Replies

OK, I have the papers in front of me and I’m prepared to dig in.

To begin with I want to review the papers the Daly used and you presented as proof of warming and cooling. The first reports on the temperature of the Sargasso Sea. While this paper is used a great deal (Soon used it in the OISM Petition Project) there are a number of details in it that seem to get overlooked. TO begin with let me quote from the paper. This is in reference to Figure 3 in the text which shows sea surface temperature. Keigwin (the author) states: “Although, as discussed in the text, about one-third of SST variability calculated from 18O values (before stacking) may actually reflect salinity change in the Sargasso Sea, it is clear that on centennial and millennial time scales, SST variability has been greater than has been measured over the past four decades at Station "S."” So, the SST levels are significantly affected by salinity. I didn’t see this referenced by Daly and I bet that it is not discussed in CO2 Science. Also, note that it says that the variability (not temperature) has been greater in the past.

Moving on to look at Keigwin’s next paper we see that he is not looking at Bermuda but has moved north to the Laurentian fan where he finds that water temperature increased during the little ice age. I pointed this out in an earlier post, not to counter Daly facts, but to counter his methodology. From this information Keigwin has deduced that temperature changes in the Atlantic are due to changes in circulation patterns of the Gulf Stream (the SWC is a offshoot of the Gulf Stream). To quote Keigwin from the paper “Lowered SST over the Bermuda Rise during the LIA and the Dark Ages has been likened to the climatic response expected during a minimum phase of the NAO (9). Our evidence that the slope water current seems to have moved northward during the LIA, causing a local warming over the Laurentian Fan, is thus consistent with the notion that the slope water system oscillates on shorter (interannual to decadal) time scales in phase with the NAO”.

Moving on the second paper you used from Daly’s selection. In it, the paper shows a decrease in SST of 3 – 4 degrees as you state. However if you read the paper (instead of assuming that it means a decrease in global temperature) you find that it also is related to current patterns. To quote from the paper “The faunal assemblage variations at Hole 658C indicate that the Holocene cold events reflect the dual influences of increased southward advection of colder subpolar waters and enhanced regional upwelling.” Nothing about an actual cooling of temperatures over the globe but simply the addition of cold waters to that part of the world. I find it a little ironic that this paper is so clear in what it says yet it is the one that caused to question my reading comprehension!

Finally, you quote from a paper by Demezhko and Shchapov. I don’t have that one in front of me so I will need to rely on you to provide some of the following details. They recorded elevated temperatures, what were the temperatures, what reconstruction method did they use and what were the statistics on the data?

However I am very glad to see that you regard their study as good work. I am interested if just this one is good work or do they generally produce good work. I ask because I have read the following paper Surface temperature trends in Russia over the past five centuries reconstructed from borehole temperatures which has Demezhko (Primary author of the paper you cite) and Shchapov (the other author) both as authors of this report. The abstract to this paper says: “The results show that over the past 500 years, the investigated areas have on average warmed 1 K, with more than half of the warming occurring in the 20th century alone, and 70–80% in the 19th and 20th centuries taken together.” That sounds pretty clear to me and it would see that the borehole reconstruction in Russia does not support your claim that they put “Mann's work and his easy-to-munge-into-your-preconceived-conclusions-PCA to shame.” (your words)

Anyway, that is a quick analysis of the papers we have been looking at. In summary, they do not show what either Daly or CO2 Science claim they do. As always, refer to the initial papers and see what they have to say, don’t depend on someone else’s interpretation of them. As you can see, that leads you into trouble.

Regards,

Yelling

Yelling,

Our discussion has been over a few key questions:
1. Was the Medieval warming period a discernable climate anomaly? Was it global in its extent?
2. Was the LIA (Little Ice Age) a discernable climate anomaly? Was it global in its extent?
3. Is there an observable anomoly in the 20th century that is most extreme? Are recent temperatures the highest in a millenia?

There is no debate that LIA and MWP existed at some level, the debate is whether it is global in extent enough to show in the kind of global or hemispheral reconstruction such as Mann made.

Soon and Baliunas, Climate Research Vol 23:89-110, 2003, ask and answer the 3 questions under discussion here directly, with a number of studies from around the world.

http://guisun3.gkss.de/G/Mitarbeiter/storch/pdf/soon+baliunas.cr.2003.pdf

We could gainsay back and forth, but my own sense, which is what the S+B paper states well and backs with over 130 studies, is this:
1. The MWP (warming period of 800-1300) was a real climactic anomaly and was global in extent.
2. The LIA (little ice age of 1300-1900, particularly at in 17th century) was a real climactic anomaly and was global in extent, with temperatures lower than present day.
3. There has been significant warming in the 19th and 20th centuries, but temperature level is not unique to the past millenium. We cant say with any confidence that recent temperatures are the warmest in 1000 years, or warmer than the MWP.

Having just read S+B, I'd just reference that and call it a day. As a PhD in another field (Comp Sci), I am a layperson with a good BS detector. I've read Mann, M+M, and S+B in the past 3 days. Of the papers, S+B impresses me the most as being clearest, most informative, and easiest to verify. The references I have looked at DO verify what they say; it's solid. The Mann work leaves way too many hidden variables and has a suspect way of merging proxy data; this is exactly what M+M is attacking them on. This lack of reproducibility is IMHO bad way to write papers and do science; that he has defenders attacking M+M is a sad commentary on politics trumping good scientific practice here. Anyway, S+B notes general issues with the concept of merging such data (See S+B on page p. 104); the global climate is not a homogeneous entity but a merging of regional climates. Better to take the timelines as individual representations for a regional or local climate. This reduces biasing errors that occurs with wieghting of different proxies.

It also puts in context these other papers that constitute those regional data points, which frankly are rabbit trails in our discussion ...

"The abstract to this paper says: “The results show that over the past 500 years, the investigated areas have on average warmed 1 K, with more than half of the warming occurring in the 20th century alone, and 70–80% in the 19th and 20th centuries taken together.” That sounds pretty clear to me and it would see that the borehole reconstruction in Russia does not support your claim that they put “Mann's work and his easy-to-munge-into-your-preconceived-conclusions-PCA to shame.” (your words)

----

This is consistent with the LIA hypothesis and other studies that show cooler temperatures in 15th-18th century (LIA) and warmer trend in 19th and 20th.

This borehole tells us well what happened to temperature (give or take some error margin in measurement) in this region. Climate changes (eg jet stream, humidity change etc.) may make a region warmer even if the globe is cooling, but it's a data point. (viz. your Keigwin cite.)

Collating the regional pictures is the best way to get a global picture, which is what S+B did. Of the over 100 studies that covered the timescales in question, only a tiny fraction (less than 5%) were inconsistent with the hypothesis of LIA and MWP. On the other hand, the majority of studies and were NOT consistent with the hypothesis that 20th century temperatures were the highest in 1000 years.

As abstract of S+B states, "Across the world, many records revealt that the 20th century is probably not the warmest nor a uniquely extreme climatic period of the last millenium."

... this does not btw invalidate global warming as a hypothesis or invalidate that humans can impact climate, it just invalidates the incorrect extrapolation of Mann's work into the non-error-bar'd 'hockey stick' as unfounded speculation.

As I said, I'll leave it at that: LIA and MWP have more climate science and studies to back them up than the 'hockey stick'.

Since S+B are stating what I've pretty much concluded independently, I'll let that be the 'authority' on my side and end it. I know its had its share of controversy, due to the politicization of this area ...

http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/000219scientists_and_the_p.html

... but we wont resolve that here anyway.