Is the Current Global Warming a Natural Cycle?

Guest post by W. Jackson Davis and Peter Taylor

We were delighted to see the paper published in Nature magazine online (August 22, 2012 issue) reporting past climate warming events in the Antarctic similar in amplitude and warming rate to the present global warming signal. The paper, entitled “Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history” and authored by Robert Mulvaney and colleagues of the British Antarctic Survey (Nature, 2012, doi:10.1038/nature11391), reports two recent natural warming cycles, one around 1500 AD and another around 400 AD, measured from isotope (deuterium) concentrations in ice cores bored adjacent to recent breaks in the ice shelf in northeast Antarctica.

Public media in the U.S., including National Public Radio (NPR), were quick to recognize the significance of this discovery. The past natural warming events reported by Mulvaney et al. are similar in amplitude and duration to the present  global warming signal, and yet the past warmings occurred before the industrial revolution and therefore were not caused by anthropogenic greenhouse gases. The present global warming cycle lies within the range of these past natural warming cycles, suggesting that the present global warming cycle may be of natural origin and not caused by human activity–as climate skeptics have been arguing for some time.

A couple of years ago we performed a similar but more extensive analysis of the historical temperature record from the ice core data obtained from the Vostok site in the Antarctic, not far from the ice core evaluated in the recent Mulvaney et al. Nature paper. We defined a NWE as a monotonic  increase in temperature encompassing at least three consecutive Vostok temperature data points and terminated by at least one temperature data point less than the peak reached during the NWE. We found 342 natural warming events (NWEs) corresponding to this definition, distributed over the past 250,000 years at apparently irregular intervals (though we have not analyzed for subtle regularities, which may exist). The 342 NWEs we identified by this method are reminiscent of the two more recent NWEs reported in the Mulvaney et al. paper.

Figure: Time series showing temperature anomaly (temperature difference from the recent past) during the final segment of the Vostok paleoclimate ice core record (the Holocene) in which conterminous proxy temperature and carbon dioxide measurements are available. Each arrow designates the peak temperature reached during a natural warming event (NWE). Blue arrows and font identify the peaks of low-rate warming events (LRWEs; < 0.74oC/century), while red arrows and font designate the peaks of high-rate warming events (HRWEs; > 0.74oC/century). In each case the first number associated with each arrow is the exact YBP at which the indicated NWE began, while the symbol # designates the number of the NWE in ascending chronological order, which permits cross-referencing of each peak with corresponding data in the accompanying table.

The 342 NWEs contained in the Vostok ice core record are divided into low-rate warming events (LRWEs;  < 0.74oC/century) and high rate warming events (HRWEs; ≥ 0.74oC /century) (Figure). Warming rates of NWEs were calculated as the peak amplitude (oC) divided by the duration (centuries).The threshold for HRWEs of 0.74oC /century is useful because this is the estimated rate of the current global warming event according to the Intergovernmental Panel on Climate Change (IPCC). Of the 342 NWEs in the Vostok record, 46 are high-rate warming cycles (HRWEs). The mean warming rate of these recurrent HRWEs is approximately 1.2oC per century,  the mean amplitude is 1.62oC, and the mean duration of the warming phase is 143.8 years. For comparison, the current warming rate estimated by the IPCC is about 0.74oC/century, the current amplitude so far is about 1oC, and the current duration to date is 197 years. The current global warming signal is therefore the slowest and among the smallest in comparison with all HRWEs in the Vostok record, although the current warming signal could in the coming decades yet reach the level of past HRWEs for some parameters. The figure shows the most recent 16 HRWEs in the Vostok ice core data during the Holocene, interspersed with a number of LRWEs. Note the highest rate of warming beginning at 8,226 YBP, near the beginning of the agricultural revolution (taking into account the north-to-south hemispheric phase lag or climate see-saw).

Each of the 46 HRWEs contained in the 400,000-year Vostok temperature record is shown in the Table along with its time of onset, peak amplitude, duration, and mean warming rate. The 16 HRWEs shown in the Figure can be cross-referenced to the corresponding Table entries using the time of HRWE onset. The original Vostok temperature data are accessible to anyone with internet access, and can be downloaded free of charge from the World Paleoclimatology Data Center website operated by the National Oceanic and Atmospheric Administration of the U.S. (NOAA). The easiest and quickest way to confirm our results is to select any HRWE in the Table, locate the corresponding time in the published Vostok temperature record, and measure the subsequent warming event using the operational definition of NWEs we adopted. Cross-referencing the Figure with the Table provides such confirmation for the most recent 16 HRWEs.

Table: Compendium of high-rate natural warming (HRWEs) events in the Vostok temperature record in chronological order. A natural warming event (NWE) is defined as a temperature increase of at least 0.38oC consisting of at least two consecutive increases in temperature followed by at least one decline in temperature from the peak reached.

