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A new study suggests that dinosaurs may have helped keep an already overheated world warmer with their flatulence and belching 200 million years ago.

The research published on Monday in Current Biology suggests that large dinosaurs made a significant contribution to the greenhouse effect back then. Study author David Wilkinson of Liverpool John Moores University in England estimated that about 570 million tons of methane came from dinosaurs. That is similar to total atmospheric levels of methane today produced by livestock, farming and industry. Cows alone now produce nearly 100 tons a year of methane.

The study looks at the biggest and presumably gassiest dinosaurs, called sauropods. These were the long-necked plant eaters that munched on the top of trees. They were large animals that had food fermenting in their guts for long periods of time because of their gigantic size, said University of Maryland paleontologist Thomas Holtz, who was not part of the study.

Wilkinson said dinosaur gas was just one factor at a time when the world was quite tropical, about 18 degrees warmer than now. But he said some in the media and blogosphere have misinterpreted his study to say it was the main cause of ancient warming. In a phone interview, Wilkinson said it was only one of the causes, but dinosaur gas "is big enough to be a measurable effect".

What caused the ancient pre-human world to be so hot - just the way the dinosaurs needed it -was a variety of factors. Volcanoes spewed much more greenhouse gases than now, Holtz said. Swamps, water currents, shallow seas and plentiful plankton combined to raise greenhouse gas levels far higher than today, he said.

Outside climate experts say the study makes some sense, but the warming from dinosaur gas back then is dwarfed by man-made carbon dioxide today from industry.

NASA climate scientist Gavin Schmidt quickly ran some calculations based on Wilkinson's figures. Dinosaur methane would have increased temperatures about half a degree, which is a fraction of what has been caused by the burning of fossil fuels like coal and oil in the 20th century, he said.

It also is wrong to suggest the study blames dinosaur flatulence for their extinction, Holtz said. He noted that the sauropods started showing up, and getting gassy, around 200 million years ago and did not die off until 65 million years ago.

University of Victoria climate scientist Andrew Weaver said: "Frankly, methane emissions from dinosaur burps is probably not the number one thing we should be concerned about in modern society."

Questions:

1. How many tons of methane came from dinosaurs?

2. What were the biggest and gassiest dinosaurs?

3. What is warming from dinosaur gas dwarfed by?

Answers:

1. An estimated 570 million tons.

2. Sauropods.

3. Man-made carbon dioxide.

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About the broadcaster:

Emily Cheng is an editor at China Daily. She was born in Sydney, Australia and graduated from the University of Sydney with a degree in Media, English Literature and Politics. She has worked in the media industry since starting university and this is the third time she has settled abroad - she interned with a magazine in Hong Kong 2007 and studied at the University of Leeds in 2009.