Friday, June 08, 2007

On The Divergence Problem

The Divergence Problem refers to an anomalous reduction in forest growth indices and temperature sensitivity which has been detected in tree-ring width and density records since around the middle 20th century in forests from the Northern Hemisphere. In essence, while instrument temperature readings have shown distinct temperature increases since that time, tree ring records, which are often used as "proxies" to determine temperature changes in the period before instrumentation, have not shown a comparable increase.

Obviously, if the trees sampled in tree ring record studies differ over time in their sensitivity to temperature change, this lessens their ability to serve as proxies, and makes it difficult, for example, to come to any conclusion as regards to modern temperatures vs. those experienced during the alleged "Medieval Warm Period".

The issue has been examined extensively since it was identified in the mid-1990s, and a number of studies have suggested that the divergence witnessed is a recent, one-off event brought about by the effects of "anthropogenic forcings" on the forests where it has been seen. This conclusion has been dismissed by climate changed skeptics as invoking warming to explain why there is no evidence of warming in recent tree-ring cores. However, to understand why it still serves as at least a good partial explanation for the Divergence Problem, take a look at this very recent (not yet published, as far as I can tell) paper by Rosanne D’Arrigo et al, which summarizes a decade of literature on the topic. While concluding that there is probably not "a single "divergence" phenomenon", Arrigo also points to several consequences of global warming that may well impede the ability of Northern Hemisphere forests to act as natural thermometers and, more ominously, could slow or reverse their future ability to sequester carbon.


Anonymous said...

"climate changed skeptics"

There you go with the Big Lie again

Where on his site has Steve McIntyre ever denied that climate changes ?

Goebbels would be so proud of you.

Steve McIntyre simply exposes the lies, flaws, poor scientific methods, terrible statistical abuses of the WarmOnger crowd.

Put up or apologize.

bigcitylib said...

Don't quibble. The phrase "climate change skeptic" is pretty much the wiki apporved term for someone outside of the IPCC consensus. It does not mean someone who believes climate has never changed.

Anonymous said...

The fact is that it does not matter what McIntyre's opinion is, because it is worthless. As explained here in this article which shows how he became famous for no adequate reason.

"...“All I can say is that story gave an undeserved amount of attention to a controversy that most scientists regard as ludicrous,” says Michael Oppenheimer, professor of geoscience and international affairs at Princeton University..."

"...Oddly, the McIntyre incident is not an anomaly, according to Kevin Trenberth, head of the climate analysis section at the National Center for Atmospheric Research. “There have been several examples of people who have come into the field of climate change and done incredibly stupid things by applying statistics in ways that are inappropriate for the data,” he says...."

Anonymous said...

More accurately, AGW skeptic.

Anonymous said...

The proxies can't match up to actual recorded temperatures. So the problem must lie with the recorded temperatures, or so you truthers believe.

I love that WarmOnger bit.

intelligert said...

@Holly Stick: How funny that your linked article ain't on the web no more.
May it be that Mcintyre was proven to be correct after all? Oh, yes.

Anonymous said...

If you do a research on the solar activity, you will find out that is not our own planet who is warming, the entire solar system is changing and becoming hotter, maybe the climate change is something different that what we are been told.

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