Natural Warming Event # (HRWE) Time of Onset(Years Before Present) Amplitude (oC) Duration (Years) Warming Rate(oC/century)
1 234,984 4.99 573 0.871
2 131,506 2.60 256 1.016
3 129,486 3.09 162 1.907
4 126,851 1.33 102 1.304
5 122,064 0.96 113 0.850
6 119,221 0.89 120 0.742
7 118,796 1.46 120 1.217
8 103,205 1.17 132 0.886
9 102,942 1.22 130 0.938
10 102,117 0.89 65 1.369
11 98,712 1.24 140 0.886
12 97,439 1.11 145 0.766
13 94,164 1.72 138 1.246
14 93,615 1.17 147 0.796
15 92,897 1.14 138 0.826
16 90,128 1.99 155 1.284
17 87,482 1.37 140 0.979
18 82,352 2.31 139 1.662
19 81,381 1.16 141 0.823
20 80,173 2.72 153 1.778
21 79,557 1.17 155 0.755
22 78,437 2.97 160 1.856
23 74,651 2.18 167 1.305
24 71,905 1.32 162 0.815
25 45,315 1.47 176 0.835
26 44,800 1.29 166 0.777
27 43,619 1.26 155 0.813
28 28,420 1.33 173 0.769
29 24,363 1.52 177 0.859
30 12,323 1.41 179 0.788
31 12,087 0.90 114 0.789
32 10,315 1.82 97 1.88
33 9,782 1.36 147 0.93
34 9,396 1.08 144 0.75
35 8,811 1.15 95 1.21
36 8,226 2.93 91 3.22
37 6,823 1.65 146 1.13
38 6,385 1.87 98 1.91
39 6,004 1.18 95 1.24
40 4,880 1.39 94 1.48
41 3,778 1.28 132 0.97
42 3,511 1.13 89 1.27
43 3,289 0.76 88 0.86
44 2,980 1.99 133 1.50
45 2,760 1.95 90 2.17
46 1,585 1.66 84 1.98

We submitted these findings sequentially to Science Magazine, Nature, and Nature Climate Change. The editor of Science Magazine replied that the results were not of sufficient general interest, suggested we submit the work to a specialty journal, and declined to proceed with external scientific review.  Nature also rejected the paper without external scientific review, for reasons that we considered spurious.  Nature Climate Change initially rejected the paper, but after some discussion the paper was assigned to a senior editor and reviewed by two anonymous reviewers. Given the context of their comments, both reviewers appeared to be climate modelers.

The Nature Climate Change reviewers concluded that the natural warming cycles we identified in the Vostok record could not possibly be real or significant, but instead represented irrelevant statistical “noise” in the temperature record. We replied respectfully that the warming events we detected and measured are similar to or larger than many well-accepted temperature fluctuations in ice core records, including Dansgaard-Oeschger oscillations, Heinrich events, and Antarctic Temperature Maxima. Indeed, the Vostok HRWEs are similar to or larger than the present global warming signal. These arguments were ignored by the reviewers, however, and the paper was rejected by the chief editor of Nature Climate Change.

As written in our rejected paper two years ago, if the current global warming event has the same underlying cause as the 342 previous similar NWEs spread over the preceding 250,000 years–and we can think of no obvious scientific reason to think otherwise–then based on the statistical properties of all natural warming events in the Vostok record, the current global warming event will reverse by 2032 with 68% probability and by 2105 with 95% probability. If the current warming event is homologous with a HRWE, climate reversal and global cooling are already overdue. Here is how we put it in our rejected paper.

” ….the estimated rate of contemporary global warming (0.74oC/century)2 lies well within the range of temperature increases exemplified by NWEs in the Vostok paleoclimate record. More than 13% of Vostok NWEs exceeded this estimated contemporary warming rate. The mean warming rate over all Vostok HRWEs (x̄ = 1.195oC/century, Table) exceeded the estimated contemporary global warming signal2 by nearly two-thirds (61.5%), while the highest rate of natural warming (3.22oC/century; 8,226 to 8,135 YBP) exceeded the rate of the current warming signal by 435%. Most of the Vostok HRWEs occurred during recent warm periods when temperature was similar to the contemporary global temperature. Therefore, the properties of the contemporary global warming signal2are consistent with a natural climate variation homologous to the Vostok HRWEs. In this case, and assuming that the contemporary period of global warming began in 181530, global temperature is projected with 68.2% confidence to peak and begin declining toward pre-industrial levels by 2032 (1,815 years + mean HRWE duration of 144 years + 1 s of 73 years, Table; confidence limit associated with 1 s), and is projected with 95.4% confidence to peak and begin to decline by 2105 (1,815 + mean HRWE duration + 2 s, Table; confidence limit associated with 2 s).”

In the middle of the editorial review by Nature Climate Change, the senior editor in charge of our paper abruptly and inexplicably ceased working for the journal.  We were notified of this change by an automated “no longer working here” response to a routine e-mail from us.  We were advised later that responsibility for our paper had been transferred to the Chief Editor of Nature Climate Change, who issued the final rejection. A few weeks later, the climate journalist Christopher Booker wrote an opinion piece in the Sunday Times of London to the effect that Nature magazine continues to reject scientific findings if they contradict the prevailing anthropogenic global warming hypothesis. We have no way of knowing whether or how the departure of the Nature Climate Change editor or the Sunday Times article was related to the rejection of our paper.

