>Atlantic Multidecadal Oscillation Index Reconstruction

>INTRODUCTION

The Climate Reconstruction webpage…
http://www.ncdc.noaa.gov/paleo/recons.html
of the NOAA Paleoclimatology Program and World Data Center for Paleoclimatology, Boulder contains a number of multi-century SST anomaly reconstructions. Though I posted the AMO reconstruction dataset in an earlier thread, SST Reconstructions, I thought it deserved an individual post. So what I’ve done in the following is presented the write-up provided by NOAA, with graphs trailing.

A link to the paper:
http://www.nrmsc.usgs.gov/files/norock/products/GCC/GeophysResLetters_Gray_04.pdf

NOTE

Keep in mind that the AMO Reconstruction data presented at the end of this post is not the same as the AMO presented by the NOAA ESRL. The NOAA ESRL AMO data is detrended North Atlantic SST data. The long-term reconstruction of the AMO has not been detrended. It is “the 10-yr moving average of annual SSTA values. Values are reported as standard deviations.”

NOAA WRITE-UP

Link:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/amo-gray2004.txt

NAME OF DATA SET: Atlantic Multidecadal Oscillation (AMO) Index Reconstruction

LAST UPDATE: 10/2004 (Original Receipt by WDC Paleo)

CONTRIBUTORS: Stephen Gray and Julio Betancourt, USGS Desert Laboratory; Lisa Graumlich and Greg Pederson, Big Sky Institute, Montana State University.

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2004-062

SUGGESTED DATA CITATION: Gray, S.T., et al.. 2004.Atlantic Multidecadal Oscillation (AMO) Index Reconstruction.IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-062. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

ORIGINAL REFERENCE: Gray, S.T., L.J. Graumlich, J.L. Betancourt, and G.T. Pederson. 2004.
A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A.D. Geophysical Research Letters, 31:L12205, doi:10.1029/2004GL019932.

ABSTRACT:

We present a tree-ring based reconstruction of the Atlantic Multidecadal Oscillation (AMO) which demonstrates that strong, low-frequency (60–100 yr) variability in basin-wide (0–70°N) sea surface temperatures (SSTs) has been a consistent feature of North Atlantic climate for the past five centuries. Intervention analysis of reconstructed AMO indicates that 20th century modes were similar to those in the preceding ~350 yr, and wavelet spectra show robust multidecadal oscillations throughout the reconstruction. Though the exact relationships between low-frequency SST modes, higher frequency (~7–25 yr) atmospheric modes (e.g., North Atlantic Oscillation/Arctic Oscillation), and terrestrial climates must still be resolved, our results confirm that the AMO should be considered in assessments of past and future Northern Hemisphere climates.

GEOGRAPHIC REGION: North Atlantic Ocean (0-70º N)

PERIOD OF RECORD: 1567-1990 AD

FUNDING SOURCES: National Science Foundation (USA), U.S. Geological Survey.

DESCRIPTION:

Reconstruction of North Atlantic sea surface temperature anomalies and the Atlantic Multidecadal Oscillation index based on tree ring chronologies from eastern North America, western Europe, Scandinavia and the Middle East.

These data represent a tree-ring based reconstruction of annual sea surface temperature anomalies (SSTA) for the North Atlantic Ocean (0-70º) and a reconstruction of the Atlantic Multidecadal Oscillation (AMO) index derived from these SSTA values. The AMO is the leading mode of low frequency, North Atlantic SST variability. Over the instrumental period (1856-Present) the AMO exhibited a 65-80 yr cycle (0.4 º C range), with warm phases at roughly 1860-1880 and 1930-1960 and cool phases during 1905-1925 and 1970-1990. The AMO appears to have returned to a warm phase beginning in the mid 1990s.

The AMO has been linked to multi-year precipitation anomalies over North America, and appears to modulate the strength of El Niño-Southern Oscillation (ENSO) teleconnections over large portions of the Northern Hemisphere. Multidecadal variability in the North Atlantic is also thought to play a role in Atlantic hurricane formation, rainfall over the Caribbean and northeastern Brazil, African drought frequency, and winter temperatures in Europe. Instrumental observations capture only two full cycles of the AMO, so a need exists for developing proxies to assess low-frequency North Atlantic SST variations and their climatic effects.

These SSTA and AMO reconstructions span the period from A.D. 1567 to 1990 and were developed using 12 tree-ring records from eastern North America, western Europe, Scandinavia, and the Middle East. We first reconstructed annual SSTA values for the North Atlantic and then smoothed this time series with a 10-yr moving average to produce the Atlantic Multidecadal Oscillation index. Correlations between the observed and reconstructed SSTA and AMO values were high (r = 0.64 and 0.81, respectively) and numerous tests confirmed that the model has significant skill in predicting SSTA values.

