• Geoengineering the globe to reduce global warming
• Sulfate aerosol injection into the stratosphere

• Could reduce average temperature of the globe

• Omission: Does not counter direct effects of CO2, including:

• Ocean acidification that leads to, among other things, loss of coral reefs
• Altered land-plant competition
• Negative effects:
• Sulfate aerosols are projected to cool low latitudes, but may even accentuate warming at high latitudes
• Acidity of sulfate aerosols that ultimately get deposited in oceans is non-negligible
• Placing numerous reflective elements in orbit
• Omission: Does not counter direct effects of CO₂, noted above
• Neutral: Models show no significant effects on the global hydrological cycle
• Unassessed effects on
• Global photosynthetic productivity
• Hydrologic cycle
• Fertilizing the Southern Ocean with its most-limiting nutrient, iron, so that plantkon flourish and, upon dying, take carbon to depth in the ocean
• Limitation: Responses in experiments to date are smaller than expected; economic cost may be too high
• Negative effects: Ecosystem disruption is likely to be extensive
• Abiotic (chemical) capture of CO₂ from open air with numerous towers
• Neutral: Costly, but no more than other schemes, according to initial analyses
• Failure to maintain the schemes that only block solar radiation (aerosols, space-borne reflectors) from economic collapse, wars, or other causes would subject the earth to rapid, probably catastrophic warming
• Niche for us: while some highly competent groups have pointed out the pros and cons, especially the latter, the dissemination of the analyses to the public, to interest groups, and policymakers still has deficiencies that we could remedy with advanced presentations