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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Serie: Astrobiology Perspectives on Life in the Universe
- Sprache: Englisch
This important and timely book assembles expert scientists from both sides of the debate to discuss Earth-based and space-based climate intervention technologies including the scale, deployment, risk management, and moral philosophy behind these technologies.
The role that geoengineering might play, within the context of global warming amelioration, has long been contentious. For all this, geoengineering is about getting down and dirty with respect to the issue of climate intervention. Often dismissed as an option of last resort, geoengineering is now emerging as a key component in humanity’s drive to bring the impacts of global warming under some form of mitigation and control. While geoengineering does not solve the fundamental problem of continued anthropomorphic carbon dioxide emissions, the root cause of global warming, it is an option that can effectively buy humanity some much-needed time. Time, that is, to act positively, and time to introduce meaningful emission reductions, and deploy large-scale sequestration technologies. Indeed, the failure to meaningfully corral greenhouse gas emission levels, and the slow development of large-scale carbon capture technologies, will, by the close of the 21st century, likely see global temperatures increase by at least 2 or 3 degrees above pre-industrial levels. What geoengineering can potentially do for us is to offset the more extreme climate change scenarios that are presently projected to come about. An integrated geoengineering program to cool Earth’s atmosphere, running in parallel with the development of sequestration technologies, and substantial emission reductions, can work to limit the worst effects of climate change that will, without geoengineering, surely come about. Geoengineering is not a neutral or benign action, however, and if it is to be deployed, then much more research, and field testing of ideas and technologies is urgently needed.
The authors in this book present a cross-section of philosophies, engineering approaches, and reactions to the idea of geoengineering. Through their words, the reader is introduced to the historical and contemporary debate concerning the potential deployment of geoengineering actions. Indeed, there are many ways in which geoengineering, as a grand worldwide initiative, or as a combined set of independent actions, might proceed in both the near, and the deep future, and here the reader is introduced to these topics by experts in their field.
Audience
This book will be of interest to engineers, chemists, geologists, physicists, biologists, environmentalists, meteorologists, philosophers, mathematicians, computer modelers, and policy managers. General readers interested in geoengineering will find the book very readable and scientifically reliable.
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Table of Contents
Cover
Table of Contents
Series Page
Title Page
Copyright Page
Preface
Acknowledgments
1 Prolegomenon: A Geoengineering Primer
1.1 Introduction
1.2 The Paris Agreement
1.3 Tipping Points – Where Are We?
1.4 The Size of the Problem
1.5 Geoengineering – Where, When, and How?
1.6 Moving Forward
1.7 The Role of Industry
1.8 What Now?
References
2 Two Generations of Ethical Debate on Geoengineering
2.1 Introduction
2.2 Ambiguities in Defining Geoengineering
2.3 Geoengineering Technological Schemes
2.4 History of Geoengineering
2.5 Two Generations of Ethical Debate
2.6 Research Priorities Towards Maturing Debate
2.7 Conclusion
References
3 Risky Business: Complex Risks of Solar Geoengineering
3.1 Introduction
3.2 Framework for Risk Assessment
3.3 Understanding the Dangers of Solar Geoengineering
3.4 Complexities of Risk Comparison
3.5 Best of a Bad Bunch
3.6 Slippery Slopes
3.7 Conclusion
References
4 Climate Justice and the Dangers of Solar Geoengineering
4.1 Prioritizing Transformative Climate Justice
4.2 Solar Geoengineering: Illustrating the Dangers of Climate Isolationism
4.3 The Injustices of Advancing Solar Geoengineering
4.4 Climate Justice Resistance to Solar Geoengineering
4.5 Conclusions
References
5 Solar Geoengineering: An Insoluble Problem?
Abbreviations
5.1 Introduction
5.2 The Many Forms of Solar Geoengineering
5.3 Controversies about SG Methods
5.4 Argument: Why SG is Needed
5.5 Argument: The Case Against SG
5.6 The Comparative Economics of SG
5.7 Discussion and Conclusions
5.8 Research Priorities
References
6 Potential Mental Health Risks Associated with Stratospheric Aerosol Injection Methods Using Aluminum Oxide
1
6.1 Introduction
6.2 Methods
6.3 Results
6.4 Conclusions
References
7 What to Consider When Considering Solar Geoengineering
7.1 Introduction
7.2 The Options
7.3 Geography
7.4 Climate Action
7.5 Public Participation
7.6 Geopolitics
7.7 Conclusion
References
8 Moral Hazard of Geoengineering to Decarbonization
8.1 Introduction
8.2 Modeling Decarbonization and Climate Change Impacts
8.3 Moral Hazard
8.4 Discussion
8.5 Conclusion
Acknowledgment
References
9 The Preeminent Question of Environmental Philosophy: Where Should We Set the Envirostat?
9.1 Introduction
9.2 Geoengineering and the Envirostat
9.3 Animals’ Interests
9.4 World Park
9.5 Animal UN
9.6 Justice and Possible Animals
9.7 The Current Solar Geoengineering Debate
9.8 The Preeminent Question of Environmental Philosophy
References
10 Climate Hegemony and Control Over the Global Thermostat
10.1 Introduction
10.2 Collective Action Problem
10.3 Hegemonic Stability Theory
10.4 Auction Theory
10.5 Conclusion
References
11 Designing
A Priori
Scenarios for Stratospheric Aerosol Injections to Mitigate Climate Change: An Optimal Control Technique Application
