Earth’s Climate Evolution

summerhayesRating: ★★★½☆

Colin P Summerhayes. 2015. Earth’s Climate Evolution. Wiley. ISBN 978 1 118 89739 3

There are so many books published on global warming that it’s hard to keep track of them. Most say variations on the same theme – the anthropogenic warming of the planet and the impacts that might befall us quite soon (or, instantly, in geological time!). This side of the debate quotes innumerable studies, scientists and data. There’s the other side of the debate that deny anything is happening. Given recent events, such views might even be in the ascendancy in some nations. Here, the common retort is that the climate is always changing so there’s no need to worry. True, but its the timescale of change that is crucial! One issue, rarely mentioned explicitly in the press, is the massive task of trying to understand the climate system and how it responds to a wide range of inputs. It’s no wonder that people find it difficult to comprehend when the quantity and complexity of the underlying material is such that not even trained scientists can unravel every part of the system.

Here we have a completely different take on the subject. Yes, it’s about climate change and human activity. It’s also about past climate and the information needed to decode it. For good measure, it includes pen portraits of leading writers in the field. The basic premise of the book is that to understand present climate change we need to look into the (geological) past – a sort of anti-uniformitarianism if you like. For a book whose preface considers climate change (notably warming), to start with chapters on cooling is unusual to say the least. The point is to outline where the science really started and this is with the founders of Geology in the C18th. Here we see who started examining rocks and rock formation and the insights they gained. They considered that the climate was cooler than previously and that led, ultimately, to the recent Ice Ages (the book considering only the past 450 million years, thus missing Snowball Earth). Not long after these ideas, scientists started to consider why the planet was as warm as it was. We now know that it’s due to carbon dioxide but this took some proving. Once proven, ideas spread rapidly to develop the notion of a “greenhouse” Earth. By the late C19th, we had the major pieces in place – carbon dioxide, warming/cooling cycles and water vapour. Joining all of the pieces together took time but we finally had a grasp of climate variations.

Atmosphere is only one part of the puzzle. The author now turns to other forces to explain the finer details of climate evolution. If atmosphere was the only component, modelling climate change would be far easier. However, as we see, the development of what is now known as plate tectonics along with a far greater understanding of tectonic mechanisms has helped shape our knowledge of weathering and erosion and the subsequent release or uptake of gases and minerals. This gets us the data but it’s the development of palaeoclimatology that puts it together and shows how past climates worked. As the science became more sophisticated, so the research and modelling got better. We could measure carbon dioxide accurately. From there, it was possible to make comments about cooling and warming although there does not appear to have been the consensus that we have now. From this point in the science of carbon, the big discoveries seem to have been made due to increasingly sophisticated equipment.

From this point, the author starts to pull ideas together and uses the science in the preceding work to help explain the patterns being found. We start with a look at the major climatic cycles and the role of geological processes in shaping them taking as our base the Mesozoic era. Three chapters focus on the Ice Age “mystery” showing how different techniques can create different understandings. The two penultimate chapters take a far closer look at the climate close to present times.

The final chapter summarises the whole text, putting brief snippets in order, to create a picture of knowledge evolution in studying this phenomenon. Here we see the various key writers with their views and the ways in which they contributed to the whole. Towards the end, the author moves into the future to see what might be reasonably expected to occur and how it might be mitigated.  Global warming is happening but the rate of change might not be as severe as thought. Our evidence here is not the comments made by looking at recent change in the atmosphere but by following the paths of those who slowly and systematically built up our knowledge to the state it is today.

Overall, this is a fascinating text not so much for the topic but the way it covers it. There are very few books that seek to tell the story and the storytellers at the same time. It puts progress into perspective. More importantly, it avoids the strident tone of many of the climate change books by piecing together not just evidence but the wide range of disciplines needed to get anywhere near an accurate representation of the real situation. It’s worth reading for the approach alone but those wanting a more measured treatment of climate change would do well to read this book.

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