Or another way to consider the question. What's the worst thing you can possibly do to contribute to global warming?
Is it to procreate?
The average American causes 18 metric tons of CO2 emissions. That's the equivalent of flying from LA to New York and back 3.4 times per month. If you flew that route 3 times a month rather than have a child you'd be doing the world a favor.
The comedian Bill Burr is onto something here (language warning).