11.1 Introduction
11.2 Statement of the Optimal Control Problem
11.3 Designing Optimal SAI Scenarios: Problem Formulation
11.4 Solution of the Optimal Control Problem
11.5 Results and Discussion
References
12 Testing the Limits of the World’s Largest Control Task: Solar Geoengineering as a Deep Reinforcement Learning Problem
12.1 Introduction
12.2 Solar Geoengineering as a High-Dimensional Control Problem
12.3 A Fast GCM Environment: Introducing HadCM3
12.4 Building a GCM Emulator
12.5 Geoengineering in the Mesosphere: A Research Agenda
12.6 Closing the Reality Gap
12.7 Conclusions and Outlook
Acknowledgments
References
13 Geochemical Drivers of Enhanced Rock Weathering in Soils
13.1 Introduction
13.2 Fundamental Geochemical Considerations
13.3 What do ERW Experiments Teach us and Where from Here?
13.4 Conclusion
Acknowledgment
References
14 Geoengineering Cities with Reflective and Pervious Surfaces
14.1 Introduction
14.2 Physics of UHI
14.3 Mitigation of UHI
14.4 Research Priorities
14.5 Conclusion
References
15 Urban Geoengineering
15.1 Introduction
15.2 Background
15.3 Cities, Sustainability and Decarbonization
15.4 Global Trends in Decarbonization
15.5 Achieving Net Zero and the SDGs with Urban Geoengineering
15.6 Urban Geoengineering Interventions
15.7 Governance for Urban Geoengineering
15.8 Concluding Comments and Future Research
References
16 Cooling Down the World Oceans and the Earth
16.1 Introduction
16.2 Methodology
16.3 Results
16.4 Discussion
16.5 Conclusion
Acknowledgments
References
17 Ice Preservation: A Research Priority for Climate Resilience and Sustainability – Experience in the Field
17.1 A Personal Introduction
17.2 How Bad is the Climate Situation?
17.3 Ice Preservation – A Research Priority for Climate Resilience
17.4 Now is the Time to Preserve Bright Ice
17.5 Minnesota Pond Work
17.6 Iceland Glacial Test, August 2023
17.7 Our Work at Bright Ice Initiative
Acknowledgement
References
18 Cirrus Cloud Thinning
18.1 Clouds, Radiation, and the Physics of Cirrus Cloud Thinning
18.2 Past and Present CCT Research
18.3 Suggestions for Improving the Treatment of CCT in Climate Models
18.4 Possible Relation to Midlatitude Extreme Winter Weather
References
19 Can the COVID-19 Decrease in Aircraft Flights Inform us of Whether the Addition of Efficient INP to Cirrus Altitudes Cools the Climate?
19.1 Introduction
19.2 The Relative Importance of Heterogeneous and Homogeneous Nucleation
19.3 Model Description
19.4 Evaluation of Model Aerosols and Ice Concentrations
19.5 Discussion: What Does This Mean for Cirrus Seeding?
19.6 Conclusion
References
20 Biogenic Iron Oxides as a Source of Iron for Ocean Iron Fertilization
20.1 Introduction
20.2 Biogenic Iron
20.3 Production of BIOX
20.4 Additional Aspects of OIF
20.5 Social Considerations
20.6 Conclusions and Recommendations
Acknowledgment
References
21 Space Bubbles: The Deflection of Solar Radiation Using Thin-Film Inflatable Bubble Rafts
21.1 Introduction
21.2 A Bubble Sunshade
21.3 Future Developments
References
22 Optimal Sunshield Positioning
22.1 Introduction
22.2 Sunshade Area
22.3 Sunshade Position
22.4 Optical Properties
22.5 Getting to the First Lagrange Point L
1
’
References
23 Could the Well of an Orbital Lift Be Used to Deposit Greenhouse Gases into Space?
23.1 Introduction
23.2 Basic Features of the Proposed System
23.3 Discussion and Outlook
References
24 Ionospheric Perturbations from Satellite Dust
24.1 Introduction
24.2 Model Considerations
24.3 Conclusion
Acknowledgments
References
25 Geoengineering and Beyond – Planetary Defense, Space Debris, and SETI
25.1 Introduction
25.2 Earth in the Firing Zone
25.3 Impactor Populations
25.4 Impact Probabilities
25.5 The Day the Climate Changed
25.6 Lead Times
25.7 Impact Risk
25.8 Planetary Defense
25.9 Signs of Life and Technosignatures
25.10 Space Debris
25.11 What Next? – Research Priorities
References
26 Future Imperative and the Inevitable Technofix
26.1 Introduction
26.2 The Aging Sun
26.3 The Faint Young Sun Paradox
26.4 Lifetime of the Biosphere
26.5 Actions
26.6 Albedo Modification
26.7 Sunshades
26.8 Orbit Change
26.9 Far-Out Methods
26.10 Terraforming
26.11 Engineering the Sun
26.12 Pastures New
26.13 Conclusions
References
Index
Also of Interest
End User License Agreement
List of Tables
Chapter 5
Table 5.1 Summary of geoengineering proposals and references.
Chapter 8
Table 8.1 Key variables and parameters of the energy-economy model.
Chapter 11
Table 11.1 Estimated changes in GMST from year 2020 to 2100 (changes relative ...
Table 11.2 Maximum values of GMST anomalies for the period 2020–2100 relative ...
Table 11.3 Total masses of aerosols injected into the stratosphere from 2020 t...
Chapter 12
Table 12.1 An overview of HadCM3 emulator state variables, and their stash ids...
Chapter 13
Table 13.1 Potentially limiting factors affecting ERW large-scale development ...
Table 13.2 List of some acid-base reactions directly or indirectly impacting E...
Table 13.3 Fundamental rock and soil geochemical parameters affecting ERW effi...
Table 13.4 Suggested parameters that future field experiments should include t...
Chapter 16
Table 16.1 Heat balance of the Arctic Ocean, comparing the albedo effect with ...
Table 16.2 Comparison of influence of temperature and salinity difference on s...
Table 16.3 Arctic Ocean superficial salinity mass balance.
Table 16.4 Comparison of strategies to reduce the input of fresh water into th...
Table 16.5 Advantages, disadvantages, and unknown impacts of strengthening the...
Chapter 19
Table 19.1 Difference in the median and average Ni (L
-1
) between April-May 201...
Table 19.2 Model-calculated difference in the median and average Ni (L
-1
) betw...
Table 19.3 Model results for sulfate and organic matter coated on contrail-pro...
Chapter 20
Table 20.1 Comparison of the amount of Fe(II) extracted from different Fe sour...
Chapter 25
Table 25.1 Characteristics of the potential Earth-impacting bodies. Column 1 i...
Table 25.2 Closest approach distances of comets to the Earth. Column 1 is the ...
Table 25.3 Known NEAs passing within a few lunar distances (LD) of the Earth (...
Chapter 26
Table 26.1 Characteristics of the Sun’s evolutionary path from formation throu...
List of Illustrations
Chapter 1
Figure 1.1 Change in global average temperature during the past 2000 years, in...
Figure 1.2 Projected changes in regional temperature (relative to 1850–1900) f...
Figure 1.3 Locations of climate tipping points.
Figure 1.4 A schematic illustration of several geoengineering options. The reg...
Figure 1.5 Schematic trajectories for future climate change outcomes. The acti...
