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Policy and funding

Policy and funding

Knowledge from a vast effort

01 Sep 2010

A Vast Machine: Computer Models, Climate Data, and The Politics of Global Warming
Paul N Edwards
2010 MIT Press
£24.95/$32.95 hb 518pp

Weather men

In climate science as in quantum mechanics, the observer is part of the system being observed. We can no more take ourselves out of the picture when gathering data and developing models of the Earth’s climate than we can eliminate the detector from a double-slit experiment. The fact that knowledge cannot exist on its own – we are all part of our own knowledge – means that sometimes, knowing how we know the things we know is as important as the knowledge itself. Such is the deeper message of Paul N Edwards’ new book A Vast Machine: Computer Models, Climate Data, and the Politics of Global Warming.

The range of subjects covered by A Vast Machine is indeed vast, involving fields as diverse as philosophy, history, computer systems, networks, climate models, politics and globalization. I found it refreshing to see how such a broad range of topics relate to each other, and the sheer scope of the book ensures that most physicists will find something to interest them. Edwards takes a novel view in explaining how various types of infrastructure – including systems for collecting data and sharing knowledge, which involve both technical and social networks – are essential for the design of climate models. As an information scientist at the University of Michigan in the US, he also exhibits a deep understanding of computers, programming, climate models, data and physics. His explanation of how satellite-borne instruments measure the atmosphere by interpreting measured radiances though vertical emission profiles is useful and clear, as is the discussion of how weather models incorporate observations to derive the best description of the current weather.

I particularly liked the way that Edwards deliberately breaks down old barriers by blurring the difference between data and models. One common misconception about climate science is that conclusions drawn from “data” are more accurate than predictions based on “models”. In fact, most observations involve some kind of model for interpreting measured signals in terms of atmospheric variables; so without models, there will be no data. However, Edwards also points out that most models involve data: the truth is that these two forms of knowledge are inseparable, and both play a vital role in our understanding of climate. Indeed, reading about the relationship between the two reminded me of a problem that appeared in one of my old physics exams, where we were asked to define a model equation for a thermistor based on data that described its response to different temperatures. This interconnected aspect of science is often forgotten, and I found it reassuring to read that such thinking is not dead.

The book is rich with details of the history of climate and meteorology. I found it fascinating to learn about legal issues with satellites that cropped up during the Cold War. For instance, after an American U-2 spy plane was shot down over Sverdlovsk in May 1960, the Soviet Union argued that photography from space – including weather photography such as that taken by the first weather satellite, TIROS – was illegal. The sheer vastness of the effort involved in developing weather forecasts, satellites, the observational network and other infrastructure should make most people humble, and Edwards’ description of it serves as an important reminder that our weather forecasts and knowledge of climate have not come without effort.

In the wake of recent allegations against the Intergovernmental Panel on Climate Change (IPCC) and the climate-research community, A Vast Machine is also quite a topical book, and reading it helps to put such allegations into their proper context. Although some climate scientists have been criticized for being unwilling to share data with their critics (as exposed in the – misnamed – “Climategate” controversy), in fact both the meteorology and climate-research communities have long traditions of openness and data sharing. Moreover, the often acrimonious public debate around climate change has produced at least one good result: climate science has been thoroughly scrutinized by various interest groups and is now one of the most carefully examined scientific disciplines.

One of the most recent developments in this tradition of openness has come from the World Meteorological Organization, which in 2009 launched an initiative for “Global climate services” that aims to provide “climate information for everyone”. Similar climate initiatives have, according to the book, happened several times over the last century in various forms. So I was left with the question: will they make further progress this time? In fact, reading about some of the previous initiatives was a revelation to me, and it gave me some insight and tacit knowledge about why sometimes there is not as much action and progress as one would expect – thanks to various types of interpersonal and inter-organizational “friction”, as well as diplomatic and political obstacles.

Edwards has clearly spent a fair bit of time within the climate-research community, and while this lends valuable authority to his story, it is also apparent that he has adopted some of the community’s misconceptions. One statement that I have encountered several times is the notion that the climate models are “physically consistent”. This phrase appears to be meaningless, as to date I have never seen it defined. It is also well known that all climate models are, strictly speaking, not physically consistent: water and energy budgets sometimes do not add up, while depending on the choice of parametrization packages, one can easily get different models with mutually inconsistent solutions. The parametrization schemes, also known as “model physics”, are really just statistical descriptions of unresolved small-scale processes such as clouds, of which we often do not have a clear understanding. Basically, models are not the real world, and since Edwards spends a great deal of space discussing this in an articulate way, it seems a bit ironic that he still cites this statement.

Aside from this, there are not many criticisms I can make about Edwards’ book, although there are some minor issues. The acronyms he uses are not always explicitly defined, for example, and the story he tells involves several convoluted and intertwined threads. In order to account for all these details, the book jumps back and forth in time, resulting in a chronology that sometimes is confounded by many parallel events, which may make it seem a little repetitive in parts. However, these faults are almost inevitable for a book that attempts to put together different pieces in a giant historical mosaic of events. So although A Vast Machine‘s enormous breadth and richness sometimes verge into too much detail and technicalities, for the most part the level of detail is the book’s main strength because it allows Edwards to summarize meticulous research in an organized way. As a result, I would recommend this book to everybody interested in weather forecasting or climate change. It would make a valuable addition to the syllabus of any course on climatology and meteorology, while the general physics community will also find it useful to help understand the context of the public debate around climate change.

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