Scientists have long known that carbon dioxide
is the main cause of most of the warming we've seen since
pre-industrial times. But there are periods in the Earth's distant
past when the connection between carbon dioxide and temperature
rise has been harder to see.
research into Greenland's ice sheets now seems to have
explained one of the mysteries of our climatic past, confirming the
importance of carbon dioxide on global temperature changes.
Around 20,000 years ago the Earth was emerging
from an ice age as orbital changes meant it received slightly more
of the sun's energy.
As ice sheets melted into the oceans, sea levels
rose and ocean circulation patterns changed.
think these changes caused carbon dioxide
from the oceans to be released into the atmosphere.
Yet despite the planet being closer to the sun
and higher levels of carbon dioxide, records for Greenland didn't
seem to show much change in temperature. While the rest of the
northern hemisphere appeared to warm, Greenland didn't seem to
follow suit for another 3,000 years. Scientists
couldn't explain why, and it was even dubbed the 'mystery interval'
But now the new
study published in the journal Science
suggests that temperatures actually had
risen - but the rise wasn't captured by earlier ice core