by David Keith and Ben Peltz
Climate systems engineering lives at the intersection of systems engineering, Earth system science, and anthropogenic climate change.
Climate science is, as we see it, a subfield of environmental geosciences – one that works to understand the forces that shape Earth’s climate, and the ways climate, in turn, shapes humans and nature. It sits within the even broader field of Earth system science, which studies how the atmosphere, oceans, ice sheets, land, and living organisms interact as an interconnected system.
Systems engineering is the interdisciplinary practice of designing, managing, and evaluating complex systems so that the whole system meets some intended goal.1
The notion that systematic analysis might help manage the complex interactions between humans and the natural world keeps re-emerging under various names: system dynamics, sustainability science, industrial ecology, and many more. Each has its flawed history. “Climate systems engineering” is also imperfect, but we find it useful.
Navigating complex systems
In a complex system, everything is in some way connected with everything else. True, but unhelpful on its own. Systems engineering helps figure out which connections matter most for the decision at hand, and which uncertainties matter enough to affect that decision.
Further, the connections and uncertainties that matter most will be specific to the decision-maker and the decision they face. These decisions and priorities are not universal. For instance, a poor island nation in the South Pacific deciding whether to support SRM governance will face a different set of uncertainties than a richer nation in the Global North or major fossil-fuel exporting nation. The consequences of SRM will be unequal, both the good and bad. Systems engineering must serve the needs of users, and it should not prejudge their values.
Climate science lives mostly in the natural sciences, which aim to understand how the world works and predict what might happen next. But there is no overarching algorithm, as far as we know, governing nature or instilling it with a “purpose.” One need not consider a goal to study why the Athabasca glacier flows slow and then fast, or how pikas survive cold winters. Nature has no goal.
Systems engineering, on the other hand, lives among what Nobel Laureate Herb Simon called “the sciences of the artificial.” One cannot make sense of a wheel, or a large language model, without considering the goals of the humans who created them. Engineering is nothing more than the application of scientific knowledge to achieve some end. And because those ends are chosen by people with various (and often competing) goals, and not some divine “purpose,” systems engineering must remain useful across a wide range of goals rather than acting as a tool to advance any single goal.
The aims of climate systems engineering
As we see it, the scope of climate systems engineering includes deliberate intervention in the climate system with the goal of reducing large-scale climate changes caused by anthropogenic emissions of long-lived greenhouse gases.2
One obvious critique of “climate systems engineering” is that it’s a hubristic fantasy to imagine the climate system can be engineered – applying “engineering” to Earth’s biosphere implies a mechanistic and domineering view of the natural world. We reject this view. Of course, some engineers are guilty of hubris and domination, as are practitioners in many other fields, but we think “systems engineering” is appropriate because it’s about highlighting uncertainties that matter for policymaking, not concealing them, and about understanding the limits of control.
Like geoengineering, climate systems engineering applies to a range of methods intervening in the Earth system. The most important of these are carbon removal and sunlight reflection, but our program also includes ice sheet interventions because they hold the promise of global-scale reduction in one aspect of climate change – sea-level rise.
Within carbon dioxide removal (CDR), our focus is on open-systems approaches. These include ocean alkalinity enhancement (OAE) and enhanced rock weathering (ERW), which interact directly with the broader Earth system. The rationale for covering only open-systems CDR is that understanding and development of open-systems CDR rests on Earth system environmental science, whereas understanding and development of direct air capture (DAC) is an applied chemical engineering problem with little substantive overlap with Earth system science. Those Earth-system complications make open-systems carbon removal an ideal subject for climate systems engineering.
CDR and SRM are sharply distinct, most obviously in the fact that CDR works on the stock of greenhouse gases – so it is inherently slow – while SRM alters the climate response but cannot (much) alter the stock of accumulated greenhouse gases that drive long-term climate risks. Yet, we find it useful to gather them together in one program to encourage researchers to look for generalities in the way we think about the interconnections of science, technology, and public policy across these distinct domains.
The limitations of other terms
This is where “geoengineering” falls short. It names a set of technologies, not a discipline. It doesn’t tell you what standards of evidence apply, what kind of expertise is relevant, or how to weigh a proposed intervention’s benefits against its costs and uncertainties. Climate systems engineering does; it borrows the practice of systems engineering, which has decades of experience designing, managing, and evaluating complex systems against explicit goals, and applies that practice to the climate.
Some want to call this field “climate stabilization.” We prefer climate systems engineering because it describes a discipline of study, not a specific goal. Stabilization is one specific (and worthy) goal, but it’s only one of many. For our part, we would vote instead to return climate toward the pre-industrial: restoration rather than stabilization. Others, many economists among them, aim to maximize human utility, and sunlight reflection may be an extraordinarily cost-effective way to reduce deaths from heat and accelerate economic growth in hot, poor regions. That, too, is a worthy goal – though we are not persuaded that decisions about managing climate can be usefully collapsed into a single metric of discounted utility.
That is the case for climate systems engineering over geoengineering or climate stabilization; it represents the formation of a proper discipline rather than just a new name for the same set of technologies, or a particular goal. It signals where the standards of evidence come from, and it makes room for genuine disagreement about goals.
Endnotes
- NASA defines systems engineering as “a methodical, multi-disciplinary approach for the design, realization, technical management, operations, and retirement of a system. A ‘system’ is the combination of elements that function together to produce the capability required to meet a need.”
- This is based on a previous definition of geoengineering as “the intentional large-scale manipulation of the environment, particularly manipulation that is intended to reduce undesired anthropogenic climate change” found in “Geoengineering the Climate: History and Prospect” (Keith, 2000). Full context on “geoengineering” as a term can be found in the Royal Society’s 2009 report, “Geoengineering the climate: Science, governance and uncertainty.”