Tag Archives: quadratic

Craig Loehle on the Divergence Problem

Tree rings are widely used for reconstructing climate and past climates are critical for putting the current climate (including global temperatures) into the proper perspective. Is current warming unusual? Only a comparison to the past can tell. To help gain a better understanding of the past and how global temperatures may have behaved, researchers frequently […]

More on Positive and Negative Responders

(2012 Update…) CA was the first blog to discuss the recent papers by Wilmking and his associates on “positive and negative responders” – the opposite response of trees to recent warming in which – at the same site – some trees responded positively and some negatively. This is an important observation in trying to provide […]

Survivorship Bias

bender has sent in the following interesting graphic showing how drought-caused dieback could bias a tree ring chronology and interfere with interpretation of past records, emphasizing the continued need to keep U-shaped temperature response functions firmly in one’s mind when considering these series. [image being re-sized] (2012 note) For reference, here are some related postings […]

bender on Gaspé

New poster bender has written some very thoughtful posts, including some comments on Gaspé which I I’d like to recover from deep in a political thread. The growth pulse in Gaspé cedars seemed very improbable to me as a temperature proxy; bender has some detailed knowledge on the topic.

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 […]

Post-1980 Proxies #1: Twisted Tree Heartrot Hill

I get a lot of questions about post-1980 proxies and I find it a very interesting question. One would expect that 1998 – the "warmest" year of the millennium – and the 1990s – the "warmest decade" of the millennium would leave a loud signal in a valid proxy. I’m going to start discussing some […]

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