In 2020, scientists from TU Berlin calculated that a 30 kg dog emits around one ton of CO2 per year. Factors such as the production of dog food and the environmental damage caused by dog waste were also taken into account. For comparison: a dog causes about the same amount of CO2 emissions as a passenger on a flight from Berlin to Washington. Cats perform slightly better in model calculations, but their ecological balance is also staggering: Swiss scientists calculated in 2019 that keeping a cat causes about as much CO2 per year as driving from Berlin to Venice by car.