Students at Harvard University are staging a sit-in to demand their school join the growing list of institutions divesting from fossil fuels. The campus-led divestment movement calls for purging investment portfolios of assets tied to companies that drive and profit from global warming. Harvard’s endowment is the largest of any school in the world, at $36.4 billion. The students launched their sit-in inside a building housing the offices of school administrators, including President Drew Fast. Hundreds of actions are expected around the world today and Saturday as part of Global Divestment Day.