Why did the Earth got warmer in the Mesozoic Era 150 million years ago? Science has the answer: dino fart.
By scaling up the digestive wind of cows, they estimate that the population of dinosaurs - as a whole - produced 520 million tonnes of [methane] gas annually.
Just some scientists disabusing the unproven theory that there is a positive feedback to greenhouse gasses. Take that away, and they have nothing. Besides, there have been plenty of times where CO2 concentrations were very much higher, and temperatures lower than today. None of it adds up. Well, it does add up to something that smells like methane.