"Vegetation helped save Earth from runaway cooling that would have encased the planet in ice, according to a study published on Wednesday.
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.
Belching volcanoes provided the main source of this CO2 -- in contrast to today, when the gas comes overwhelmingly from burning fossil fuels and is driving dangerous climate change.
But there was also a force which removed CO2: a chemical reaction that occurs when silica rocks are weathered.
Over the aeons, the gas is dissolved into groundwater, which flows to the sea and eventually the carbon is sequestered on the ocean floor.
Climate scientists have long puzzled about what happened at a key point in this weathering process.
Around 25 million years ago, Earth was wrenched by a period of mountain building that threw up the Himalayas and the Andes."
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.
Belching volcanoes provided the main source of this CO2 -- in contrast to today, when the gas comes overwhelmingly from burning fossil fuels and is driving dangerous climate change.
But there was also a force which removed CO2: a chemical reaction that occurs when silica rocks are weathered.
Over the aeons, the gas is dissolved into groundwater, which flows to the sea and eventually the carbon is sequestered on the ocean floor.
Climate scientists have long puzzled about what happened at a key point in this weathering process.
Around 25 million years ago, Earth was wrenched by a period of mountain building that threw up the Himalayas and the Andes."
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