SRM Science 2015 – Engineering the Climate
March 12 – 14, 2015 - Cambridge, UK.
Programme At A Glance
Thursday, March 12, 2015
18.00 – 19.30
Welcome Reception and Registration
Fitzwilliam Museum
Friday, March 13, 2015
08.00 – 09.00
Registration and Coffee
LR4 & Marquee
09.00 – 09.30
Welcome and Introduction
LT0
09.30 – 10.00
Keynote Lecture: Ken Caldeira
LT0
10.00 – 10.30
Keynote Lecture: Phil Rasch
LT0
10.30 – 11.00
Coffee
LR4 & Marquee
11.00 – 12.30
Technical Session 1: Climate Modelling
LT0
12.30 – 14.00
Lunch
LR4 & Marquee
13.30 – 14.00
Lunchtime Perspectives
LR6
14.00 – 14.30
Keynote Lecture: Duncan McLaren
LT0
14.30 – 15.00
Keynote Lecture: Lynn Russell
LT0
15.00 – 15.30
Coffee
LR4 & Marquee
15.30 – 17.00
Technical Session 2: Impacts, Implications & Consequences LT0
19.00 – 21.00
Panel Discussion
LMH, Sidgwick Site
Saturday, March 14, 2015
09.00 – 09.30
Coffee
LR4 & Marquee
09.30 – 10.00
Keynote Lecture: David Keith
LT0
10.00 – 10.30
Keynote Lecture: David MacKay
LT0
10.30 – 11.00
Coffee
LR4 & Marquee
11.00 – 12.30
Technical Session 3: Engineering Systems
LT0
12.30 – 14.00
Lunch
LR4 & Marquee
13.30 – 14.00
Lunchtime Perspectives
LR6
14.00 – 14.30
Keynote Lecture: Tom Ackermann
LT0
14.30 – 15.00
Keynote Lecture: Matthew Watson
LT0
15.00 – 15.30
Coffee
LR4 & Marquee
15.30 – 17.00
Technical Session 4: Atmospheric Effects
LT0
19.00 – 21.00
Conference Dinner
Trinity College
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Contents
Welcome Message
4
Keynote Lectures
5
Technical Sessions
9
Lunchtime Perspectives
21
Posters
24
Maps
37
Suggestions for Friday dinner
39
Notes
40
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Welcome to SRM Science 2015
We are extremely pleased to welcome you to this conference on Solar Radiation Management
Science. Solar Radiation Management (SRM) has been proposed as a form of climate engineering
that could be rapidly deployed to reduce global mean temperatures. SRM techniques include
stratospheric aerosols, cloud brightening, space-based reflectors and surface albedo
enhancement. These techniques attempt to offset some of the effects of increasing greenhouse
gases, namely by reducing absorption of solar radiation. SRM does not address the root cause of
climate change, and does not eliminate the urgent need to reduce global carbon dioxide
emissions. Apart from the scientific uncertainty surrounding SRM, there are ethical, political and
social issues that also need to be addressed.
This conference is being hosted by the Stratospheric Particle Injection for Climate Engineering
(SPICE) Project at the Department of Engineering, University of Cambridge. The primary purpose
of the conference is to provide a forum for scientists and engineers to present and discuss recent
research results in a manner that is comprehensible to all participants. There will be four technical
sessions on atmospheric chemistry, climate modelling, engineering systems and impacts,
implications and consequences. These sessions will be interspersed with keynote lectures from
leading scientists, and a panel discussion that examine topics such as trust, justice, intention and
responsibility. With accountability and reflectiveness woven into every session, this conference
will provide a forum for participants to discuss the practicalities of SRM, with a particular focus on
identifying the ‘known unknowns’ and future research priorities.
We hope that you will find this conference to be a stimulating, thought-provoking and
constructive experience.
Welcome to Cambridge!
Hugh E. M. Hunt
Conference Chair of SRM Science 2015
University of Cambridge
Organizing committee
Hugh Hunt - Conference Chair (University of Cambridge)
Kirsty Kuo - Conference Secretary (University of Cambridge)
Chris Burgoyne (University of Cambridge)
Jack Stilgoe (University College London)
Don Grainger (University of Oxford)
Matthew Watson (University of Bristol)
Stephen Watson (University of Cambridge)
Advisory Group
Oliver Morton (The Economist)
Duncan McLaren (McLaren Environmental)
Stefan Schaefer (IASS-Potsdam)
Phil Rasch (Pacific Northwest National Laboratory)
Ken Caldeira (Stanford University)
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Keynote Lectures
Ken Caldeira (Stanford University)
Solar geoengineering, hydrology, and land plants
9.30am, Friday March 13, 2015
There have been a number of studies showing that a high-CO2 world with solar geoengineering
would have less precipitation than would a high-CO2 world without solar geoengineering. This
talk will review the physics behind this finding and discuss what it means for water availability on
land, including consequences for land plants.
Before there is any appreciable change in global mean temperature, an imposed radiative forcing
can affect the vertical stability of the atmosphere, clouds and other aspects of the climate system.
These responses collectively are known as the ‘fast response’ to an imposed climate forcing.
Later, as the Earth heats up additional changes occur to the climate system as a consequence of
this heating. These responses collectively are known as the ‘slow response’ to an imposed climate
forcing. To a first approximation, fast and slow responses sum linearly to produce the overall
climate response to a forcing.
The fast response to an increase in atmospheric CO2 leads to a moistening of the atmospheric
boundary layer, particularly over the ocean. Over land, the stomata of plants close, reducing
evaporation over land. Solar geoengineering reverses the warming-induced increase in
precipitation associated with the slow-response to excess CO2, revealing the decrease in
precipitation associated with the fast response to CO2.
Because, globally, precipitation must equal evaporation, reductions in evaporation must
necessarily cause reductions in precipitation, but reductions in precipitation do not necessarily
imply a drying of the land surface or insufficient water supply to land ecosystems. Precipitation
minus evaporation equals net atmospheric water vapor transport to an area, and in steady state
also equals runoff. Model parameters such as river runoff and net primary productivity of
ecosystems provide a window into what hydrological cycle changes would likely mean for land
plants.
This talk will discuss what reduced evaporation and precipitation mean for the hydrological cycle
on land, and especially what it is likely to mean for land plants. Results will be shown from
GeoMIP and other climate model simulations.
Phil Rasch (Pacific Northwest National Laboratory)
On using models to understand Climate Engineering: "all models are wrong,
but some are useful".
10.00am, Friday March 13, 2015
Scientist’s best and most careful attempt to provide quantitive understanding and characterization
of Earth’s climate (and its component processes and features) are encapsulated by models. A
great deal can be learned from models with carefully thought through studies, yet they are
inherently incomplete and imperfect renditions of the Earth System. In this talk I will discuss: 1)
some of the limitations of models, 2) identify classes of conclusions are likely to be robust, 3)
outline where one must be cautious or skeptical in interpreting their results for issues relevant to
climate engineering, and 4) identify opportunities for improving the situation.
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David MacKay (University of Cambridge)
What is the scale of successful climate change action?
2pm, Friday March 13, 2015
This talk will explore the assumptions underlying scenarios that halt anthropogenic climate
change, examining the role and scale of deployment of technologies such as bioenergy and
carbon capture and storage. Typically these scenarios envisage, this century, the creation of a
carbon burial industry five times as big as today's oil industry. The recently published Global
Calculator (globalcalculator.org) allows alternatives and trade-offs to be explored. The talk is
intended to motivate an openness to research into deliberate carbon dioxide removal and solar
radiation management.
Lynn Russell (University of California, San Diego)
What are the possible ecosystem impacts of SRM?
2.30pm, Friday March 13, 2015
Climate engineering methods are intended to reduce climate change, and sunlight reflection
methods (SRM) are designed to increase the Earth’s albedo by increasing by a small percentage
the fraction of incoming sunlight that goes back into space. This cooling effect causes an offset
in the warming from greenhouse gases. However, this shortwave cooling does not perfectly
offset greenhouse gas warming (GGW). SRM targets incoming solar radiation, which is higher
near the equator than the poles, making the cooling also concentrated in lower latitudes. SRM
changes atmospheric temperatures at both the surface and aloft, creating differences in both
evaporation and precipitation of water. However, since GGW also changes the hydrological cycle
in many regions, current research suggests that SRM might diminish the impacts of climate
change on ecosystems by reducing changes in temperature as well as precipitation. There are
also concerns that reducing the fraction of direct sunlight that reaches the surface could affect
net primary productivity. Certainly the biggest concerns about SRM is that it would be carried out
in the absence of substantive carbon dioxide mitigation efforts, in which case sudden cessation of
SRM would exacerbate rather than alleviate the climate effects on ecosystems. The many risks
and uncertainties associated with these new kinds of purposeful perturbations to the Earth system
are not well understood and require cautious and comprehensive research.
David Keith (Harvard University)
An environmental case for solar geoengineering
9.30am, Saturday March 14, 2015
The combination of inertia and uncertainty makes the coupled climate-human system dangerously
hard to control. Emissions cuts are necessary to manage climate risks, but they are not
necessarily sufficient. I will argue for a broad solar geoengineering research program--from
laboratory to outdoor field experiments--that aims to develop new technologies that can limit
climate risks while minimizing side effects. I will show new results on human health impacts and
on the use of solid artificial aerosols in the stratosphere. Finally, I will discuss the public policy of
deployment suggesting strategies that are moderate, temporary and responsive.
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Duncan McLaren (McLaren Environmental)
Science and Ethics in the Anthropocene
10.00am, Saturday March 14, 2015
With great power comes great responsibility. As a paradigmatic ‘Anthropocene’ technology SRM
promises power to change not only the world, but also our very conceptions of what it is to be
human. In this context ethics and science cannot be disentangled. With reference to the
experiences of the SPICE project, I will explore some lessons for SRM research from ethics and
social science, and how SRM science might help us understand the changing nature of ethics in
the Anthropocene.
