Exploring the certainty of AGW!

“Certainty is perfect knowledge secure from error or doubt.”

You may wonder what this post is all about opening, as it does, with a definition of ‘certainty’.

What that definition might imply is that ‘certainty’ is a tantalising ‘will of the wisp’ creature.  Excepting for pure mathematics, of course! “Pure mathematics is, in its way, the poetry of logical ideas.” – Einstein quotation.

Whatever your views on the effect of man’s behaviours on our planet’s climate, it’s a long way from the logical idea of ‘2 + 2‘!  So when Oakwood, a reader of Learning from Dogs, submitted a long, carefully written comment rejecting Anthropogenic Global Warming (AGW), the idea came to me that perhaps this comment should stand on its own two feet, so to speak, as a separate post.  I asked Martin Lack, a passionate believer in AGW, to counter the points set out by Oakwood.  Both Martin and Oakwood are scientists; both hydrogeologists.

Now please take a moment to read and assimilate the next few sentences.  The length of the ‘dialogue’ runs to two posts.  Making it without question the longest post that has ever been published on Learning from Dogs.  It is also the most important!  If there is one question above all others for these times, it is the question of whether or not mankind is changing the climate of this planet; the only one we have.

These posts are not an easy read.  They can’t be skim read. They don’t have pictures! But I hope with all my heart that you will settle down today and tomorrow and read each post carefully to the end.

Now to some background information on the two gentlemen.  ‘Oakwood’ is a nom-de-plume.  However, he and I have exchanged emails and I support his need for anonymity. This is how Oakwood describes himself:

  • I am an Earth systems scientist
  • I have followed the AGW scientific arguments on both sides for many years
  • Hydrogeology (my field) and climate science have quite a lot in common, the main one being they require some knowledge and expertise in a wide range of disciplines. It’s not a simple case of saying ‘you are an expert or not’.
  • For example, I need to know quite a bit about chemistry, although I am not an ‘expert chemist’.
  • I am experienced in studying long-time period data, and judging its credibility (this also in common with climate science). Many of the key AGW arguments are based on data and statistics.
  • There are many reasons for being an AGW-sceptic, needing many pages. I give one main example: The ‘divergence problem’ applies to tree ring proxy temperature graphs. Most (perhaps all), proxy graphs cannot reproduce modern temperature data from about the 1980s onwards (in fact the very period of detectable man-made global warming). Because of this, we cannot rely on proxy graphs to conclude now is warmer than the past. Although climate scientists claim the divergence problem is only a modern thing, and does not affect historic data, this is purely a statement or belief. There is no convincing science to back that view.
  • For that reason, I am sceptical of the value of proxy graphs to show current temperatures are unprecedented.
  • I list a number of other brief examples.
  • I do not believe in conspiracy theories and have no problem with climate scientists believing in AGW. But in view of the examples I give, I do have a problem in them saying ‘the science is settled’.
  • There are some benefits from acting on the AGW scare now, such as improved energy efficiency and reduced pollution. There are also negatives, such as wind-farms on pristine countryside and biofuels causing increased hunger.
  • Too much focus on the AGW threat (based on relatively weak scientific arguments) diverts effort and money from more immediate and certain problems.
  • I am an environmentalist who cares about the future of our planet and sustainability. My views on AGW are based purely on the science.

Martin‘s background is encapsulated on his Blog, from which I extract:

I have 25 years of professional work experience, as a geologist and hydrogeologist, in both public and private sectors.

St Albans School, Hertfordshire, 1976-1983.
BSc (Hons) in Geology (Portsmouth), 1983-1986.
MSc in Hydrogeology (Birmingham), 1989-1990.
Postgrad. Cert. in Education (Keele), 1998-1999.
MA in Environmental Politics (Keele), 2010-2011.

Professional Qualifications:
Fellow of the Geological Society (FGS) since 1992.
Chartered Geologist (CGeol) since 1998.
Member of Chartered Institution of Water and Environmental Management (MCIWEM) since 2000.

