Originally published in the Skeptic Volume 29, No.2 • June 2009

Heaven + Earth - Global Warming:
The Missing Science
By Prof. Ian Plimer
Connor Court, 2009 ISBN 978-1-921421-14-3

Ian Plimer’s Heaven and Earth has been a long awaited contribution to the discussion of climate change and the attribution of Anthropogenic Global Warming (AGW). The cover notes call Ian Plimer “Australia’s best known geologist”, which is no exaggeration given his prominence as a tireless skeptic and scientist.

Professor Plimer gives a geological perspective on climate change with a very detailed and informative narrative describing geological, atmospheric and solar effects on the climate, with a surprising emphasis on history. The text is equation-free, and technical jargon is kept to a minimum but it is still a challenging read at 493 pages, 54 diagrams and an impressive 2311 references and footnotes. Heaven and Earth represents a successful attempt to meld the “two cultures” with history and social issues being woven into a scientific narrative using the evocative chapter titles of History, The Sun, Earth, Ice, Water and Air.
Before I read this book, I read the most recent IPCC technical summary, a text book, a popular science book on the subject, and the occasional academic article. Based on my reading I had considered AGW a plausible explanation for the climate changes of modern times. I was aware of alternative theories that also explain these changes, such as Friis-Christensen and Svensmark’s Cosmic Ray theory, which I think are worthy of further scientific inquiry.

The book has three major themes: The earth is a dynamic system that has been climactically changing for millions of years before humans were present; Climate change can be explained as a ‘natural phenomenon’ and it is naïve to assume that man affects the climate, as he does the weather; The way that the Intergovernmental Panel on Climate Change (IPCC) do their reporting works against scientific norms, and its findings have been adopted as the strictures of an emerging green secular religion.

Professor Plimer presents his readers with a swathe of extreme climates from earlier geological ages and historical times. He summarises the studies of historical climate, which show that temperatures were 2ºC hotter during Roman times, and that wine was cultivated in Germany and the UK during the Medieval Warm Period.

A recurring theme is that cold periods are associated with mass extinctions and human suffering, while warm periods equate with
burgeoning speciation and the highlights of human endeavour. In the course of this discussion many of the failings of the climate science work, as represented by the IPCC, are highlighted.

A book on climate change controversies would not be complete without mention of Michael Mann’s 1000-year temperature reconstruction, which will be forever known as the “hockey stick” graph.

Professor Plimer accepts Stephen McIntyre’s critique of Mann’s methodology. While I don’t want to delve into the issues of the
debate, I was disappointed by the way the graph itself was presented in the book (Figure 11, p89). In the original graph the dark line of the curve was surrounded by an exceptionally broad grey region, showing the 95% confidence range and clarifying that the part of the graph predating historical temperature records was constructed with great uncertainty. In an act of mischievous caricature, the grey confidence range in Professor Plimer’s book is replaced with a grey hockey stick. Below this graph is an alternative reconstruction of global temperatures on the same time span with the peak of the Medieval Warming Period about 0.5°C hotter than current temperatures. No source is acknowledged for this graph, but it is implied that it was derived “from hundreds
of studies”. While it is fair to criticise the methodological
errors involved in Mann’s technique, why present an alternative graph that conforms to the author’s viewpoint without giving any explanation as to how it was derived?

A major omission from the book was a comprehensive outline of the case for AGW. Climate modelling is dismissed with the words (p15) “A model is not real. A model is not evidence.” The reader is left assuming that the hypothesis is premised only on a recent correlation between CO2 levels and global temperature. Other physical evidence such as observed changes over decades of spectral analysis of outgoing infrared radiation is ignored.

Many of the arguments made against AGW presume that it can be refuted by past extremes in temperature. Consider this argument:

If it is acknowledged that there have been rapid large climate changes before industrialisation then the human production of CO2 cannot be the major driver for climate change. The evidence is overwhelming that another mechanism or combination of mechanisms drives climate, such as variations in solar activity, cosmic ray input, orbit and terrestrial processes. This being the case, then the whole purpose of the IPCC ceases to exist. (p87)

This misrepresents the AGW case as a denial of the prior temperature variations. AGW proponents aren’t suggesting that CO2 is “the major driver” in climate change; they only suggest that it is a significant factor, and that models can better explain recent warming trends when greenhouse gas emissions are included, rather than when they are excluded. Nor do climatologists dispute that there were more rapid warming events during the Pre-Boreal period 10 700 years ago, when the temperatures appear to have risen by 7°C over just 50 years. Professor Plimer refers to bizarre conditions long ago:

The proof that CO2 does not drive climate is shownby previous glaciations. The Ordovician-Silurian (450-420 Ma) and Jurassic Cretaceous (151-132 Ma) glaciations occurred when the atmospheric CO2 was more than 4000 ppmv and about 2000 ppmv respectively. The Carboniferous-Permian glaciation (360-260 Ma) had a CO2 content of about 400 ppmv, at least 15 ppmv higher than the present figure. (p165)

The argument here is that if atmospheric levels of CO2 occurred during earlier glaciations then current CO2 can’t be responsible for global warming. This argument would only be valid if other conditions were similar in these earlier periods. For example, if the atmosphere is saturated with coolants such as SO2 after extreme volcanic activity, then the warming effect of a high level of CO2 will be counteracted.

Similarly, other factors such as the continental drift of landmass towards the South Pole have been blamed for the Ordovician-Silurian glaciation.

On page 380, Professor Plimer attempts to calculate the total error of the historical temperature record:

Measurement errors [due to thermometers being calibrated, or temperatures being reported, in whole degrees] are ±0.5°C, errors due to a siting of a Stevenson Screen may be ±0.3°C, errors due to wood or plastic may be ±0.1°C and errors due to the urban heat island effect may be ±0.4°C. The total errors are ±1.3°C. Therefore, over the last century global temperatures have risen
by 0.7°C ± 1.3°C. This is a meaningless figure.

The “measurement errors” are rounding errors for which 0.5°C is the absolute error only in the worst case. Over a course of many temperature measurements with different thermometers, the impact of rounding error will actually be much less significant. Also,
instead of these absolute error ranges, a 95% confidence range is a more typical way to express uncertainty, and as there are no obvious references for the other numbers in this paragraph, it is unclear if they are absolute error ranges or confidence intervals, and it is not apparent why they should be added in this manner. Indeed 0.7°C ± 1.3°C is a meaningless figure.

These instances that I have raised may seem like nit-picking in the context of such a large volume. It should be stressed that I am confident that Professor Plimer is able to write a factual narrative of the Earth’s climatic history. However there seems to be a recurring eagerness in this book to provide a falsifying argument to AGW with little regard to the accuracy of the data or the validity of the argument. While computer modelling is dismissed as non-empirical, back-of-an-envelope calculations of temperature errors are used to ignore major collaborative research programs into historical temperature records.

There certainly are valid reasons for criticising the IPCC approach to summarising the scientific knowledge of climate change, and the prominence of Mann’s 1000-year temperature reconstruction in the IPCC’s Third Assessment Report was excessive, given its high level of uncertainty. The IPCC’s process of evaluating uncertainty is an unnecessarily opaque process. It is not unreasonable to have doubts about this methodology and to note that there may be political biases in it.

Does Heaven and Earth succeed in giving an accurate summary of our current scientific understanding where the IPCC might fail? Professor Plimer subtitles his book “Global Warming: The Missing Science”, but one wonders if much of this science is missing because it is either too conjectural or too discredited.