I intend to highlight the socially embedded and ethically loaded nature of technology, drawing
lessons from science and technology studies and from psychological and cultural research. I will
explore how increased public engagement and deliberation, and reflexive consideration of
research design and reporting could both build trust in SRM science, and enhance it substantively,
with ways to recognise and help avoid the so-called ‘moral hazard’ and ‘slippery slope’ problems. I
will suggest further ‘opening up’ of the geoengineering debate with recognition and respect for
diverse cultural values and epistemological positions, and better understanding of the political and
social context of research, including its justice implications for present and future generations.
The scope of SRM to determine the living conditions of all of humanity, and of SRM science to
reveal new knowledge and identify new unknowables about earth systems arguably change the
nature of ethics. I will suggest that we must reconsider virtue ethics as well as the
consequentialist philosophies that dominated the 20th century. I will suggest some ways in which
approaches to justice that draw on recognition and capabilities appear better suited to address
the implications for both people’s functioning and freedoms. I will discuss concepts of climate
restoration in the context of lessons from ecological and architectural restoration to suggest that
new forms of a ‘virtue of repair’ will be needed.
I will conclude with an urgent call for continued SRM science which can inform and be informed
by an open, deliberative and reflexive politics of social resilience and reconciliation in our
engagement with the climate and other environmental systems.
Tom Ackermann (University of Washington)
A Limited-Area Field Test of Marine Cloud Brightening
2pm, Saturday March 14, 2015
Ship-tracks demonstrate that the microphysics of marine boundary layer clouds can be and are
being modified by aerosol emissions. Marine cloud brightening (MCB) proposed as a climate
engineering strategy requires that cloud microphysics can be modified in a predictable way using
particles of known composition and size generated in a controlled manner. Our research
consortium has developed a plan for a limited-area field test of MCB that will provide much
needed data on the dispersion of aerosol in the boundary layer and the modification of boundary
layer clouds by interaction with a well-characterized aerosol population. It is also environmentally
benign
Our experimental design incorporates several phases:
1.
Design and development of a sprayer to produce seasalt aerosol at the rate of at least
1015 particles per second. A prototype nozzle has been developed and demonstrated in the
laboratory.
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2.
Testing of a sprayer incorporating many nozzles in the atmospheric boundary layer. This
phase requires locating the sprayer at an outdoor site and monitoring the generation and
dispersion of the seasalt particles in space and time.
3.
Testing the interaction of the aerosol with boundary layer clouds. Given the high cost of
ship time, we propose an initial test in a coastal environment that experiences incursions of
marine clouds.
4.
Testing the interaction of the aerosol with boundary layer clouds in the marine
environment. This phase requires the ability to place the sprayer or sprayers onboard ships in the
coastal marine boundary layer.
This phased approach is intended to examine physical processes under controlled conditions and
in sequential steps. Data from these phases will have considerable relevance to the general
science of aerosol interaction with clouds and the indirect aerosol effect. The latter is one of the
largest uncertainties in changes in radiative forcing in climate models and we have very little data
with which to address it.
There are, of course, ethical and governance issues associated with our experiment. Given
limitations of time, we briefly touch on some of these issues.
Matthew Watson (University of Bristol)
The SPICE Project
2.30pm, Saturday March 14, 2015
The Stratospheric Particle Injection for Climate Engineering (SPICE) Project will end in March
2015, and this talk will present the key findings and some of the lessons learned during the
course of the project. Key findings include the reactivity of titania and sulphates in the
stratosphere and their corresponding effects on ozone destruction; the scale and timescale of
engineering a tethered-balloon delivery systems; the feasibility of pumping sulphur dioxide; the
effect of SRM on Sahelian rainfall and the importance of modelling stratospheric dynamics in
order to capture effects such as northern hemisphere winter warming. The talk will also discuss
some of the legal, ethical and social issues encountered during the project, and how these
lessons can shape future research directions.
Page 8 of 45
Technical Session 1: Climate Modelling
Chair: Lesley Gray (University of Oxford)
Jim Haywood (Met Office)
Results from GEOMIP and SRM simulations with the Hadley Centre Model
11am, Friday March 13, 2015
The Geoengineering Model Intercomparison Project (GeoMIP) provides a framework for
comparing results from nominally identical idealised SRM geoengineering simulations. Initially,
GeoMIP established four baseline idealised scenarios (G1-G4) which modified the solar constant
(G1 and G2) and injected sulphur dioxide into the stratosphere (G3-G4). Based on these results
we will provide a brief overview of what "we know we know", "what we know we don't know",
and postulate on "what we don't know we don't know". Further specific results from the Hadley
Centre model (HadGEM2-ES) will be explored to provide a process level understanding of the
merits, perils and pitfalls of potential stratospheric SRM geoengineering schemes.
Scott Osprey (University of Oxford)
L. J. Gray, J. Haywood, S. Driscoll and A. Jones
The long-standing dynamical impacts of climate engineering using
stratospheric sulphate aerosol
11.20am, Friday March 13, 2015
Discussions of our response to climate change invariably involve issues of adaptation and
mitigation. The former presupposes unavoidable climate consequences and recognises a need to
lessen their impact. The latter attempts to lessen the effects of increasing greenhouse gases
(GHG) by (1) reducing GHG emission, (2) creating CO2 sinks (e.g. carbon sequestration) or by
blocking the effects of solar radiation (solar radiation management - SRM).
The SPICE project was set up to investigate the feasibility of implementing a practical method of
SRM using the stratospheric injection of aerosols. SPICE remit includes: engineering design for
the delivery of stratospheric aerosol, laboratory measurements for characterising the properties of
optimal aerosol, and modelling studies looking into the parameterisation and impact of
stratospheric aerosols within a state-of-the-art global climate model. The project has also pressed
for the need for governance of climate engineering research.
We describe idealised experiments investigating the environmental impact following sulphate
aerosol injection into the tropical low-mid stratosphere. We compare a geoengineering scenario
(GeoMIP G4), which includes a constant injection rate of SO2 (5Tg/year) beginning at 2020,
against a control simulation of increasing greenhouse gas forcing, as outlined by the CMIP5
RCP4.5 scenario. We use the well-documented stratosphere-resolving Hadley Centre model,
which has been employed in previous CMIP5 and climate engineering studies. We examine for
high-latitude impacts following tropical aerosol injection, and in particular the Holton-Tan effect
observed in the wintertime extratropical stratosphere. These dynamical sensitivities provide an
important link, bridging tropical stratosphere forcing with the near-surface response often seen at
high latitudes.
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Andrew Jarvis (Lancaster University)
Deeply ignorant rationality: A solar radiation management case study
11.40am, Friday March 13, 2015
For most geoengineering simulations deployment capability is assumed either explicitly or
implicitly. However, as we all know, this capability is governed by a broad range of critical factors
ranging from the imagined nature of the technology itself, through the uncertainties of its efficacy
in the real world, to the societal structures required to sanction, invest in, deploy and regulate
such technology. It would be impossible to expand current geoengineering simulation
experiments to fully embrace this range of practical and social issues, but there is at least one
aspect of this spectrum of unknowns that is open in part to simulation experiments using
standard climate models, namely the handling of uncertainites over the efficacy of a given
geoengineering intervention on deployment (Jarvis and Leedal, 2012; McMartin et al. 2013;
Kravitz et al. 2014).
Assuming a given technology such as stratospheric aerosol injection is technically deployable and
that governance structures exist to manage the deployment through setting objectives and
making the necessary strategic investments, then real world deployment to achieve these
environmental end goals is subject to the deep uncertainties surrounding what effect the
deployment will elicit. These uncertainties include knowing a priori how potent the technology is
and what side effects it elicits. Because these uncertainties cannot be resolved by improved
modelling efforts, any deployment will necessarily involve a significant element of learning-bydoing. The question that then arise is what form this learning-by-doing would and should take
and how, when coupled with the technology, will the process play out at least in terms of
managing environmental end points and the allied side effects?
In this study we exploit a Model Predictive Control (MPC) architecture to represent the necessary
learning-by-doing process that would be associated with controlling Artic sea ice loss using
stratospheric aerosol injection. The reason MPC is applicable in this context is because it shares
many features in common with candidate climate decision making frameworks. Firstly, as the
name suggests, decisions are guided using model-based predictions, a key element of the current
climate change science paradigm. However, a less appreciated but equally important element of
contemporary climate change negotiation is that long lead time predictions from e.g. climate
models, are adjusted in the short to medium term light of new observations and learning, a
process akin to MPC in that only first steps of a forecasted policy are ever considered before a
review cycle is used to re-evaluate the present position in light of the current observed state of
the system in question. Such review cycles are ubiquitous in environmental management
applications because of the deep uncertainties surrounding the prediction of the response of
environmental systems to human interventions.
In the Artic sea ice application considered here, models are used to forecast the (optimal)
response of the summer extent of ASI in response to scheduled sulphate aerosol injections.
However, because of the imperfect nature of these forecasts, a review cycle is then used to reevaluate the aerosol injection schedule in light of the observed performance. Obviously this is a
simulation exercise and so we take as our virtual reality a climate model to represent to real
world. This model is genuinely complex and hence the relationship between the point injection of
stratospheric aerosol and Artic sea ice extent (and the associated side effects) is an emergent
property that cannot be accurately predicted given we approach this simulation ‘blind’ i.e. without
the benefit of having performed it previously on this model. That said, we clearly know much
more about this model than we do the real world!
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Although highly contrived, a meaningfully challenging learning-by-doing simulation presents itself:
How to restore Artic sea ice extent to some desirable value within some achievable timeframe
using sulphate aerosol injection? Furthermore, we place further constraints on this exercise in
order to present additional challenges as might be experienced in reality. These include; only
being able to observe the state(s) of our systems imperfectly; restricting the speed with which we
can deploy a technology; only having access to limited portions of the stratosphere due to
technological restrictions; and our system experiencing significant exogenous shocks particularly
from volcanic events. The net effect of these restriction is that we approach the task rationally,
but from a position of deep ignorance.
