Deep-Sea Corals Reveal Stories of Past Climates
We know a lot about how carbon dioxide (CO2) levels can drive climate change, but how about the way that climate change can cause fluctuations in CO2 levels? New research from an international team of scientists reveals one of the mechanisms by which a colder climate was accompanied by depleted atmospheric CO2 during past ice ages.
The overall goal of the work is to better understand how and why the earth goes through periodic climate change, which could shed light on how man-made factors could affect the global climate.
Earth’s average temperature has naturally fluctuated by about 4 to 5 degrees Celsius over the course of the past million years as the planet has cycled in and out of glacial periods. During that time, the earth’s atmospheric CO2 levels have fluctuated between roughly 180 and 280 parts per million (ppm) every 100,000 years or so. (In recent years, man-made carbon emissions have boosted that concentration up to over 400 ppm.)
About 10 years ago, researchers noticed a close correspondence between the fluctuations in CO2 levels and in temperature over the last million years. When the earth is at its coldest, the amount of CO2 in the atmosphere is also at its lowest. During the most recent ice age, which ended about 11,000 years ago, global temperatures were 5 degrees Celsius lower than they are today, and atmospheric CO2 concentrations were at 180 ppm.