Abstract: A refrigeration system having a low stage and a high stage circuit. Each stage having a compressor, an evaporator or a condenser. The low stage includes a low stage refrigerant comprising R744. The high stage includes a high stage refrigerant having a GWP less than 500. The system further includes a heat exchanger configured to transfer heat from the low stage refrigerant to the high stage refrigerant allowing the circuits to provide cooling in two stages.