Jarvis AJ, Leedal DT. (2012) The geoengineering model intercomparison project (GEOMIP): A
control perspective. Atmospheric Science Letters, 13, 3, p. 157-163
MacMartin DG, Kravitz B, Keith DW, Jarvis AJ. (2013) Dynamics of the coupled human–climate
system resultingfrom closed-loop control of solar geoengineering. Climate Dynamics, DOI
10.1007/s00382-013-1822-9
Kravitz BS, MacMartin D, Leedal DT, Rasch PJ, and Jarvis AJ. 2014. Explicit Feedback and the
Management of Uncertainty in Meeting Climate Objectives with Solar Geoengineering.
Environmental Research Letters 9(4):Article No. 044006. doi:10.1088/1748-9326/9/4/044006
Stephen Salter (University of Edinburgh)
Can we get a win-win result for the side effects of marine cloud brightening
by use of coded modulation of condensation nucleus concentration?
12.00am, Friday March 13, 2015
Until now the spray patterns used by climate modellers have not exploited the mobility and rapid
response of spray vessels, the phase of monsoons or el Nino, or the expectation that for short
summer periods there should be increased susceptibility at high latitudes giving a chance of
saving Arctic ice. They have shown that spray could offset the thermal effects of double
preindustrial CO2 but that, depending on local conditions, it does not always produce cooling.
They show that spray can affect precipitation in both directions far from the spray source and that
the largest reductions in precipitation are over the sea with some useful gains over drier land.
What we need to know is what happens everywhere from spray anywhere at any time and in any
conditions.
This might be done by adjusting model settings of the concentration of condensation nuclei by
multiplying or dividing initial values in different patterns at a number of spray regions and
correlating each of the sequences with subsequent model predictions for observing stations
around the world. Subsequent analysis of subsets of the same model results can reveal the
effects of Boolean combinations of groups of spray regions and the influence of the phases of
monsoons and el Nino without need for more model runs.
The usefulness of the technique can be judged from the scatter of predicted transfer function
results from a number of model runs with code sequences changed for each source and each run.
A number of artificial changes of temperature with different magnitudes to a real temperature
record can be detected with a precision of 1 or 2% of the standard deviation of the record. This
would require a very expensive thermometer. The effects of spray on precipitation has been
tested as part of a PhD by Ben Parks at Leeds. He showed that for most regions, the scatter of
results was usefully below the magnitude of the change.
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Nobody has yet tried variation of spray patterns in the light of day-to-day meteorological
observations. This omission is the equivalent of road-testing vehicles with the driver blind-folded
and the steering locked.
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Technical Session 2: Impacts, Implications&
Consequences
Chair: Naomi Vaughan (University of East Anglia)
Piers Forster (University of Leeds)
J. A. Crook, L. S. Jackson, S. M. Osprey
Potentially damaging precipitation side effects from solar radiation
management
3.30pm, Friday March 13, 2015
Intentional modification of Earth’s climate by solar radiation management (SRM) can restore
global mean temperature in climate model simulations but is expected to cause regional shifts in
precipitation. In simulations of twenty-first century climate using the UKMO HadGEM2 climate
model, we assessed the impact of SRM on 2040-2059 mean precipitation applying SRM from
2020 and using RCP4.5 for projected changes in greenhouse gas and aerosol concentrations. We
simulated the impact of one regional scale SRM method (desert albedo modification) and three
large scale geoengineering methods (ocean albedo modification, marine cloud brightening, and
stratospheric sulphur injection). All SRM methods decreased global precipitation compared to
RCP4.5 with the change occurring rapidly after the start of geoengineering while global mean
temperature cooled. Once global mean temperature resumed its warming trend, global
precipitation resumed its increasing trend tracking the rate of precipitation increase in RCP4.5.
Desert albedo modification produced a large decrease in precipitation over land, particularly in the
tropics (e.g. extreme drying over northern South America, the Sahel, India, and parts of China).
Precipitation changes for ocean albedo modification, marine cloud brightening and stratospheric
sulphur injection, were greatest over tropical oceans. A decrease in precipitation south of the
equator and an increase to the north was consistent with a northward shift in location of the
ascending branch of the Hadley cell circulation. Although precipitation changes over the global
land area were small relative to the global ocean, there were large regional scale changes over
land (e.g. wetting of the Sahel) that were strongly correlated with changes in net atmospheric
radiative cooling. To assess the significance of precipitation changes over land, we applied bias
correction to adjust the 2040-2059 global mean temperature under SRM to its 1986-2005
climatology and compared 2040-2059 precipitation to RCP4.5 and its 1986-2005 climatology.
Regional changes to precipitation over land where SRM either magnified the difference between
RCP4.5 and climatology or over-compensated for RCP4.5 changes were widespread. We
conclude that large scale SRM could result in potentially damaging changes to regional scale
precipitation.
Ben Kravitz (Pacific Northwest National Laboratory)
SRM Impacts on the Hydrological Cycle
3.50pm, Friday March 13, 2015
Here I present the latest climate model results from the Geoengineering Model Intercomparison
Project (GeoMIP), particularly related to the impacts of Solar Radiation Management on the
hydrological cycle. I will focus my presentation on GeoMIP experiment G1, in which an abrupt
quadrupling of the CO2 concentration is offset by a reduction in total solar irradiance.
Hydrological cycle changes can be understood both from a precipitation/evaporation perspective
Page 13 of 45
and from a surface energy budget perspective; I will show how the latter can reveal mechanistic
changes in precipitation. Although an increase in CO2 will cause changes in precipitation due to
both mean evaporation and circulation changes, changes in precipitation under GeoMIP
experiment G1 are largely due to changes in mean evaporation, suggesting circulation changes
are small.
Geoengineering not only offsets mean hydrological changes due to CO2, but also changes in
extreme events. One of the signatures of anthropogenic climate change is "the rich get richer,
and the poor get poorer", in that areas that receive heavy precipitation will receive even more
precipitation under climate change, and areas that receive moderate amounts of precipitation will
receive less. Simulations show a reversal of that signature for geoengineering.
I will also discuss regional effects on the hydrological cycle due to geoengineering, particularly
related to temperature and precipitation changes. If only temperature is considered, moderate
amounts of geoengineering offset the effects of global warming in nearly all major continental
regions (Giorgi regions) without making any region "worse off". However, if only precipitation is
considered, any amount of geoengineering exacerbates the effects of anthropogenic CO2
emissions in at least one region of at least one model. Most combinations of temperature and
precipitation show that moderate amounts of geoengineering are capable of offsetting the effects
of increased CO2.
Andy Wiltshire (Met Office)
Katie Brown, Jim Haywood, Chris Jones
Future Ecosystem Services, Climate Mitigation and Geo-Engineering
4.10pm, Friday March 13, 2015
Climate change will impact upon ecosystem provisions of water resources, food, carbon sink.
Current climate policy aims at avoiding dangerous climate change with a political consensus
around a 2 degree warming target.
Reaching the two degree target through mitigation is challenging and many Integrated
Assessment Model derived emission pathways require overall negative emissions to stabilise
climate at low levels. Negative emissions are a form of GeoEngineering via Carbon Dioxide
Removal (CDR). The main alternative approach is Solar Radiation Management (SRM), one option
of which is emit cooling aerosols.
Using the HadGEM2-ES Earth System model we investigate three scenarios based on mitigation;
BioEnergy Carbon Capture and Storage (BECCS) CDR, and SRM with the aim of stabilising climate
around the 2C target.
We show that different climate options exert deviating regional impacts on the land carbon sink,
ocean acidification, runoff and agricultural productivity. Climate pathways consistent with a 2C
target may have markedly different impacts as well as implications for available land in the case
of large scale deployment of BECCS.
Page 14 of 45
Sebastian Eastham (Massachusetts Institute of Technology)
Debra K. Weisenstein, Christopher D. Holmes, David Keith, Steven
R. H. Barrett
Sensitivities of Human Health to Aerosol Climate Engineering
4.30pm, Friday March 13, 2015
Geoengineering has been proposed as a way to offset a component of climate change. The most
researched method is the injection of sulfate aerosol precursors into the stratosphere in order to
reflect a fraction of incoming solar radiation and thereby cool the planet. Although the climate
and ozone related impacts have been quantified, the potential for sulfate aerosol injection to
cause air quality degradation and therefore increased premature mortality rates has not been
recognized or quantified. In this work we identify mechanisms by which sulfate geoengineering
can cause human mortality via degradation of air quality and the ozone layer, and approximate
the sensitivity of each mortality mechanism to sulfate precursor emissions. We use a global
chemical-transport model to estimate the sensitivity of surface air quality to the effects of sulfate
aerosol engineering in 2040 and provide a first estimate of associated changes in global mortality.
Applying linear scaling factors to the calculated temperature, precipitation, mass injection and
stratospheric burden mortalities, we estimate the total premature mortality associated with each
aspect of reversing 1.6 K of global warming using idealized sulfate aerosols. We disaggregate the
relative contributions of ozone and particulate matter to the total, with the preliminary finding
that over 100,000 premature mortalities worldwide are expected due to increased PM2.5
exposure. However, these are partially offset by reductions in ozone-related premature
mortalities, with some regions experiencing a net decrease in surface air quality related mortality.
We also find that over 75% of surface air quality impacts are due to reduced temperature and
precipitation compared to the unique side effects of sulfate aerosol injection as a specific route to
mitigating climate change. Although the surface air quality impacts of sulfate aerosol engineering
are found to be an order of magnitude smaller than those due to climate change, we find that the
associated stratospheric ozone depletion will result in increased surface UV-B intensity which
could pose a significant risk to human health through increased skin cancer mortality.
