Category Archives: Post-1980 Proxies

"Explaining" a Positive NAO

Trouet et 2009 posit a positive NAO as the “explanation” of the Medieval Climate Anomaly, pausing only briefly to ask what might have caused a centuries long (“temporally pervasive”) positive NAO, falling back on an arm-waving attribution to a stronger Atlantic meridional overturning circulation: The persistently strong winter MCA NAO and its weakening during the […]

Craig Loehle Reconstruction #2

Continuation of Craig Loehle Reconstruction

Hughes and the Ababneh Thesis

I’ve had a few requests to comment on Eli Rabett’s recent post, observing that he was unable to observe a Medieval Warm Period in the bristlecone chronology reported in Salzer and Hughes 2006. Looking at the tree ring index one can clearly see many large eruptions, the little ice age, but no European Warm Period, […]

A Little Secret

Don’t you think that someone on the Team might have been a little curious as to what bristlecone ring widths have done during the past 25 years? For this, we have the classic excuse of Michael Mann and the Team for not updating bristlecone and proxy records is that it’s not practical within the limited […]

Replicating the Briffa et al 2001 MXD Reconstruction

Paul H made the following statement in the context of the Swindle discussion: If a practising scientist selected a 1987 data set over more recent versions, failed to cite it correctly, altered the appearance of the data without a clear explanation and didn’t include the data from the last 20 years then I think we’d […]

Up-to-Date White Spruce Ring Widths

“Bring the proxies up to date” was the title of one of my earliest posts. Michael Mann had explained that doing so required the use of heavy equipment (like tree ring borers) and travel to out-of-the way sites such as Bishop, California or even Niwot Ridge, a full 45 minute drive from UCAR world headquarters […]

Up-to-Date Proxies: Colorado

Another large batch of tree ring chronologies was archived on June 21, 2006, this time with records up to 2003. Are the results for the 1990s and 2000s off the chart?

Some New Tree Rings in Alberta

8 new tree ring measurement data sets have archived this week at WDCP in northern Alberta by Meko. The sites are around 58N, 111W , well to the northeast of the Jasper site (52N, 117W) which is used in nearly all the multiproxy studies. I did a “standard” type chronology fitting negative exponential curves by […]

Cook et al[2004]: More Cargo Cult?

Reader Bart S. has argued that Cook et al [QSR 2004] disposed of the "Divergence Problem", the name applied at the NAS panel on March 2-3, 2006 for the problem that, if the proxies do not record late 20th century warming, how can we be sure that they recorded potential earlier warming in the MWP. […]

Upside-Down Quadratic Proxy Response

David Stockwell has suggested a discussion of nonlinear responses of tree growth to temperature. I’ve summarized here some observations which I’ve seen about bristlecones, limber pine, cedars and spruce – all showing an upside-down U-shaped response to temperature. The implications of this type of relationship for the multiproxy project of attempting to reconstruct past temperatures […]