We hasten to disclose that the central thrust of our paper dealt with climate (temperature) sensitivity to atmospheric carbon dioxide, and not with natural warming cycles, which we used simply as a tool to explore climate sensitivity. We developed a new method for analyzing climate (temperature) sensitivity to atmospheric carbon dioxide based on analysis of NWEs and their responses to naturally-varying atmospheric carbon dioxide levels, and found that the climate (temperature) sensitivity to atmospheric carbon dioxide is far less than currently-accepted estimates. The Nature Climate Change reviewers rejected this conclusion for the same reason as above, however, namely their assertion that the NWEs we identified are irrelevant climate “noise.”

It is encouraging that in light the Mulvaney et al. paper the editors and reviewers of the Nature Publishing Group apparently no longer consider these natural warming events in ice core records as irrelevant climate “noise.” Among other implications, this change in editorial interpretation and practice opens a new avenue for analysis of ice core data and a new method for demonstrating that in historic terms, the current global warming cycle is far from exceptional. It appears to us that the current global warming signal lies well within natural limits. In this case, it seems to us difficult to argue that the current global warming signal is the result of human activity.

We invite free and unrestricted duplication and use of the Figure and Table with appropriate credit to the source.

W. Jackson Davis and Peter Taylor

Dr. Davis is Emeritus Professor of Biology, University of California at Santa Cruz, Emeritus Professor and founding director of the International Environmental Policy Program at the Monterey Institute of International Studies, and President and Chief Executive Officer of the Environmental Studies Institute, a charitable organization headquartered in Boulder, Colorado, U.S.A. Peter Taylor is senior science and policy analyst for the charitable organization Ethos and author of “Chill: A reassessment of global warming theory.”

This paper is also available in PDF form here: Davis and Taylor WUWT submission

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ibbo

Wow.

David Larsen

Does the bear dump in the woods?

The obvious question is how to distinguish these events from red-noise. And if they are not just red noise, do they represent a local signal, or a regional signal. It would be a mistake to compare the expected regional trend with local variability, which is always expected to be greater. The simple check here is to demonstrate that the same events are found (at the same time) in the other Antarctic records. Are they?
Since you define HRWEs as being large than modern warming, it is inevitable that the modern warming will be the smallest of these.

Gary Hladik

“It is encouraging that in light the Mulvaney et al. paper the editors and reviewers of the Nature Publishing Group apparently no longer consider these natural warming events in ice core records as irrelevant climate ‘noise.'”
Has the paper been resubmitted?

Doug H

Yes, it’s difficult to get accepted to the journals. For instance, Nature has an acceptance rate of about 1 in 15 papers submitted. You need not only a great story but also rock solid science.
Regarding the Mulvaney et al. study, you say, “The present global warming cycle lies within the range of these past natural warming cycles, suggesting that the present global warming cycle may be of natural origin and not caused by human activity–as climate skeptics have been arguing for some time.” This is a mischaracterization of their key finding. To quote the actual publication:
From the Figure 4 caption:
“Warming at JRI has been ongoing for several centuries, although the warming by 1.56 °C over the past 100 yr (red lines in a and b) is highly unusual in the context of natural variability. b, This is shown by a histogram analysis of temperature trends calculated in moving 100-yr windows of annual-resolution data from the JRI ice core starting at 2,000 yr BP.”
From the text:
“Over the past 100 yr, the JRI ice-core record shows that the mean temperature there has increased by 1.56 ± 0.42 °C (Fig. 4a). This ranks as one of the fastest (upper 0.3%) warming trends at JRI since 2,000 yr BP, according to the moving 100-yr analysis windows, demonstrating that rapid recent warming of the Antarctic Peninsula is highly unusual although not outside the bounds of natural variability in the pre-anthropogenic era (Fig. 4b). The JRI ice core shows that the recent phase of warming on the northern Antarctic Peninsula began in the mid 1920s and that over the past 50 yr the temperature has risen at a rate equivalent to 2.6 ± 1.2 °C per century. Repeating the temperature trend analysis using 50-yr windows confirms the finding that the rapidity of recent Antarctic Peninsula warming is unusual but not unprecedented.
The long-term climate history provided by the JRI ice core shows that natural millennial-scale climate variability has resulted in warming on the eastern Antarctic Peninsula that has been ongoing for a number of centuries and had left ice shelves in this area vulnerable to collapse during the recent phase of rapid warming. If warming continues in this region, as is suggested by its attribution in part to rising atmospheric greenhouse gas concentrations7, 23, then temperatures will soon exceed the stable conditions that persisted in the eastern Antarctic Peninsula for most of the Holocene. The association between atmospheric temperature and ice-shelf stability in the past demonstrates that as warming continues ice-shelf vulnerability is likely to progress farther southwards along the Antarctic Peninsula coast to affect ice shelves that have been stable throughout the Holocene, and may make them particularly susceptible to changes in oceanographic forcing24.”
Have a look at Figure 4b. If you don’t have access to the paper, you can see a thumbnail of the figure here: http://www.nature.com/nature/journal/v489/n7414/carousel/nature11391-f4.2.jpg . In the bottom panel the grey bars are a histogram of the number of times a given rate of warming is observed (degrees C per 100 years, X-axis). The peak of the histogram curve is at ~ 0. The red line is where we are at now.
Yes, the current warming “lies within the range of these past natural warming cycles”, but it is the is at the extreme limit, a fact which you neglect to mention. The authors’ conclusion is that we are getting close to exceeding the limits of stable conditions that have existed for >1500 years, and that the result may be an unprecedented collapse of ice sheets that have been stable over that period. And you think this is good news?

