Thursday, June 10, 2010

More record global heat for May, Jan-May, and a new 12-month record. Maybe the ostriches might even feel it on their beaks beneath the sand.

See Climate Progress for the rundown (GISS tied record for May, longer time periods are records, snow and ice covers are terrible etc.).  I'll just add that UAH satellite records are getting very close to their 13 month running average high, and I think they'll beat it in 2-3 months.

Per my posts on previous months, the scientific relevance is how the trends fit into the giant mountain of evidence of human-caused change.  The news peg is important too to get people to pay attention.

Slightly-related new fact for me:  "the tree rings that diverge from the instrumental record are not all tree ring datasets, but rather a subset of tree ring datasets. In particular, the divergence problem applies to the Briffa 2000dataset taken from trees close to the Arctic Circle. Other tree ring datasets don’t show the same divergence issue"

I thought the leading explanation for why tree rings in recent decades didn't match temperature records was that they were affected by the increased CO2.  I'm not sure exactly how that works if not all trees were affected - maybe Briffa's Arctic species were especially sensitive to CO2.

UPDATE:  Skeptical Science lists potential causes for the divergence and doesn't mention CO2.  Hmmm.  I know I've seen it described that way though.


  1. How come the CO2 doesn't enhance rather than suppress growth?

  2. Not sure. Skeptical Science lists other potential anthropogenic causes like pollution and drought:

    Doesn't even mention CO2.

    Pielke Sr. does:

    I'm quite certain I've seen it emphasized in more respected sites than that one, but just going off memory.

  3. Nobody knows why the *negative* divergence happens - that odd downturn in 1960 or 1980 (depending on which record you use) that "tricks" were necessary to hide is hypothesized as caused by some unknown anthropogenic process but not C02 specifically. IIRC, CO2 was proposed as a reason for an entirely different divergence issue, the issue of *positive* divergence. Specifically, the fact that MBH-style multiproxy studies show too large of an upturn. In many of the spaghetti chart studies the blade of the hockey stick climbs much faster than local recorded temperatures and that is a separate puzzle. Even the idea of "teleconnections" - that temperatures rising somewhere else are making it rain more there or some such - doesn't really do help. But CO2 fertilization seemed a likely candidate for a while.

    As for the downturn, I always assumed it was plain old "regression toward the mean". If your validation procedure selects from random noise series only the signals that have a steep climb at the end and calls those "temperature", some fraction of those signals will turn down again in the future, indicating that no, they weren't really temperature after all. If you then toss the ones that do that and say the ones that still climb, now *those* are true temperature, you might just be extending the cherry pick. Wait another decade or two and some of those also will inexplicably turn downward.

  4. Lets have some evidence for the human-caused change Schmidt. You ought to stop lying about it and make good with the evidence.

  5. You might want to reread that S&R post. Angliss originally wrote "If the scientists had actually substituted or replaced the tree ring proxy data with instrument data, then McIntyre and Fuller would have a valid claim of fraudulent behavior by Phil Jones et al. However, nothing was substituted or replaced.". Angliss has now retracted that part (with an overstrike), since subsequent discussion has made it clear that McIntyre and Fuller are right and the scientists did do the things which he said would lead to "a valid claim of fraudulent behavior by Phil Jones et al". Other retractions seem likely to follow that one.

    As for the "new fact for you", Briffa's data set was quite large and had been selected specifically on the basis that those trees were claimed to be especially temperature sensitive. Trees "near the arctic circle" might not be representative of trees generally but they are representative of trees that are thought to be temperature-limited. That is to say, if there are trees anywhere on the planet that would be likely to do better if it got a little warmer, the place you're most likely to find them is at high altitudes and northern latitudes. If you want to claim some much smaller group of trees somewhere else are better "treemometers" and more representative of planetary temperatures than Briffa's set, that needs an argument. Or better yet, a documented relationship with local measured temperatures.

    The skeptic claim is not that all trees everywhere "diverge", but that the specific trees being chosen to represent climate in studies such as Mann's (a) have been the object of cherry-picking and (b) tend to diverge as soon as you start getting a decent amount of out-of-sample data.


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