Figure 1.6 A schematic comparison of geoengineering options in terms of their ...
Figure 1.7 Geoengineering by stratospheric aerosol injection seeks to mimic vo...
Figure 1.8 The simulations shown to the left indicate the expected change in g...
Figure 1.9 Cloud formation trails induced by aerosol emissions from ocean-goin...
Figure 1.10 Schematic summary of the ways in which aviation emissions interact...
Figure 1.11 Illustration of a polar umbrella as envisioned by Derek Pirozzi (2...
Figure 1.12 Schematic for the design of an ocean (vertical transport) pipe. Co...
Figure 1.13 Schematic of the Stratospheric Controlled Perturbation Experiment ...
Figure 1.14 Number of US patents related to controlling weather systems (inclu...
Figure 1.15 Simulated stream of dust launched between the Earth and Sun. The d...
Chapter 5
Figure 5.1 Plot of Scopus articles with the term “solar geoengineering” or “so...
Figure 5.2 Diagram showing all solar geoengineering options.
Chapter 8
Figure 8.1 Optimal energy levels in three cases without climate damages, with ...
Chapter 11
Figure 11.1 Optimal albedo of aerosol layer.
Figure 11.2 Optimal surface temperature anomaly.
Figure 11.3 Optimal rate of aerosol injection.
Figure 11.4 Optimal mass of aerosol particles.
Chapter 12
Figure 12.1 Regional effects of uniform stratospheric aerosol injections, as f...
Figure 12.2 A depiction of different proposed methods for performing solar geo...
Figure 12.3 A Markov Decision Process (MDP), with Earth as environment.
Figure 12.4 Left: A typical latitudinal equilibrium temperature profile in res...
Figure 12.5 Depiction of latitudinal sulfate aerosol injections emulated throu...
Figure 12.6 HadCM3 grid locations in the Pacific Ocean whose aerosol optical d...
Figure 12.7 When aerosol distributions are simple latitudinally-confined strip...
Figure 12.8 When aerosol distributions are simple latitudinally-confined strip...
Figure 12.9 A graphical overview of the full control loop, including both GCM ...
Figure 12.10 An example of a 5-year aerosol injection pattern used for initial...
Figure 12.11 A graphical overview of the data preprocessing pipeline.
Figure 12.12 Preliminary results illustrating the emulation process: We here d...
Figure 12.13 The upper atmosphere’s vertical temperature profile and dominant ...
Figure 12.14 An overview of the bi-level multi-fidelity optimization approach.
Chapter 13
Figure 13.1 Goldich stability series (right) and mean lifetime of several key ...
Figure 13.2 Weathering rate of several silicate minerals as a function of pH.
Figure 13.3 Changes observed in soil pH during ERW mesocosm and field experime...
Chapter 14
Figure 14.1 Percentage of population living in urban areas for countries at di...
Figure 14.2 Heat transfer at the surface of a road.
Figure 14.3 Albedometer used to measure albedo of a road in the field.
Figure 14.4 Spectrophotometer used to measure albedo in the lab.
Figure 14.5 D-SPARC instrument used to measure albedo in the field.
Figure 14.6 (a) Development of vortices in urban canyons; (b) energy balance i...
Chapter 15
Figure 15.1 Percentage of world population living in rural areas versus cities...
Figure 15.2 Global installations of selected clean energy technologies, 2010–2...
Chapter 16
Figure 16.1 Method proposed for increasing the thickness of the Arctic ice cov...
Figure 16.2 (a) Thermal insulation potential of ocean ice, (b) climate model r...
Figure 16.3 Average monthly temperature change in the Arctic Ocean from 1960–1...
Figure 16.4 Cross section of the (a) temperature and (b) salinity of the Arcti...
Figure 16.5 Northern hemisphere topographic map highlighting the area that con...
Figure 16.6 Major rivers in (a) Canada and (b) Russia [16.30] [16.31]; and (c)...
Figure 16.7 (a) Longitudinal representation of the barriers and dams in front ...
Figure 16.8 Diagram of the Arctic Ocean mixer proposed in this paper.
Chapter 17
Figure 17.1 Field testing to slow glacial melt in the Himalayas will begin in ...
Figure 17.2 Preparing the pond surface ice with hollow glass microspheres (for...
Figure 17.3 Aerial view of the Minnesota test lake. The effect of adding hollo...
Figure 17.4 Preparing an ice albedo modification experiment on Langjökull glac...
Chapter 18
Figure 18.1 Seasonal (winter and summer) sampling density of cirrus clouds sam...
Chapter 19
Figure 19.1 Flight tracks for the ATom-1 (orange) and ATom-2 (blue) field camp...
Figure 19.2 Profiles of observed and model simulated sulfate aerosols for diff...
Figure 19.3 Profiles of observed and model simulated organic matter for differ...
Figure 19.4 Profiles of observed and model simulation BC concentrations for AT...
Figure 19.5 Profiles of observed and model simulation dust concentrations for ...
Figure 19.6 Overlay of model simulated sulfate diameter in the tropics for dif...
Figure 19.7 Comparison of median and average CALIPSO satellite observed concen...
Figure 19.8 Model predicted occurrence frequency of homogeneous nucleation (%)...
Chapter 20
Figure 20.1 Growth results for
T. pseudonana
over a 12-day test period. Error ...
Figure 20.2 This experiment tests the growth response of
T. pseudonana
to 100 ...
Figure 20.3 Different sources of Fe-oxides used to compare reactive vs. nonrea...
Figure 20.4 Example of an Fe mat formed by Fe-oxidizing bacteria in a temperat...
Chapter 21
Figure 21.1 A schematic diagram representing the impact of a sunshade, placed ...
Figure 21.2 Schematic image of satellite components in the sunshield proposed ...
Figure 21.3 A schematic representation of a bubble raft acting as a sunshade. ...
Chapter 22
Figure 22.1 The dominating forces on a sunshade on the line between the Sun an...
Figure 22.2 Examples of sunshade principles.
Figure 22.3 Tilted sunshade, total force F
SRP
from sunlight reflecting at angl...
Chapter 23
Figure 23.1 Artist impression of a space elevator and climber as seen from geo...
Figure 23.2 Stability landscape (time versus stability) showing possible traje...
Chapter 24
Figure 24.1 Schematic image of the anticipated Starlink mega-constellation. Th...