Page 15 of 45
Technical Session 3: Engineering Systems
Chair: Hugh Hunt (University of Cambridge)
Hugh Hunt (University of Cambridge)
K A Kuo, H Costello, C J Burgoyne, P Davidson
Delivering particles to the stratosphere - SPICE WP2
11am, Saturday March 14, 2015
It is widely assumed that the hard part of Climate Engineering is the modelling of climate. True,
climate modeling is full of uncertainty and we must be very careful not to create a situation worse
than unabated climate change. But supposing we gain confidence in the modelling of climate and
we are ready to try out some climate engineering at scale. Will it be possible to deliver, say, 10
million tonnes of SO2 per year to an altitude of 20km? That's 20 tonnes per minute. The
engineering challenge is non-trivial. It is quite likely that SO2 will solidify if released into the cold
low-pressure stratosphere. Large numbers of specially-designed aircraft will be needed, perhaps
several thousand flights per day. Alternatively we might consider missiles or artillery to deliver
SO2. We might need 100 thousand missiles a day. Even then, the SO2 will probably solidify.
Maybe we need to consider something other than SO2, perhaps TiO2 transported in liquid
nitrogen. The slurry would be pumped up long pious held up by hydrogen-filled balloons. Here
the engineering challenges are even greater, but the scale is smaller. There is nothing trivial
about the delivery of particles into the stratosphere.
Chris Burgoyne (University of Cambridge)
M L T Causier
Some engineering aspects of a geoengineering balloon and tether
11.20am, Saturday March 14, 2015
The SPICE project is based around the idea of dispersing particles into the stratosphere from a
balloon at height, supporting a pipe through which material can be pumped. This sounds trivial
but is at the limit of what is possible. This paper looks at some of the engineering issues that the
project entails. The weight of the tether depends on the material to be pumped; if a liquid, the
tether will have a relatively small cross-section, which reduces the effect of wind drag, but will be
relatively heavy, which increases the size of the balloon. If pumping a gas, the tether becomes
larger, although lighter, and the sideways drag increases. To counteract this effect, the balloon
diameter must increase. Both options lead to very large balloons as the height increases. There
is a relatively narrow band of heights at which the balloon is providing sufficient lift and where the
balloon skin is both pressurised but not overstressed.
The stresses in the tether itself are also considered. What material should be used? What form
of construction should be used? It is concluded that very high strength, lightweight, nonconducting fibres are available, but they will be used to their full capacity.
Julian Evans (University College London)
The quest for ingenerate resources to promote longevity of the ocean mirror
11.40am, Saturday March 14, 2015
The reflectance of ocean foam is in the region 0.4-0.6 and higher reflectance may be obtained
from fine cell foams. This compares favourably with the reflectance of the unfoamed ocean of
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~0.05. Although the energy for foam maintenance is drawn from wind or wave, this energy
demand determines the capitalization of equipment. Progress in promoting foam persistence has
been made in laboratory experiments by using combinations of biomass-sourced foaming agents
and gelling agents such that lifetimes of ~3 months can be obtained. The next stage in the
experimental programme at UCL is to explore the use of proteins that originate from
phytoplankton in conjunction with gelling agents that derive from seaweed. Although, there is no
correlation between ingenerate materials and toxicity, they nevertheless offer three possible
advantages: abundance, in-situ procurement and enhanced public acceptability.
John Latham (University of Manchester)
Alan Gadian, Jim Fournier, Ben Parkes, Peter Wadhams
Marine Cloud Brightening
12.00am, Saturday March 14, 2015
The concept behind the marine cloud-brightening (MCB) climate engineering technique – first
proposed by Latham, in Nature, 1990 - is that seeding marine stratocumulus clouds with copious
quantities of roughly mono-disperse sub-micrometre sea-water particles might significantly
enhance the cloud droplet number concentration, and thereby the cloud albedo and possibly
longevity. This would produce a cooling, which general circulation model (GCM) computations
suggest could – subject to satisfactory resolution of technical issues – maintain the Earth’s
average surface temperature at roughly current values up to at least a doubling of pre-industrial
carbon dioxide.
We offer herein brief accounts of recent research on a number of critical issues associated with
MCB: (i) GCM studies, so far our primary tools for evaluating the effectiveness of MCB, assessing
impacts on polar sea-ice cover and thickness, and rainfall distribution; (ii) high-resolution
modelling of the effects of seeding on marine stratocumulus needed to understand the complex
array of interacting processes; (iii) microphysical modelling sensitivity studies examining the
influence of seeding amount, seed-particle salt-mass, air-mass characteristics, updraught speed
and other parameters on cloud–albedo change; (iv) sea water spray-production techniques; (v)
computational fluid-dynamics studies of large-scale periodicities in Flettner rotors; (vi) planning of
a (100 x 100 km) limited-area field research experiment, with the objectives of testing technology
and quantifying cloud albedo enhancement by seeding; (vii) our primary emphasis herein,
application of MCB to three regional issues: (1), elimination or reduction of coral bleaching; (2),
weakening of developing hurricanes; and (3), recovery of polar ice loss; where the preservation
of sea-ice could, in principle, also prevent methane release from thawing sub-sea permafrost; (ix)
the possibility that a localized application of MCB might be capable of cooling specific ocean
currents to stabilize the ice shelf supporting the West Antarctic Ice Sheet; (x) regional issues
suggest that future MCB modelling also include seeding in the 1W/m2 range.
A crucial question is whether deployment could cause reduction of rainfall in regions suffering
from drought. Subsequent modelling indicates that the flexibility of MCB seeding locations could
circumvent this problem, but no definitive statement can be made until more research has been
conducted.
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Technical Session 4: Atmospheric Effects
Chair: Matt Watson (University of Bristol)
Markus Kalberer (University of Cambridge)
Tang MJ, Telford PJ, Rkiouak L, Abraham NL, Keeble J, Archibald
AT, Braesicke P, Pyle JA, Camp J, McGregor J, Watson IM, Ward
AD, Cox RA, Pope FD
Atmospheric chemistry of mineral particles in the stratosphere: implications
for ozone chemistry and stratospheric particle injection
3.30pm, Saturday March 14, 2015
Injection of aerosol particles (or their precursors) into the stratosphere to scatter solar radiation
back into space has been suggested as a solar radiation management scheme for climate
engineering. Most of the stratospheric particle injection studies to date have focused on the use
of sulfuric acid particles. Several minerals, including TiO2, have been discussed as possible
candidate particles to be injected into the stratosphere, due to their high refractive indices.
However, their heterogeneous reactivity towards important reactive trace gases in the
stratosphere has seldom been investigated, impeding us from a reliable assessment of their
impact on stratospheric O3.
In this work, the heterogeneous reactions of airborne TiO2 particles with N2O5, ClONO2 and O3
have been studied at room temperature and at different RH using an atmospheric pressure
aerosol flow tube, a single particle optical trap and fixed bed reactors. The uptake coefficient of
N2O5, γ(N2O5), increased from ~1.8×10-3 at 5% RH to 4.5×10-3 at ~60% RH for TiO2, is
significantly smaller than that for sulfuric acid particles in the stratosphere and mechanistic
aspects of this reaction were explored with single particle optical traps. The uptake of ClONO2
onto TiO2 aerosols particles have been found to be quite inefficient, with γ(ClONO2) not larger
than 1×10-3. Therefore, compared to stratospheric sulfuric acid particles, TiO2 particles show
similar reactivity towards ClONO2 and much lower reactivity towards N2O5. In addition, the direct
decomposition of O3 on a wide range of mineral was assessed.
The UKCA chemistry-climate model has been used to assess the impact of TiO2 particles on
stratospheric chemistry. Scenarios were modelled for TiO2 particle injections to have the same
radiative effect as the eruption of Mt. Pinatubo. The effects of all three reactions on ozone
concentrations and on other important traces gases in the stratosphere are quantified.
Graham Mann (University of Leeds)
S.S. Dhomse, K.S. Carslaw, M. P. Chipperfield, L.A. Lee, K. M.
Emmerson, L. Abraham, P. Telford, P. Braesicke, J. A. Pyle, M. Dalvi,
N. Bellouin, C. E. Johnson
Quantifying the radiative forcing from the 1991 Mt Pinatubo eruption
3.50pm, Saturday March 14, 2015
The Mt Pinatubo volcanic eruption in June 1991 injected between 14 and 23 Tg of sulphur dioxide
into the tropical stratosphere between about 21 and 28km altitude. Following chemical
conversion to sulphuric acid, the stratospheric aerosol layer thickened substantially causing a
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strong radiative, dynamical and chemical perturbation to the Earth's atmosphere with effects
lasting several years.
In this presentation we show results from model experiments to isolate the different ways the
enhanced stratospheric aerosol from Pinatubo influenced the Earth’s climate.
The simulations are carried out in the UK Chemistry and Aerosol composition-climate model
(UKCA) which extends the high-top (to 80km) version of the HadGEM3 climate model.
The
HadGEM3-UKCA model uses the GLOMAP-mode aerosol microphysics module coupled with a
stratospheric chemistry scheme including sulphur chemistry.
By running no-feedback and standard integrations, we separate the main radiative forcings due to
aerosol-radiation interactions (i.e. the direct forcings) from those induced by dynamical changes
which alter meridional heat transport and distributions of aerosol, ozone and water vapour.
Peter Davidson (Davidson Technology)
The impact, implications and consequences of the use of manufactured
particles to improve the feasibility and reduce risk for a Stratospheric Solar
Radiation Management (SRM) Insurance
4.10pm, Saturday March 14, 2015
Sulphate aerosols have the tremendous advantage that they are natural: every few decades the
Earth has been subject to large injections of volcanic sulphur dioxide which converts into a fine
light-scattering sulphuric acid mist and reduces the global mean temperature by up to a degree
centigrade.
Unfortunately the kinetics of formation of sulphate aerosols (taking weeks to form in the
stratosphere from precursor sulphur dioxide) makes small-scale experiments impossible. Hundred
of thousands if not millions of tons of injected material is needed when the precursor materials
have the chance to circulate the planet before the mists are created. Two further issues make the
use of artificial sulphate aerosols problematic - even as a measure of last resort: deleterious
reduction of ozone in the stratosphere is likely; and regional weather patterns may be disturbed
through altered stratospheric circulation patterns as a result of infra – red absorption heating by
the mist.
