David Karoly: Ian Plimer's new book Heaven + Earth claims to shed new light on the science of climate change. It states that 'human-induced global warming has evolved into a religious belief system', that 'atmospheric carbon dioxided does not create a temperature rise' and that 'global warming and a high CO 2 content bring prosperity and lengthen your life'.

Are these claims justified and based on science? They are in marked contrast to the scientific understanding of the causes of recent climate change reported in the assessments of the Intergovernmental Panel on Climate Change (often referred to as the IPCC), as well as by other scientific bodies including the US National Academies, the British Royal Society and the Australian Academy of Science. They have all reached the same conclusion; that the observed increase in global-average surface temperature since the mid-20th century is mainly due to the increase in greenhouse gases in the atmosphere, caused by human activity.

Heaven + Earth claims that this conclusion and almost all the conclusions of the IPCC are wrong. It suggests that there is a conspiracy amongst climate scientists to hide the 'truth' and that the learned scientific societies of many countries have been hoodwinked. He implies that this conspiracy involves all the hundred-plus national governments that unanimously approved the conclusions of the IPCC assessments. Not surprisingly, the book has attracted attention from the media, politicians and some scientists, as well as the public. Nothing sells like a good conspiracy story.

But is this book the story of a conspiracy, or even a good read? Is it about science or is it science fiction? The book is impressive and possibly interesting, but very disappointing. Impressive because of the time and effort that must have been spent writing the 500 pages with 2,000-plus footnotes. Interesting because it seeks to link many aspects of geology, astronomy, biology, glaciology, oceanography and meteorology to explain climate change over the Earth's multi-billion-year history, including the last hundred years. It's disappointing because a senior professor should not have produced such a book with so many errors, so many internal inconsistencies, and with no sources for its graphs.

The average reader will find it difficult to sort the fact from the fiction, to disentangle the inconsistencies, and separate the personal opinions and interpretations of the author from the well-established science. The book is built around six sections that consider history, the Sun, earth, ice, water, and air. In these, 18 questions are considered, and many scientists would agree with some aspects of the answers presented. However, there are major errors in many of the answers, making the conclusions invalid. The best description of the problems with the book is provided by Plimer himself. He writes, 'Trying to deal with these misrepresentations is somewhat like trying to argue with creationists, who misquote, concoct evidence, quote out of context, ignore contrary evidence, and create evidence ex nihilo.'

There are some sensible things in Heaven + Earth. Yes, it is important to 'look at climate over geological, archaeological, historical and modern time'. Throughout Earth's history there have been natural climate variations driven by many factors, including variations in the Earth's orbit around the Sun, volcanic eruptions, tectonics, and changes in greenhouse gas concentrations. For most of Earth's history, global temperatures and carbon dioxide concentrations in the atmosphere have been higher than present. Plimer is wrong to claim that 'the IPCC has essentially ignored the role of natural climate variability', as natural climate variability is carefully considered in all four of the IPCC's comprehensive assessments since 1990. In its 2007 report, a whole chapter on palaeoclimate focuses on natural climate variations over Earth's history. Yes, water vapour is the most important greenhouse gas in the atmosphere. However, as Plimer states, 'Water vapour tends to follow temperature change rather than cause it,' so water vapour changes cannot initiate climate change.

Now let me address some of the major scientific flaws in Plimer's arguments. He claims 'it is not possible to ascribe a carbon dioxide increase to human activity' and 'volcanoes produce more CO 2 than the world's cars and industries combined'. Both are wrong. Burning fossil fuels produces carbon dioxide enriched with carbon isotope 12C and reduced 13C and essentially no 14C, and it decreases atmospheric oxygen, exactly as observed and as Plimer states on pages 414 and 415. Scientists have estimated emissions from volcanoes on land for the last 50 years and they are small compared with total global emissions from human sources.

Plimer even argues that the recent sources must be underwater volcanoes. This is not the case, because the net movement of carbon dioxide is from the atmosphere to the ocean, based on measurements that the concentration of dissolved carbon dioxide in the ocean is less than in the atmosphere. In addition, measurements show that the concentrations of two other long-lived greenhouse gases with human-related sources, methane and nitrous oxide, have increased markedly over the last 200 years, at the same time as the increases in carbon dioxide. This is not possible due to sources from underwater volcanoes.

Next, he states that CO 2 does not drive climate. He then contradicts himself by writing 'CO 2 keeps our planet warm so that it is not covered in ice'. There is ample geological evidence of increased CO 2 causing climate change, such as the Palaeocene-Eocene thermal maximum about 55 million years ago. He writes 'land and sea temperatures increased by five to ten degrees with associated extinctions of life' when methane was released into the atmosphere due to geological processes and rapidly converted to CO 2.

Plimer writes repeatedly that global warming ended in 1998, that the warmth of the last few decades is not unusual, and that satellite measurements show there has been no global warming since 1979. He is correct that on time scales of the last 100 million years, the recent global-scale warmth is not unusual. However, it is unusual over at least the last 1,000 years, including the Medieval warming. Plimer makes the mistake of using local temperatures from proxy evidence rather than considering data from the whole globe at the same time. The report of the US National Academy of Sciences in 2006, cited by Plimer, states 'Presently available proxy evidence indicates that temperatures at many, but not all individual locations, were higher during the past 25 years than during any period of comparable length since AD 900.'

We do not expect significant warming to always occur for short periods, such as since 1998. Natural climate variations are more important over short periods, with El Nino causing hotter global-average temperatures in 1998 and La Nina cooler global temperatures in 2007 and 2008. Global-average temperature for the current decade from surface observations and from satellite data is warmer than any other decade with reasonable data coverage. Plimer is wrong to write 'Not one of the IPCC models predicted that there would be cooling after 1998'. Actually, more than one-fifth of climate models show cooling in global average temperatures for the period from 1998 to 2008.

Plimer writes that solar activity accounts for some 80% of the global temperature trend over the last 150 years. This doesn't fit the observational evidence. Increases in solar irradiance would cause more warming in the daytime, in the tropics and in summer, as well as warming in the upper atmosphere, and these are not observed. Changes in solar irradiance and cosmic rays show a large 11-year sunspot cycle and negligible trend, but observed global temperatures show a large warming trend and small 11-year cycle.

Plimer is wrong again when he writes 'An enrichment in atmospheric CO 2 is not even a little bit bad for life on Earth. It is wholly beneficial.' This is contradicted when he writes that the Palaeocene-Eocene thermal maximum was associated with mass extinctions. There are many other errors, both large and small, including volcanoes emitting CFCs and that the Sun consists mainly of the same elements as the rocky planets. Many of the figures have mistakes, either in the caption or in the data, and have no sources provided.

Given the errors, the non-science, and the nonsense in this book, it should be classified as science fiction in any library that wastes its funds buying it. The book can then be placed on the shelves alongside Michael Crichton's State of Fear, another science fiction book about climate change with many footnotes. The only difference is that there are fewer scientific errors in State of Fear.

Robyn Williams: David Karoly is a Federation Fellow at the University of Melbourne. He was reviewing Ian Plimer's book Heaven + Earth, now in the bestseller lists.