A for-profit company led by Yanai Yedvab, an Israeli scientist, has recruited about 25 scientists and engineers and raised $15 million in a first round and then $60 million in a second round to research practical, safe, and effective methods for cooling the planet using aerosol particles injected into the stratosphere. Neither the composition of the proposed particles nor the hardware for lifting them to the stratosphere have yet been revealed. More information can be found in this article in Politico and this article in Undark. Commentators are speculating that the business plan is to be paid by governments to cool the planet.