Martin’s MA dissertation topic was “A Discourse Analysis of Climate Change Scepticism in the UK“  An abstract of that dissertation may be read here.

So two highly professional persons with diametrically different views.  Here’s the ‘debate’.



I have been posed a couple of questions [by Martin Lack, Ed.] which Paul has invited me to respond to.

  1. Why do you think the vast majority of relevantly-qualified and active researchers in earth systems science have reached the conclusion that we need to stop pumping CO2 into the atmosphere as fast as we possibly can because it will get harder to avoid excessive climate change the longer we take to do so?
  2.  Explain why you think the time to act has not yet arrived?

If I may, I’m going to treat those questions more like this:

  1. Why do the majority of climate scientists claim to believe man-made climate change (AGW)  is significant and serious?
  2. Why am I an AGW-sceptic?

Martin Lack

I am grateful to Paul for inviting me to respond to Oakwood’s thesis.

My carefully constructed question was:

Why do you think the vast majority of relevantly-qualified and active researchers in earth systems science have reached the conclusion that we need to stop pumping CO2 into the atmosphere as fast as we possibly can because it will get harder to avoid excessive climate change the longer we take to do so?

I am very pleased to see that Oakwood does not dispute the reality of a scientific consensus regarding AGW although I prefer – because it is more accurate – to call it anthropogenic climate disruption (ACD). Sadly, however, he does not appear to accept its validity. Although I asked Oakwood not to deconstruct the question, he clearly felt it necessary to both deconstruct it and re-word it (emphasis here is mine):

  1. Why do the majority of climate scientists claim to believe man-made climate change is significant and serious?
  2. Why am I an AGW-sceptic?

Right from the start, therefore, Oakwood appears to suggest that the majority of climate scientists are either being stupid, unprofessional, or deceitful. I say this because, by replacing my “have reached the conclusion” with his “claim to believe”, Oakwood would appear to think that the majority of climate scientists have reached a conclusion that is:

  1. Reasonable when it is in fact unreasonable; or
  2. Highly-probable when it is highly-improbable; or
  3. Near-certain when they know it is very uncertain.

Bearing this in mind, let us look at the arguments Oakwood then uses to justify his ‘scepticism’.


I am an ‘earth-systems’ scientist with degrees in Geophysics and Hydrogeology and around 25 years working experience in both those fields, but mostly hydrogeology.

Note: working scientists are every bit as important to our advancement as academics and researchers. Academia is a career choice available to the better scientists. (Though a few ‘duds’ manage to survive by playing the right games.) But many excellent scientists and engineers choose to work in the ‘real world’ where science is applied which often includes active research, written up in reports, but not necessarily in peer-reviewed journals. Those scientists and engineers often have a far more immediate level of responsibility in terms of the quality and implications of their work.

If an academic ‘gets it wrong’, the worst things that may happen are embarrassment, loss of research grant or even loss of job. If a working scientist or engineer gets it wrong, then bridges may collapse, planes may crash, people may be poisoned, etc. Also ‘peer review’ doesn’t mean its right, but just that it adds to the debate.

I have followed the scientific debate for many years, reading much that is written on both sides, including a big proportion of the IPCC reports.

Martin Lack

Oakwood starts by attacking academics for being detached from the real world and suggesting that some  may be “duds” that are just playing games, (although he does not say whom exactly)!

He then attacks the peer review process but fails to provide any reasonable explanation as to why only 24 out of nearly 14 thousand articles about ongoing climate change do not consider human activity to be its primary cause (unless the science is of course near certain).

Oakwood claims to have read a big proportion of IPCC reports (more than me I suspect) but, even so, fails to address the reality that IPCC reports have consistently under-reported the scale and urgency of the problems we face. The AR5 report due out later this year will also do this because it still does not include positive feedback mechanisms causing current rates of change to accelerate.


Very much like hydrogeology, climate science is a multi-disciplinary science dependent on a level of knowledge and expertise in a whole range of disciplines. For example, I need to understand quite a lot about chemistry, although I don’t have a degree in chemistry.