The article reports a nice analysis with an interesting and important finding. But I notice that there was difficulty getting it published as a paper.
I especially noticed that the article says

Nature also rejected the paper without external scientific review, for reasons that we considered spurious.

I had the same experience with Nature ; see
http://www.publications.parliament.uk/pa/cm200910/cmselect/cmsctech/memo/climatedata/uc0102.htm
It would be interesting to know how many others have had the same experience with Nature.
Richard

About what you would expect from an inherently chaotic system that is not near a bifurcation point.

GlynnMhor

“If the current warming event is homologous with a HRWE, climate reversal and global cooling are already overdue.”
And we can see that the globe has not warmed in over a decade, despite all the CO2 ‘causing’ we humans have been doing.

“It appears to us that the current global warming signal lies well within natural limits. In this case, it seems to us difficult to argue that the current global warming signal is the result of human activity.”
It is wonderful to see this sort of thing in print. I have argued for some time that there is no CO2 signal in any temperature/time graph using data from the 20th and 21st centuries. Since there is no signal that is discernable above the noise of natural variations, it follows that the total climate sensitivity of the additional CO2 in the atmosphere is indistinguishable from zero. By “total climate sensitivity”, I mean the rise of global temperatures as a function of the change in concentration of CO2 in the atmosphere at current levels.

cui bono

If it agrees with AGW, it’s ‘signal’, otherwise ‘noise’.
Nice work gents. Is there any paper or site which ‘compares and contrasts’ various ice core anomalies? A superposition of these would surely be instructive.

tommoriarty

Profs. Davis and Taylor,
Your WUWT article is very good. I will be quickly reading the PDF that you link to.
This data is for the Antarctic (Vostok). Any thought on whether these are global events? Is there a way to tell from this data?
Events 37, 38, and 39 are of particular interest to me. I have found many papers using a variety of proxies that indicate the Arctic was warmer in that era (about 6000 years ago) than it is today.
You can see my list here…
http://climatesanity.wordpress.com/2008/10/15/dont-panic-the-arctic-has-survived-warmer-temperatures-in-the-past/
Tom Moriarty
ClimateSanity

Doug H:
It would have helped if you had read the above article before making your post at September 5, 2012 at 10:41 am which provides alarmist nonsense about “unprecedented collapse of ice sheets”.
You say:

Yes, the current warming “lies within the range of these past natural warming cycles”, but it is the is at the extreme limit, a fact which you neglect to mention.

Firstly, if it “lies within the range” then it “lies within the range”.
And the article actually says about relationship to the “extreme limit”

The threshold for HRWEs of 0.74oC /century is useful because this is the estimated rate of the current global warming event according to the Intergovernmental Panel on Climate Change (IPCC). Of the 342 NWEs in the Vostok record, 46 are high-rate warming cycles (HRWEs). The mean warming rate of these recurrent HRWEs is approximately 1.2oC per century, the mean amplitude is 1.62oC, and the mean duration of the warming phase is 143.8 years. For comparison, the current warming rate estimated by the IPCC is about 0.74oC/century, the current amplitude so far is about 1oC, and the current duration to date is 197 years. The current global warming signal is therefore the slowest and among the smallest in comparison with all HRWEs in the Vostok record, although the current warming signal could in the coming decades yet reach the level of past HRWEs for some parameters.

(emphasis added: RSC)
Richard

dp

Looks like the gatekeepers are still hard at it. Good thing this kind of censorship doesn’t extend to the blogosphere and these analyses are available for our consideration. Yet another strike against the peer review system that APOD commentators are so fond of.
It is frankly astonishing the ease with which the gate is slammed on submissions that don’t follow the alarmist agenda. What else are we missing out on?
It would probably be a popular thing to create a site that accepts science papers such as this. NotSeenAtNatureMag.com has a nice ring.

JJ

“The current global warming signal is therefore the slowest and among the smallest in comparison with all HRWEs in the Vostok record, …”
Well, ya. That is how you defined HRWE …

davidmhoffer

I have several problems with this paper. For example, dividing the data into “high” and “low” RWE’s on the basis of what is essentially an arbitrary number, and then applying mathematical analysis to the two data sets such as arithmetic means is pretty much meaningless. Change the arbitrary dividing line and the data sets change too. The same goes for the discussion regarding the events having common cause. The assumption seems to be a single common cause. Perhaps I’m reading this part of the explanation wrong, but it seems far more likely to me that 300+ events have more than one potential cause, and indeed, there are likely events that are “cooling causes” that could occur simultaneously with “warming causes” and cancel each other out, or produce a LRWE that otherwise would have been an HRWE and so on.
I think there’s a ton of good information in this paper that is important to understand and expand upon. There’s a lot of good info here, and a lot of potential for improving our understanding of climate. I just think there’s a lot of chaff mixed in with the wheat.