Figure 24.2 Schematic illustrating the relationship of human space activities ...
Figure 24.3 CCMC data for the electron Debye length indicates an increase in t...
Figure 24.4 CCMC data for the electron Debye length at 100 km versus time in y...
Chapter 25
Figure 25.1 (left) Apollo asteroid 101955 Bennu. Image taken on 2 December 201...
Figure 25.2 Eccentricity versus semi-major axis diagram for near-Earth asteroi...
Figure 25.3 The size distribution of known near-Earth asteroids (complete to 2...
Figure 25.4 Dashcam image of the Chelyabinsk fireball of 15 February 2013.
Figure 25.5 Cumulative number of impactors above a given mass striking the Ear...
Figure 25.6 Gravity anomaly map of the Chicxulub crater. The central uplift ri...
Figure 25.7 The Torino Scale for quantifying the impact hazard of Earth-impact...
Figure 25.8 Composite images from the DART mission. The top image shows the 30...
Figure 25.9 The towing geometry for a space tug.
Figure 25.10 High Earth orbit space debris distribution (for 25 August 2009). ...
Figure 25.11 Visualization of ClearSpace-1 in the process of grappling with it...
Chapter 26
Figure 26.1 Evolution of the Sun, from the onset of core hydrogen burning, thr...
Figure 26.2 Change in the Sun’s radius as it evolves through the main sequence...
Figure 26.3 Schematic feedback network envisaged by Lovelock and Whitfield [26...
Figure 26.4 A characteristic 2-species Daisyworld simulation. (Top) The fracti...
Figure 26.5 Location of the first Lagrange point L
1
– a stable point in the re...
Figure 26.6 Configuration of the Sun-Sail-Earth three-body system for expandin...
Guide
Cover Page
Table of Contents
Series Page
Title Page
Copyright Page
Preface
Acknowledgments
Begin Reading
Index
Also of Interest
WILEY END USER LICENSE AGREEMENT
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Astrobiology Perspectives on Life in the Universe
Founding Editors: Richard Gordon and Joseph SeckbachSeries Editor: Martin Beech ([email protected])Advisory Board: Richard Gordon and George Mikhailovsky
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Geoengineering and Climate Change
Methods, Risks, and Governance
Edited by
Martin Beech
Department of Physics, Campion College at the University of Regina, Regina, Saskatchewan, Canada
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Front cover image courtesy of Pixabay.comCover design by Russell Richardson
Preface
Geoengineering is an action intended for the betterment of humankind. There, I have written it. Let the debate begin. Certainly not everyone will agree with my opening statement, and indeed, there are many very good arguments for not initiating geoengineering as a means of addressing the problems of global warming. For my part, however, I would argue that it is time to embrace geoengineering (in all its many guises) for what it really is, and that is a set of well-defined, innovative actions that can be deployed, monitored, and controlled, and which work towards achieving a better future for humanity—indeed, a better future trajectory than the one we are currently moving along. The time to begin the serious contemplation, planning, investment, field-testing, and initiation of geoengineering actions is pressingly upon us. Indeed, time is of the essence, since effective, affordable, large-scale carbon capture and retrieval capabilities are currently nonexistent, and meaningful global carbon emission reductions have not come about. Fortunately, the way forward is relatively clear, and, along with dramatically reducing our dependency on fossil fuels and eventually extracting excess CO2 from the atmosphere, various forms of geoengineering will be needed to counter the ever-growing, long-term detrimental effects of global warming on the environment. Importantly, geoengineering provides us with the possibility of “peak shaving,” thereby ameliorating the worst of the inevitable, already inbuilt and set to appear, consequences of global warming. Again, not everyone will agree with what I have just written. Indeed, one counter argument that is often leveled against geoengineering is that it typically exploits the same physical processes that have resulted in the current acute situation of global warming. With no distinction being drawn between the harmful release of CO2 and pollutants by cars, airplanes, ships, agriculture, and industry, and those relatively benign compounds used in, say, stratospheric aerosol injection—a key geoengineering action demonstrably capable of cooling the Earth. There is, I would argue, a great fallacy in confusing these two actions. The former being a known set of relatively unregulated harmful byproducts of life choices and industrial processes that are unequivocally linked to present-day global warming. The latter, in contrast, being a deliberate, temporary, and controllable set of actions, directly aimed towards the achievement of a greater common good—that is, a cooler Earth for all. The argument that runs along the lines that past and present human actions have directly caused the current global warming crisis, and ipso facto, that we (that is humanity) must be excluded from all future engagement with the climate system, is, I would contest, ill-founded. Indeed, the actions of past generations in no way negates the promise and potential of present-day human actions putting the situation right in the future. The imperative of moving on, remaking, and improving upon what went before lies at the very core of each and every new human generation. To argue, point blank, against the deployment of geoengineering actions denies the scientific advancements, technical developments, teachings, and collective understandings garnered in past decades. This is not to say that geoengineering is a panacea; there are still many technical, ethical, political, medical, and governance issues to hear, solve, and deal with. If geoengineering is to be rejected as a means of addressing global warming, then it must be a reasoned rejection. And, to argue against something, one needs to have hard data and measurements upon which to base a sound discussion. At present, such practical data and experimental experience are lacking, and indeed, one of the underlying themes of this book is to see how such experience and data might be obtained.
