Chapter 3 of Earthopolis: A Biography of Our Urban Planet discusses the crucial role of cities in enabling small elite groups to amass large pools of wealth while guaranteeing poverty for the large majority of people whose labor made that wealth possible. This is the first of two chapters on the subject. It shows how state actors and wealthy elites controlled rural land and exploited wealth created by agricultural laborers and the energy of the Sun and Earth. It argues that building pre-modern cities and deriving wealth from them always involved the enslavement of millions of laborers for a wide diversity of tasks. Finally, it traces the origins and proliferation of urban artisans, shops, and marketplaces as well as the built hinterlands they required to create smaller pools of wealth in cities. This wealth served as cities’ economic lifeblood despite obstacles artisans and shopkeepers faced within their complex political relationship to urban states and wealthier elites.

Chapter 6 of Earthopolis: A Biography of Our Urban Planet discusses the “realm of consequence,” the oscillating space occupied by life-destroying impacts of our city-enabled actions and habitats. In addition to forms of destruction generated solely by “endogenous” forces of political violence and war and by “exogenous” natural forces emanating from the Sun and Earth, the chapter explores places where our own city-enabled actions and impacts caused natural destruction, partly accounting for moments when urban worlds and the human population retreated in size. Cities incubated disease more prolifically than villages, resulting in many city-destroying and multi-continental pandemics. Expansions of agriculture to feed cities, the wider use of wood as fuel, and the resulting deforestation also had often city-destroying consequences via soil degradation and rising levels of river-water and silt. Urban industry and food systems, especially rice production, expanded human emissions of smoke and greenhouse gasses to Earth’s atmosphere as a whole for the first time during pre-modern times.

Chapter 24 of Earthopolis: A Biography of Our Urban Planet explores the Great Acceleration of the “global petroleumscape,” and the immensity of the human waste we generate in a distended Urban Planet fueled by hydrocarbon. It surveys spaces of mineral extraction of all kinds before following the growth of the post-World War II petroleumscape and its many drastic effects on global geopolitics, the priorities of capitalists, and the wasteful shape of Cities of Hydrocarbon. From there, we visit the waste streams of Earthopolis, following them from their disgorgement in factories and spaces of consumption across the continents, down the rivers, across the oceans, and into the atmosphere as a whole.

Chapter 7 of Earthopolis: A Biography of Our Urban Planet explores cities’ role as creators and creations of the global gunpowder arms race that ensued in the wake of the discovery of the interconnected World Ocean from 1500 on. While giant imperial capitals played a continuing role in this drama, an Age of Parity between the empires of Afro-Eurasia persisted as transformations in urban fortification systems spread throughout the world along with the invention of wall-breaking cannon and gunpowder battleships. Europeans took the lead in sparking this arms race – especially along the shores of the Atlantic Ocean ironically because of their initially disadvantaged position – though the arms race involved numerous acts of ocean-ward expansion and military resistance based in the polities of cities and smaller settlements on all continents. The result was the construction of hundreds of new fortified cities on all shores of the World Ocean and the merging of all pre-modern urban worlds into a truly planetary realm of city-enabled human action for the first time.

The front matter to “Cities of the Rivers,” the first of three parts of Earthopolis: A Biography of Our Urban Planet, retells the myth of the founding of the city of Uruk by the goddess Inanna (Ishtar), after she stole the many characteristics of city life from her father Enki and delivered them up the river by boat to the settlement of Uruk. This story, which emphasizes cities as tools of both creation and destruction, serves as a pivot point in discussions of urban theory and the life of the Urban Planet throughout the rest of the book.

Chapter 13 of Earthopolis: A Biography of Our Urban Planet explores cities’ role as creators and creations of nineteenth-century imperialism in all of its forms. It shows how imperial rivalries between London, Paris, and Washington DC, the three most “liberal” capitals on Earth, led imperialists to invest in “gun cities,” where arms manufacturers used coal-fueled technologies to produce new guns, cannons, and battleships that ended the “Age of Parity” between the gunpowder empires of Afro-Eurasia. The city of Calcutta served as the pivot-point of the new era of European dominance, serving as headquarters of the British conquest of India, and later as key port to undermine the power of the Qing Dynasty in Beijing by means of shipments of opium into Guangzhou (Canton) that resulted in European “concessions” in key ports of East Asia. The chapter also demonstrates how the settler colonial conquest of the Americas relied upon and resulted in the proliferation of new cities across the continent. Finally it shows how the imperial Scramble for Africa relied on all of these city-enabled techniques. In most cases, European imperial officials deemed some form of segregation by “race” crucial to the effectiveness of their urban weapons of conquest and imperial rule.

Chapter 18 of Earthopolis: A Biography of Our Urban Planet explores cities’ role as creators and creations of totalitarian states on the left and the right and the march toward humanity’s most horrific acts of self-destruction and “urbicide” during World War II. The chapter begins with a section on the promising urban gender, sexual, and racial revolutions of the 1920s that opened up new urban spaces of pleasure and expression for many people who had lived far more circumscribed roles before. Nonetheless, totalitarians found ways to leverage many different urban spaces into power. They rebuilt cities to strengthen their grip, then to arm themselves for a war of annihilation. New facilities devoted to drilling for petroleum, transporting it, and refining it became central to the course of the war. Acts of mass imprisonment, torture, and racial extermination led to the construction of some of world history’s most horrific built spaces. Meanwhile, the aerial bombing of cities and civilian neighborhoods became routine, culminating in fire bombings and the nuclear explosions in Hiroshima and Nagasaki.

