..................!!!!!
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Re: New paper shows Medieval Warm Period was global
Reply #12 - Nov 3rd, 2013 at 1:25pm
 
German Ears

liar
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Re: New paper shows Medieval Warm Period was global
Reply #13 - Nov 3rd, 2013 at 1:30pm
 
Chimp_Logic wrote on Nov 3rd, 2013 at 1:25pm:
German Ears

liar



Tell me how where the temperatures of the deep ocean layers taken hundreds thousands and millions of years ago....????

Then tell me how the temperatures of the deep oceans are acutually taken today................????

I'm all ears..................!!!!!
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Re: New paper shows Medieval Warm Period was global
Reply #14 - Nov 3rd, 2013 at 1:39pm
 
ImSpartacus2 wrote on Nov 3rd, 2013 at 12:08pm:
Ohh look its sunday morning and sock puppet Ajax is already hard at work cutting and pasting deceitful propaganda for his fossil fuel corporate masters. Well, you know what they say "No rest for the wicked".



Sunday morning- 12:08PM....

(Sorry I had to  Cheesy)
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