As Bill Gates built a reputation as a climate leader, his foundation's endowment continued to hold substantial investments in fossil-fuel companies, prompting The Guardian's 2015 'Keep It in the Ground' campaign — backed by hundreds of thousands of people — to call on the Gates Foundation to divest. Gates publicly rejected the divestment movement, calling it a 'false solution' that he said had reduced 'about zero' tonnes of emissions, and argued the real answer was investing in breakthrough clean-energy technology. The foundation later sold off most of its fossil-fuel holdings, including its stake in BP, though Gates maintained that divestment was the wrong strategy. Critics saw a tension between his climate advocacy and his investments.