Update: Keith Briffa responds to the issues discussed below here.
Sorry I am a bit late with the latest hockey stick controversy, but I actually had some work at my real job.
At this point, spending much time on the effort to discredit variations of the hockey stick analysis is a bit like spending time debunking phlogiston as the key element of combustion. But the media still seems to treat these analyses with respect, so I guess the effort is necessary.
Quick background: For decades the consensus view was that earth was very warm during the middle ages, got cold around the 17th century, and has been steadily warming since, to a level today probably a bit short of where we were in the Middle Ages. This was all flipped on its head by Michael Mann, who used tree ring studies to “prove” that the Medieval warm period, despite anecdotal evidence in the historic record (e.g. the name of Greenland) never existed, and that temperatures over the last 1000 years have been remarkably stable, shooting up only in the last 50 years to 1998 which he said was likely the hottest year of the last 1000 years. This is called the hockey stick analysis, for the shape of the curve.
Since he published the study, a number of folks, most prominently Steve McIntyre, have found flaws in the analysis. He claimed Mann used statistical techniques that would create a hockey stick from even white noise. Further, Mann’s methodology took numerous individual “proxies” for temperatures, only a few of which had a hockey stick shape, and averaged them in a way to emphasize the data with the hockey stick. Further, Mann has been accused of cherry-picking — leaving out proxy studies that don’t support his conclusion. Another problem emerged as it became clear that recent updates to his proxies were showing declining temperatures, what is called “divergence.” This did not mean that the world was not warming, but did mean that trees may not be very good thermometers. Climate scientists like Mann and Keith Briffa scrambled for ways to hide the divergence problem, and even truncated data when necessary. More here. Mann has even flipped the physical relationship between a proxy and temperature upside down to get the result he wanted.
Since then, the climate community has tried to make itself feel better about this analysis by doing it multiple times, including some new proxies and new types of proxies (e.g. sediments vs. tree rings). But if one looks at the studies, one is struck by the fact that its the same 10 guys over and over, either doing new versions of these studies or reviewing their buddies studies. Scrutiny from outside of this tiny hockey stick society is not welcome. Any posts critical of their work are scrubbed from the comment sections of RealClimate.com (in contrast to the rich discussions that occur at McIntyre’s site or even this one) — a site has even been set up independently to archive comments deleted from Real Climate. This is a constant theme in climate. Check this policy out — when one side of the scientific debate allows open discussion by all comers, and the other side censors all dissent, which do you trust?
Anyway, all these studies have shared a couple of traits in common:
- They have statistical methodologies to emphasize the hockey stick
- They cherry pick data that will support their hypothesis
- They refuse to archive data or make it available for replication
The some extent, the recent to-do about Briffa and the Yamal data set have all the same elements. But this one appears to have a new one — not only are the data sets cherry-picked, but there is growing evidence that the data within a data set has been cherry picked.
Yamal is important for the following reason – remember what I said above about just a few data sets driving the whole hockey stick. These couple of data sets are the crack cocaine to which all these scientists are addicted. They are the active ingredient. The various hockey stick studies may vary in their choice of proxy sets, but they all include a core of the same two or three that they know with confidence will drive the result they want, as long as they are careful not to water them down with too many other proxies.
Here is McIntyre’s original post. For some reason, the data set Briffa uses falls off to ridiculously few samples in recent years (exactly when you would expect more). Not coincidentally, the hockey stick appears exactly as the number of data points falls towards 10 and then 5 (from 30-40). If you want a longer, but more layman’s view, Bishop Hill blog has summarized the whole story. Update: More here, with lots of the links I didn’t have time this morning to find.
Postscript: When backed against the wall with no response, the Real Climate community’s ultimate response to issues like this is “Well, it doesn’t matter.” Expect this soon.
Update: Here are the two key charts, as annotated by JoNova:
And it “matters”
McIntyre showed that you’d get a hockey stick with red noise, not white noise.
One minor quibble. The evidence that the MWP took place has less to do with Greenland’s name than the fact that we know the Vikings were practicing forms of agriculture and animal husbandry that would have been impossible given the historic (by which I mean 18th-19th century) temperatures there.
Similarly, the presence of extensive vineyards throughout the English midlands during the MWP that declined in the 14th century to virtually nothing buy the 19th century is a good indicator that England was a good deal warmer during that period than it had been historically.
I once left a very respectful but skeptical comment over at DeSmogBlog.
It was deleted.
I refuse to have major parts of my life dictated by people who abuse science by dismissing inquiry.
very prescient prediction about real climate.
this just in from “tamino”:
“As for Steve McIntyre’s latest: I’m really not that interested. He just doesn’t have the credibility to merit attention. I have way better things to do.”
nice to see ad hominem alive and well.
watts linking to an AGU presentation confirming SM’s results.
http://wattsupwiththat.com/2009/09/30/agu-presentation-backs-up-mcintyres-findings-that-there-is-no-hockey-stick-in-yamal/#more-11328
morganovitch,
For Tamino, the king of de nile, to pretend he can simply pretend the fraud issue with the underpinnings of AGW does not exist, is frankly an honorable distinction which McIntyre has earned.