Doug H

Richard:
My quote was from the published scientific article, not an analysis that was rejected by peer review and now is a blog post. Why was the data not published in a specialty journal, where virtually all papers are published? Forgive me if I trust a peer-reviewed study more than a blog post.
And “within the range” can mean a number of different things, just look at Figure 4. It is misleading to characterize these findings as meaning that everything is normal.
But it’s fruitless to argue with you, I can see. Good luck with the future. I hope you’re right, despite all the evidence to the contrary.
d

David A. Evans

Of course the warming you noted was either spurious or noise!
They couldn’t replicate it with their models! /sarc (as if it’s needed.)
DaveE.

richardscourtney

JJ and davidmhoffer:
You make the same point – but use different words – in your posts at September 5, 2012 at 11:15 am and September 5, 2012 at 11:27 am.
Simply, the authors of the paper define HRWE by consideration of recent change.
However, I do not accept that the cut-off of the definition is “arbitrary”. The purpose of the paper was to discern if the recent change (i.e. the present HRWE) is within natural variability.
If only one HRWE detected in the Vostock ice core were greater than the present HRWE then it could be said that the present HRWE lies inside observed natural climate variability indicated by the ice core. The authors report that they detected 342 natural warming events and 46 of these (i.e. 13.5%) are HRWE.
The definition of HRWE as a discriminator is novel but seems appropriate for its use in the paper.
Richard

Juraj V

Poor peninsula, it is the only tiny piece of Antarctica which is warming /probably sea or air current changes/ so everyone is wanking on it, ignoring the cooling mainland of Antarctic.
Since CO2 is well mixed; the alleged increased downward IR should warm the surface uniformly and everywhere; it does not. Ice cores show the present is colder than thousands years of holocene, that recent warming was nothing different than previous events, that most of the recent warming started before CO2 has risen by few millionths. Never forget, that only the post-1975 warming is allegedly human-caused.

davidmhoffer

Doug H;
You need not only a great story but also rock solid science.
>>>>>>>>>>>
Bull. There have been any number of papers published in Nature and other “respected” journals that featured science that hardly met the standard of fluff piece let alone rock solid.

Doug H:
re your comment to me at September 5, 2012 at 11:31 am.
It seems to have escaped your attention that we are discussing the above article. If you wish to cite other information (e.g. that disagrees with the article) then fine, but say what it is you are citing and why.
And the above article is not about “unprecedented collapse of ice sheets” which has not happened whatever your crystal ball says may occur in the future. I choose to consider the article under discussion in preference to the indications of your crystal ball.
Richard

Bill Illis

How many other papers are there about the numerous natural warming cycles in the Holocene?
None.
None of you have seen this before.
Because only a hockey stick shape is acceptable to the pro-CO2-warming editors. A warm Holocene optimum leading to a cold LIA leading to the recent CO2-based-warming is all that is allowed.
So, given the lack of the papers on this subject, it should have definitely been accepted on this basis alone.
I encourage the authors to try for publishing in other journals if possible.

tjfolkerts

How accurate is this temperature proxy?
For example:

Though the accuracy of the temperatures thus inferred [from ice cores] are no better than ± 1.5oC, and become less accurate the further back in time we go, the data can be used to establish long term, climatological trends … http://www.climatethoughts.org/GWChapter3.pdf

This suggests that variations of 1.5 C are possible due simply to random variations. Even if the values is +/- 0.5 C, almost all of the variations seen could be chalked up to random luck — one point that by the luck of the draw was low, one that was mid, and one that was high. (If the results are accurate to +/- 0.1 C, then the peaks presumably are mostly real). No one doing serious statistical analysis would consider three points in a row as strong evidence of an actual trend.
The instrument simply seems incapable of resolving the signal the authors of this post are seeking. Instead, they may well be chasing statistical noise.
I would appreciate hearing from the authors of this post as to the intrinsic variability inherent in this technique and the strength of the correlation between the proxy and the temperature record. in other words:
* how accurately can the isotope ratios be measured?
* how closely do those ratios correlate to temperature?

I hope it turns out that the authors find a bigger audience here than they would have had through “Nature” or “Science”, and one that is freer to respond intelligently.

Paolo

Doug H says:
September 5, 2012 at 11:31 am
My quote was from the published scientific article, not an analysis that was rejected by peer review and now is a blog post. Why was the data not published in a specialty journal, where virtually all papers are published?
================================
Because:
“The editor of Science Magazine replied that the results were not of sufficient general interest, suggested we submit the work to a specialty journal, and declined to proceed with external scientific review. Nature also rejected the paper without external scientific review, for reasons that we considered spurious.”
Thus a paper can be rejected by claiming “not sufficient general interest” if it in any way challenges the view that the 20th century rate of warming is extremely unusual. What they mean by “not sufficient general interest” is: “we don’t like what you found”. Or it can just be rejected offhand, or on the grounds that past warming events from the Vostok ice are “noise”, while current ones are pleasant music.
Since all contrary views are rejected one way or another, the peer review process in many sciences, but especially in cllimate science, functions effectively as a merry-go -ound of mutual flattery and validation, and also as collective gatekeeping of different views.
This makes the peer review process in climate science look particularly worthless, maybe even repulsive, and it makes those who invoke it as if it meant anything at all except cronism, look particularly silly.

