Abstract
I am sure I am not alone when I say that many of us with a responsibility for teaching begin our courses on Holocene or Quaternary climate change by making reference to the – probably over-used – quote saying that ‘the present is the key to the past’. I have it emblazoned on the first page of my final-year undergraduate module ‘Global Climate Change’. We use it, of course, to highlight the concept of uniformitarianism. Many readers will recognise that one of the requirements in teaching Holocene Climate Change is to help students distinguish natural from anthropogenic drivers of climate change; the expected from the unusual. Where past agency can no longer explain observed changes then something new must be the cause! We seek to give students the skills to find reason for the changes observed in the past and therefore appropriately comprehend the evidence for the consensus belief that modern change is caused by human activity. In turn, then, most teachers of Holocene Climate Change hope that those bright minds can enter the ‘real world’ and continue the task of communicating to others how the modern evolution of climate is clearly influenced by human activity. This task is necessarily one of looking back in time. The question, I expect, for many readers of The Holocene, sitting back to review and plan their courses, is just how far to go back in time. Several textbooks already cover the Holocene or the Quaternary period in some good detail to be valuable for setting context (e.g. Cronin, 2013; Roberts, 2013). Cronin covers the observed climate changes of the Quaternary and their likely drivers in the order of progressively shorter timescales. Others do well on the mechanistic understanding of climate change and modern global warming (e.g. Dessler, 2011; Houghton, 2015). Rarely, however, is a book published that brings together processes of deep time with modern climate change. In Earth’s Climate Evolution, Colin Summerhayes chooses 450 million yr BP as the starting point because this is when land plants and hence the terrestrial biosphere component of the carbon cycle were established. For those consequently believing this book then resides on the reading list of geology majors only, you would be sorely mistaken. In fact, it represents the ideal place from which to start if only to fully grasp the range of different timescales of relevant earth system mechanisms as well as to understand how the Quaternary period is unusual in the context of the last 450 million years and also how the current interglacial is similarly not that warm (yet).
What makes this book particularly distinctive is how well it builds in the narrative of change in ideas over time. This book provides something of a chronology of thought over the first chapters, highlighting the parallel development of and role of new technologies in the acquisition of knowledge to change ideas. Passing through advances in subsurface investigation and in geochemical techniques, the book then takes the reader to the modern use of supercomputers in numerical modelling of climate, and in particular past climate, on which the models themselves can be validated using geological data. There follows a more traditional exploration of climate change phenomena through time, getting progressively closer to the present day, as the relevant mechanisms of climate change are explained, before a resume chapter that sets out clearly the evolution of Earth’s climate and its likely future based on modern human influence and what we know from the geological record.
The early focus on the development of ideas, bringing the reader, not excessively but sufficiently, through the moments of inspiration and the turning points in understanding, paints a very clear picture of how we have arrived at our current understanding of climate and the earth system. To that extent, this book also has something to offer to courses in the philosophy of science as well as its more obvious offering, at the very least through case studies of changing thought. It highlights the human nature of the production of knowledge; how ideas can be forgotten for some time, only to be revisited, when called upon much later. The easily readable text is supplemented regularly by box entries with brief biographies of the characters that make up the narrative. These are valuable for students and teachers alike and make for easy reference material highlighting principal contributions of some of the greats in the field. Concise and digestible chapters supported by comprehensive reference lists at the end of each help in this regard by facilitating the ability to enter the book at different points for different purposes.
The figures provide valuable evidence to support the narrative and some key seminal research is highlighted. Those undergraduates that are visual thinkers often do well from access to cartoon schematics or coloured figures to ensure engagement and help smoothen the journey to understanding. Equally, most of us benefit from a photographic plate of a geological section or a key transition in a core as much as from the analytical data that may have been yielded from a site. While some useful and relevant diagrams are presented, there is nothing in the way of photographic illustrations, unlike others in the market (Houghton, 2015; Roberts, 2013) but many will find the published figures and engaging narrative alone sufficient to support their imagination.
As Summerhayes states in the introduction, ‘[…] this book is a wake up call, introducing the reader to what the geological records tell us […]’. In so far as it neatly captures not just the Holocene or Quaternary geological record, but smoothly brings together 450 million years, the author’s proposition is a fair one. Some of the motivation for the book, it seems, was to answer a need to counter some of climate sceptics’ statements that the author had encountered. Equally, Summerhayes’ goal with this book was to go further than what had been achievable in the summary reports produced by the Geological Society of London, from a team which he chaired, to explore and expose to broader public consumption, ‘the human stories behind the long development of modern climate science or the full extent of advances emerging through … research’. That goal is certainly achieved! It was a pleasure to read. Summerhayes’ accessible style, built on a vast foundation of knowledge and experience both from academia and from industry made me, for the time I was able to, forget the administrative burdens of academia and rediscover the inspiration that brought me into this field of enquiry. Like real escapism, I was as excited as an undergraduate might be learning this material for the first time. So, I would expect strongly that this would engage current undergraduates similarly. This book will be incredibly valuable for readers, scholars and teachers of the Holocene alike and I will be adding it to my reading lists.