Book Tour

Well known, but who could resist


Excerpts

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28 February 2012 4:26PM

Mr Mann,
The other day I thought I’d play around with some randomly generated time-series and see if I could ‘reconstruct’ northern hemisphere temperatures. The reconstructions clearly show a ‘hockey-stick’ trend. Rhis is precisely the phenomenon that Steve Mcintyre has been talking on about.
Have you attempted to process random data with your statistical procedures in order to verify that they don't make hockey stick shapes simply as a result of an incorrect methodology?

28 February 2012 4:33PM

Response to RobinsonRM, 28 February 2012 4:26PM

Hmm. You really need to read the book, since I discuss this in some detail. That claim is been refuted in a number of actual studies in the peer-reviewed literature, by folks like Von Storch, Huybers, Wahl & Ammann, etc. McIntyre engaged in some rather dubious cherry-picking to falsely make this claim. Among other things, he sorted through thousands of random series to eventually find some that had the shape he was looking for. There is a good discussion at the site "DeepClimate", search on "mcintyre": http://deepclimate.org/?s=McIntyre
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28 February 2012 4:34PM

Dr. Mann,
James Hansen is widely quoted as saying that climate-sensitivity is "nailed" at 3C by paleoclimate. What are your views on this?
PS, loved the book.

michaelemann

28 February 2012 4:39PM

Response to aphillips, 28 February 2012 4:34PM

thanks for the kind words about the book. Jim is a great scientist, who has made substantial contributions to our field, and I never take anything he has to say about the science lightly. I am surprised if he stated this, as there is still a very vigorous debate within the climate research community about precisely how much constraint we can put on equilibrium climate sensitivity. In my own (somewhat expert) assessment I would suspect that the range is somewhere between 2-4C for the "fast feedback response", but larger, for the long-term response where land surface and carbon cycle feedbacks fully kick in. but here especially there are many 'known unknowns' and almost certainly quite a few 'unknown unknowns'. As I remarked earlier, there is no reason at all to assume that uncertainty will cut in our favor. Indeed, there is more reason to be believe it will cut against us, because of the possibility of some very high cost albeit low probability impacts.

aphillips

28 February 2012 4:46PM

Thanks for the reply Mike. I've had a look - Hansen said it at an AGU meeting, and did add "plus or minus half a degree." Good luck with the book - great bit of science communication, even if I still don't quite grasp the details of PCA.
All the best.

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lionelsacks

28 February 2012 4:40PM

As someone who did not cope well with the level of bullying that can occur in academia, between colleagues! ... I was deeply moved, reading your book by what you and others been subjected to. Being anti-science is one thing, but the violence that's involved in this debate is astonishing...
What can be done to re-civilize the debate on climate change policy?

michaelemann

28 February 2012 4:47PM

Response to lionelsacks, 28 February 2012 4:40PM

thanks for your comment. well sadly, I think it is symptomatic of something much deeper, at least in the U.S. Its part and parcel to the poisoning of our public discourse, where every issue seems to have to be construed as falling along partisan political divide, and immediately you have gridlock and stagnation when it comes to advancing policy solutions to read problems. Part of the problem is the loss, in our media, of an honest broker. It wasn't that long ago that, as legendary New York Senator Patrick P. Moynihan once said, "you're entitled to your own opinion, but not your own facts". Unfortunately, it now seems that with climate change---and so many other matters of policy relevance--people seem to think they are entitled to their own facts. Sadly, much of that is evident even in some of the comments that have been posted here today. There seems to be a loss of good faith in the public discourse. And until we solve that problem, I see little hope for substantial progress in solving just about any substantive problem faced by society.
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Salamano

28 February 2012 4:48PM

Thank you for your consideration :) My sister-in-law had you in class as a student at UVA...
My question concerns the 'loading the climate dice' studies that are starting to pop up in the literature. What are your thoughts on the validity of such studies? In my view, it's either the methodology is uniformly applicable, skillful, and revelatory, or the methodology is flawed.
For example, Stefan Rahmstorf's study showing the 'loading of the climate dice' when it comes to attribution of the Moscow heat wave (y'all discuss this at RC as well) ... What if his same methodology (or others like it) were to be applied to the extreme cold gripping Eastern Europe / Balkans this winter?

michaelemann

28 February 2012 4:55PM

Response to Salamano, 28 February 2012 4:48PM

Thanks. Please say hi to your sister for me. I hope she had a positive experience! Your question is a great one. Generally speaking, we expect the "climate dice" to be increasingly loaded towards more "sixes" (extreme heat) and fewer "ones" (extreme cold). Certainly, we see that for the U.S., where the incidence of extreme heat over extreme cold has doubled over the past several decades to where the records run 2-to-1 (in the absence of climate change, it should be 1-1). Last summer in the U.S. it was closer to 10-to-1. So we are seeing climate change in the collective rolling of the weather dice. W.r.t. the Moscow heat wave, the Rahmstorf finding was recently reaffirmed in an independent study using so-called "detection-plus-attribution" approaches by some scientists at Oxford.
Now, the extreme cold during parts of the winter in Europe for the past few years is very interesting. I would have guessed that there was no particular connection to climate change. However, a number of recent peer-reviewed articles have argued that there may indeed be a connection: the loss of Arctic Sea Ice in the summer and the impact that has one the transfer of heat form the Arctic ocean into the overlying atmosphere in fall and winter, may be perturbing the jet stream in such a way that you get more frequent wiggles favoring northerly (arctic) air flow over parts of Europe during winter. But the jury is still out on this. That's what makes the science so interesting. There are real uncertainties & controversies, and they have implications. Were that the discourse was over these issues, rather than the false debate we're still having in the public discourse about whether or not climate change is even real :(

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thefandango

28 February 2012 4:47PM

Micheal
Given that the term "denier" has obvious holocaust denial connotations, do you think that your use of that word is:
1. unacceptable for a scientist to use
2. one that could incite certain elements to violence against people who question the concensus
Or do you consider it a reasonable term?

michaelemann

28 February 2012 5:06PM

Response to thefandango, 28 February 2012 4:47PM

Frankly, I think those who complain about this are often just producing crocodiles tears. As someone who lost relatives to the religious persecution of the jewish people, I would be as sensitive to anyone if I really though the use of the term has anything whatsoever do do with the holocaust. I find that argument quite disingenuous if not downright dishonest. For those who are denying mainstream science, the logical thing to call them is "deniers". they are certainly not "skeptics" and even "contrarian" doesn't always fit the bill. Given that some of the fiercest of our detractors have proudly declared themselves deniers (one such individual even wrote a book "The Deniers") I find that this argument has no currency at all. I suspect its often used as a somewhat disingenuous ploy to get journalists and other commentators to grant the highly undeserved term of "skeptic" to those who are nothing of the sort.
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