Showing deception, prejudicial cherry picking, and irreproducible results is, in the world of real science and any ethical inquiry, a devestating problem.
For AGW, not so much.
For AGW true believers, they do not even understand the problem.
Dr. Roger Pielke Jr. is taking a thoughtful approach.
“If Steve has discovered a smoking gun, then I’d expect Nature and Science to both be candidate publications. And I would really hope that some of those members of the relevant expert community who (I know) frequent his blog would join with him, perhaps as co-authors, to help bring the new analysis into the mainstream scientific discussion. That is how science moves forward.”
http://rogerpielkejr.blogspot.com/
I agree with Pielke. Publication in Science or Nature would get the attention of the larger scientific community and hopefully the mainstream press. Is it the tipping point? If Steve McIntyre can get this published in one of those two journals, it might be. It would, at very least, be very hard to ignore.
The chances of either magazine, in their current editorial stance, of publishing something as devastating to AGW as this is ~0.
Hunter,
I think you hit the problem on the head here.
The problem SM faces is far harder to over come than just publishing his data. The real problem is that humans are involved. These “scientists” have invested enourmous amounts of energy, time, effort, money in to proving global warming ™ is man made! These same people arent just going to roll over and accept SM’s information without a fight.
Yes SM maybe right, however human nature dictates that these so called scientists will fight him tooth and nail to protect their reputations!
After all, their reputations are far more important than the science itself!
Mailman
As for Tamino’s latest: I’m really not that interested. He just doesn’t have the credibility to merit attention. I have way better things to do.
As for Tamino’s latest: I’m really not that interested
This made me tear up…….
And that is some serious paneling, my friend.thank u post…..
I agree with the author. The findings of McIntyre and McKitrick is a bit of a denoument. Similar to taking a sat photo of Earth to show as proof that the world is not flat. A bit pedestrian and mundane (a bit of “I told you so”) but probably necessary as long as people continue to believe the Earth is flat. In continuing the simile, some will continue to believe the Earth is flat, i.e., that man is warming the globe through CO2. The AGW theory was faulty merely on the basis of basic science as well as the natural errors that can occur in temp proxies, regardless of what statistical norming or adjustements one can make. For example, tree ring growth can also be a function of other factors, not just temperature. Currents and air flow bring other nutrients or failing to bring other nutrients could little or nothing to do with temp.
In the end, it may not matter much as to why Briffa only selected 12. Even if he meant well or had what he thought was a valid reason to reject the evidence from the rest of the data sets. The fact of limiting to just some of the data from some of the 12 trees is suspect in itself. Let me explain with an example of weather extremes where I live.
I live in north Texas, about 60 miles generally north of Dallas. In March 2006, I was working in McKinney and we had a 100 F day, in spite of the general flat line of the Earth’s global temp. In March 2008, we had two snow blizzards in one week. Each one dumping 8 inches of snow. I have lived in Texas since 1974 and that is the first time I remember seeing that much snow in March. Neither event, in and of itself is a sign of warming or cooling, necessarily. But each should be added into the weather variations to come up with whatever average we have. I also have a hard time remembering any March before 2006 that had a 100 F day. But a true scientist will collect all the evidence to make an average, which may turn out to show a net increase or decrease of zero, and that’s fine, too. An average is just that, a collection of data, some at extreme ends of the spectrum and usually a whole bunch clustered around the middle. But even a collection of extremes will have an apparent average between them.
The more data you have, the more accurate your average is. We normally get a lot of tornados. This season has been drastically down in counts. Even though we had two in my county this year. On average, we don’t get tornados in my county very often but we had two this year. It’s a local event but the greater average is down. Why? We have a large data set every year. What do tornados have to to with climate change or global warming? Not much. What makes a tornado is the meeting of a cold front, moist air from the Gulf of Mexico, and a dry line from the west Texas desert meeting and creating a tall enough storm in a low pressure area that it rises up to near the jet stream. If the jet stream is changing directions (has a bend in it) which it usually does in Texas and Oklahoma, voila, tornado. And temp differentials have nothing to do with global average temp.
Dr. Roger Pielke Jr. is taking a thoughtful approach.
“If Steve has discovered a smoking gun, then I’d expect Nature and Science to both be candidate publications. And I would really hope that some of those members of the relevant expert community who (I know) frequent his blog would join with him, perhaps as co-authors, to help bring the new analysis into the mainstream scientific discussion. That is how science moves forward.”
http://rogerpielkejr.blogspot.com/
I agree with Pielke. Publication in Science or Nature would get the attention of the larger scientific community and hopefully the mainstream press. Is it the tipping point? If Steve McIntyre can get this published in one of those two journals, it might be. It would, at very least, be very hard to ignore.