Our Common Future Under Climate Change

International Scientific Conference 7-10 JULY 2015 Paris, France

Menu
  • Home
  • Zoom Interactive Programme
Cliquer pour fermer

Thursday 9 July - 17:30-19:00 UPMC Jussieu - ROOM 101 - Block 24/34

3301 - Climate Intervention: Evaluating its Risks, Benefits, and Potential

Parallel Session

Lead Convener(s): A. Robock (Rutgers University, New Brunswick, NJ, United States of America)

Convener(s): M. Maccracken (Climate Institute, Washington, DC, United States of America), S. Schäfer (Institute for Advanced Sustainability Studies, Potsdam, Germany)

17:30

Climate Intervention: A Summary of the U.S. National Research Council Report on Geoengineering

K. Caldeira (Carnegie Institute of Science, Stanford, CA, United States of America), W. Abdalati (University of Colorado, Boulder, CO, United States of America)

Abstract details
Climate Intervention: A Summary of the U.S. National Research Council Report on Geoengineering

W. Abdalati (1)
(1) University of Colorado, CIRES, Boulder, CO, United States of America

Abstract content

Climatologically, humans are in unfamiliar territory.  Failure over the last few decades to adopt substantive climate mitigation strategies has continued to stress the planet in ways that present some well-understood and some poorly understood risks that pose a threat to human livelihood across the globe.  These risks, which continue to increase as greenhouse forcing proceeds unabated, have raised some important questions about the viability of climate intervention (often referred to as geoengineering) as a means to avoid or reduce some of the consequences of climate change.  Strategies for such intervention fall into two categories, representing two very different approaches to addressing the climate challenge.  The first is carbon dioxide reduction – the removal from the atmosphere and reliable storage of carbon, which has elements of a mitigation approach in that it seeks to reduce the amount of CO2 that enters or remains in the atmosphere.  The second is albedo modification, which seeks to increase the amount of sunlight reflected from the Earth, thus reducing the surface incident radiation. 

 

There is a pressing need for a careful and clear scientific foundation that can inform ethical, legal, and political discussions surrounding climate intervention.  Toward that end, the National Research Council (NRC) of the U.S. National Academy of Sciences undertook a study to assess the current state of knowledge associated with climate intervention, which resulted in a set of recommendations to inform future decisions on possible climate intervention research and deployment. This talk will present the NRC committee’s findings and recommendations, which speak to: the state of readiness of climate intervention methods and the associated challenges, their value in the context of mitigation and adaptation strategies, research needs for advancing our understanding of climate intervention approaches in order to make informed decisions on their deployment, and governance considerations for such research.  

 

Climate intervention is fraught with a wide range of risks and uncertainty. The key question that underpins the need for and approach to research is whether climate change may push society to a state in which the risks associated with non-intervention may outweigh the risks of intervention. Making such an assessment requires a foundation of knowledge and understanding.

17:45

Volcanic Eruptions as an Analog for Stratospheric Geoengineering

A. Robock (Rutgers University, New Brunswick, NJ, United States of America)

Abstract details
Volcanic Eruptions as an Analog for Stratospheric Geoengineering

A. Robock (1)
(1) Rutgers University, Department of Environmental Sciences, New Brunswick, NJ, United States of America

Abstract content

            In response to the global warming problem, there has been a recent renewed interest in geoengineering “solutions” involving “solar radiation management” by injecting particles into the stratosphere, brightening clouds or the surface, or blocking sunlight with satellites between the Sun and Earth.  No systems to conduct geoengineering now exist, but a comparison of different proposed stratospheric injection schemes, using airplanes, balloons, and artillery, shows that using airplanes to put sulfur gases into the stratosphere would not be expensive.  Nevertheless, it would be very difficult to create stratospheric sulfate particles with a desirable size distribution.  While volcanic eruptions have been suggested as innocuous examples of stratospheric aerosols cooling the planet, the volcano analog also argues against geoengineering because of ozone depletion, regional hydrologic responses, and other negative consequences.  Volcanic eruptions are an imperfect analog, since solar radiation management proposals involve the production of a permanent stratospheric aerosol layer, while volcanic layers are episodic.  Nonetheless, we can learn much from the volcanic example about the microphysics of stratospheric sulfate aerosol particles; changes in atmospheric circulation, producing regional climate responses, such as changes to the summer monsoon; atmospheric chemistry; changes of the partitioning of direct and diffuse insolation; effects on satellite remote sensing and terrestrial-based astronomy; and impacts on the carbon cycle.  There are 26 reasons why geoengineering may be a bad idea, and five reasons why it might be a good idea.  Some of these can be evaluated with climate modeling, and some using the volcanic analog.  Observations of the next large volcanic eruption will help to understand the evolution in stratospheric sulfate aerosol size distribution over the first few months after the eruption.  Much more research is needed before we can quantify each of these, so that policymakers in the future can make informed decisions about whether to ever implement stratospheric geoengineering.  Given what we know today, global efforts to reduce anthropogenic emissions and to adapt to climate change are a much better way to address anthropogenic global warming.

