Dear Allstatters,
As promised here is my summary of the responses I received. The original
email I sent is attached at the bottom. In total I only received 6
responses (7 if you include me) to the questions I posed. In addition,
there were 6 other responders who sent comments but who did not answer the
questions. I have also decided to include the 3 responses to Anatoly
Zhigljavsky's query on temperature records that went to the ALLSTAT list
instead of direct to Anatoly himself.
My main reason for posting this query was to find out the level of
involvement & interest of statisticians in the climate debate. Although no
meaningful conclusions can be drawn from the responses to my questions, I am
going to contrast the total number of responses (12 or 15 if you include
Anatoly) I received with other questions I have posed in the past. Looking
through my email folders, I received 6 responses to an SPC query, 11
responses to a classification analysis query and 8 responses to a variant of
the Monty Hall problem (the summary was posted on my website which received
over 200 visits). The total number of responders to this query was higher
than before but given how topical climate change is at present and its
importance in world affairs, I am disappointed that the response was not
significantly higher than what I received for quite technical queries. If I
assume that the ALLSTAT list is a representative sample of statisticians
around the world (perhaps with a bias to English-speakers & academics), I
think the answer to the question in the title in my query ("Where are the
statisticians?") is that they aren't there and they are not involved in
climate science to the extent they should be. Given the importance of the
debate and the inherent statistical nature of the science I find that
extremely worrying.
The 7 responses to my questions can be summarised as follows:
1. Before reading the above links, how knowledgeable do you think you
are about the science and statistics behind the global warming debate?
Please respond on a scale from 1 to 9 where 1 is no knowledge at all, 9 is
you know everything:- RANGE FROM 1 to 7, MEDIAN & MODE WAS 3.
2. Do you work in the field of climate research in any way? NOBODY
WORKED IN CLIMATE RESEARCH
3. Prior to reading the 3 links below, can quantify your prior belief
in the relative merits of the warmist/sceptic views? Happy for you to
choose your own way of quantifying this but as an example, I would have said
my prior belief was 60:40 in favour of the sceptic camp. 4 FAVOURED THE
SCEPTIC VIEW (FROM 60:40 TO 99:1 IN FAVOUR), 3 FAVOURED THE WARMIST VIEW
(FROM 60:40 TO 90:10 IN FAVOUR). JUST TO BE CLEAR, SCEPTIC MEANS SCEPTICAL
ABOUT THE EXTENT OF HUMAN INFLUENCE ON CLIMATE, NOT ABOUT WHETHER THE
CLIMATE IS CHANGING IS CHANGING IN THE FIRST PLACE.
4. On reading the 3 links below and any others you find, has your
prior belief changed? If so, how would you now quantify your posterior
belief in the light of what you have read? ONLY 1 PERSON CHANGED THEIR PRIOR
BELIEF BUT IT WAS A SMALL CHANGE FROM 65:35 SCEPTIC TO 55:45 SCEPTIC. THE
OTHER 6 POSTERIOR BELIEFS WERE UNCHANGED FROM THEIR PRIORS.
5. If your posterior belief is little changed from your prior, what do
you think is missing from the debate that would help you change your belief
either way? MANY COMMENTS RECEIVED WHICH I AM SURE WOULD BE PART OF ANY
STATISTICAL DEBATE. MAIN ONES LISTED BELOW.
. 3 mentioned lack of availability of the raw data as opposed to the
summarised data currently available.
. 2 wanted to see an examination of the strengths & weaknesses of
the measurements involved including recent temperature records, CO2
emissions, historical temperature reconstructions.
. 1 wanted a review of the statistical models used and the
assumptions that have been made and whether they were able to separate
common cause variation from special cause variation.
. 1 wanted greater clarity of whether a temperature series was
derived from global data or local data.
. 1 had concerns about the quality and validity of the peer review
process.
. 1 wanted more encouragement for free debate of all views &
expressions.
6. Should statisticians be more involved in the debate? If so, how
should this happen? AGAIN MANY COMMENTS, MAIN ONES WERE.
. Climate science papers should have statistical referees.
. RSS should encourage media to check quality of climate data with
statisticians.
. Statisticians should be part of multi-disciplinary climate
research teams.
. RSS to set up a working party to pull together all climate data
and assess its quality.
. RSS should be more willing to speak out when bad data & modelling
techniques are being used.
. Being a statistician doesn't automatically make you an expert on
climate science.
If I couple the responses to question 6 with the other comments I received,
I was left with the impression that nearly everyone felt statisticians did
need to be more involved in the whole debate, particularly when it came to
passing comment on the data & modelling techniques being used. As one
responder put it, "being pure-minded methodologists, statisticians are not
naturally attracted to policy debates like the one on climate change".
Another stated "I have often been "too busy" to participate in these kind of
dialogues. Perhaps it is time that I got "unbusy" and deliver some time
series expertise to the subject at hand." I think it is quite noticeable
that whilst many professional bodies have taken a view on anthropogenic
climate change, the statistical bodies such as the RSS have not done so. I
don't think that the RSS should have a view on the science involved but I do
think it is in a unique position to pass comment on the data and modelling
methodology. For example, we all see the following kind of statistical
errors being made by both warmist & sceptic camps in the media and elsewhere
and it should be quite easy for us to speak out and criticise instances such
as these:
. Too short a time span e.g. "the world has cooled for the last 10
years therefore global warming is a myth" .
. Inferring global effects from local data e.g. "Mount Kilimanjaro
glacier has been receding for decades, we must do something!"
. Using extremes to infer cause & effect e.g. worst flood on record,
clearly due to mankind activities.
. Confusing probability with possibility when making forecasts. I
have seen confidence intervals given which were actually the ranges of
expected outcomes from a number of different scenarios as opposed to being
based on the prediction error from a single scenario.
