For example, significant cooling and strong dynamical effects after the Laki event and other high-latitude eruptions are believed to have caused decreased flow of the Nile River in Egypt and weakened African and Asian monsoons based on climate model simulations, with potentially very significant impacts on food and water supplies.
The basic concept is the same as that underpinning the "white roads" idea -- the development of a technology that can reflect a proportion of the sun's radiation away from the earth's surface and back out into space, thereby cooling the atmosphere and slowing, or even reversing the damaging effects of global climate change.