Here we grasp the tool in this side of our box with the most promise to exert a material cooling impact on the planet in the foreseeable future. It also however comes with the greatest likelihood of problematical unintended consequences. Volcanoes provide a helpful analog for how SAI might operate and demonstrate that aerosols suspended in the atmosphere can and do immediately and substantially cool the earth. The mechanics of recreating such a volcano effect in a deliberate fashion are explained and situated in both space and time. It is also noted that relative to any other climate intervention or solution, SAI would be stunningly cheap, giving rise to the prospect of the “free driver” hypothesis. In addition to exerting force upon the climate variable (temperature), it may well interfere with ones we do not, such as rainfall. The problematical dynamics of stopping such a program (“termination shock”) are explored, as are difficulties that would arise in seeking to attribute observed climate impacts in an engineered climate to their causes. SAI is presented as an enigma to be explored rather than a remedy to be implemented.

This initial chapter in the carbon removal section focuses on several of the more tangential possible solutions, each of which may form a wedge in a portfolio of carbon removal solutions but will by no means constitute the primary intervention. After touching upon the Gaia hypothesis, we move to everyone’s favorite climate solution – trees. Though afforestation/reforestation appear superficially attractive and cheap, they are merely a fragile and temporary bank of carbon with a storage capacity that is woefully subscale for our problem. Bio energy with carbon capture and sequestration would ameliorate the land saturation problem that limits the capacity of forests, but is also far less green than it appears and confronts similar scaling constraints. Regenerative agriculture, blue carbon, biochar, and other soil carbon enhancement techniques are further wedges in the portfolio, but each with substantial scaling limitations. Enhanced chemical weathering faces cost problems, and ocean iron fertilization is more nearly pollution than a climate solution. While some of these techniques will prove relevant, none promises climate salvation.

My personal reflections upon completing the book.

Magnificent piece of statecraft though it is, the Paris Agreement is unlikely to spare us from a future climate reckoning. Paris can be seen as the successor to a series of prior global emissions limitation agreements including the breathtakingly effective Montreal Protocol that addressed the cause of the “ozone hole” and the Kyoto Protocol, the world’s first attempt to address climate change. Kyoto collapsed in failure and Paris was therefore midwifed with the Kyoto lessons in mind. We then delve into the structure, status, and limitations of the Paris Agreement before looking ahead to how it might evolve.

A deep dive is taken here into the nuts and bolts of what a global SAI deployment program would actually entail, based upon my own primary research. Noting first that there is currently neither a scientific basis to understand the impacts of such a deployment nor a governance structure that could confer legitimacy upon it, the logistics of deployment would be straightforward. Getting the aerosol to the right place in the sky would require a newly developed fleet of dozens and soon hundreds of high-altitude high-payload tankers. Such aircraft do not currently exist but could be developed within a decade at a cost of a few billion dollars. Several aerosol candidates could reasonably be considered, but sulfates would likely top the list. Deployment would occur in the tropics in both the northern and southern hemispheres and would be continuous for decades at least. Bases would ideally be in many countries, making this a multilateral effort. An organizational structure for a deployment effort is presented. The annual cost to cool the earth by 1°C is estimated to be in the range of $18 billion.

One of the most destructive features of modern life is to deprive people of the sense that they are essentially creative beings. The industrialization and commercialization of work have a lot to do with this, but so too does the elevation of the fine artist as a lonely (often tortured) genius, and the reduction of people to passive consumers. In this chapter, Wirzba gives an account of good work as an indispensable means through which people contribute to the making of a beautiful world and thriving communities. To be creative is to respond to the sanctity of fellow creatures with the skill and devotion that contribute to shared flourishing. But for people to be creative in this way, the personal, social, economic, and political contexts through which they live need to be properly cultivated. The highest form of creativity is to focus and train one’s love into practical skills that join with the sacred love that is already at work in the world.

The teaching of creation has been much misunderstood and under-developed because it has been taken to be primarily about how the world began a long, long time ago. Religious naturalists have often abandoned this teaching so as to give a more scientifically informed characterization of our cosmos and humanity’s place within it. Wirzba argues that this is a big mistake because the rejection of the idea that our world is a divinely created world makes it impossible to speak of life as a gift. This chapter develops what it means to say that each creature is gift cherished and sustained in its being by God. As such, it opens the idea of creation to encompass life’s meaning and purpose, and it creates a way for people to become involved in the nurture and healing of our world and our shared life. The logic of creation, upon further examination, is not about God’s power “over” the world but about God’s presence to the world in the forms of love that invite human participation in it.

Recent developments in artificial intelligence (AI) and genetic engineering/bio-enhancement reflect a deep-seated discontent with humanity’s embodied condition. This discontent is a contemporary variation on the long-standing dualisms that elevate mind/soul/intelligence over bodies and materiality. The (increasingly well-funded) desire to redesign human bodies and the habitats of our world grow out of the same logic that is reflected in an impatience with imperfection, vulnerability, and frustration. The end-result of transhumanism leads to a strange outcome, namely the eclipse, surpassing, and obliteration of the form of humanity itself. As such, transhumanism reflects a refusal to be in bodies and places, and thus is a particularly striking example of humanity’s rejection of its creaturely condition.