Appropriate manufactured light scattering particles have been suggested as a better alternative.
It is possible to envisage small injections of manufactured particles at altitude, creating a small
localized plume where the atmospheric chemistry, the light scattering and local circulation
patterns can be closely observed. A slow, careful progressive expansion of such injection could
be managed to minimize risk with attendant governance.
Analytical modeling, laboratory experiments and climate modeling to date have suggested some
of the difficulties with sulphuric acid mists may be readily overcome, but much further research is
needed. From simple light scattering theory it is possible that much smaller quantities of well
known, non-toxic materials would be needed for ameliorating global temperature rises than
sulphuric acid mists, and that atmospheric circulation changes and their impact on the ozone
layer could be far lower, possibly undetectable.
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Three scenarios will be presented describing the experiments needed and their methodology,
addressing dispersion tests, modeling, and chemistry. The implications and consequences of
carrying out the research work in a responsible timely manner, or not at all, will be addressed.
Peter Irvine (Institute for Advanced Sustainability Studies)
Detection, Attribution and Climate Control - the Limits to Solar Radiation
Management
4.30pm, Saturday March 14, 2015
Climate engineering via solar radiation management (SRM) has been proposed as a means to
offset some of the harmful effects of anthropogenic climate change. This study investigates an
apparent tension between claims that climate engineering could be controlled and optimized in
the face of inevitable uncertainties and the difficulties evident in the detection and attribution of
observed climate change. This study distinguishes two types of climate control: global-mean
climate control, where for example global-mean temperatures are kept at some target level using
a single control variable, e.g. a certain global mean sulfate aerosol loading, and climate pattern
control where the pattern of climate response across the world is controlled by multiple control
variables, e.g. by controlling the pattern of radiative forcing. Here, by analyzing climate control
from the perspective of detection and attribution of climate change a consistent picture of the
challenges and technical limitations of climate control emerges. The large internal variability of
the climate, the limits of climate models, particularly at regional and smaller scales, and the
challenges of attributing multiple climate drivers simultaneously will pose serious challenges for
climate pattern control but have little effect on the robust “thermostat” approach of global-mean
climate control. However, detecting and attributing the pattern of climate response to SRM
geoengineering would remain a challenge, i.e. it is possible to control the global-mean
temperature and still be highly uncertain about the detailed response of the climate to that
control. Whilst SRM geoengineering has been characterized by some as a “fast, cheap and
imperfect” response to climate change, it seems reasonable to characterize climate control itself
as “slow, painstaking and imperfect”: slow due to the decadal timescales of attribution and
validation, painstaking given the great demands that would be made on the climate modeling
community, and imperfect due to the inevitable errors in projections of the response of the
climate system.
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Lunchtime Perspectives
Friday Chair: Olaf Corry (The Open University)
Saturday Chair: Duncan McLaren (McLaren Environmental)
Ian Simpson (www.look-up.org.uk)
Evidence and theory of current climate engineering programs
1.30pm, Friday March 13, 2015
The proposed programs to engineer our climate are already well underway in the UK and Europe
at least, and probably the rest of the world, and have been for a number of years. There are
many ways we can deduce this with simply observation of weather patterns, new cloud types and
the resulting climate extremes caused by the interference and manipulation of weather systems
both on a large scale and at a local level. Also residue from those programs is clearly visible in our
environment. There are 3 main programs identified to date. Atmospheric changes are hard to
prove without large budgets and access to scientific knowledge and equipment, however we can
prove the existence of these program in other ways. The amalgamation of virtually all the worlds
airlines into 3 airline alliances. The modifications to Airbus A320/A380 aircraft and Boeing 737
among others. The behaviour of aircraft, both on a national and international level, show clear
patterns consistent with current climate engineering programs. Statistics also proves that local
weather patterns are not at all natural.
Josefina Fraile-Martin (Terra SOS-tenible)
Civil Society vs. Geoengineering
1.45pm, Friday March 13, 2015
SRM debates seem to be purposefully confined to scientific and academic circles. Despite the risks
of deployment for the planet, exposed by some reputed institutions such as the Royal Society in
its 2009 report: Geoengineering the Climate, Science, Governance and Uncertainty, or by some
scientists, e.g. Alan Robock, the subject is not treated by the mainstream mass media. As a
result, for the sake of averting any counter reaction to these programs, civil society is kept
ignorant of a serious issue that will affect every living being on earth.
In this context, instead of promoting a genuine public debate and information campaigns some
social scientists have decided to become an interface between society and geo-engineers,
arrogating to themselves, on no grounds, the representation of civil society. An example of this
curious exercise in self appointment is the Five Oxford Principles, published in 2009.
Given the lack of neutral informative campaigns and serious public debates, the time has come to
rectify this undemocratic approach all along and allow civil society to take part in academic
debates, expressing citizens’ concerns, experiences and demands on these matters. Engagement
of civil society in these academic and scientific debates is moreover crucial today in a context of
SRM deployment being pushed by some geo-engineers on the grounds of extreme weather
episodes, the failure of CO2 mitigation measures and in face of political institutions which avoid to
openly positioning themselves in favor of the issue for fear of the political consequences. In this
real vacuum legitimization of decisions is at stake, given that some geo-engineers do indeed claim
that power. But neither legality nor civil society will recognize this legitimization of those not
directly elected by citizens, who in addition have so far ignored society and the common interests
in their climate engineering formulas.
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In the light of all the above a set of pertinent questions will be presented to geo-engineers and
policy makers at the SRM Science 2015 event; proof of ongoing geoengineering programs will be
provided and relevant Civil Society initiatives at the European Parliament will be outlined.
Holly Buck (Cornell University)
Contested infrastructure: insights from large-scale development projects
1.30pm, Saturday March 14, 2015
Infrastructure is often a flashpoint for social discussions of emerging technologies. Infrastructure
is more than a technological construction— it can become a symbol. The infrastructure protests
over the Keystone XL or Northern Gateway oil pipelines became symbolic proxies for discussing
the kind of energy development desired in North America; mega-dam projects and offshore wind
farms have been contested around the world. Even the designers of Google Glass became
surprised when their hardware became a site of contestation about social issues like data privacy
and social inequality.
While much scholarship looks how social values influence the design of emerging technologies,
this study suggests that analogies from development projects may be most useful to examine.
Many infrastructure-for-development projects are backed with public funds or by international
institutions, and require a different type of social license than commercial technologies do.
Examples of infrastructure development projects which were informed by social conditions include
the downscaled Desertec solar initiative in North Africa, the Grand Ethiopian Renaissance Dam on
the Blue Nile, and the Nicaragua Canal, designed by the Hong Kong Nicaragua Canal
Development Group. All of these have provoked varying degrees of contestation, and have been
seen as symbolic political or social projects, as SRM likely would.
This paper aims to bring some of these lessons from development and infrastructure deployment
into consideration for engineers and designers thinking about SRM. Since the feasibility and cost
of technology deployment is determined by social considerations, we will also explore this. The
cost, especially if a project is unpopular, is far greater than the material inputs and labor: it
includes insurance, political concessions, and security, among other costs. Many development
projects have been abandoned for these reasons. The paper suggests some ways the dynamics
from previous infrastructure development projects are relevant to the design of SRM
infrastructure and technology.
Bronislaw Szerszynski (Lancaster University)
Paul Oldham, Jack Stilgoe
A bibliometric study of solar radiation management science: publications and
patents
1.45pm, Saturday March 14, 2015
In this paper we present the findings of a bibliometric analysis of solar radiation management
science, looking at both scientific publications and patent filings.* In the study we identified a
dataset of 825 scientific publications on climate engineering up to the end of 2013, including 193
on solar radiation management; for the patent dataset, we identified 143 first filings directly or
indirectly related to climate engineering technologies – of which 28 were related to SRM
technologies – linked to 910 family members. We then use bibliometric techniques to chart the
main trends in research and patenting; to map the emerging networks of co-authorship, mutual
citation and patent activity; to trace the evolving pattern of disciplinary involvement; and to map
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patterns of funding and co-funding. Finally, we use a combination of natural language processing
and manual qualitative analysis to trace the rise, fall and distribution of various justificatory
‘frames’ for solar radiation management research used in the literature. We conclude by arguing
that the bibliometric monitoring of research and patenting activity can make an important
contribution to ensuring responsible innovation in solar radiation management science, by making
visible the often-hidden networks of collaboration, funding and problem-definition.
* See Oldham, Paul, Szerszynski, Bronislaw, Stilgoe, Jack, Brown, Calum, Eacott, Bella, Yuille,
Andy (2014) ‘Mapping the landscape of climate engineering’, Philosophical Transactions of the
Royal Society A, 372(2031): 20140065. http://dx.doi.org/10.1098/rsta.2014.0065
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Posters
Session 1: Climate modelling
S. Driscoll (University of Oxford)
Climate Impacts of Stratospheric Particle Injection
This talk presents the results of the SPICE Work Package 3. The talk begins with identifying the
need for robust ways to verify the accuracy of models are in simulating the effects of
geoengineering given no observations of a geoengineering programme. Accordingly, the ability of
Coupled Model Intercomparison 5 climate models to reproduce the observed response of volcanic
eruptions is analysed. Models are shown to be unable to produce the major observed Northern
Hemisphere dynamical response to tropical volcanic eruptions which is noted as a cause for
concern of the accuracy of geoengineering simulations.
Simulations are then performed with the HadGEM2 climate model (HadGEM2-L38) and its
enhanced stratospheric resolution counterpart (HadGEM2-L60). The HadGEM2-L60 model is
shown to reproduce a response substantially closer to that observed than HadGEM2-L38 and
mechanisms behind the response are analysed and explained.
With the HadGEM2-L60 model shown to be substantially better in reproducing the observed
dynamical response to volcanic eruptions, simulations of GeoMIP’s G4 scenario are performed.
