How will we know the effects and timing (permanence) of injecting the stratosphere with aerosols that block out solar radiation? Is it localized (how will such gases stay over particular areas such as the poles), because gases expand indefinitely...right? How would we control these aerosols so the earth doesn't get too cold?<p>I think it seems like a good idea, and I'm sure there are experts that could answer these questions.<p>I give the Whitehouse kudos for proposing such an initiative, at least through research we will know more about what is possible and the effects of such actions.<p>The paper provides a great overview of how to achieve a more sustainable earth. Hopefully these actions could be consistent over the long term.