In October 2012, Steyer stepped down from his position at Farallon in order to focus on advocating for alternative energy. Steyer decided to dispose of his carbon-polluting investments in 2012, although critics say he did not dispose of them quickly enough and noted that the lifespan of the facilities he funded would extend through 2030. A 2014 New York Times article said coal-mining companies that Farallon invested in or lent money to under Steyer had increased their coal production by 70 million tons annually since receiving money from Farallon, and that Steyer remained invested in the Maules Creek coal mine. Prior to Steyer leaving Farallon, a student activist group called UnFarallon criticized the company for investments in companies with anti-environmental policies. In 2016, some critics noted that Farallon had also invested in private prisons while Steyer was leading the hedge fund. According to SEC filings, Steyer was at the helm as the hedge fund purchased nearly $90 million of Corrections Corporation of America stock (5.5% of the company's outstanding shares). After leaving Farallon, Steyer hosted a two-day think-tank entitled the 'Big Think Climate Meeting' to discuss how to address climate change.
In 2012, Steyer was the leading sponsor of Proposition 39 on the ballot in California. Its purpose was to close a loophole that allowed multi-state corporations to pay taxes out of state, mandating that they pay in California. Steyer contributed $29.6 million, saying that he could wait no longer for the change.
In 2012, Steyer hosted a fundraiser at his home for President Obama. At a private meeting, Steyer, along with fifteen other top donors, reportedly pressed the president regarding the Keystone pipeline, which Steyer opposed. Obama was said to be supportive of Steyer's views, but reluctant to put his full weight behind any initiatives without better proof. Steyer was critical of Obama's decision to keep an energy initiative as a low priority.
After holding several conversations during the summer of 2012 with environmental writer Bill McKibben, Steyer decided to focus much of his attention on the Keystone Pipeline. Steyer officially left Farallon in 2012. He was criticized by some Republicans for attacking the pipeline even though he held some investments in the fossil-fuel industry. The investments included stock in Kinder Morgan, which had its own pipeline connecting the Canadian bitumen sands to a port on the Pacific, which could be seen as a rival to the Keystone pipeline. Steyer promised to fully unload his holdings there within a year. In September 2013, Steyer appeared in a series of commercials in opposition to the proposed pipeline.