Kasuha

To Doug H:
As you mention, the Nature article performs analysis of ice cores starting 2000 BC. From all major events reported in this WUWT article, the Nature article covers four. I don’t wonder they find current warming period “unlikely but within natural boundary”. Calling something that occurs five times over 4000 years “unlikely” sounds perfectly reasonable to me. Even if they extended their analysis over the whole Holocene, they would likely find it quite as unlikely as with only 4000 years processed because there may be more such events but they are spread over longer time.
The main message here is: however unlikely to occur completely at random, current warming is not unprecedented. Based on either of these two analyses (Nature article and this article) it can be completely anthropogenic, completely natural, or anything in between. It may quite well be 70% natural and 30% anthropogenic, for example. We may evaluate probabilities for these but can’t tell for sure which case it is. Not just from ice cores.
So certain people should finally shut up about this warming being unprecedented and that being the sole proof it is anthropogenic.

James Allison

Doug H says:
September 5, 2012 at 11:31 am
Tell us Doug H what you particularly disagree with about this article apart from the fact it’s been spuriously rejected by a journal having a reputation for readily accepting shoddy alarmist papers and rejecting papers that show opposing research?

Jim G

Since CO2 lags temperature in historical data and since for the last 12 or so years CO2 has continued to increase while temperature has not and since the accepted climate models have shown no predictive capability using CO2 as their main causal variable for warming, and since we are in an interglacial warming period and have been for about 12,000 years, why would one not consider the possibility that the warming we have experienced is of natural causes?

Arvind

Is the Current Global Warming a Natural Cycle? No.

Arvind,
Post your evidence, please. Make sure it directly connects human CO2 emissions with global warming, per the scientific method. Testable and reproducible, based on raw data.
Otherwise, your answer of “No.” is only belief based. That is not good enough here.

jlc

WTF is an NWE

JJ

richardscourtney says:
JJ and davidmhoffer:
You make the same point – but use different words – in your posts at September 5, 2012 at 11:15 am and September 5, 2012 at 11:27 am.

No.
David makes the point that splitting the data on an arbitrary value and performing certain statistical analyses on the two subsets is meaningless.
I make the point that splitting the data on the value of observation X, and then “finding” that observation X is an endpoint of the subset is tautological.
However, I do not accept that the cut-off of the definition is “arbitrary”. The purpose of the paper was to discern if the recent change (i.e. the present HRWE) is within natural variability.
It isn’t necessary to split the data into separately analyzed substes to do that. If you want to demonstrate that an observation is within the range of the data, you compare it to the range of the data. If you want to demonstrate where an observation is within the distribution of the data, you compare it to the distribution of the data.
I’m just happy they didn’t call the subsets “rural warming events” and “urban warming events”.
🙂

leftinbrooklyn

Is the Current Global Warming a Natural Cycle?
Ok, I’ll say it:
‘Well, duuuuh…”

Theo Goodwin

Bill Illis says:
September 5, 2012 at 12:27 pm
“Because only a hockey stick shape is acceptable to the pro-CO2-warming editors. A warm Holocene optimum leading to a cold LIA leading to the recent CO2-based-warming is all that is allowed.”
Actually, things are much worse. Modelers are committed to Trenberth’s “radiation only” model of Earth’s temperature and reject all references to natural cycles or natural regularities that are not direct effects of radiation exchange among Earth, Sun, and CO2. They argue in peer reviewed journals that ENSO, AMO, you name it, are just epiphenomena of radiation and have no causal role to play in determining Earth’s temperature.

D. J. Hawkins

Doug H says:
September 5, 2012 at 10:41 am

I note that the period of interest you cite is 2,000 BP. The authors of the paper under discussion identify 46 HRWE’s, which, if distributed randomly throughout the record would be about 8,700 years apart. Considering this, it seems a bit of luck for Mulvaney to have found even one event in the last 2,000 years. Are you sure you want to hang your hat on the last 2,000 years (exemplified by Mulvaney et al’s JRI core analysis) as being a representative sample of the available 400,000 year record? Since their article is paywalled I don’t see off hand if they could have gone back further, but I don’t think it’s reckless to speculate that if they had applied their methods to the Vostock core, they might have seen a patter similar to what Davis et al uncovered.

richardscourtney

JJ:
re your post at September 5, 2012 at 2:20 pm.
I stand corrected. You are right. Thankyou.
Richard

LazyTeenager

[snip – I’m not interested in your denigrating opinions, especially when you haven’t the courage to put your name to them. Take a 48 hour time out. – Anthony]

