Many scientists are understandably nervous about tinkering on a grand scale with the atmosphere and the oceans. The Intergovernmental Panel on Climate Change—a scientific body appointed by the United Nations to assess the risks of a changing climate—has described geo-engineering as “largely speculative and unproven, and with the risk of unknown side-effects”.An excellent summary on the topic.
Broadly, there are two types of fears. The first is of technological hubris. History is littered with plans that went awry because too little was known about complex natural systems.
The other fear is of moral hazard—the possibility that people would see the promise of geo-engineering their way out of trouble, despite its risks and uncertainties, as an excuse to continue to pollute the atmosphere as usual.
Bottom Line: I am willing to support reversible pilot schemes to test geo-engineering only after we stop doing stupid things, e.g., subsidizing fuel consumption (Iran, Indonesia, Venezuela, India, et al.).
Addendum: Read about the impact of $0.04/liter gas in Venezuela, e.g., 30 km commute that takes 3 hrs.