18:00

The governance of solar geoengineering

S. Schäfer (Institute for Advanced Sustainability Studies, Potsdam, Germany), N. Moore, (Institute for Advanced Sustainability Studies, Potsdam, Germany)

Abstract details
The governance of solar geoengineering

S. Schäfer (1) ; N. Moore, (1)
(1) Institute for Advanced Sustainability Studies, Potsdam, Germany

Abstract content

This talk will give an overview of past developments in the governance of solar geoengineering research, contextualize these developments within broader debates on research governance, and conclude with an outlook on how the early governance of solar geoengineering research is relevant to potential future dynamics of international conflict and cooperation on solar geoengineering. Solar geoengineering research has proven fertile ground for calls for and adoption of understandings that reflect new characterizations of science (for example, as ‘post-normal’), new ways of assessing scientific results (for example, through ‘extended peer review’ or ‘technologies of humility’), and new processes for conducting research (for example, ‘transdisciplinarity’ or ‘mode 2 science’), which aim to foster cooperation between broader sets of stakeholders and thereby to accommodate their values and beliefs into the research process. Whether these can be put into practice or not will set precedents and norms that are carried forward into negotiations over future activities, including those that may be deployment-related.

18:15

The Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP)

D. Keller, (GEOMAR, Kiel, Germany), A. Lenton (CSIRO, Hobart, Australia), V. Scott (University of Edinburgh, Edinburgh, United Kingdom), N. Vaughan (University of East Anglia, Norwich, United Kingdom)

Abstract details
The Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP)

D. Keller, (1) ; A. Lenton (2) ; V. Scott (3) ; N. Vaughan (4)
(1) GEOMAR, Helmholtz centre for ocean research, Kiel, Germany; (2) CSIRO, Hobart, Australia; (3) University of Edinburgh, School of geosciences, Edinburgh, United Kingdom; (4) University of East Anglia, Tyndall Centre for Climate Change Research, Norwich, United Kingdom

Abstract content

Continued anthropogenic greenhouse gas emissions are changing the climate threatening “severe, pervasive and irreversible” impacts. Inadequate emissions reduction is resulting in increased attention on Climate Intervention (CI) – deliberate interventions to counter climate change that seek to either modify the Earth’s radiation budget, or remove the primary greenhouse gas from the atmosphere – Carbon Dioxide Removal (CDR). The majority of future scenarios that do not exceed 2°C warming by 2100 include CDR methods.  At present, there is little consensus on the impacts and efficacy of the different types of proposed CDR. In response, the Carbon Dioxide Removal Model Intercomparison Project (or CDR-MIP) is proposed. This project aims to bring together a suite of Earth System Models (ESMs) and Earth System Models of Intermediate Complexity (EMICS) in a common framework to explore the potential, risks, and challenges of different types of proposed CDR. At present the proposed simulations for CDR-MIP include: Direct–air capture simulations, Afforestation and Ocean alkalinisation as well as a modified Diagnostic, Evaluation, and Characterization of Klima (DECK) experiment.  These experiments are designed to answer key questions related to quantifying efficacy, feedbacks, response time scales, and potential side effects of specific CDR methods, as well as questions of climate “reversibility”.  Here we present details on the proposed experiments, and encourage feedback from the community on their design and implementation. It is anticipated that this will be the first stage of a continuing project exploring CDR, and as such we strongly encourage interested modeling groups to participate. CDR-MIP aims to commence in September 2015.

18:25

Cirrus cloud thinning: Do the right conditions exist, and how can it be tested with observations?

D. Mitchell (Desert Research Institute, Reno, Nevada, United States of America), A. Garnier (UPMC-UVSQ-CNRS, Paris, France), M. Avery (NASA, Hampton, United States of America)

Abstract details
Cirrus cloud thinning: Do the right conditions exist, and how can it be tested with observations?

D. Mitchell (1) ; A. Garnier (2) ; M. Avery (3)
(1) Desert Research Institute, Atmospheric Sciences, Reno, Nevada, United States of America; (2) UPMC-UVSQ-CNRS, Laboratoire atmosphères, milieux, observations spatiales, Paris, France; (3) NASA, Atmospheric composition, Hampton, United States of America

Abstract content

        This presentation will describe recent scientific developments on a climate intervention (CI) method sometimes called cirrus cloud thinning, addressing (1) new evidence that supports its underlying physical assumptions; (2) a means of field testing the CI method without affecting the environment (i.e. without cloud seeding); and (3) how to reduce uncertainties concerning its radiative and climate impacts.

