A team at St Andrews University, Scotland, led by Prof Graeme Ruxton, said the giant animals spent 150 years emitting methane. In fact, large plant-eating sauropods would have been the main culprits due to huge amounts of greens they consumed.
The scientists calculated the animals would have collectively produced more than 520 million tons of methane a year -- more than all today's modern sources put together.
It is thought these huge amounts could easily have been enough to warm the planet.
It is even possible that the climate change was so catastrophic that it caused the dinosaurs eventual demise, the 'Daily Mail' reported.
One of the animals, a 90-ton argentinosaurus, which measured 140ft in length, would have consumed at least half a ton of food in one day.
After breaking down in the animal's stomach it would have produced thousands of litres of the greenhouse gas compared with a modern cow which only produces 200 litres of methane daily, according to the scientists.
Methane is up to 20 times more effective in trapping heat in the atmosphere than carbon dioxide (CO2). It is created from a variety of natural and human-influenced sources which include landfills, natural gas and petroleum sources.
It's claimed humans have pushed levels of the gas up 2.5 times higher than they should be and estimate this is responsible for 20 per cent of modern global warming. Cows and other livestock only emit about 100m tons of methane a year.
According to Prof Ruxton, this is only a fifth of what was produced when Dinosaurs walked the Earth. "In fact, our calculations suggest these dinosaurs may have produced more methane than all the modern sources, natural and human, put together," Wilkinson told 'The Sunday Times'.