What makes the geoengineering issue particularly challenging is the chorus, even cacophony, of voices for and against it. There is no escaping this, but it is important that all voices are heard, and appreciated—they are all valuable, and consensus on future actions can only be achieved through dialog. The collection of articles presented here spans the spectrum of opinions, the yeas, nays, and maybes, concerning the initiation of geoengineering actions, and it also attempts (especially in the last several chapters) to broaden the topic beyond the domain of Earth’s atmosphere. In the opening section, we have a number of positioning articles. Chapter 1 provides an introduction to the topic of geoengineering, looking at its possibilities, aims, and future requirements. Chapter 2, in contrast, looks at how the geoengineering position has evolved over the past decades. Following this, in Chapters 3 through 10, various voices and approaches are presented. As will be seen, the hard, indeed, very hard part of geoengineering, is not the science (as such), but rather the scale, deployment, risk management, and moral philosophy behind what is actually being done. People’s lives, health, and livings are literally at risk, and this changes the dialog, moving it away from a decision-making process based purely upon the strict logic of equations, physics, and chemistry, to a process including politics, human justice, human health, and human well-being. How we (that is humanity in the here and now) resolve these intertwined issues, and how we attempt to find a consensus viewpoint, is going to be crucial for our collective future, and indeed, they will literally define where humanity goes in the latter half of the 21st century. The authors of Chapters 11 through 20 forge ahead, however, and explore a number of possible geoengineering actions, all of which aim towards the cooling of Earth and/or the restoration of a degraded environment. Chapters 11 and 12 look at various theoretical issues with respect to the application and control of geoengineering processes, examining, head-on, the complexity of the issues at hand. Chapters 13 through 19 present the details behind several specific geoengineering actions, looking at their rationale, testing, and means of possible deployment. More than just looking at the mechanics, however, these later chapters also consider how geoengineering actions might be tested, monitored, and regulated. The final section, Chapters 21 through 27, look towards the much deeper future, and the deployment of yet hardly imagined technologies to address future global warming issues. These options are generally space-based, and will entail humanity adopting a direct, ongoing, and active role in the stewardship of the Earth. The deep future will inevitably require that our descendants move towards a complex, proactive, and large- scale technofix engagement with the Earth’s climate system. The long journey ahead of us, however, is predicated on what it is that we do in the here and now. Most of all, perhaps, humanity will need to find a unity of purpose, in a cooperative global sense, as never before achieved in history. In our current unsatisfactory situation, the denial of environmental geoengineering is nothing less demanding than that of a boxer that must enter an upcoming prize fight with both hands tied behind his back. Global warming requires that humanity acts, and acts quickly, deploying and wisely using all possible means of climate amelioration that are available. Well, these are some of my thoughts. Not everyone will agree with them—and “so it goes.”
Martin Beech, PhD
Professor Emeritus, Department of Physics, Campion College and University of Regina, Regina, Saskatchewan, Canada
Acknowledgments
Four hundred years ago, in 1624, John Donne, poet and vicar at St. Dunstan-in-the-West, argued in a devotional work that, “No man is an island, entire of itself; every man is a piece of the continent, a part of the main”. This oft quoted piece (its masculine specificity aside) is prescient with respect to our times, and especially so with respect to the problem that is global warming. The idea of a book being written by a single author also finds resonance in Donne’s words, and in this case, it is very much the situation that many researchers have contributed to its assembled pages. As editor I thank all the contributing authors for their thoughts, ideas, ingenuity, enthusiasm, and conversations.
The impetus for starting what has become this book grew from conversations with Joseph Seckbach, Richard Gordon, and Martin Scrivener, and I thank them for all their help, patience, and assistance in this project. Many reviewers, and correspondents provided insightful, timely, and highly pertinent responses to my emails and questions as this book was in development. Other correspondents offered highly impertinent responses – but, such is the nature of the passions insighted by the topic at hand. To all, however, thank you, and perhaps the most important point is that the dialog continues. After all, it will only be through a merging of all voices, that we shall find the ways and means to negate, and reverse, the seemingly relentless climate, and ecological harms being wrought by both human actions, and inactions.
It is usual to provide a short personal dedication to a book such as this, but it seems appropriate, given the nature of its topic, to dedicate this book to the Roman god Janus, overseer of beginnings, and transitions, passages, and endings. Janus is typically shown with two opposing faces, to depict his ability to simultaneously see into the past, and also read the future, and it is this characteristic, to appreciate the lessons of history, and to work in good faith towards a better future, that humanity very much needs in the here and now. There is work to be done.
1Prolegomenon: A Geoengineering Primer
Martin Beech
Department of Physics, Campion College at the University of Regina, Regina, Saskatchewan, Canada
Abstract
Geoengineering encompasses many potential actions that set out to deliberately lower the aggregate temperature of the Earth’s atmosphere. Such actions typically look to enhance the Earth’s albedo, thereby causing a greater fraction of sunlight, over and above that at the present time, to be reflected back into space. Other actions seek to limit solar insolation by directly blocking sunlight, or by increasing cloud cover. This introduction seeks to examine not only how but why geoengineering might be deployed, but seeks to position it as a necessary part of future efforts directed towards combating global warming. A review is made of the various methodologies and protocols necessary for the future development and deployment of geoengineering actions.
Keywords: Global warming, geoengineering, tipping points, solar radiation management
1.1 Introduction
Geoengineering [1.1][1.2][1.3] is a big, bold and brash idea, possibly now coming of age. It is a human-directed process, taking-on many potential forms, all of which act upon the environment with the specific aim of changing the environment. The primary reason for and goal of geoengineering1 is to attempt the re-establishment of a common good—that is, to bring about a cooler Earth. Furthermore, geoengineering sits amongst the suite of actions that seek to address the principle causes of global warming [1.4]. This being said, geoengineering is often considered a controversial action, in part, because of the fact that it seeks to enhance human engagement with the environment, rather than reduce it. Importantly, however, while geoengineering seeks to cool the Earth’s atmosphere, it does not address the root cause issues that are driving the global warming problem. While geoengineering is a strategic ameliorating action, it is limited in scope.
That a decision concerning the deployment of geoengineering must to be made, and made very soon, reflects a remarkable, and inherently unsatisfactory state of affairs—a state of affairs that has grown out of past and present-day inaction. This stubborn inaction is related to the prolonged political and societal failure in addressing the underlying causes of global warming—especially in the form of greenhouse gas emissions derived from the burning of fossil fuels. It is now established beyond any reasonable doubt that the Earth’s average temperature is increasing, and compared to past millennia, it is increasing very rapidly. In the past one-hundred years alone, the global average temperature has increased by about 1.1 °C [1.1][1.2][1.3]. Global warming, in spite of tergiversate counter arguments, is indisputably happening, and it will be with us for many centuries to come. Indeed, even if all anthropogenic derived greenhouse gas emissions stopped this very instant, the present levels of atmospheric CO2 will continue to drive a significant increase in the Earth’s temperature. The question is not whether global warming will continue to occur, but rather, what can be done now, and over the next several decades, to offset the worst of the changes that are latent within Earth’s climate system [1.4][1.5].