             While GCM testing of cirrus cloud thinning suggests it has some advantages over stratospheric aerosol injection, cirrus CI will not work when ice is primarily formed through heterogeneous nucleation for T < -38°C.  Field campaigns have shown that ice in cold cirrus is generally produced heterogeneously, but these campaigns have not addressed the cirrus at high latitudes that would determine the effectiveness of cirrus CI.

          A new understanding of thermal absorption in two split-window channels has rendered a reinterpretation of a standard CALIPSO satellite retrieval (the effective absorption optical depth ratio, or βeff), and a tight correlation between βeff and the N/IWC ratio has been demonstrated, where N = the ice particle number concentration and IWC = ice water content.  When applied to cold semi-transparent cirrus clouds having emissivities between 0.4 and 0.8, we find that (1) polar cold cirrus (T < -38 C) occur much more often during winter than during summer and (2) N/IWC is relatively high at high latitudes during winter, suggesting that homogeneous nucleation occurs frequently there.  Homogeneous nucleation is further supported by the fact that high N/IWC values tend to coincide with regions of low mineral dust concentration as predicted by CAM5 (Storelvmo and Herger, 2014, JGR). This high N/IWC during winter (and probably from Dec. – April) is likely to have a strong greenhouse effect that may increase high latitude temperatures by 2-5°K relative to cirrus conditions where heterogeneous nucleation dominates (Storelvmo et al. 2014, Philos. Trans. A, Royal Soc.). Thus, implementing cirrus CI at high latitudes (in both hemispheres) only during the months when noontime solar zenith angles are very low or when the sun never rises (i.e. seeding only 15% of the planet) may have a comparable cooling effect at high latitudes where global warming is most severe, and may have a mean global cooling of 1.4°K as shown in Storelvmo et al. (2014, Philos. Trans. A, Royal Soc.).  These satellite findings indicate that cirrus CI is a real possibility.

           These N/IWC satellite retrievals also show that N/IWC at high latitudes during summer is relatively low and characteristic of heterogeneous ice nucleation.  This may be the result of higher mineral dust concentrations, expected to be higher during summer at high latitudes.  This apparent changing of ice nucleation mode from winter to summer may provide a natural means of field testing the cirrus CI method, without any need of cloud seeding from aircraft.  The DOE ARM program is considering a field program for sampling wintertime Arctic cirrus (T < -40°C) in response to these satellite retrievals due to their importance to climate science.  In situ measurements of wintertime cold Arctic cirrus would enable their microphysical properties to be parameterized (i.e. cloud temperature related to effective diameter De; De related to mass-weighted ice fall speed) and contrasted with microphysical properties/parameterizations associated with cirrus formed at similar temperatures through heterogeneous ice nucleation.  GCM simulations using these parameterizations would then be able to evaluate the actual potential climate impact of cirrus cloud seeding (i.e. cirrus CI) at high latitudes, thus reducing various uncertainties associated with cirrus CI such as its cooling impact.

            If a large scale CI field experiment were ever conducted on winter high latitude cirrus, this satellite method could be used to monitor these clouds and to determine whether the CI method was working (i.e. seeding with efficient ice nuclei was changing the nucleation mode).

         Finally, it is noteworthy that cirrus CI appears to be the only radiation management CI approach that preferentially cools the Polar Regions where the effects of global warming are most severe.

18:35

Low-cost low-risk space-based geoengineering – is it possible?

A. Ellery (Carleton University, Ottawa, ON, Canada)

Abstract details
Low-cost low-risk space-based geoengineering – is it possible?