Simulated asymmetries between the immediate onset and immediate cessation (‘termination’) of
geoengineering are analysed. Whilst a rapid large increase in stratospheric sulphate aerosols
(such as from volcanic eruptions) can cause substantial damage, most volcanic eruptions in
general are not catastrophic. One may therefore suspect that an ‘equal but opposite’ change in
radiative forcing from termination may therefore not be catastrophic, if the climatic response is
simulated to be symmetric. HadGEM2 simulations reveal a substantially more rapid change in
variables such as near-surface temperature and precipitation following termination than the
onset, indicating that termination may be substantially more damaging and even catastrophic.
A. Jones (University of Exeter)
The climate response to stratospheric aerosol injection in the RCP8.5 concentrations scenario
Many robust climate changes associated with stratospheric aerosol injection (SAI) have been
identified including a weakening of the hydrological cycle, high-latitude ozone depletion, and
changes to stratospheric dynamics. Most of the research on SAI has concentrated on assessing
the climate impacts of sulfate injection in a middle-ground greenhouse gas (GHG) concentrations
scenario such as RCP4.5. However, Peters et al (2013) showed that recent global GHG emissions
have actually exceeded the most carbon-intensive SRES scenario, RCP8.5. In order to
comprehensively assess the robustness of the climate changes associated with SAI, it is therefore
necessary to simulate aerosol-injection in a high end GHG concentrations scenario.
Using HadGEM2-CCS, we have simulated a suite of sulfate-injection strategies in a baseline
RCP8.5 scenario over the course of the 21st century. In addition, we have also ran
complementary simulations of soot and titania injection scenarios in order to understand the
dependency of climate changes on aerosol composition. In this presentation, I will describe the
climate changes associated with aerosol injection in the RCP8.5 scenario and discuss to what
extent these changes are dependent on injection-rate and aerosol composition. Additionally, I will
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compare the robust SAI climate changes (such as monsoon impacts) highlighted by previous
research with the results of our simulations. Finally, I will contrast the regional climate changes in
our simulations, using a vulnerability-weighted damages metric, in order to assess the relative
magnitude of climate change with and without geoengineering.
D. G. MacMartin (California Institute of Technology),
B. Kravitz (Pacific Northwest National Laboratory)
Feedback is essential to manage uncertainty in solar geoengineering
A major concern regarding solar geoengineering is how to manage inevitable uncertainties. From
an engineering perspective, the answer is straightforward – by using feedback of observations to
adjust one’s strategy. This could include adjusting both the distribution (e.g., latitude and
seasonality) and amount of radiative forcing. Whether planned or not, some feedback is
inevitable: it is highly unlikely that society would stick to a predefined strategy independent of
outcomes, yet this is what most studies implicitly simulate. We present initial results using
feedback, and discuss fundamental limitations.
Design of any feedback strategy requires a model of the climate response. However, this model
only needs to be “good enough”: the sign of the response must be known, but the magnitude
need only be known within a factor of 2-3. We present results illustrating feedback with a simple
design model and a distinct “evaluation” model (a state-of-the-art climate model) which serves as
a proxy for the real world.
We discuss three limitations to the use of feedback in solar geoengineering:
1.
Climate variability leads to poor signal-to-noise ratio (SNR). While this does not present
any theoretical challenge (the feedback will guarantee convergence in the mean at any SNR), the
feedback necessarily responds to natural variability, hence either the desired solar reductions will
be “noisy” or the adjustments must be slow. Some regional effects may take so long to detect
that feedback to manage them is not plausible on societal time-scales.
2.
Model accuracy should not be an issue for managing global mean temperature. However,
geoengineering objectives may require balancing multiple, regional, criteria. Model predictions
are less reliable at smaller spatial scales – with disagreement on even the sign of regional
precipitation responses. This presents a fundamental limitation on the ability to meet certain
climate objectives given current modeling capability.
3.
Decisions are ultimately made by human societies and are not necessarily based on model
projections or statistical analysis. Thus while decisions about the level of geoengineering will
almost certainly be influenced by observations, the actual feedback rule is not made through
some simple engineering metric but through messy, poorly understood, societal processes.
B. Kravitz (Pacific Northwest National Laboratory)
A. Robock (Rutgers University)
Progress in the Geoengineering Model Intercomparison Project (GeoMIP)
We provide key highlights from the latest developments in the Geoengineering Model
Intercomparison Project (GeoMIP). Results from the original four climate model experiments,
dealing with solar irradiance reduction and stratospheric aerosols, continue to be analyzed, in
particular with a focus on ocean dynamics and variability. We present results regarding changes
in ocean circulation, effects on the El Niño Southern Oscillation, and impacts on the terrestrial and
oceanic carbon cycles. Preliminary results from three newer experiments on marine cloud
brightening will also be presented, highlighting both robust model responses and key areas of
uncertainty. We focus our attention on how such simulations can inform ongoing investigations of
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aerosol-cloud-precipitation interactions, which are some of the most prominent sources of
uncertainty in climate science. We conclude with a presentation of the experiment design for four
Tier 1 experiments in the new phase of GeoMIP, which are part of GeoMIP’s application to be
included in the Coupled Model Intercomparison Project Phase 6. In particular, we introduce a
GeoMIP experiment looking at the relatively new idea of cirrus cloud thinning, which would allow
more longwave radiation to escape to space. We welcome any feedback to GeoMIP from the
climate engineering community, the climate modeling community, or the larger climate science
community.
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Posters
Session 2: Impacts, Implications and Consequences
J. Falk (University of Melbourne)
SRM Governance - What, Whether, How, When...?
Too often, SRM is examined as if stratospheric sulphate injection was the only proposal on the
table, and thus the only one to be considered from a policy and physical perspectives. This
proposed paper will bring together work in progress on systematically examining the combined
physical, social and governance dimensions of the multiple SRM proposals which have appeared
in the literature.
Two pieces of previous work will support this analysis. The first is the study of the evolution of
governance developed by Joseph Camilleri and myself in Camilleri and Falk, “Worlds in Transition:
Evolving governance across a stressed planet” (London: Edward Elgar, 2010), and the dynamics
of climate challenges to which governance responses, and in particular SRM initiatives may
emerge as contenders to solve.
In addition, the analysis will build on a categorisation of the multitude of SRM proposals which
have emerged in the literature. Following work presented in CEC--‐ 14 in Berlin
(http://metastudies.net/pmwiki/uploads/Publications/Jim_Falk_Berlin_Poster.pdf), this will be
developed in the context of current and potential “footprints of different styles or SRM
intervention, combining consideration of what I have categorised as Intensity and Urgency,
Leverage and Risk, Development Stage, Anticipated Impact, and Ownership. These footprints
provide a handy way of summarising multiple characteristics of different interventions.
Different types of interventions (as characterised above) can then be considered in terms of their
potential time development in relation to these different variables. The likely motivation for
introducing SRM interventions across a spectrum of different time scales (from slow scale, low
impact reversible interventions to play an ancillary role in tackling climate impacts to full scale
urgent response to perceived “climate emergencies” which themselves will require careful analytic
attention.
This analysis will then lead on to considerations of policy options which arise in relation to various
forms of SRM research, field testing, and deployment. The paper is a further step towards a book
on climate engineering which is intended to be published by Pluto Press (London) early in 2016. It
should form a useful framework for bringing together impacts, implications and consequences of
SRM within a careful and integrative, and helpful framework.
Z. Zhuo (Zhejiang University)
Historical Implication on Geoengineering - From the Perspective of China’s Monsoon Precipitation
Response to Volcanic Aerosols
The effect of volcanic aerosols on China’s monsoon precipitation over the past 700 years has been
studied using two volcanic indices with the Monsoon Asia Drought Atlas. Histories of past
volcanism were compiled from the IVI2 [Gao et al., 2008] and Crowley2013[Crowley and
Unterman, 2013] reconstructions, and classified into 2×Pinatubo / 1×Pinatubo / more than 5 Tg
sulfate aerosols injection into the northern hemisphere (NH) stratosphere for IVI2, and NH sulfate
flux more than 20/15/10/5 kg/km2 for the latter, then Superposed Epoch Analysis (SEA) with a
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10,000 Monte Carlo resampling procedure is undertaken for each category and individual grid.
Results show a significant drying trend over mainland China from year 1 to 4 after the eruptions,
and the more sulfate aerosol injected into the NH stratosphere or the larger the sulfate flux, the
more severe this drying trend seem to reveal, while a minor wetting trend is observed in the
years following Southern Hemisphere only injections. Monte Carlo hypothesis tests showed that
95.5% (92%) of the observed MADA values are statistically significant at the 95% (99%)
confidence level. Results from spatial analysis show a southward movement of significant dry
areas in eastern China from year 0 to 2 after volcanic perturbations that are either equal to or
double the 1991 Mt. Pinatubo eruption (15T sulfate aerosols in NH), and northeast and northwest
China experienced substantial droughts in years 2 to 5. On the other hand, with only SH injection,
north and east china turn to wet in the eruption year and show a southward movement of the
wettest areas, when compared to NH injection more than 2×Pinatubo. These results are in good
agreement with SEA analysis of China’s historical meteorological records. These results illustrate
the important role the different magnitude, latitude and hemispheric volcanic aerosols have
played in altering China’s precipitation, which shed light on the possible effects stratospheric
geoengineering may have on China’s precipitation.
O. Wingenter (New Mexico Institute of Mining and Technology),
O. Oluwaseun (New Mexico Institute of Mining and Technology),
S. Elliott (Los Alamos National Laboratory),
D. Blake (University of California),
N. Blake (University of California)
Intended and unintended consequences of SRM: Zeus' Lever
The uneven heating of the planet creates wind. Changes in temperature distributions can lead to
wanted or unwanted changes. Unintended anthropogenic changes have already repositioned the
Westerly Winds in the Southern Hemisphere. These winds are important in climate modulation
(Toggweiler & Russell, 2008; Anderson et al., 2009). Global warming, loss of Antarctic ozone and
increased DMS flux (a feedback of the increased westerlies proposed here) have already
increased the temperature difference (T) between the southern mid- and high–latitudes (Shindell
& Schmidt, 2004; Wingenter et al. in preparation), causing an increase in the velocity of the
Westerly Wind and also shifting them ~3-4° southward (Sen Gupta et al., 2009). Continued
climate change and/or Stratospheric SRM can lead to additional cooling over the poles (Tilmes et
al., 2009) which is expected to intensify these winds. The alignment of the westerlies with the
wind-driven Antarctic Circumpolar Current is key to the amount of ocean meridional overturning
circulation and in determining the Earth's climate mode, i.e. glacial versus interglacial (Toggweiler
& Russell, 2008; Anderson et al., 2009). Upwelling of warm, salty Circumpolar Deep Water (CDW)
is the chief process for venting deep water.
