IPCC Expert Meeting on Geoengineering

Summary of the Synthesis Report
The risks and impacts of geoengineering techniques might be best assessed within the context of the risks and impacts
of climate change and other responses to climate change such as mitigation and adaptation, rather than in isolation.
CDR and SRM methods might be assessed with a common framework of criteria; for a holistic (i.e., inclusive of all
potentially relevant aspects) comparison of response options, it could be valuable if the framework were also applied
simultaneously to mitigation and adaptation responses. The following list of criteria is proposed for consideration by
AR5 authors but is likely not to be comprehensive and would need to be carefully evaluated as part of the assessment
process:
Effectiveness – could assess how effective the technique would be at achieving its specified goal (i.e., in
removing CO 2 out of the atmosphere for CDR methods, or changing the radiative budget and/or reducing
specific climate change impacts for SRM methods);
Feasibility – could assess the state of technological/engineering readiness for deployment of the
technique (at a small scale; i.e., separate from assessing the physical or social challenges of expanding it
to large-scale deployment);
Scalability – could combine assessments of both physical (i.e., climatic, environmental, resource-related)
and social (i.e., economic, political) limits on how much and how fast deployment of the technique could
be scaled up to achieve a specified goal;
Sustainability – could combine assessments of the reversibility of impacts and assumed longer-term
commitments associated with deployment of the technique, evaluated against baseline scenarios for
climate change and diverse socioeconomic pathways. Links to the precautionary principle could be
considered;
Environmental risks – could identify and assess the physical, chemical, biological and climatic risks
associated with the technique (including, but not limited to, residual climate change impacts, unintended
consequences, risks inherent in the irreversibility or termination issues assessed in the sustainability
criteria);
Costs and affordability – could combine assessments of (a) the costs of implementing and operating the
technique (direct costs) with (b) the cost valuations for potential social and environmental externalities
generated by the technique or its failure (indirect costs). Costs would need to be evaluated against a set
of baseline mitigated and unmitigated climate scenarios;
Detection and attribution – could assess the extent to which both targeted and unintended consequences
of the technique could be detected and attributed to its deployment (i.e., verification of CO 2 withdrawal
for CDR, or identification of climatic impacts for SRM);
Governance challenges – could assess the legal and regulatory issues (local, national and international)
that are or could be associated with the technique, along with an assessment of whether/how current
institutions address these issues;
Ethical issues – could identify the variety of ethical issues that are or could be raised by the technique;
Social acceptability – could assess current knowledge of the social acceptability of the technique;
Uncertainty related to all of the above mentioned criteria.
In order to ensure consistency in the treatment of geoengineering in the AR5 using a common framework, an informal
group of AR5 Lead Authors from all three working groups might be formed. This might help to arrive at a ‘holistic’
assessment of geoengineering in the AR5.
Once sufficient knowledge and published literature on SRM and CDR methods become available, the <strong>IPCC</strong> might want
to consider a joint Special Report on Geonengineering post AR5.
As the deployment of some geoengineering technologies could have profound long-term implications for global
society, assessment of the proposed methods will need to consider timescales extending at least up to, and likely well
beyond, 2100.
<strong>IPCC</strong> <strong>Expert</strong> <strong>Meeting</strong> on Geoengineering - 4