NC Media Watch

A quest for reason and accuracy in letters to the editor, guest editorials and other issues of interest to the citizens of Western Nevada County.

Sunday, August 28, 2005

Hockey stick argument discussion

The MBH98 Debate for Dummies by Ray Soper is included in his post on Climate Audit. Tou have to scroll down to the comments. However, I wanted to highlightSoper's summary and discussion with some bold highlights, so it is included below. Sorry for the long post. Remember it is your tax dollars that the California Legislature is using to promote solutions to junk science problems.

Ray Roper:
I am doing the best that my limited capacities allow to try to keep up with the fascinating debate on these pages. Would you mind if I try to summarise the Bristlecone issue in simple terms for fellow lay readers? Maybe there is a simple summary somewhere on this site. If so, I have missed it.

1. MBH proposition is that the thickness of the annual rings on living and fossil Bristlecone pine trunks over the past 1000 years is a proxy for temperature.

2. The rings thickened during the 20th century thus “proving” that temperatures were warmer than the previous 9 centuries.

3. The “proven” rise in temperature correlates with rising CO2 levels and is therefore caused by the rising CO2 levels.

4. The rising CO2 levels are due entirely to man’s activities in burning fossil fuels.

5. The conclusion from this chain of “logic” is that if the world population wants to stop temperatures rising by perhaps 5-6 deg C over this century, we have to work together to get CO2 levels back down, and temperatures will follow.

The opponents argue:

1. That on available data released by MBH there are clearly errors and anomalies in how MBH drew their conclusions. MBH are not exactly being helpful in tracking these errors and anomalies down, and correcting them.

2. There may be factors other than temperature that correlate with, and perhaps drive, the thickness of the Bristlecone pine annual rings. These include differences in water-use efficiency that may have caused more growth in the 20th century. They could also include CO2 fertilisation due to the increased levels of CO2 in the atmosphere.

3. It is not demonstrated that temperatures are in fact rising. There are significant difficulties in measuring the temperature of a large complex system such as earth, where there are many heterogeneous process going on. This is especially true when we try to gauge average temperatures going back centuries.

4. It is not demonstrated that even if temperatures are rising, that they correlate with or in any way are caused by rising CO2 levels. It is much more likely that temperature fluctuations correlate most closely with solar activity.

5. It is also not demonstrated that the rising CO2 levels (at least that much seems to be not controversial) are caused by man’s activity. We don’t even seem to know how much of the rising CO2 levels are accounted for by man’s activity. There are natural sources of CO2 that can make a significant impact - bush fires, volcanoes etc. There are also natural systems that regulate CO2 levels including absorption by the ocean and forests, and we understand little about these systems.

6. It is not demonstrated that reducing anthropogenic CO2 emissions will reverse rising CO2 levels.

7. It is not demonstrated that lowering CO2 levels will in any case lead to a global cooling. There are clearly many questions involved that require rigorous gathering of data, and rigorous application of scientific method and sound scientific practice. Given that the Kyoto proponents are proposing the expenditure of trillions of dollars and the disruption of whole communities, and even whole economies, it is incumbent on all to adhere to the highest standards of objective science to ensure a) that we understand what is going on and b) are choosing the right course. Joe Barton is merely being a responsible custodian of public moneys in asking the questions that he is. It is also incumbent on all to avoid the temptation to resort to sloganeering propaganda such as “the consensus of scientists” (never supported by numbers, and demonstrably wrong) agree (science was never decided by opinion polls - ask Copernicus!) that global warming is occurring, that it is caused by rising CO2 levels, that the rising CO2 levels are caused by man’s activities, and that if we want to stop temperatures rising, we must find a way to bring CO2 levels back down again.

We need the leading journals in the field to demonstrate their understanding of the issues, and their commitment to truth and sound scientific practice. Unfortunately, many of those journals seem to have lost their way and forgotten that their main role is to educate the wider public on matters scientific.

Comments on this post by Ross McKitrick:
Re #3: Points 1-7 stake out more territory than is argued by Steve and I in our papers. The specific point in this thread, which relates to the discussion at large on this site, is that the hockey stick graph is an incompetent representation of world climate history. The hockey stick matters because of its dominant role in IPCC Reports, as well as many other continuing citations (see the ‘Spot the Hockey Stick’ thread on this site for more examples). The methodology of Mann et al was not properly disclosed in their papers: it contained an algebraic tweak that heavily favours hockey stick shapes. It loaded heavy weighting on the bristlecone pine series, overstated the bristlecones’ explanatory power for the temperature data and overstated the overall statistical significance of the results. The hockey stick data base looks large but most of it is just for show: the bristlecones determine the shape and the appearance of statistical power (the Gaspe cedar series enhances the effect). Remove them from the data base and the famous results collapse. Even if the bristlecones were temperature proxies this would inicate the fundamental weakness of the hockey stick: the fact that the bristlecones do not even constitute a temperature proxy renders the graph worthless.


At that point, the fact that these problems were never discerned by the publishing journals during peer review, nor by the paleoclimate community itself in follow-up analysis over 7 years, nor by the IPCC, government ministries and other high-level authorities before they grabbed the hockey stick graph and began promoting a policy agenda with it; puts all sorts of other questions on the table. If they got this argument that wrong, how do we know they didn’t get their other arguments wrong too? What exactly is the level of due diligence being applied to climate studies and assessment reports that now loom so large over the world’s energy policy agenda?


So questions 1-7, and many others, do follow on from this episode, beyond the specific issues arising from Steve’s and my papers.

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