I have to keep learning; by reading, researching, learning from expert colleagues, etc. I also need to know something of maths, statistics, fluid mechanics, weather patterns, computer modelling, microbiology, water treatment, etc.

There are better experts in each one of those subject areas, but that’s their focus and they would not normally be able to pull things together to develop a ‘conceptual model’ of a hydrogeological system.

Martin Lack

Oakwood highlights the similarities between hydrogeology and climate science but fails to mention that both make extensive use of probabilistic computer models (of the kind used by climate scientists). These are models that deal with uncertainty in modelled parameters by being run hundreds if not thousands of times using parameter values picked at random from within user-defined ranges. This produces a range of modelled outcomes with accompanying probabilities of being realised.


There is much overlap between scientific disciplines, especially in ‘Earth systems’. Therefore, to suggest you must be a ‘climate scientist’ to understand all of the scientific and statistical arguments, is incorrect. For example, the hockey stick tree ring studies are principally statistical exercises rather than ‘climate science’, and require an understanding of how the Earth’s climate has changed in the past, which geologists are only too aware of.

As a hydrogeologist, I am very experienced in studying time-series data, and judging whether conclusions drawn from them are plausible and reliable. Of course, my conclusions may not always be correct. Others may disagree with me. But that’s how science develops.

It would take me pages to explain all my reasons for being an AGW-sceptic, so instead I will focus on one key example of where I find a key conclusion unreliable.


I will refer to a ‘typical’ paper by Michael Mann et al, 2008, Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia, Proceedings of the National Academy of Sciences of the United States of America – PNAS.

Its main conclusions are:

Recent warmth appears anomalous for at least the past 1,300 years whether or not tree-ring data are used. If tree-ring data are used, the conclusion can be extended to at least the past 1,700 years, but with additional strong caveats. The reconstructed amplitude of change over past centuries is greater than hitherto reported, with somewhat greater Medieval warmth in the Northern Hemisphere, albeit still not reaching recent levels.

Thus, they claim their work shows current temperatures are unprecedented in at least the past 1,300 years, including the Medieval Warm Period (MWP). This is extremely important. If current temperatures are not warmer than the MWP, then there is far less reason for alarm about the current climate. For example, we don’t have records of such things as droughts, hurricanes, tornadoes, etc.,  being noticeably worse or more common during the MWP. (I know, some will respond: ‘regardless of whether its warmer now, predictions are it will get much worse’. But that is a separate argument). Thus, it seems to be very important to the AGW-case that current temperatures are unprecedented, and changing more quickly than in the past 1,000 to 2,000 years.

Despite, their stated conclusions, their work does not show that now is warmer than the MWP. On their graphs in their Figure 3, current temperatures show as warmer. But the proxy data themselves do not show this. The only data that do are the instrumental data. So if proxy data do not align with instrumental data since the 1980’s onwards, how can we rely on them to show us the MWP was cooler than now? We can’t.

They try to address this with the following statement:

The observed warming rises above the error bounds [ie., the highest possible temperature indicated by proxy data – my words] of the estimates during the 1980s decade, consistent with the known ‘‘divergence problem’’, wherein the temperature sensitivity of some temperature-sensitive tree-ring data appears to have declined in the most recent decades. Interestingly, although the elimination of all tree-ring data from the proxy dataset yields a substantially smaller divergence bias, it does not eliminate the problem altogether. This latter finding suggests that the divergence problem is not limited purely to tree-ring data, but instead may extend to other proxy records.

If you look around at other literature, despite what we hear about ‘settled science’ nobody knows the cause of the ‘divergence’ problem. There is only speculation that it might be something to do with modern air pollution or perhaps CO2 itself.

Here’s what SkepticalScience says:

The divergence problem is a physical phenomenon – tree growth has slowed or declined in the last few decades, mostly in high northern latitudes. The divergence problem is unprecedented, unique to the last few decades, indicating its cause may be anthropogenic. The cause is likely to be a combination of local and global factors such as warming-induced drought and global dimming. Tree-ring proxy reconstructions are reliable before 1960, tracking closely with the instrumental record and other independent proxies.

