IPCC Expert Meeting on Geoengineering

Annex 5: Breakout Group Reports
Regional SRM – regional climate change
There are limitations in current ability to predict regional climate change patterns from global mean forcing over several
decades (e.g., from greenhouse gases), and hence the ability to project local, regional responses to local SRM (e.g.,
associated with roofs or agriculture) is also limited, with corresponding consequences for assessment possible at this time.
Verification
Verification of an SRM's impact on climate forcing may be through a set of simple metrics relating to reflectivity, rather
than the much more difficult task of measuring a change in radiative forcing. Given surprises of non-linearity (e.g., as
associated with Mt. Pinatubo) and indirect effects (e.g., as associated with anoxic oceans), there needs to be scientific
verification that a geoengineering action actually has the pre-calculated results. The AR5 might assess the current state of
scientific understanding regarding such verification.
Extent of AR5
Do <strong>IPCC</strong> authors focus on specific SRM topics or cover all equally? A table with similar format across all the Working
Groups could help guarantee that all reasonable, published approaches are included, with assessments focused on
approaches with more mature analyses and literature.
Proposal:
A table on geoengineering that cuts across the Working Groups and could be combined for the Synthesis Report. All
Working Groups could use the same format, with the same rows (SRM and CDR proposals) but with different columns.
Approaches: (sectioned, with multiple rows, to include SRM and CDR)
Major SRM sections are:
Space-based reduction in incident sunlight
Stratospheric aerosols (e.g., sulfate, others, engineered)
Cirrus modification (e.g., ice nuclei)
Cloud brightening (e.g., marine stratus)
Surface albedo change (e.g., no roofs, deserts, crops, ocean bubbles)
Columns: (columns specific to each Working Group)
Realizable potential radiative forcing (possible global radiative forcing, also considering economic/social
limitations)
Scalability – in terms of climate and indirect environmental effects (Working Group 1 and 2), e.g., scalable from
pilot to climate-effective implementation?; in terms of economic and social costs (Working Group 3)
Indirect effects – in terms of the climate system (Working Group 1 and 2); in terms of social costs (Working Group
3)
Potential for unpredictable effects
Sustainability / Ability to be corrected (scientific or socio-economic)
Affordability / Costs
Verification of climate impacts
Governance / Challenges (including ability to be invoked by individuals, impacts beyond boundaries, timescales of
response)
Subsections on scientific understanding and confidence level
<strong>IPCC</strong> <strong>Expert</strong> <strong>Meeting</strong> on Geoengineering - 73