Matthew R Marler

Richard S. Courtney: If only one HRWE detected in the Vostock ice core were greater than the present HRWE then it could be said that the present HRWE lies inside observed natural climate variability indicated by the ice core. The authors report that they detected 342 natural warming events and 46 of these (i.e. 13.5%) are HRWE.
I think your interpretation is solid. Think of it as a null hypothesis test. With natural variability, how many natural warming events have been greater than the observed warming event: about 13.5%. So we can say that the observed event is in the upper tail of the distribution of natural warming events, but not in the upper 5% or upper 1% tail. Rounding a bit to avoid a claim of excessive accuracy, p < 0.15. This is according to the null hypothesis that all the variation is independent of any particular known cause. This is a one-tailed test (test of a one-sided alternative hypothesis), but the direction of the test has been chosen a posteriori. Because in past eras people have worried about "unprecedented" cooling, the a priori argument might favor a two-tailed alternative hypothesis, in which case "P < 0.3" is a more appropriate statement of the outcome (this depends on how much credence one gives to 1-tailed tests when the tail is chosen after the fact: most of the time, such choices are not defended.)
I think the authors' approach is basically sound. We have recently been exposed to a definition of a warming period, and a claim that the warming period is unusual. The authors did not invent the definition of "warming period", they took the definition (reasonably modified, imho) and applied it consistently to a long series of temperatures to count how many warming periods there were by that definition. That's an improvement over the usual AGW practice of defining an important event or signal post-hoc, and then willy-nilly claiming it to be unprecedented. The authors add a nice caveat: the current warming period has not ended (at least not for certain), so we can't tell yet whether it will exceed all previous warming periods.
The liability of the featured paper is that the measurement of temperature that it uses has a large inaccuracy. The standard deviation is 1.5C or something like that. With such a large measurement error, the technique that is used has low power to detect a change of the magnitude that is hypothesized by the theory of AGW. That is the meaning of the rejection letter that they received from the reviewers. It's like trying to detect an increase in fever of 1F with a thermometer that has random variation with a standard deviation of 2F or so. That the change since yesterday is not "statistically significant", given such a thermometer, isn't much information.
The Nature article was analogous, but took a shorter time series and different definition of "warming event". By their definition and their count, based on the shorter time series, the current warming period is unusual. If their thermometer is more accurate than what was used in the feature paper here, then it is more publishable, and the results of the two papers are not really concordant — or rather, the claimed concordance is not too meaningful given the inaccuracy of the thermometer used in the feature article. I could not access the Nature paper, so I don't know whether in fact it was based on a more accurate thermometer.

John

What tjfolkerts said.
Seems like a lot of the warming events could be simply random variations in the measurement accuracy, given that the correlation of any individual measurement is not that close to temperature. But how does one find out?
This effect will diminish with a large quantity of data points, presumably; but the methodology in this paper does NOT demand large quantities of data points before declaring warming events.
So if there is indeed a significant +/- degrees-C error range for each measurement, requiring only 3 consecutive identical or increasing samples to declare a “warming event” would guarantee a lot of false positives over time, no? Think of flipping a coin hundreds of times, and counting every run of three or more heads as a significant event. Of course, in one’s own paper one can define as one pleases, but unless the temperature error range is lower than the temperature swings one is putatively measuring, especially with very short series (3 uncertainty-laden measurements, e.g.), it seems like there is a big risk of signal being swamped by noise.
Let me emphasize that I’m no expert on any of this, but I hope I’m a decently smart layman, and I’ve certainly no infatuation for CAGW theories and even less for the typical proposed “watermelon” solutions.

Peter Foster

Some time back a WUWT article made the point that an increasing number of stations on the Antarctic peninsula used a type of thermometer that allowed reflected radiation from the ice to hit the sensor and thus give up to 10°C error. Some 25 yearrs ago I spent some time living on a little spit of land at Cape Hallett on the edge of the Ross Sea. We worked both on land and on the sea ice. Moving from the gravel spit onto the sea ice was like walking into an oven and we had to ensure plently of sunblock on the underside of ears, nose chin etc to avoid being burnt. So I fully appreciate the reflective effect of ice.
Question is; was the temp data for the peninsula corrected for this sensor error or are the results such as in this post, when it mentions a very high rate of warming at present, merely reflecting the increasing use of this defective sensor ?

Rob JM

Considering the antarctic is cooling at the moment, I’m pretty sure the non existent warming would be within the bounds of previous warming events.
Of course the alarmist are quite happy to use the dubious uncalibrated ice core CO2 level proxy despite the data matching a decompression curve and having incorrect carbon dating while simultaneously disregarding other proxies and measurements that showed the CO2 level to be higher.

No once a hockey stick always a hockey stick.

