Elemental : How Five Elements Changed Earth's Past and Will Shape Our Future Stephen Porder Princeton University Press 2023

 Earth has experienced evolutionary changes, as described by Darwin, and revolutionary changes. This book claims to examine the latter, ""world-changing events--events precipitated by life itself" (p. 1).  Fortunately, these biological changes occur infrequently, once in a billion year time span. What connects each of the changes are the five basic elements, common to all cells: "hydrogen (H), oxygen (O), carbon (C), nitrogen (N), and phosphorus (P), the author's fundamental elements of life. The elements also generate warmth, except phosphorus, in our atmosphere. The book migrated from the first phase, the time of the "single-celled cyanobacteria" (p.3), to the land plants created two billion years later, and finally, the so-called "Anthropocene", the current era of human domination of the environment. As you can guess, this exploration lead to the question and title of Chapter 4: "How We Know What We Know about Climate Change" (p. 79). 

To answer the preceding question, the author started with a common assertion. The author claimed, "Humans are causing climate change by burning fossil fuels" (p. 80). Obviously, this statement articulated a cause and effect relationship, and what the author called "attribution" and not merely denotes a trend. What derived from the assertion and attribution, "human emissions of green house gases are causing the climate change we see today" (p. 80). As a scientist, the author must build his case.   He defined his terms. Climate, "the long-term (decadal) average of weather in a place" (p. 80), provided the reader with a standard measurement for climate, with the variables of temperature and rainfall. He cited the decades of the 1980s, 1990s, 2000s, and 2010s and their temperature increases, with rainfall data, as proof of a trend.  The author continued his investigation by citing the scientific discoveries and documentation to substantiate his claim.   

This statement the author puts forth as a given:"we know greenhouse gases play a big role in driving climate and we know human combustion of fossil fuels has increased the concentration of greenhouse gases in the play a big role in driving climate and we know human combustion of fossil fuels has increased the concentration of green house gases in the atmosphere by almost 40 percent" (p. 81). To prove this requires a simulation of the earth via a computer, the hypothetical "Planet B" (p.84). Scientists have engaged in experiments about climate measurements since the 1890s, beginning with chemist Svante Arrhenius, a Swede, concerned about a reoccurring ice age. Arrhenius' paper, On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground" noted that "burning fossil fuels will increase the amount of CO2 in the air" (p. 85) and that and increase of CO2 results in an increase in temperature.