Many of you forwarded additional links to a variety of topics related to
this query. Rather than make this summary even bigger, I will send these in
a separate email to the list.
Finally, can I thank the list for being far better behaved than what I saw
in the links I sent through. Every reply bar two was courteous and
thoughtful which is what I would expect from my fellow statisticians.
Hopefully we can set an example to others on how to conduct a civilised
debate!
Regards
Nigel Marriott
Chartered Statistician
<http://www.marriott-stats.com/> www.marriott-stats.com
Ground Floor, 21 Marlborough Buildings, Bath BA1 2LY, United Kingdom
Tel (office) +44 (0)1225 489033
Fax +44 (0)870 6221969
Marriott Statistical Consulting Limited, Company No. 5577275, VAT No.
883304029
Registered in England, Registered Office - Equity House, 4-6 School Road,
Tilehurst, Reading, RG31 5AL
From: Nigel Marriott [mailto:[log in to unmask]]
Sent: 07 December 2009 12:20
To: ALLSTAT ([log in to unmask])
Subject: Climate Change: Where are the statisticians?
Dear Allstatters,
First of all, can I thank Anatoly Zhigljavsky for having the courage to open
the debate on global warming on ALLSTAT. Although this is not an open forum
and I do not want people to breach the ALLSTAT guidelines, I would be very
interested to hear your responses to my questions. With the Copenhagen
conference taking place, it is a topical subject and I am very happy to take
responsibility for preparing a summary of the responses I receive once the
conference itself is over which is next Friday I believe.
Some contributors have already mentioned that Anatoly's argument was based
on only 30 years or so which I agree is not long enough for any definitive
conclusions. Personally, I believe the debate needs to start with whether
today's climate is significantly different from the past. For me, the past
has to include the years before industrialisation so as to avoid issues
with confusing correlation with cause & effect which is a real risk if you
only look at the last 100/150 years. To my mind, we need to look at the
last 1,000 or 2,000 years. Unfortunately, since we have no thermometer
temperature records going back before 1700 (the Central England Temperature
series is I believe the longest such record), this requires the use of proxy
measures such as tree rings, ice cores, coral reefs, etc which have been
calibrated against thermometer records. If you reread this paragraph, you
will see that what I have written is an inherently statistical subject
involving time series analysis, multivariate analysis, modelling, sample
design, etc. If we statisticians are not involved in this work, then the
possibility of errors in both the sceptics & warmers camps are enormous.
Yes I know scientists can be trained in statistical methods, but we all know
that even then, they are capable of making statistical errors with profound
consequences for us either way.
After reading a number of blogs, articles & websites, my perspective is that
the warmers & sceptics do not radically disagree over the temperature record
for the last 100 years or so but they violently disagree over the last 1,000
years. At the bottom of this email are 3 links which seems to capture the
heart of this particular argument as far as I can see. Frankly, by the time
I got to the 3rd link, I was heartily sick of personal vitriol being cast by
both sides with each attacking each other's motives instead of the methods
used. In particular, I am finding it hard to evaluate the statistical side
of the argument and I am left with the belief that statisticians are simply
not involved in the climate change debate to the degree we should be.
So to find out what your views are, I would like to ask you the following
questions. I am very happy to collate responses by the end of the
conference and publish the results. I'm sure some of you will criticise my
survey design (I've tried to be Bayesian here!) but I'm only trying to do an
indicative survey here.
7. Before reading the above links, how knowledgeable do you think you
are about the science and statistics behind the global warming debate?
Please respond on a scale from 1 to 9 where 1 is no knowledge at all, 9 is
you know everything.
8. Do you work in the field of climate research in any way? Basically
a yes/no question, not interested in your life's CV!
9. Prior to reading the 3 links below, can quantify your prior belief
in the relative merits of the warmist/sceptic views? Happy for you to
choose your own way of quantifying this but as an example, I would have said
my prior belief was 60:40 in favour of the sceptic camp.
10. On reading the 3 links below and any others you find, has your prior
belief changed? If so, how would you now quantify your posterior belief in
the light of what you have read?
11. If your posterior belief is little changed from your prior, what do
you think is missing from the debate that would help you change your belief
either way? Open question here.
12. Should statisticians be more involved in the debate? If so, how
should this happen? This is an open question and I will do my best to
summarise.
Here are the 3 links I have found (among others) but no doubt you may wish
to click through the other links listed.
. The people at the centre of the ClimateGate storm include authors
of a famous paper published in 1999 which has since become known as the
hockey stick. It is a central piece of the IPCC report. You can find a link
to an updated version published in 2008 this near the bottom of this BBC
article
http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2009/copenhagen/8393855.stm .
The authors are Mann, Zhang, Hughes et al but as you can see, links to a
number of other sources are given as well.
. The original hockey stick paper was criticised by Steve McIntyre
as explained in this essay written by Chris Monckton
http://scienceandpublicpolicy.org/images/stories/papers/monckton/monckton_wh
at_hockey_stick.pdf
. I have not found any paper directly written in response to
McIntyre's criticisms but this blog on the real climate website seems to be
the best so far
http://www.realclimate.org/index.php/archives/2004/12/myths-vs-fact-regardin
g-the-hockey-stick/
Kind Regards
Nigel Marriott
Statistical Consultant
<http://www.marriott-stats.com/> www.marriott-stats.com
Ground Floor, 21 Marlborough Buildings, Bath BA1 2LY, United Kingdom
Tel (office) +44 (0)1225 489033
Fax +44 (0)870 6221969
Marriott Statistical Consulting Limited, Company No. 5577275, VAT No.
883304029
Registered in England, Registered Office - Equity House, 4-6 School Road,
Tilehurst, Reading, RG31 5AL
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