Nature's carbon balance confirmed
The researchers used data stored in the Epica ice core

Scientists have found new evidence that the Earth's natural feedback mechanism regulated carbon dioxide levels for hundreds of thousands of years.
And they say humans are now emitting CO2 so fast that the planet's natural balancing mechanism cannot keep up.

Carbon spewed out by volcanoes is removed from the air by rock weathering and transported to the ocean floor.

Using evidence from an Antarctic ice core, the team calculated that over a period of 610,000 years the long-term change in atmospheric CO2 concentration was just 22 parts per million (ppm), although there were larger fluctuations associated with the transitions between glacial and interglacial conditions.
This suggests a natural thermostat which helps maintain climate stability
By comparison, two centuries of human industry have raised levels by about 100 ppm - a speed of rise about 14,000 times faster.
"These long term cycles are way too slow to protect us from the effect of (anthropogenic) greenhouse gases," said Richard Zeebe from the University of Hawaii in Honolulu.
"They will not help us with our current CO2 problem. Right now, we have put the system entirely out of equilibrium."
Scientists have long believed that the Earth’s climate was stabilised by a natural carbon thermostat.
In their model, carbon released into the atmosphere, primarily by volcanoes, is slowly removed through the weathering of mountains, washed downhill into oceans, and finally buried in deep sea sediments.
Volcanic eruptions are historically a significant source of carbon dioxide
"A lot of people had tried to refute this hypothesis, but our study provides the first direct evidence (that it is correct)," said Dr Zeebe.