In 2018 Ken Griffin’s Citadel hired a group of scientists and analysts whose weather forecasts were more accurate than those of most meteorological offices. The recruitment of the 20-strong team was unusual for a big hedge fund in a sector largely focused on stocks, bonds and currencies. But it has been a key part of a push by Griffin’s $54b-in-assets firm to build out a wide-ranging commodities business encompassing both futures and physical trading.