they drifted out of position, or coalesced, or came back down sooner than we anticipated? Not only could the result be a massive waste of valuable resources, we could end up having done irreparable harm to the planet. But if we could manage to put into the sky something that actually accomplishes what it was designed to do, i.e., reduce the amount of radiation reaching Earth by just the amount necessary to compensate for the reduction in outgoing radiation caused by the greenhouse effect; wouldn't that solve the problem of climate change without having to deal with any of the political and economic obstacles to more conventional measures? Unfortunately, Earth's climate is a very complex system, and it responds to far more than just the amount of energy in and energy out averaged over the four seasons and the entire surface of the planet.  The precise spatial and temporal variations in energy distribution can have very different effects on global climate, and different SRM measures will lead to different effects.  Furthermore, SRM measures are in no way equivalent to reducing greenhouse gas emissions. And should SRM measures fail, we are still left with too much greenhouse gases in our atmosphere. It is not hard to see why the differences should matter. For example, an important factor in driving the weather is the differences in temperature and pressure between neighbouring areas. The onshore breezes that are so common in coastal areas in the summer arise because the air over the land