A. Ellery (1)
(1) Carleton University, Mechanical & Aerospace Engineering, Ottawa, ON, Canada

Abstract content

Space-based geoengineering is often discarded as an approach to geoengineering on the basis of cost and feasibility. The Angel approach is to launch modular component spacecraft into the Sun-Earth L1 point forming a solar shield to reduce the amount of solar energy incident on the Earth. The cost and feasibility constraints generally revolve around the issue of launch capacity from the Earth’s surface. The proposed American lunar Resource Prospector Mission (PRM) slated for launch in 2018 offers another approach – the robotic use of lunar resources to bootstrap the feasibility of lower-cost space missions by reducing the amount of launched material. We present a preliminary feasibility and technological development assessment to manufacture the modular spacecraft required to realise a modular solar shield concept. The RPM mission will be investigating the extraction and processing of lunar soil – in particular, ilmenite (FeTiO3). It may be extracted magnetically and ilmenite grains are preferentially enriched in volatiles. Although dominated by hydrogen – itself a useful reductant as well as propellant with oxygen - these volatiles include carbon compounds that may potentially be manufactured into plastics (silicone plastics in particular to conserve the carbon inventory). These volatiles may be evolved by heating the ilmenite grains to ~600oC using a simple fractional distillation column. The ilmenite is further heated to >900oC with recycled hydrogen (from lunar water ice or recovered volatiles) to yield oxygen, wrought iron and titania ceramic/glass: FeTiO3 + H2 → TiO2 + Fe + O2. Although the primary interest for RPM is in the recovered oxygen to support human lunar colonisation, our interest is in the iron to form the basis of a robotic industrial infrastructure. As well as iron, cast lunar basalt offers the possibility of compressive material as sacrificial structures to conserve iron for incorporation into manufactured spacecraft structures – wrought iron is a perfectly adequate structural material. The Moon exhibits a hostile thermal environment so thermal control materials will be essential in any infrastructure as well as the spacecraft modules. TiO2 is an excellent thermal (and electrical) insulator which may be formed into fibreglass. As well as thermal conduction, thermal conduction material is required – fernico, an alloy of iron, nickel and cobalt, is an excellent thermal and electrical conductor. Both Ni and Co may be sourced from mass concentration regions of the Moon, marking the locations of iron meteorite material. Semiconductor material – silicon - is available from lunar silicates minerals. From these materials, we have the basic elements we require to build a spacecraft mechanically, electrically and thermally. The only Earth-imported reagents required for isolation of these materials are Na and Cl which nevertheless are recycled. The materials must be formed into useful structures, components and parts. The advent of 3D printing offers a versatile means of manufacturing that can handle plastics, metals and ceramics. Selective laser sintering is an approach that uses lasers to thermal fuse particles into layers, thereby building 3D structures that cannot be manufactured in any other way. Electronics without solid state manufacturing techniques represents a particular challenge though progress has been made in printed plastic electronics. Another option is to use 3D printing to manufacture vacuum tube-based electronics for simple control systems. This approach is favoured because it relies on ceramics and metals already extracted. Indeed, thermionic emission with vacuum tubes offers a viable form of electric energy generation from thermal sources. My group has been exploring how to 3D print electric motors using multiple lunar-derived materials – core of iron plates, insulating plates and bobbins, and conducting wire – to construct a 3D printable universal motor. If successful, this offers the prospect that 3D printing could manufacture further manufacturing tools – lathes, milling stations, etc to perform further manufacturing functions. Furthermore, electromagnetic launchers are derivatives of electric motors arrayed linearly rather than radially (different scale of course). This offers the prospect of launch with minimal fuel use. Indeed, 3D printers could potentially manufacture complete robotic devices – manipulators for assembly of parts, rovers for geological surveying and 3D printers themselves for self-replication. A corollary to this capability is that such 3D printing systems could manufacture the spacecraft modules required to implement a solar shield with a modest inventory launched from Earth.

18:45

Climate Engineering and Policy Interaction Networks: The Challenges of Regulating a Complex System

J. Lawhead (University of Southern California, LOS ANGELES, United States of America)

Abstract details
Climate Engineering and Policy Interaction Networks: The Challenges of Regulating a Complex System

J. Lawhead (1)
(1) University of Southern California, Earth Science / Philosophy, LOS ANGELES, United States of America

Abstract content

     The global climate is a complex system.  Among other things, this means that a complete analysis of the climate as a whole involves attending to the ways in which various geophysical and biological subsystems influence and constrain one another's behavior.  This fact is widely appreciated.  Less widely appreciated is the fact that climate policy design and analysis involves very similar considerations.  Global policy initiatives like climate engineering will not be implemented in a social vacuum, and the emerging consensus is that climate engineering would be best employed as part of a multi-faceted strategy that also involves mitigation and adaptation programs. In light of this, it is vitally important that we think about the ways in which different climate-related policies might influence and constrain one another before we begin to implement any significant global policy.

     While feasibility analyses and impact studies exist for many proposed climate engineering programs, very little attention has been paid to the ways in which such programs might interact with and constrain other international and national climate policies.  This paper explores this “interaction problem” from an interdisciplinary perspective, focusing on a detailed hypothetical case study in which a solar radiation management by stratospheric aerosol injection program is combined with a global system of economic carbon credits.  The conjunction of these two programs raises practical, theoretical, and ethical concerns that don’t appear when either policy is considered alone, and which might significantly alter the effectiveness and feasibility of both programs.  This incomplete picture, arising from analyzing climate engineering proposals in isolation, is a potentially dangerous oversight as we move closer and closer toward possible implementation.