Chapter 9 of Earthopolis: A Biography of Our Urban Planet explores cities’ role as creators and creations of the first world religions, of new “scientific” knowledge of the Earth, including its cities, and a global consumer culture based on goods sourced from urban hinterlands that spanned all continents for the first time. It also explores the expanding consequences of the earliest years of Earthopolis as a truly planetary Urban Planet. These included the first global pandemics of disease and the expansion of human destruction of the habitats of other life forms, including those of the World Oceans so crucial to the period’s expansion of urban-enabled human actions, habitats, and impacts.

The front matter to “Cities of Hydrocarbon,” the third of three parts of Earthopolis: A Biography of Our Urban Planet pivots from an interview with a rickshaw driver in Delhi about the effects of the city’s smoky air to announce the major themes of modern global urban history. These include the acceleration of growth due to the powerful new way of harnessing geo-solar energy, the growing turbulence of political life due to the rise of revolutionary movements in cities and their enlarged hinterlands, the emergence of a truly planetary city-dominated human habitat, as well as a vastly expanded realm of human impact. It finishes by reminding readers of the growing consequences we face as an urban species in command of the planet, in the form of increased pandemic disease and atmospheric heating.

This is our climate change status check, and the first three things to understand are that climate change is real, anthropogenic (i.e., caused by humans), and dangerous. To drive home those points, this chapter relies heavily on the science of the landmark IPCC climate assessments and particularly the most recent AR5 report. We drill down on a key figure from the AR5 to clarify the observed data since 1850 in respect of global average surface temperatures, sea level rise, atmospheric concentrations of several greenhouse gases, and annual CO2 emissions. With a second figure we examine the sources of climate forcing since 1950 and clarify the degree to which they are caused by humanity or by nature. We then divert to key facets that we don’t yet fully understand about climate change, including tipping points, “climate sensitivity” and the likely emissions pathway that humanity will choose over the remainder of the century. We conclude with the observation that irrespective of how these mysteries play out, substantial climate change is in our future. It’s coming.

Here I examine flue gas capture of CO2 along with geologic sequestration. While CCS could reasonably be categorized as a form of emissions reduction rather than a climate intervention, I present it as the latter because the capture step is so similar to what would be required for direct air capture, and the sequestration step is identical. I first clarify that the real value in BECCS is the carbon capture, not the inefficient bio energy production. After delving into the mechanics and economics of the CCS process, I review the status of large CCS facilities around the world, noting that we are scaling this technology at a small fraction of the pace required. While there is a small market for carbon use in products, the vast majority of what we might extract needs to be pumped underground in secure storage sites. As there is no market value in such carbon sequestration, this technology will not begin to scale substantially until government policy mandates or incents it via regulation or carbon charges.

On the SRM side of the toolbox, we are at an even earlier stage, so the go-forward imperative here is not development but simply research. We need a much more sound understanding as to whether and how these interventions might work and how we might domesticate them via thoughtful and inclusive governance. The SRM sibling to the National Academies report described above was issued in spring 2021. It recommends an expenditure of $100–200 million over five years, a small fraction of the proposed budget for CDR. Nonetheless, this would be a vast expansion of resources for the field. My personal path forward entails working with colleagues to design aircraft that could be useful in such research.

This is our quick jog through climate science, intended to ground future climate discussions in a solid factual context. We review: the earth’s energy budget via the Trenberth diagram; the role of greenhouse gases, the Keeling Curve, and global warming potential; atmospheric structure and the environmental lapse rate; global atmospheric and oceanic circulations; paleoclimatology over both the last million and the last 1,500 years; and the role of oceans and ice.

Despite the many challenges in achieving complete decarbonization of our energy supply, succeeding in that Herculean task would solve merely two-thirds of our greenhouse gas emissions problem. This chapter addresses how we might tackle the other third. Topics covered include: fugitive methane emissions from fossil fuel production; CO2 emissions from both traditional and industrial biomass combustion; emissions of CO2, methane, and nitrous oxide from the agricultural sector; CO2 emissions from land use changes and the forestry sector; the full range of greenhouse gas emissions from the industrial sector unrelated to energy; and the ongoing release of methane from our waste streams. Tackling these diverse and myriad emission sources will greatly tax the ingenuity and budgets of humanity.

The final carbon capture chapter focuses on DACCS and notes that due to difficulties in remediating ongoing emissions from recalcitrant economic sectors such as aviation, long-distance transport, agriculture, and waste streams, DACCS will almost certainly be necessary simply to get to net zero emissions. However, if by then temperatures are unacceptably high, DACCS will be required on an utterly massive scale to reduce atmospheric carbon concentrations. The mechanics of DACCS are quite similar to those required for flue gas capture, but the much reduced concentration of carbon in ambient air elevates the cost of DACCS substantially. While there remains material uncertainty as to the mature cost of DACCS, the size of a future DACCS industry needed to substantially reduce future atmospheric CO2 concentrations would rival the size of the fossil fuel industry today. The three leading companies in the DACCS field are reviewed to illustrate the promising but nascent status of this industry today.