GRAPHS

http://i48.tinypic.com/241ml5g.png
North Atlantic SST Reconstruction
####################################
http://i47.tinypic.com/ekkhuc.pngAMO Reconstruction “The AMO index is the 10-yr moving average of annual SSTA values. Values are reported as standard deviations”

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About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
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8 Responses to >Atlantic Multidecadal Oscillation Index Reconstruction

  1. Anonymous says:

    >BobI read this via a paper liniked through Roger Pielke's blog:The results of our modeling study indicate that the 2008 NA cooling can be mainly attributed to theobserved SST anomalies, and in particular to the local cooling of the tropical Pacific SST(especially the Niño 4 region) associated with natural variability of the climate system.Our appraisal of the natural SST conditions in the Niño 4 region, with anomalies of about -1.1K suggests a condition colder than any in the instrumental record since 1871.Paper quoted is "A strong bout of natural cooling in 2008" Judith Perlwitz et alComments/ observations please?

  2. Bob Tisdale says:

    >Anonymous 9:50AM: FYI, the Perlwitz et al (2009) paper was discussed at WUWT a couple of weeks ago:http://wattsupwiththat.com/2009/12/07/noaa-paper-north-american-2008-cooling-attributed-to-natural-causes/The link to the full paper:http://www.leif.org/EOS/2009GL041188.pdfI did leave a comment in the thread that read:Leif: Thanks for the link to Perlwitz et al (2009). Their Figures 1, 2, 3 and 4 illustrate how poorly the models reproduce the observed decadal trends and annual variations. They then twist the logic somehow to, “North American temperatures would have been considerably colder in 2008 had there been no human-induced warming influence present.”

  3. Anonymous says:

    >Well, this natural variability pattern were much stronger in the past.Then, if you go to the Arctic, the paper "Recent Warming Reverses Long-Term Arctic Cooling" by Kaufman et al.(2009), show that there was a robust cooling trend in the last 2000 years with VERY LITTLE VARIABILITY, that is,not only the AMO, PDO and AO had had little impact in Arctic temperatures for the last 2000 years, there isn´t even a hint of the LIA and "Medieval Warm Period" in the recontructed temperatures.Then the last 100 yers completely broke the trend, and now the Arctic Region is more than 1,5°C warmer than the temperatures expected in the area according to the 200-year trend.NOTE: the last paper of Mann et al. "Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly (Mann et al 2009) shows that:1]) the "MWP" was not a Global Warming event, as the warming affected the North Atlantic Area(so, it impacted European and North American temperatures), but…2) there was WIDESPREAD COOLING ELSEWERE, specially in the Tropical Pacific, thanks to a protracted dominant La Niña pattern(so it isn´t surprising to have strong warming in the Indo-Pacific Warm Pool, as La Niña concentrated the warm Pacific waters there)Now is crystal clear that something really unprecedented in 2000 year-long Arctic climate happened in the last 100 years.

  4. Bob Tisdale says:

    >Anonymous 12:34PM: You concluded your comment with, "Now is crystal clear that something really unprecedented in 2000 year-long Arctic climate happened in the last 100 years."Really? I believe if you plot the individual proxies used by your referenced Kaufman et al (2009) you might have a different opinion.There's a spreadsheet down towards the bottom of the following webpage:http://lwf.ncdc.noaa.gov/paleo/pubs/kaufman2009/kaufman2009.html

  5. Bill illis says:

    >Nice post Bob.Have a look at this presentation given by Phil Jones in Boulder last June.Two points; Slide 21 shows the new HadSST3 corrections again – they look a little higher post-1944 than the others we have seen – any thoughts?The corrections in the data pre-1940; it looks like the raw SST measurements were much, much lower in the past (and have been adjusted upward); do you know what the reason(s) for this are? http://www.cgd.ucar.edu/cas/symposium/061909presentations/Jones_Boulder_june2009.ppt

  6. Bob Tisdale says:

    >Bill Illis: Thanks for the link. The HADSST3 in Slide 21 shows yet another increase after 1997/98, which would cause their data to be a bigger outlier in recent years. It will be interesting to plot the new data against NINO3.4 SST anomalies to see if global SST anomalies better represent the response to NINO3.4 SST variations during the 1930s to 1960s.Thanks again.

  7. Anonymous says:

    >I said:"Then the last 100 yers completely broke the trend, and now the Arctic Region is more than 1,5°C warmer than the temperatures expected in the area according to the 200-year trend."I wanted to say:"Then the last 100 years completely broke the trend, and now the Arctic Region is more than 1,5°C warmer than the temperatures expected in the area according to the 2000-year trend."(I just mistyped "200-year trend" instead of "2000-year trend")A nice review of the last Mann et al. paper can be found at:http://www.skepticalscience.com/Was-there-a-Medieval-Warm-Period.html

  8. Bob Tisdale says:

    >Anonymous: In my earlier comment I noted that you should plot the individual proxies used by Kaufman et al, because they illustrated something entirely different than the average, which Kaufman present. No need for you to do it. I've done it in my most recent post.http://bobtisdale.blogspot.com/2009/12/look-at-individual-proxies-used-in.htmlThanks for the idea.Regarding your Mann reference and links, personally I feel his manipulation of data has reached comical levels. If you were to read the multiple posts at Climate Audit, you may come to the same conclusion.Regards

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