A booming market for carbon credits could become mainstream under a plan to make it easier for financial firms to create products such as exchange-traded funds. State Street STT 2,45 %increase; green triangle pointing upwill start providing its back-office services to clients who want to invest in carbon credits. The giant custodian bank and fund manager says the move will make it easier for large investors to trade the products, a key step in making them an accessible mainstream investment (Amrith Ramkumar)

individuals.