Using weed recreationally might change the climate inside your head. But cannabis production is generating large amounts of gases that heat up Earth’s physical climate.

Indoor cannabis farming is booming in the United States thanks to the legalization of the drug in Colorado and elsewhere. Jason Quinn and his colleagues at Colorado State University in Fort Collins looked at how much electricity and natural gas are needed in various states to grow marijuana in an artificial indoor climate, which allows for a consistent product in any weather. The researchers then calculated the greenhouse-gas emissions associated with this energy consumption.

The team found that the energy required to yield one kilogram of dried cannabis flower produces the equivalent of 2–5 tonnes of carbon dioxide. Moving weed production from indoor facilities to greenhouses and the great outdoors would help to shrink the carbon footprint of the nation’s legal cannabis industry, the researchers say.