During glacial periods, T is at a minimum and the westerlies are closer to the equator having less
overlap with the Antarctic Circumpolar Current. This results in decreased Ekman pumping of
CDW, which further reduces the flux of CO2 to the atmosphere, cooling the Earth (Toggweiler &
Russell, 2008; Anderson et al., 2009). During these periods, Antarctic sea ice extends much
farther north resulting in greater albedo and even less coupling between the westerlies and the
Antarctic Circumpolar Current (Sen Gupta et al., 2009).
Conversely, slight warming, such as that caused in the past by changes in the Earth's orbit, can
activate the poleward shift of the westerlies. The greater wind stress acting on the Antarctic
Circumpolar Current moves more water northward. This in turn pulls more CDW to the surface,
releasing CO2 into the atmosphere and prompting further warming and upwelling (Toggweiler &
Russell, 2008; Anderson et al., 2009). Levels of CO2 in the southwest Indian Ocean and portions
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of the Southern Ocean are increasing faster than they are in the atmosphere, indicating a reduced
ocean CO2 sink that appears to be caused by enhanced CDW upwelling (Metzl, 2009; Takahashi
et al., 2009). The portion of upwelled CDW that moves southward supplies heat to Antarctic sea
ice, ice shelves, and ice sheets, causes them to melt, potentially accelerating sea level rise
(Walker et al., 2007).
To restore atmospheric and ocean circulation, greater cooling north of the westerlies by cloud
brightening may be needed but could exasperate the condition. We propose applying two marine
cloud-brightening methods. Limited iron fertilization (Wingenter et al., 2007; 2008) for the
production of DMS and sulfate aerosol and injection of sea spray aerosol (Salter et al., 2009;
Rasch et al., 2009) for this purpose.
M. Stankoweit (Universität Hamburg),
H. Schmidt (Max Plank Institute for Meteorology),
E. Roshan (Universität Hamburg),
H. Held (Universität Hamburg),
Cost-effective integrated mitigation and solar radiation management scenarios under combined
temperature and precipitation guardrails
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Posters
Session 3: Engineering Systems
A. Lockley
Geoengineering on Exoplanets
Solar radiation management (SRM) geoengineering can be used to deliberately alter the Earth’s
radiation budget, by reflecting sunlight to space. SRM has been suggested as a response to
Anthropogenic Global Warming (AGW), to partly or fully balance radiative forcing from AGW [1].
Approximately 22% of sun-like stars have Earth-like exoplanets[2]. Advanced civilisations may
exist on these, and may use geoengineering for positive or negative radiative forcing.
Additionally, terraforming projects [e.g. 3], may be used to expand alien habitable territory, or
for resource management or military operations on non-home planets. Potential observations of
alien geoengineering and terraforming may enable detection of technologically advanced alien
civilisations, and may help identify widely-used and stable geoengineering technologies. This
knowledge may assist the development of safe and stable geoengineering methods for Earth.
The potential risks and benefits of possible alien detection of Earth-bound geoengineering
schemes must be considered before deployment of terrestrial geoengineering schemes.
1. Royal Society (September 2009). Geoengineering the Climate: Science, Governance and
Uncertainty (Report). p. 1. ISBN 978-0-85403-773-5
2. Petigura, E. A.; Howard, A. W.; Marcy, G. W. (2013). "Prevalence of Earth-size planets orbiting
Sun-like stars". Proceedings of the National Academy of Sciences 110(48): 19273.
arXiv:1311.6806. Bibcode:2013PNAS..11019273P.doi:10.1073/pnas.1319909110
3. Gerstell, M. F.; Francisco, J. S.; Yung, Y. L.; Boxe, C.; Aaltonee, E. T. (2001)."Keeping Mars
warm with new super greenhouse gases". Proceedings of the National Academy of Sciences 98
(5): 2154–2157. doi:10.1073/pnas.051511598
C. McInnes (University of Glasgow)
Micro-to-Macro: Solar Radiation Management as a problem of Engineering Science at extremes
of length-scale
The challenges posed by solar radiation management directly link the micro-scale physics of
scattering particles to macro-scale engineering interventions in the dynamics of the climate
system. Furthermore, given the long residence time of carbon dioxide in the atmosphere, climate
engineering interventions could well be long-lived ventures. Solar radiation management
therefore represents a unique problem for Engineering Science at extremes of both length-scale
and time-scale. I will explore the links between these extremes of scale, illustrated through new
work on space-based solar radiation management methods.
First, stratospheric aerosols offer a near-term route to insolation reduction, although
gravitational settling and tropospheric washout would require replenishment to ensure continued
atmospheric aerosol loading [1]. Similarly, new concepts for space-based climate engineering
envisage clouds of dust grains deposited close to the interior Sun-Earth Lagrange point [2].
However, dust residence time near the Lagrange point is limited by strong perturbations due to
solar radiation pressure.
In both cases, the utility of macro-scale climate engineering is limited by the micro-scale physics
of the scattering particles. However, for stratospheric aerosols artificially engineered particles
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exploiting photophoretic levitation are seen as a possible means of increasing atmospheric
residence times [3]. Similarly, for Lagrange point dust clouds, it will be shown that engineered
microspheres with thermal-sensitive optical properties can passively stabilise such clouds [4].
These ideas will be taken further to speculate on future prospects for solar radiation
management using engineered ‘smart dust’ devices, rather than passive aerosols or reflectors.
Such speculative schemes could in principle enable the optical properties of the scattering
devices to be actively controlled, thus enabling closed-loop control of solar radiation
management, either for stratospheric deposition or future space-based schemes.
Finally, the challenges posed by such closed-loop control will be considered, with adaptive
strategies presented which are robust to uncertainty in both actuation effectiveness and the
dynamics of the climate system. Again, this represents a problem at extremes of both lengthscale and time-scale, given the short relaxation time constant of the atmosphere to changes in
solar insolation, but the long residence time of carbon dioxide in the atmosphere.
1. Crutzen, P.J.: ‘Albedo enhancement by stratospheric sulfur injections: A contribution to resolve
a policy dilemma?’, Climatic Change, 77, 3-4, 211–219, 2006.
2. Bewick, R., Sanchez, J.P., and McInnes, C.: ‘The feasibility of using and L1 positioned dust
cloud as a method of space-based Geoengineering’, Advances in Space Research, 49, 7, 12121288, 2012.
3. Keith, D.W.: ‘Photophoretic levitation of engineered aerosols for geoengineering’, PNAS, 107,
38, 16428-16431, 2010.
4. Biggs, J.D., McInnes, C.R.: ‘Passive orbit control for space-based geo-engineering’, Journal of
Guidance, Control and Dynamics, 33, 3, 1017-1020, 2010.
S. H. Salter (University of Edinburgh)
Updated design of hydrofoil spray vessels for marine cloud brightening for increased energy
demand.
Simulation by Tsiamis of the Rayleigh jet breakup with piezo excitation using the COMSOL
Multiphysics software shows that we can make mono-disperse spray with the right diameter for
Latham’s marine cloud brightening but that the drive pressure must be 85 bar. This needs more
power, about 400 kW, than could easily be generated by dragging turbines through the water as
previously proposed because the dominant force on the turbine is in the direction to oppose
vessel motion.
An alternative design uses four, variable-pitch hydrofoils on parallelogram linkages driving a
digital hydraulics system. Each foil will carry a nominal quarter of the 90-tonne vessel weight
but, by foil pitch variation, this can be increased or reduced with opposite phases port and
starboard and fore and aft. This generates energy with large forces nearly perpendicular to the
direction of travel which cancel their effects on the main hull. With information on pitch and roll,
the foils can also provide greatly improved sea keeping. They can act like active suspensions on
road-vehicles to reduce shock loads from wave action, and even convert shock loads to useful
energy. By lifting the hull clear of the water they provide a large reduction in wetted area and
wave-making drag. In non-spray mode the vessels will be able to move at high speed, 30 knots,
even in moderate winds to allow rapid tactical changes of spray patterns to suit day-to-day
meteorological observations and seasonal changes.
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The availability of high-pressure oil removes one of the problems of pumping plankton-rich salt
water through ultrafiltration plant and micro nozzles. The pumping mechanism can use oil to
squeeze rubber tubes.
J. Sanchez (Cranfield University)
Optimal Sunshade Configurations for Solar Radiation Management near the Sun-Earth L1 Point
The possibility to shade the Earth from space in order counteract an energy imbalance due to
greenhouse gas (GHG) emissions was first suggested a quarter of a century ago. Today
however, with a much wider recognition that climate change is happening, global emissions have
yet to show any sign of declining. Despite policy efforts should remain focused on drastically
reducing global GHG emissions, fundamental research into alternatives to counteract
anthropogenic climate change is today generally regarded as prudent.
As shown by previous work, large occulting structures could potentially offset the increase of
global mean temperatures due to GHG emissions. This work however revisits the concept of
deploying a large sunshade or occulting disk near the Sun-Earth L1 Lagrange equilibrium point,
and investigates optimal configurations of orbiting occulting disks that not only offset the global
temperature increase, but also mitigate regional differences in temperature. In this work, Earth
shading patters were sought capable to mitigate regional effects measured as latitudinal and
seasonal differences of monthly mean surface temperature. Near the Sun-Earth L1 point, natural
periodic and quasi-periodic motion exists that allows a nonuniform reduction of the solar
radiation across the Earth surface. However, the periodicity of these natural motion does not
match that required for geoengineering purposes (i.e., one year period), thus forced orbits were
designed that require small changes to the disk attitude in order to control its motion by taking
advantage of the solar radiation pressure.