So, the proxies are “reliable before 1960’s”. But back until when? Around 1880, when temperatures were cooler. There is no evidence whatsoever that the proxies were reliable at other periods of higher temperatures. And we are expected to accept this as ‘settled science’.

In fact, it is possible the divergence problem happens every time it’s warmer. They certainly don’t know this is not the case. The real answer is from very basic statistics:

If the proxy data cannot reproduce the higher temperatures of today, we cannot rely on them to compare with other warmer periods in the past. I don’t care if 99.9% of climate scientists tell me this is acceptable science, I will not agree with them, unless they can produce convincing scientific evidence (not just speculation) to back it up.

(I’ve seen one very comical response more than once: ‘We don’t need recent proxy data to be accurate because we have instrumental data to tell us the temperature.’ For example, a John Havery Samuel says: “A technical concern with one proxy since 1960, when we have perfectly good temperature records already, is an irrelevance.” This COMPLETELY misses the point (and I don’t know whether through ignorance or deliberate distortion). Accurate proxy data today are needed, not to tell us the temperature, but to demonstrate that proxy data are reliable for understanding historical temperatures. That’s simple, basic science. )

Martin Lack

Much of what Oakwood writes is an attack upon the Hockey Stick graph of palaeoclimatic temperature reconstructions first produced in 1998 (MBH98).

However, the fatal flaws in Oakwood’s scepticism regarding MBH98 are as follows:

  1. MBH98 has been validated by at least 14 other reconstructions (as cited in IPCC AR4 in 2007) using a wide variety of other proxy data(see Wikipedia for relevant links)
  2. Hockey Stick-shaped graphs turn up in reconstructions of CO2 levels and temperature – now going back over thousands of years – because they are not ‘statistical noise’ –
  3. Arguments about splicing instrumental data onto proxy data only serve to challenge the extent to which the speed of late 20th Century warming is unprecedented.
  4. Such arguments do not invalidate the conclusion that it is now almost certainly warmer than it has been at any time since the last Ice Age (i.e. a period of relative climate and sea level stability that has made agriculture, urbanisation and civilisation possible).

However, this is no reason for us to be complacent because, as Oakwood must know, the 50 to 100 metres of sea level rise that will be caused by the melting of terrestrial ice sheets will necessitate the mass migration of millions of people. This makes his concerns about current poverty and starvation (i.e. the main reason he eventually cites for not believing action is yet necessary) look very trivial indeed.


Part two continues tomorrow.

17 thoughts on “Exploring the certainty of AGW!

  1. I am afraid that I remain very concerned about the extent to which the denialosphere is occupied by people who hide beneath a cloak of anonymity. It is very easy to critisicise the conclusions of the vast majority of appropriately qualified active researchers (AQAR) from the safety of an anonymous armchair. It is quite something else to falsify the evidence for ACD. Indeed, whenever one or more of a handful of AQARs try to do the latter, their conclusions are very quickly proven to be unreliable. This therefore resolves down to a very simple question: Whose position requires the rejection of the most evidence?

    With regard to Oakwood’s focus on MBH98 and the divergence of tree-ring proxy data for late 20th Century temperature data, I have recently had a very interesting exchange of emails with John Havery Samuel (as selectively quoted by Oakwood). In this exchange, John mentioned that he has spotted numerous instances of Oakwood making very similar comments to this elsewhere in cyberspace; and also feigning indignation (as he has done with me on my blog) when his opinions are challenged. John has also confirmed my suspicion that Oakwood spends a lot of time reading (and posting comments on) contrarian blogs such as ‘Bishop Hill’, ‘Climate Audit’, and ‘WUWT’ (respectively written by a chartered accountant, a mining consultant, and an ex-TV weatherman)… However, the main thing John did was to provide me with a very succinct rebuttal of Oakwood’s criticisms of MBH98 (etc), which I reproduce here with his permission:

    …there are so many independent proxies that re-validate the temperature record there really is no doubt whatsoever in the scientific community. Marcott, 2013, rolls them up neatly. See http://content.csbs.utah.edu/~mli/Economics%207004/Marcott_Global%20Temperature%20Reconstructed.pdf. A technical concern with one proxy since 1960, when we have perfectly good temperature records already, is an irrelevance.