I imagine that you could even see this from the opposite side – instead of looking at the data to see if the current warming trend matches any prior HRWE’s, you could look at the DROPS in temperature. Kinda like a looking at low-rate cooling events (LRCEs; < -0.74C/century) and high rate cooling events (HRCEs; ≥ -0.74C/century).
Seeing how often they occurred in the history might help some people see just how damaging a rapid COOLING event might be (and compare them to events seen during the Maunder and Dalton Minimums).
Another thought – it's nice to see how long of a history we can get out of an Antarctic ice core (250,000 years). Pity that we can't get a comparable long-term ice core from the Arctic. That would sure clear up a lot about the history of GLOBAL sea ice.
Of course, lack of a long-term Arctic ice core could also mean that the ice hasn't been there very long.
Anybody know the OLDEST ice sample anyone has ever seen from the Arctic? I see stories about in the 50's, the age of the oldest circulating sea ice was upwards of about 10 years.

albertkallal

An absolutely fantastic and simple data analysis.
In other words, the current warming we see is absolutely of a non issue and a non event.
However the most historically funny issue is those here attempting to claim that using today’s warming rate is some type of arbitrary benchmark and making such a choice is unfair or incorrect.
In other words, apparently choosing the current warming trends and rates for comparison to this data is somehow to be considered arbitrary?
In other words why is it that the combined total of the scientific community is able to make such a claim that TODAYS WARMING RATE and the CURRENT WARMING period is some amazing and unprecedented event!
Yet, we take some data, and take todays SAME warming rate as a defined benchmark and compare it to a series of past events, we see that today’s rate of warming is simply a trivial and commonplace occurrence!
In other words it is pretty hysterically funny, and pretty much a pot calling the kettle black week in that some here would state that using today’s rates of warming is somehow an arbitrarily chosen benchmark rate when that’s what everybody else on the planet is doing right now!
In other words we see that the chicken little sky is falling and current rates of warming is a rather common occurrence, and is a common occurrence in a relatively short time of only 0.5 million years.
Now if someone can just come along and point out all of the industrialized coal plants that mathematic correspond to this series of past warming events then we just might be able to find some type of mathematical connection between man’s output of co2 and thus come up with a shred of evidence to support dishonest claims by the Al Gore’s and IPCC’s of the world that man’s co2 output is driving temperature in a fashion anything remotely close to as their unfounded claims!

thingadonta

The only thing unprecedented about the current warming is that, for the first time, ecofanatics are claiming that the 47th similar period of warming in the last 235,000 years is ‘unprecedented’. Probably no such fanatics were around the other 46 times, or at least they werent taken so seriously. Perhaps we should all go back to our caves, if that is all we can achieve in 235,000 years.

thingadonta

The graph above doesnt show any real trend, or simple cause, so it cant appeal to the masses at exotic conferences, like a hockey stick.
In fact if you tried to use it at a hockey game, the ball would go everywhere except where you want it to go. You cant control impressionable minds with such a graph, and you cant model it easily either. No wonder the modellers dont like it.

Current warming period is correlated (to a degree) with the geological data from the North Atlantic.
http://www.vukcevic.talktalk.net/CETnd.htm
This would suggest it is the natural rather than an anthropogenic event.

Accepted or not by prestigious journals is not the question here.The question is: what do we learn from this article?
Apparently the data and the analysis were rebutted for being “statistical noise”.
To my eyes this is a very point: this would imply that the current RWE (which can hardly be denied) can also be interpreted as being the same “statistical noise” as earlier ones. Did the reviewers think about this consequence of their rebuttal?
One difference remains: today there is a smoking gun in the form of human industrial activity and carbon emissions. Is it of importance? we don’t know. My own guess is that it is contributing by 30-50% to the current RWE. But it is one interpretation among others. Therefore the debate is far from being closed.

Last night there was a very biased piece about the melting of the Arctic ices on BBC Newsnight, with a really balmy professor making out everything they predicted, but worse, was now happening. It was followed by a discussion between Peter Lilley MP and the new leader of the British Green Party who was quite potty, aggressive and incoherent (not an attractive advert for the ecowarriors)
Peter Lilley made a good fist of rubbishing the biased report, starting from the position of the underdog and with inadequate time to make his points. Like most public figures he had to concede global warming was happening, and accept IPCC science, in order to be allowed to be heard at all. I think this is tactical and he must be pretending on this score.
Being a “right wing” Conservative Peter Lilley will be dismissed without a hearing by the Guardian readers, but he is a good communicator with a good logical mind. We are missing having politicians from the left.
The new minister for the British minister of the Environment in the cabinet reshuffle is said to hate wind farms. Small indications that the playing field is less steep uphill struggle.

Phil's Dad

What I take away from this is;
a) 0.74oC /century is the estimated rate of the current global warming event (so far) according to the IPCC. A High Rate Warming Event (HRWE) is defined here as “faster than the current rate” and there have been 46 of them detected in the last 250,000 years. Thus the current rate is not at all unprecedented or even unusual, whatever the cause.
b) If you don’t tow-the-CAGW-line you won’t get published (which is not at all unprecedented or even unusual, whatever the cause.)
Re: discussions about how accurate the historical measurements are (my current view FWIW is that noise is larger than signal). If you accept the work of the IPCC based on small fractions of a degree then you must also accept the work (for example) of the unpublished paper. To accept one and not the other is simple confirmation bias (which is not at all unprecedented …etc.)