1.2 The Paris Agreement
While the reasonability of using the Earth’s average temperature as the only measure of climate change is questionable [1.6], this quantity has, none the less, become the de facto measure of change. In this manner global warming is measured relative to the average temperature derived over the time interval from 1850 to 1900 (see Figure 1.1). This parameterization builds upon the notion that human actions (beginning with the onset of the modern industrial era) are at the core of the global warming phenomenon, and it further sets the goal of limiting future increases in temperature (above pre-industrial levels) to be as small as possible. Article 2(a) of the Paris Agreement contains the key motivation with respect to international efforts to curb global warming [1.7][1.8], specifically, the aim being to:
[Hold] the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change.
As with most political agreements, and especially international ones, the language promotes the positive, and downplays the devil in the details. The devil, in this case, is how to achieve the success of Article 2(a). The problem is not so much how to achieve this—of course, the solution is in fact quite clear—rather, the problem is how to overcome the political inertia (even outright hostility from some quarters) to enact and abide by policies that will dramatically reduce the emission of greenhouse gases due to anthropogenic actions. The Paris Agreement may well indicate a landmark moment in political diplomacy, but the proof by which it will be judged in the future will depend entirely upon the meaningful and timely actions taken by individual governments over the next several decades. Indeed, it is highly likely that the goals of Article 2(a) will not be achieved [1.9], with the global average temperature most likely exceeding 1.5 °C above pre-industrial levels by the mid-point of this century, if not sooner (Figure 1.1).
Geoengineering is motivated according to the dramatic increase in the Earth’s average temperature during the last century (as per Figure 1.1)—the desire being to reduce its continued increase prior to the implementation of direct actions to limit and sequester greenhouse gas emissions. While the average global temperature provides a measure of how much the Earth is warming, detailed computer modeling and ground-based observations indicate that the warming is not uniform across the globe. Indeed, warming is most pronounced in northern latitudes and especially so over land masses. Figure 1.2 shows the results from a series of detailed model calculations, performed under the guise of the Coupled Model Intercomparison Project Phase 6 (GMIP6). At a 1.5 °C temperature increase over the (1850–1900) average—similar to the Earth’s present status—it is seen that the northern boreal and Arctic regions are seeing the greatest temperature increases, with the equatorial and southern hemisphere temperatures seeing smaller temperature changes. At 4 °C average temperature change, the northern latitudes are still most dramatically affected, but now all landmasses and the Antarctic regions begin to see significant temperature increases. In general, at a given latitude, the landmass temperature increase is about twice that found over the ocean. This is partly a result of the oceans having a larger thermal inertia, and partly due to mixing with deeper, colder water layers that have not been exposed to surface warming. Changes in the Arctic are larger than those at mid-latitudes in part due to a strong temperature/albedo positive-feedback mechanism that operates there. The regional effects of temperature change are complex and difficult to model in detail, but are generally discussed in terms of tipping points.
Figure 1.1 Change in global average temperature during the past 2000 years, inferred (blue line) from proxy tree-ring, coral growth, and ice-core data [1.10], and measured (red line) since 1880.
(Image adapted from https://commons.wikimedia.org/wiki/File:Common_Era_Temperature.svg)
Figure 1.2 Projected changes in regional temperature (relative to 1850–1900) for global average warming amounting to 1.5 °C (top) and 4.0 °C (bottom).
(Diagram based on Coupled Model Intercomparison Project Phase 6 (CMIP6) calculations)
1.3 Tipping Points – Where Are We?
Current projections by the Intergovernmental Panel on Climate Change (IPCC) indicate that the Earth is likely to warm by at least 2 to 3 °C by the end of this century, and this increase will risk, if not fully guarantee, the triggering of multiple highly consequential tipping points. Indeed, tipping points delineate and underscore the risks associated with global warming. They highlight those moments and conditions under which an abrupt and rapid change, from one system state to another, takes place in an irreversible manner [1.11]. Tipping points are a characteristic phenomenon of nonlinear systems, and once breached they cannot be reset by simply reversing the driving parameters that caused the change in the first place. In the passing of a tipping point, what were previously system-stabilizing, negative feedback, mechanisms become overpowered by system-destabilizing, positive feedback mechanisms, with the system experiencing continuous change until a new equilibrium state is found. Problematically, the Earth’s climate-determining system is composed of numerous nonlinear, subtly interacting subsystems, each operating on different size and time scales, and, as such, it is an extremely complicated system to model. A recent study by McKay et al., however, has identified 16 tipping point thresholds that may be breached by 2100 [1.12]. These include the collapse of polar ice sheets, large-scale permafrost thawing, large-scale forest and coral reef diebacks, monsoon disruption, and the collapse of ocean circulation currents (Figure 1.3). Passing the threshold for any one of the tipping points listed by McKay et al. would be cause for concern, and it appears that some may have already been set in motion. Even at the present 1.1 °C warming over pre-industrial levels, it is likely, according the McKay et al., that five tipping points have been triggered, putting low-latitude coral reefs, boreal permafrost zones, polar ice sheets (including the Greenland ice sheet, the ice on Barents Sea, and the West Antarctic ice sheet) and the subpolar (Labrador Sea) gyre, at risk of collapse. Indeed, McKay et al. find that even at the 2 °C limit set by the 2015 Paris Agreement, multiple additional tipping point thresholds could be triggered, including those of Amazon Forest dieback, mountain glacier loss, and West African monsoon change. At global warming in excess of 4 degrees of pre-industrial levels, the tipping point threshold for the collapse of the entire Antarctic ice sheet could be breached. In light of the slow progress in achieving meaningful greenhouse gas reductions, geoengineering may well be the best near-term option with respect to avoiding the worst outcomes with respect to tipping point-driven changes.
Figure 1.3 Locations of climate tipping points.
(Image courtesy of Stockholm University [1.12])
1.4 The Size of the Problem
As indicated earlier, the driving force behind global warming is the anthropogenic release of greenhouse gases—especially carbon dioxide through the burning of fossil fuels. While the onset time for such emissions can be dated back to the 18th century, and the beginnings of the industrial revolution, it is really the relentless emission activity during the past half-century that has seen global warming reach problematic levels. Furthermore, during this same time interval a distinct disconnect between human society and nature has come about, with human society increasingly acting as a self-regulating entity distinct from, and exterior to, the natural world, which in turn is seen as a pure resource to indiscriminately exploit [1.13, 1.14]. Indeed, during the past century, human society, industry, and governments have increasingly positioned themselves as the owners of nature, to do with, and use as they please. This positioning stands in stark contrast to the fact that human beings are an evolved and integral part of the natural world, towards which they could act as a much better guardian, and steward. These seemingly ingrained attitudes, putting short-term gain over long-tern governance, have resulted in the unmitigated failure of society and governments to act, in any meaningful and truly substantive way, against the continued onslaught of greenhouse gas emissions. It has been the slow progress in addressing the long-term solution to such emissions that has opened the door to geoengineering options, making it an important, if not vital, part of our considerations moving forward.
