The rate of mixing between the stratosphere, where the sulfur aerosols would be placed, and the troposphere, where we live, is relatively low. The half-life of

The rate of mixing between the stratosphere, where the sulfur aerosols would be placed, and the troposphere, where we live, is relatively low. The half-life of these aerosols in the stratosphere is on the order of months -- short enough, as Curtis points out, to limit the risk of any such experiment, but long enough that the quantities required are small compared to the amount of sulfur we are already putting into the troposphere.