Since scientists first determined that atmospheric carbon dioxide was lower during ice ages than during warm phases, they have looked at why, theorizing that it may be a function of ocean circulation, sea ice, iron-laden dust or temperature. Yet no computer model has been able to explain why CO2 levels were as much as one-third lower when an ice age settled in. A newly published study offers a compelling answer -- a combination of temperature variation in sea water and iron from dust off Southern Hemisphere continents. Many past studies that analyzed ocean temperatures made the assumption that they cooled at the same rate over the entire globe. The researchers now know that the oceans cooled much more in some regions, meaning cold water may have the potential to soak up a lot more carbon from the atmosphere than past studies accounted for.
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