Rising global temperatures could increase the amount of carbon dioxide naturally released by the world's oceans, fueling further climate change, a study suggests. Scientists studied a 26,000-year-old sediment core to find out how the ocean's ability to take up atmospheric CO2 has changed over time, and found that when silicon was least abundant in ocean waters corresponded with relatively warm climates, low levels of atmospheric iron, and reduced CO2 uptake by the oceans' plankton....