The energy used by cars and their CO2 emissions could have dropped by over 30% in the past decade if not for the world’s growing taste for SUVs, a new report from the Global Fuel Economy Initiative suggests

The negative impact on the climate from passenger vehicles, which is considerable, could have dropped by more than 30% over the past decade if not for the world’s appetite for large cars, a new report from the Global Fuel Economy Initiative suggests.

Sport utility vehicles, or SUVs, now account for more than half of all new car sales across the globe, the group said, and it’s not alone. The International Energy Agency, using a narrower definition of SUV, estimates they make up nearly half.

Over the years these cars have gotten bigger and so has their cost to the climate, as carbon dioxide emissions “are almost directly proportional to fuel use” for gas-powered cars. The carbon that goes in at the pump comes out the tailpipe.

Transportation is responsible for around one-quarter of all the climate-warming gases that come from energy, and much of that is attributable to passenger transport, according to the International Energy Agency.