Finally, periodic configurations of two occulting disks are presented, which achieve important
reductions of the residual latitudinal and seasonal temperature changes with the same shading
area as previously published studies. A globally resolved energy balance model is used to provide
insight into the coupling between the motion of the occulting disks and the Earth’s climate, and
thus obtaining rough estimates of mean surface temperature in a monthly averaged 3.75°x3.75°
horizontal grid.
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Posters
Session 4: Atmospheric Effects
P. Arora (Indian Institute of Technology),
S. Mishra (Indian Institute of Technology)
The effects of Geoengineering on Tropical Climate (Indian Subcontinent): The effects of SRM on
Cloud Area Fraction
The objective of this paper is to study the effects of Solar Radiation Management (SRM) on the
climate over the Indian Subcontinent, particularly how it changes the cloud area fraction over the
region. Cloud area fraction plays a major role in governing small and large scale weather activities
in any area and a small change in it can trigger repercussions on a much larger scale. As such it
becomes extremely important to analyze the impacts of SRM on cloud area fraction. The cloud
area fraction data from two different models namely CCSM4and GISS-E2-R was studied for a
period of 70 years and the graphical results for the changes in cloud area fraction was plotted
using the NCAR Command Language (NCL). The results obtained from the plots were indicative of
the fact that the cloud area fraction, particularly over the Indian Subcontinent, is indeed a very
sensitive parameter where a small change in the solar radiation caused changes as high as 30%.
These observed changes thus further strengthen our argument that any decision, big or small,
must be pondered upon carefully, to analyze the risks and the benefits being derived from it,
before implementing it on a local, regional or global scale.
D. Peters (Rutherford Appleton Laboratory),
B. Reed (University of Oxford),
M. Watson (University of Bristol),
D. Grainger (University of Oxford)
In the search for the optimal particle: optical properties
We present the latest results from a set of laboratory studies into the optical properties of
potential SRM materials, from the SPICE project. The study has focused on submicron particles
for long term dispersal in the stratosphere combined with efficient solar scattering properties.
State of the art optical measurements have been conducted on laboratory generated aerosols at
the STFC Molecular Spectroscopy Facilities’ multi-pass aerosol cell. The study has included both
the visible and solar infrared spectra as this could have a significant effect on stratospheric
heating and hence affect atmospheric dynamics. A wide range of potential particles have been
identified, and the latest results from this study are presented.
L. Rkiouak
Characterisation of Mineral Particles for Solar Radiation Management Schemes
The aim of this work was to characterise mineral particles for their suitability for potential
stratospheric solar radiation management schemes as part of the UK SPICE project. Surface
properties of seven particle types were determined, such as particle size distribution, zeta
potential and surface area (porosity) and chemical properties (surface acidity). These
characterisations enable to indicate the influence of each property on the heterogeneous
reactivity of the particle. In addition, ozone decomposition on the particle surface was
investigated under dry conditions using a packed bed. The hydrodynamics of the fixed bed was
extensively studied to discriminate the effects of transport phenomena on the ozone
decomposition kinetics. The influence of the particle’s surface acidity on ozone decomposition was
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studied and it was found that the particle reactivity towards ozone was more dependent on the
strength of the surface acid sites rather than on the number of acid sites. Titania anatase and
silica particles were unreactive towards ozone under our conditions, and titania rutile was the only
particle that catalytically destroyed ozone. Silicon carbide, titania P25, alumina and diamond
deactivated with respect to ozone decomposition after varying time scales.
P. Nowack (University of Cambridge),
L. Abraham (University of Cambridge),
A. Maycock (University of Cambridge),
P. Braesicke (Karlsruhe Institute of Technology),
J. Pyle (University of Cambridge)
Climate sensitivity and solar geoengineering: do atmospheric composition feedbacks matter?
D. Weisenstein (Harvard University),
D. Keith (Harvard University)
Solar geoengineering using solid aerosol in the stratosphere: modelling efficacy and impacts of
alumina and diamond
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Posters
Conference Posters (not aligned to a particular technical session)
W. Weng (Chinese Academy of Social Sciences)
A survey of dynamic games in the exploration of climate geoengineering governance
Climate geoengineering, a suite of hypothetical technologies with the potential to dramatically
cool the climate, could cause fundamental interventions to the ecosystem and create problems
with high uncertainty and uneven distribution around the globe. The research on the science and
regulation of geoengineering is not evenly developed across the world either, nor transparently
disclosed. Speculations of other countries’ progress in geoengineering research could lead to a
race of actions. Apart from physical effects, risks and benefits analysis of climate engineering
depends largely on political and social elements. The paper intends to imply game-theoretic
analyses in geoengineering issues in a dynamic context and explore political and social driving
forces that are likely to shape a global governance regime within which decisions on the use of
climate engineering technologies could be taken.
A. E. Chavez (Northern Kentucky University)
Principled Geoengineering
We will not be able to curtail greenhouse gas emissions quickly enough to avoid significant
climate change. Thus, we should anticipate that society will consider implementing climate
engineering, either to avert a climate catastrophe or to minimize the consequences of climate
change. While geoengineering research is still in its infancy, we should begin to identify principles
we can use to determine whether to deploy such technologies.
This set of principles should include:
•
Natural state – does the technology return the environment to its state before human
modification? Would it create a new reality?
•
Outweighing consequences – do possible consequences of an act outweigh its perceived
benefits?
•
Unknowns – to what extent are most of the consequences of the technology foreseeable?
•
Alternatives – are reasonable alternatives available or foreseeable?
•
Precautionary principle – does application of the principle support the action, and does it
suggest requiring additional safeguards or insurance?
•
Reversibility – can the proposed action be undone?
•
Containability – can the effects of an action be limited to a defined geography and time?
•
Moral hazard – does the technology encourage the perpetuation of behaviors that gave
rise to the problem sought to be addressed?
•
Geographic distribution – will negative effects of an action disproportionately harm
populations in discrete geographic locations?
•
Intergenerational equity – is the technology likely to generate consequences that will be
passed along to future generations?
While a negative answer to any particular consideration should not be fatal to using the
technology, one or more negative answers should suggest an especially high level of caution. In
such instances, society may require additional safeguards. Furthermore, the principles should not
be weighted equally, so that a negative response on a particular consideration may carry greater
weight. Flexibility in their application, however, should be maintained.
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Application of these considerations to different SRM technologies produces different results,
depending upon the characteristics of the technology. Perhaps most importantly, we must
remember that knowledge about these methods is progressing, and so over time answers may
change. Nevertheless, these principles should help to guide future prioritization and deployment
of these technologies.
R. de Richter (Tour-Solaire.fr)
G. Song (Aston University)
T. Ming (Huazhong University of Science and Technology)
P. Davies (Aston University)
Elevation of emissions from fossil fuel power stations to reflect solar radiation
Coal-fired power stations emit both CO2 and sulphur dioxide into the troposphere. But if SO2 is
removed, global warming will get worse as SO2 delivered to the atmosphere forms aerosols with
strong negative radiative forcing, thus offsetting the positive radiative forcing from CO2
emissions.
However, because the SO2 is relatively short-lived (~days) its offsetting effect is limited. This can
be increased by delivering the SO2 at altitude: above the boundary layer its lifetime is increased
to weeks and, at 20 km it is increased to 1 or 2 years. Hence, if chimney stacks of power plants
were made taller, this would lower the net radiative forcing caused by the emission thus
ameliorating global warming.
In principle this concept should receive public acceptance on the grounds that a tall chimney is
just a benign modification to existing power stations, which can also reduce local air pollution and
thus improve human health. Nonetheless, such tall chimney stacks are not affordable to
construct.
Here we propose to substitute the idea of a tall chimney with a balloon engine to lift the
emissions to an altitude of several km. The engine will generate electricity as a by-product. The
necessary scale and design considerations for the balloon and tether are considered for illustrative
scenarios to assess the potential for the concept, which may also contribute to enhance outgoing
longwave radiation to the outer space.
R. Chris (The Open University)
Escaping the geoengineering catch-22
Much effort within the academy is devoted to reducing the uncertainties around climate change
and the responses to it in order to better inform policymaking. I argue that however many
uncertainties are resolved, uncertainty is irreducible and there is no objective level at which
uncertainty can be sufficiently low to avoid it inhibiting policymaking. The argument applies
complex adaptive systems theory and an examination of the distinction between risk, uncertainty
and surprise, to evidence that pervades the SRM discourse in academic research, academic
submissions to policymakers and utterances from policymakers at all scales. I also argue from
the complexity concept of a global controller, that the more centralised and prescriptive the SRM
governance regime, the more likely that it will stifle the creativity and diversity essential to it
fulfilling its potential in building the resilience critical to averting dangerous climate change. The
implications of this analysis are that SRM research and governance be driven more by risk
management than by uncertainty reduction, allowing policy to become experiment and
experiment to become policy. I consider the repercussions of such a reframing on the
presentation of climate change across the interfaces between the academy, policymakers, media,
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civil society and the public.
argument.
A counterfactual SPICE project will be used to illustrate the
J. Crook (Leeds University)
Geoengineering using oceanic microbubbles
N. Matzner (Alpen-Adria University)
Simulating a climate engineering crisis
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Suggestions for Friday Dinner
A number of pubs and casual dining restaurants are located between the Engineering Department
(CUED) and Lady Mitchell Hall (LMH), where the panel discussion is to be held. In no particular
order:
1. The Anchor Pub
2. The Mill Pub
3. The Granta Pub
4. Bella Italia (Italian)
5. Sala Thong (Thai)
6. India House (Indian)
7. Rice Boat (Kerala Cuisine – Indian)
8. The Eagle Pub
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Notes
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Notes
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Notes
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