The document did not source CIA director Brennan's comment. In a speech to the Council on Foreign Relations, Brennan said that he personally was interested in the potential SAI, not that they were already doing it.
https://www.cia.gov/news-information/speeches-testimony/2016-speeches-testimony/director-brennan-speaks-at-the-council-on-foreign-relations.html

"Another example is the array of technologies—often referred to collectively as geoengineering—that potentially could help reverse the warming effects of global climate change. One that has gained my personal attention is stratospheric aerosol injection, or SAI, a method of seeding the stratosphere with particles that can help reflect the sun’s heat, in much the same way that volcanic eruptions do.

An SAI program could limit global temperature increases, reducing some risks associated with higher temperatures and providing the world economy additional time to transition from fossil fuels. The process is also relatively inexpensive—the National Research Council estimates that a fully deployed SAI program would cost about $10 billion yearly.

As promising as it may be, moving forward on SAI would raise a number of challenges for our government and for the international community. On the technical side, greenhouse gas emission reductions would still have to accompany SAI to address other climate change effects, such as ocean acidification, because SAI alone would not remove greenhouse gases from the atmosphere.

On the geopolitical side, the technology’s potential to alter weather patterns and benefit certain regions at the expense of others could trigger sharp opposition by some nations. Others might seize on SAI’s benefits and back away from their commitment to carbon dioxide reductions. And, as with other breakthrough technologies, global norms and standards are lacking to guide the deployment and implementation of SAI."