clipped from: dsc.discovery.com The paper sheds light on the big natural mechanisms that over hundreds of millions of years have swung the globe like a pendulum between deep chill and intense heat.
Around 50 million years ago, the planet's poles were ice-free and crocodiles roamed the Arctic.
But that was followed by a long period of cooling, in which levels of carbon dioxide (CO2), the principal "greenhouse" gas that traps solar heat, progressively declined.
But there was also a force which removed CO2: a chemical reaction that occurs when silica rocks are weathered.
Around 25 million years ago, Earth was wrenched by a period of mountain building that threw up the Himalayas and the Andes.
Over the aeons, the gas is dissolved into groundwater, which flows to the sea and eventually the carbon is sequestered on the ocean floor.