By identifying anthropogenic actions as the primary cause of global warming, the solution to the problem is also identified. Indeed, to reiterate, the only long-term solution to global warming in the present epoch is for humanity to move beyond the indiscriminate use of fossil fuels. Not only must the means be found to curb greenhouse gas emissions, so too must ways be found to extract excess greenhouse gases (especially CO2 and CH4) from the atmosphere. This latter task, however, will require a massive investment in new technologies, and a Herculean cleansing program that will occupy the efforts of multiple human generations well into the future. The atmospheric concentration of CO2 (as of May 2022) amounts to 421 ppm, which translates to an atmospheric mass fraction of about 3.2 teratons (the total mass of Earth’s atmosphere is about 5 petatons). At the present time, human activities result in something like 40 gigatons of CO2 being added to the atmosphere annually, and the total estimated CO2 emissions since the beginning of the industrial revolution (that is, since circa 1760) is of order 2.2 teratons. To remove, say, 4 gigatons of CO2 from the atmosphere (i.e., about 0.1% of the total mass of CO2 at present), some 0.5% of the entire mass of the atmosphere (of order 25 teratons in total) will need to be sampled and scrubbed (assuming 100% efficiency in CO2 removal).2 And, this massive sampling, removal, and sequestration process will need to continue year upon year, for centuries, in order to bring the present-day atmospheric CO2 concentration down to near pre-industrial levels. While CO2 reduction and sequestration are usually discussed in terms of capture from the atmosphere, there is no reason why it cannot additionally be drawn down by extraction from the oceans, and/or by enabling enhanced weathering by surface rocks. All three of these sequestration actions (and others) will need substantive development, however, in order to reduce CO2 concentrations.
While the abundance of atmospheric CH4 (presently determined as 1895 ppb) is much lower than that of CO2, it is a much more potent greenhouse gas. Indeed, it is some 80 times more potent than CO2 during its first 20 years following release into the atmosphere, and about 30 times more potent a century after release [1.15][1.16][1.17][1.18]. Furthermore, it is estimated that by the mid-point of this century, the radiative forcing from methane will be on-par with that of CO2 in spite of its much lower atmospheric abundance [1.18]. There are in principle many ways in which CO2 and CH4 could be scrubbed from the atmosphere; the problem, however, is how to make the processes a) affordable, and b) buildable on a scale large enough to be globally effective [1.19].
1.5 Geoengineering – Where, When, and How?
The process of geoengineering is old, and in many ways, human society has been changing the landscape and atmosphere through farming, land clearance, water management, and industrial pollution for thousands of years [1.20]. In its modern guise, however, geoengineering is generally seen as the initiation of directed human actions to lower the Earth’s temperature. The first important study on climate change, which additionally introduced the idea of geoengineering as a means to combat it, can be found in the US President’s Science Advisory Committee report for 1965 [1.21]. This report identified the future longterm threat of global warming, and correctly identified anthropogenic CO2 emissions as the key driving agent for such warming. Ironically (in retrospect) the report further reasoned that geoengineering actions could be applied to limit global warming, but made no recommendations to actually curb greenhouse gas emissions. Geoengineering, as a deliberate action, was brought to the forefront of attention in a series of articles published by Paul Cruzen [1.1] in the early years of this century, and since that time numerous geoengineering actions have been identified and proposed as a means of reducing Earth’s temperature. Indeed, Figure 1.4 indicates 5 domains in which geoengineering actions might be deployed. Region 1 is the Earth’s surface, where in principle both the land and ocean reflectivity at shorter wavelengths of radiation can be increased—this enhances the Earth’s albedo term. Region 2 looks to enhance the Earth’s albedo by increasing the reflectivity of marine clouds in the lower troposphere. Region 3 takes us to the stratosphere, where the introduction of specific aerosols can be deployed to enhanced atmospheric albedo. Region 4 is above the atmosphere and here methods seek to interpose some form of physical shield (or light diffusing system) between the Earth and the Sun, thereby reducing the level of insolation. The final region, Region 5, illustrated in Figure 1.4, might see attempts to decrease the amount of high-altitude (upper troposphere) cirrus cloud, this action allowing for the enhanced escape of longer wavelength infrared radiation from the Earth’s surface.
While it is reasonably clear that the Earth’s temperature can be moderated by direct anthropogenic actions, the general consensus has been that such actions should only be initiated as a last resort—although when such a threshold for action might be attained has never been clearly articulated. In a very real sense, there appears to be a tipping point for the onset of geoengineering. The reluctance to initiate geoengineering options, on a global scale or even at a local level, is understandable since it does not address the root cause of global warming [1.2][1.3]. Indeed, many of the geoengineering methodologies seek to introduce substances (e.g., iron and sulfur dioxide) into the oceans and atmosphere that carry their own burden of potential health risks and environmental degradation. Injecting aerosol particles into the stratosphere, for example, may enhance ozone destroying reactions, and result in enhanced acid rain deposition. Furthermore, computer models indicate that while the initiation of geoengineering actions might benefit some nations and regions, it could be disastrous to the peoples and economies of others, and accordingly the aim of working towards a common good becomes highly debatable [1.5]. Indeed, while there are many unknowns, it is the unknown unknowns (Rumsfeld’s second kind of unknows3) that currently bedevil many aspects of geoengineering modeling.
Figure 1.4 A schematic illustration of several geoengineering options. The regions in which geoengineering takes place is either above the atmosphere, as in the deployment of space-based shields, or in the stratosphere, tropopause, and lower atmosphere, right down to the land and ocean surface.