    As for the “divergence problem” this is a modern phenomena that has nothing to do with the MWP. It’s covered in the literature,http://agwobserver.wordpress.com/2009/12/19/papers-on-the-divergence-problem/.  A summary is http://www.skepticalscience.com/Tree-ring-proxies-divergence-problem.htm.

    As for the MWP, have a read of http://www.skepticalscience.com/medieval-warm-period.htm.

    As over 97% of climate scientists, over 99.8% of papers on the topic and 100% of the data demonstrate, global warming is, if anything, accelerating, due to man-made CO2 emissions.


    1. Martin, your comment is a valued addition to the argument. My post on Wednesday will be an attempt to summarise what was presented by you and Oakwood from a personal perspective.

      However, let me reiterate one point. That is the issue of anonymity. Oakwood’s position on this is perfectly acceptable and completely irrelevant to the’debate’.


      1. What debate is that? As I have said to you, the only question that matters is whose position is consistent with the vast bulk of evidence?

        As was pointed out a long time ago by Patrice Ayme (someone whose anonymity is probably justified), it is may be necessary to invoke non-CO2 explanations for the current hiatus in land surface warming but it is not possible to explain the the multi-decadal changes unless the primacy of CO2 is accepted.


  2. Remarkable, Paul. One might even say ‘audacious!’ Totally agree it is not skimmable – except to whet one’s appetite – and intention – to give the contemplative study it deserves. That said, it seems to me the either-or approach does not leave room for true multidimensional consideration, particularly when there is far from agreement as to the dimensions themselves!

    Regard to you and Jeanne and the evergrowing multileggeds.

    Lew …


  3. I think it is commendable Paul, that you wish to enable discussion, but I do side with Martin [Lack ™!-) on this occasion and on this matter. There is no room for anonymity- after all, Oakwood could be a Sockpuppet of Martin’s. If the science community issued papers without names then outrageous claims could be made with no come back on the author: the reason contrarian scientists don’t have their papers classified as ‘reject AGW’ is because they are not so stupid as to wreak their careers by making the same public claims in their science papers. Scientific truth is a pretty strict mistress.

    Jules Bywater-Lees [tm]


    1. PS- the failure in the argument concerning proxies is inconsistency: Tree ring data cannot be selectively valid it is or isn’t despite the need for different climate models to explain differences.

      On the one hand reconstructed temperature models are used by ‘contrarians’ to prove the MWP existed but then rejected if it is implied or shown that it is warmer now. Contrarians also argue that CO2 forcing is low- yet fail to explain the high sensitivity existing in a MWP. What is it?


    2. Jules, don’t get me wrong: it would have been far better for Oakwood to write over his real persona. But in my private exchanges with ‘Oakwood’ I was comfortable that hiding his identity wasn’t an issue. That’s a lot different from me welcoming that hiding of his ID – I do not.


  4. Martin lack claims the hockey stick has been verified by other studies. A picture of a hockey stick shows a long flat stick and then a smal but very sharp rise at the end. So please answer me this one question. If the long flat part included the MWP and LIA how can the stick be flat? The truth is temps look more like a stock chart then a hockey stick.


  5. Tuppence from another anonymous sock-puppet:

    To my mind anyone citing ‘MWP’ is either missing the point or engaging in deliberate obfuscation, since the MWP (a) was a purely local phenomenon and (b) is a convenient sound-bite used by climate change deniers because it appeals to those willing to pick it up and repeat it without having to take time out from their busy lives trying to dig into where the ‘certain truth’ lies.

    I did read this entire post but will not bother with ‘part two’ for one simple reason: Martin’s entirely reasonable two-part question at the outset was disingenuously dismissed out-of-hand by his ‘opponent’ in a ‘debate’ that has long since been settled.


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