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A Case for Climate Engineering

A Case for Climate Engineering

by David Keith

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Climate engineering -- which could slow the pace of global warming by injecting reflective particles into the upper atmosphere -- has emerged in recent years as an extremely controversial technology. And for good reason: it carries unknown risks and it may undermine commitments to conserving energy. Some critics also view it as an immoral human breach of the


Climate engineering -- which could slow the pace of global warming by injecting reflective particles into the upper atmosphere -- has emerged in recent years as an extremely controversial technology. And for good reason: it carries unknown risks and it may undermine commitments to conserving energy. Some critics also view it as an immoral human breach of the natural world. The latter objection, David Keith argues in A Scientist's Case for Climate Engineering, is groundless; we have been using technology to alter our environment for years. But he agrees that there are large issues at stake.

A leading scientist long concerned about climate change, Keith offers no naïve proposal for an easy fix to what is perhaps the most challenging question of our time; climate engineering is no silver bullet. But he argues that after decades during which very little progress has been made in reducing carbon emissions we must put this technology on the table and consider it responsibly. That doesn't mean we will deploy it, and it doesn't mean that we can abandon efforts to reduce greenhouse gas emissions. But we must understand fully what research needs to be done and how the technology might be designed and used. This book provides a clear and accessible overview of what the costs and risks might be, and how climate engineering might fit into a larger program for managing climate change.

Editorial Reviews


Keith's proposal is audacious at first, but in the course of this brief book he makes a convincing case.

The Economist

Keith manages to keep the tone sober without ever sounding dull. His chapter on ethics deftly summarises some of the competing moral claims…Reading about proposals to alter the climate of an entire planet on purpose is dizzying. Yet scientists already talk of the dawning of a new geological age, the Anthropocene, named because humans, or rather, the industrial civilisation they have created, have become the main factor driving the evolution of Earth. [ The Case for Climate Engineering emphasises] just how seriously the idea of deliberately altering the climate is being considered, both in scientific journals and among some governments…[Keith is] a guide for the undecided.

Technology Review - Eli Kintisch

Keith deserves credit for directing attention to ideas he knows are dangerous. Accepting the concept of the Anthropocene means accepting that humans have the responsibility to find technological fixes for disasters they have created. But little progress has been made toward a process for rationally supervising such activity on a global scale. We need a more open discussion about a seemingly outlandish but real geopolitical risk: war over climate engineering.

Product Details

MIT Press
Publication date:
Boston Review Books
Sales rank:
Product dimensions:
4.60(w) x 7.10(h) x 0.90(d)
Age Range:
18 Years

Read an Excerpt


By David Keith

The MIT Press

Copyright © 2013 Massachusetts Institute of Technology
All rights reserved.
ISBN: 978-0-262-01982-8


It is possible to cool the planet by injecting reflective particles of sulfuric acid into the upper atmosphere where they would scatter a tiny fraction of incoming sunlight back to space, creating a thin sunshade for the ground beneath. To say that it's "possible" understates the case: it is cheap and technically easy. The specialized aircraft and dispersal systems required to get started could be deployed in a few years for the price of a Hollywood blockbuster.

I don't advocate such a quick-and-dirty start to climate engineering, nor do I expect any such sudden action, but the underlying science is sound and the technological developments are real. This single technology could increase the productivity of ecosystems across the planet and stop global warming; it could increase crop yields, particularly those in the hottest and poorest parts of the world. It is hyperbolic but not inaccurate to call it a cheap tool that could green the world.

Solar geoengineering is a set of emerging technologies to manipulate the climate. These technologies could partially counteract climate change caused by the gradual accumulation of carbon dioxide. Deliberately adding one pollutant to temporarily counter another is a brutally ugly technical fix, yet that is the essence of the suggestion that sulfur be injected into the stratosphere to limit the damage caused by the carbon we've pumped into the air.

Solar geoengineering is an extraordinarily powerful tool. But it is also dangerous. It entails novel environmental risks. And, like climate change itself, its effects are unequal, so even if it makes many farmers better off, others will be worse off. It is so cheap that almost any nation could afford to alter the earth's climate, a fact that may accelerate the shifting balance of global power, raising security concerns that could, in the worst case, lead to war. If misused, geoengineering could drive extraordinarily rapid climate change, imperiling global food supply. In the long run, stable control of geoengineering may require new forms of global governance and may prove as disruptive to the political order of the 21st century as nuclear weapons were for the 20th.

Many people feel a visceral sense of repugnance on first hearing about geoengineering. For some, the repugnance crystallizes into moral outrage against the very idea that the topic is being discussed; for others, exposure to debate about geoengineering brings with it an appreciation of the hard choices at its roots and an understanding that there are credible arguments for and against. That intuitive revulsion strikes me as healthy; our gadget-obsessed culture is all too easily drawn to a shiny new tech fix. A narrow focus on a technology's power too easily blinds us to its risks.