(Image courtesy Chelsea Thompson, NOAA/CIRES)
Although not specifically defined, the triggering threshold for introducing geoengineering actions has already, many would argue, been breached. Accordingly, it is perhaps time to reframe the notion of geoengineering [1.22]. Rather than seeing it as a last-ditch action, geoengineering could be reinterpreted as a useful first response, and a vital component in the toolbox of options looking to limit the effects of global warming. Indeed, geoengineering can be reframed as a means not only of moderating the Earth’s temperature, but as a way of extending the timeframe for the establishment of practical protocols that will see nations move away from fossil fuel dependency. Furthermore, the initiation of geoengineering options could provide additional time for the development and deployment of those technologies aimed at removing and sequestering atmospheric CO2. Under this reframing, geoengineering is seen as a temporary action and not as a permanent solution to global warming. In this manner, by including geoengineering options early on as an integral part of Earth-cooling initiatives, working in tandem with CO2 sequestration and emission reduction options, the current slow progress towards meaningful societal and political change might be accommodated. Accordingly, part and parcel of any reframed geoengineering option should be a clear understanding of how long it might be applied for, in combination with progress of sequestration methods, before it can be stopped. The goal of geoengineering should not be to enter into a permanent state of climate control,4 although it seems reasonably clear that the timescale for such actions will be at least of the order of centuries [1.23]. Geoengineering is, if nothing else, a multigenerational commitment.
Figure 1.5 indicates the potential role of geoengineering within the context of future CO2 emission projections [1.2]. The horizontal axis indicates the passage of time, from the recent past on into the relatively near future, with the middle of the time axis corresponding to, say, 2100. The vertical scale schematically indicates the impacts of global warming—with an increase along this axis taken to mean more extreme weather conditions, crop failures, food shortages, and worsening biosphere degradation. The business-as-usual curve shown in Figure 1.5 indicates the situation if no reductions are imposed upon fossil-fuel consumption and emissions. In this case, global warming, and all its associated ill effects will continue to grow. The effect of cutting greenhouse gas emissions is illustrated by the (black) curve in Figure 1.5. The effect of cutting greenhouse gas emissions and actively developing sequestration and CO2 removal technologies is illustrated by the green curve. The potential benefits of adding a geoengineering option to the greenhouse gas reduction and sequestration efforts is illustrated by the blue arrows. The key (schematic) action in this case is to lower (indeed, “shave-off”) the peak of the CO2 emission cuts and sequestration (green) curve [1.2]. What geoengineering brings to the narrative, therefore, is a potential easement of the worst effects of climate change that otherwise lies ahead of us [1.2][1.3][1.7]. Once the atmospheric CO2 levels have been reduced to near pre-industrial levels, geoengineering actions can be halted—this introduces the (finite) geoengineering time scale tgeo. Admittedly, tgeo is presently a poorly constrained quantity, but this is largely a result of there being no good timescale estimates for initiating a meaningful move away from our fossil fuel dependency, and on the development and deployment times for introducing effective CO2 extraction and sequestration technologies. The longer these latter two timescales run on, the longer tgeo will need to be.
Figure 1.5 Schematic trajectories for future climate change outcomes. The action of geoengineering (indicated by the downward blue arrows) is to “shave the peak,” and thereby lessen the climate impacts that would otherwise come about. The timescale of geoengineering actions tgeo is dependent upon how soon meaningful emission cuts begin and upon the development timescale for CO2 removal technologies. See text for details.
(Image adapted from [1.2])
Reframing geoengineering actions within the context of reducing greenhouse gas emissions and implementing vigorous sequestration programs, reenergizes the need for research (and the funding of that research) in potential Earth-cooling initiatives. Furthermore, the reframing requires the development of clear protocols for testing and developing geoengineering options: who will oversee such trials, how much will they cost, who will pay for them, and who should be in charge of any eventual implementation. Indeed, it is still far from clear if any of the proposed geoengineering options can be realistically made to work at the large scale required to produce a meaningful Earth-cooling effect. In addition to developing these new research directions, it will also be vital to determine what are the short- and long-term risks, both to the environment and human societies, associated with geoengineering actions [1.24][1.25]. In parallel with Newton’s third law of motion, for every action there is an equal and opposite reaction: geoengineering is neither a neutral nor an equitable option. Indeed, geoengineering, if implemented rashly and/or inappropriately, could make the present climatic situation much worse [1.6][1.26].
Figure 1.6 illustrates an attempt to arrange the anticipated effectiveness and costs of several potential geoengineering options [1.2][1.3]. In the upper right-hand corner of the diagram are the most effective, but most expensive options, and here we presently find the carbon reduction and sequestration (CO2 capture) strategies. Ideally, these strategies would plot to the upper left in the diagram, but such is not our present reality. In terms of estimated high effectiveness, the orbital sunshades [1.27][1.28] and stratospheric aerosol injection methods take us through the medium to lower cost options. Grouped in the middle of the diagram, in terms of estimated costs and ease of deployment, along with an estimate of their effectiveness, are the cloud albedo enhancement, and ocean iron fertilization options. Techniques for the modification of surface albedo are estimated to come in at a mid-range cost, but are deemed to have a relatively low climate modification benefit.
Figure 1.6 A schematic comparison of geoengineering options in terms of their estimated implementation and running costs versus the estimated climate benefits that would result from their implementation.
(Diagram adapted from [1.2][1.11])
At the present time, the leading geoengineering proposal, in terms of estimated costing and climate cooling effectiveness (i.e., a process plotting in the upper left-hand corner of Figure 1.6) is that of stratospheric aerosol injection [1.2][1.3]. This particular option is based upon presently available technologies (e.g., aircraft, balloons, and artillery shells), and is in principle ready for rapid (on a timescale of decades) deployment. Smith [1.29] has outlined a detailed operations plan, starting 2035 to 2040, for the deposition of sulfur dioxide, or sulfuric acid, into the stratosphere via high-flying aircraft. Smith envisions that by 2100 a fleet of some 100 to 1000 such aircraft (similar in design to the B-47 Stratojet) would be making daily flights, each with payloads of some 15.7 tons, to altitudes of about 20 km. Once the aircraft fleet has been assembled, the estimated cost of running the program will amount to some $18 billion per year per degree of cooling being sought.
There is a natural analog to stratospheric aerosol injection in the form of volcanic outburst emissions [1.30]. Key to the process is the injection of sulfur dioxide (SO2) high into the atmosphere, where it can react chemically to produce sulfuric acid (H2SO4) aerosols (Figure 1.7). These latter aerosols act to enhance the atmospheric albedo by reflecting additional sunlight back into space. In practice, and in contrast to stratospheric aerosol geoengineering, the short-term (of the order of years) cooling effect from volcanic sulfur dioxide release, can be off-set by the longer-term warming resulting from the concomitant emission of carbon dioxide [1.31]