It's tempting to wish climate change away by denying the science or by asserting that a quick shift to new clean energy sources provides an easy way out. But there is no magic bullet. We cannot make sound decisions by supposing the world is as we wish it were: the science of climate risk is solid, and the inertia of the carbon cycle combined with that of the world's economy mean that efforts to cut emissions can only moderate (but not reverse) climate change over this century.

As with the capacity to engineer our own genome, humanity is rapidly developing the capacity to engineer the planetary environment. Geoengineering's powerful potential demands a broad debate that must include not only credible arguments for and against such an intervention, but also, as with genetic engineering, an appreciation of the large questions it raises about nature and technology on a planetary scale.

I myself have concluded that it makes sense to move with deliberate haste towards deployment of geoengineering. You may well reach a different conclusion. My goal is simply to convince you that it's a hard choice.

* * *

In this book I attempt a synoptic view of solar geoengineering for the educated non-specialist who is willing to work their way through some complex arguments. I am not a disinterested bystander. Every author's story is shaped by their biases. The remainder of this preface discloses some of mine.

Wilderness has shaped my life. From weekend canoe trips to long solo ski expeditions in the high Arctic, I am fortunate to have spent about a year of my life traveling in the big wilds far from roads. My thinking was shaped by a family interest in environmental protection; my father played an early role in the science and regulation of DDT, and his brother helped lead the creation of birding as a social activity separate from scientific ornithology. I am an oddball environmentalist. A bit of a liberal redneck perhaps, as I have taken part in Earth First! actions and Christmas bird counts, yet I have a freezer filled with last fall's mule deer. I am also a tinkerer and a technophile. From lucking into a job at a top laser physics lab in high school, to teaching myself oxy-acetylene welding as I rebuilt the rusted frame of my first car, and then winning a prize for the best doctorate in experimental physics at M.I.T., I have always loved getting my hands dirty with hardware. Turning away from physics because it did not seem to engage real-world problems, I started to work in climate and energy before the end of graduate school. In 1989 I stumbled into geoengineering. I was drawn in by the lack of high-quality analysis of either the technology or the policy implications, a lack that seemed odd given the potential importance of geoengineering to the climate's future.

I have worked on this topic for most of my academic career. While my academic writing aims at objectivity and dispassion, here I venture educated guesses that go beyond what can be defended in an academic research paper. While I aim at objectivity I don't hide my personal views. I have done my best to draw a clear distinction my judgment about what the facts are from my personal, value-laden judgments about what we ought to do.

My passion for this topic is rooted in a concern that environmentalism has lost its way. The language of environmental advocacy has become increasingly technocratic. Calls for action rely almost exclusively on (seemingly) objective quantitative measures of cost and benefit that amount to a crude appeal to self-interest. We are urged to protect natural landscapes not because walking through them brings pleasure, but because of the ecosystem services they yield, services like oxygen and clean water. These arguments have merit, but I think they obscure much of what actually drives people's choices. If we are protecting a rainforest because it stores carbon or yields wonder drugs, then we should be happy to cut down the forest if some carbon storage machine or molecular biotech lab can better provide these services. If we are protecting a wetland for its ability to hold and purify water then we should be happy to replace it with a housing development if that development includes technologies for water storage and filtration that does these jobs better than the wetland. For me the utilitarian benefits of nature are a grossly insufficient measure of its value.

I also worry that debate about climate change has degenerated into trench warfare in which arguments are increasingly extreme with claims that climate science is a money-spinning fraud countered by claims that carbon emissions poses an immediate existential threat. As the extremes dig in, the battle has stagnated so that it now obscures many of the facts and moral values at the root of our choices. For me geoengineering matters both in its own right and because it encourages us rethink some of our root assumptions about the means and ends of climate policy.

A fuzzy love of nature is uncontroversial. We are saturated with soft-focus environmental imagery. Green exhortations have become white noise at the same time as new social technologies have accelerated the decline in people's day-to-day experience with the natural world. I suspect that Edward O. Wilson, the entomologist and writer, captured more than a grain of truth with his biophilia hypothesis, the idea that humans have an innate urge to affiliate with other forms of life. For me, the challenge is to craft an environmental ethic that recognizes non-utilitarian values in the natural world without asserting that these values trump all others and without making naïve claims of a sharp distinction between nature and civilization. Humans have shaped the natural world since long before the industrial era, before even the invention of agriculture. Stone Age hunters exterminated large animals in each new land they entered and the impact of these extinctions cascaded throughout the landscape. When humans arrived in Australia about fifty thousand years ago, to cite but one example, hunting pressure drove to extinction roughly 90% of all species weighing more than a typical human.

Recognition of humanity's role in shaping landscapes that seem "natural" does not—for me—drain them of value or turn them into an artifact. Quite the opposite; in part, their value lies in the history of how they got the way they are, the co-evolution of nature, culture and technology. In Rambunctious Garden, Emma Maris argued that environmentalists should abandon the obsessive defense of pristine nature in favor of an expanded environmental ethic that embraces the messy yet vibrant reality of landscapes shaped by human action.

I am simultaneously persuaded and repulsed by Maris' arguments, but I am convinced that we cannot come to sensible conclusions about the merits of geoengineering or about climate policy itself without engaging these hard questions at the interface of society and nature.

A note on terminology

Solar geoengineering, also known as solar radiation management (SRM) is the sole subject of this book. But the term geoengineering also describes the removal of carbon dioxide from the atmosphere, often called carbon dioxide removal (CDR). Before we dive further into solar geoengineering, it's worth a detour to explore the differences between these two classes of technology.

There is a host of ways to remove carbon dioxide from the air, from increasing the stock of carbon in soils and forests as farmers and foresters change their management practices to engineering methods that could speed up the geological weathering cycle in which the dissolution of alkali minerals into seawater pulls carbon from the atmosphere into the ocean. Technology for direct capture of carbon dioxide from the air might also play a role. Note that Carbon Engineering, a company I founded, is developing such technology, though our work aims to enable low-carbon fuels. (I address the conflicts of interest this raises in the next note.)

Solar geoengineering and carbon removal technologies are tools in our kit for managing climate risk, a toolkit that includes: consuming less (conservation), providing the same services with less inputs of energy (efficiency), supplying energy with less carbon (decarbonization), removing carbon after it's emitted (carbon removal), engineering climate change at a given level of greenhouse gases (solar geoengineering), and, finally, reducing the impacts of climate change by taking extra measures to adapt as it changes (adaptation).

A last word on climate policy jargon: anything that cuts emissions of greenhouse gases below what they would have been in some mythical business-as-usual world is called mitigation. Mitigation thus includes conservation, efficiency and decarbonization.

Solar geoengineering and carbon removal each provide a means to manage climate risk and each are sometimes called geoengineering, but they are only somewhat more related to each other than either of them is to other tools in the toolbox. First, they are wholly distinct with respect to the science and technology required to develop, test, and deploy them. And second, they distribute cost and risks very differently. Solar geoengineering has negligible deployment costs and entails benefits and risks that are regional to global in scale. Carbon removal technologies have costs that are generally similar to mitigation, in that it might cost about a hundred dollars to remove a ton of carbon dioxide using technologies that accelerated the weathering cycle and about the same amount of avoid a ton of emissions by building wind-turbines to replace fossil fueled electricity. Like mitigation they have local risks at the point of use that must be traded against global (but not local) benefits with essentially no corresponding global risks.

This divergence of costs and risks means that the challenges solar geoengineering and carbon removal raise for policy and governance are almost wholly different. Carbon removal is like mitigation in that it requires policy incentives to balance local cost and risk against a global benefit that accrues in the distant future (as we will see when we explore the inertia of the carbon cycle). Indeed, until humanity's net emissions are zero any carbon removal method has precisely the same effect on the climate as mitigation—a ton not emitted is the same as a ton emitted and recaptured.

Because solar geoengineering and carbon removal have little in common, we will have a better chance to craft sensible policy if we treat them separately. For the remainder of this book I will use geoengineering to describe solar geoengineering only.

A final note about money and conflict of interest:

My work on solar geoengineering has been funded by academic research grants and by a personal grant from Bill Gates for whom I act as an occasional informal advisor on climate change and energy technologies. All my work on this this topic is academic with open publication and no patenting.

I also have my hands dirty running Carbon Engineering, a small start-up company that is developing technology for direct capture of carbon dioxide from the atmosphere. We hope this technology will make it cheaper to reduce carbon emissions from parts of the transportation infrastructure such as aircraft that are otherwise hard to decarbonize, and we see ourselves competing with other ways to accomplish this goal, such as biofuels.

I see a sharp distinction in the role of private enterprise in solar geoengineering and carbon removal. The development of solar geoengineering technologies should be as public and transparent as possible. The extraordinary global power of these technologies means that they cannot be effectively governed by the local rules appropriate for more conventional technology. I believe that private, for-profit development (and patenting) of the core technologies for solar geoengineering should be strongly discouraged.

Direct carbon capture from the atmosphere is very different. Succeed or fail, the technology we are developing in Carbon Engineering is a contained industrialy process with local risks similar to other industrial energy or mineral processing technologies. Our job at Carbon Engineering is to develop a technology but not to decide how or if it's used. Because of my involvement I do not claim to speak as an academic about carbon capture from the air. Governments ought to regulate it in the public interest, and it's wrong for corporations (who are not people!) to preempt that regulatory role.


Excerpted from A CASE FOR CLIMATE ENGINEERING by David Keith. Copyright © 2013 Massachusetts Institute of Technology. Excerpted by permission of The MIT Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Meet the Author

David Keith has worked near the interface between climate science, energy technology, and public policy for twenty years. He is currently the Gordon McKay Professor of Applied Physics in the School of Engineering and Applied Sciences (SEAS) at Harvard University and Professor of Public Policy at the Harvard Kennedy School.

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