Phytoplankton may play large role in Earth’s climate

A new study shows that ocean phytoplankton exert a significant and previously uncalculated influence on Earth’s climate, absorbing the sun’s radiation and warming the planet’s surface by up to 0.6 degrees Fahrenheit.

The study, conducted by researchers at US Scripps Institution of Oceanography using satellite imagery, shows that radiation that otherwise might be reflected back to space is absorbed by phytoplankton, resulting in climate warming of 0.1 to 0.6 degrees Fahrenheit.

In their paper, published in the Journal of Geophysical Research, the scientists argue that without phytoplankton, the Earth would be cooler. “This is a problem that we have to look at more carefully if we want to conduct more accurate predictions of climate change,” said Robert Frouin, a research meteorologist at Scripps.

The latest findings also affect ongoing discussions of potentially reducing global warming through ocean ‘fertilization’. The idea is to reduce global warming by fertilizing the oceans with iron, thus increasing the ocean’s biological pump by feeding organisms that would ‘pump’ carbon dioxide from the atmosphere. The Scripps findings contradict these proposals, suggesting more iron would mean more phytoplankton would mean more warming.

“We are saying that if you increase the amount of phytoplankton in the ocean, which would probably be a consequence of this iron fertilization, instead you would contribute to warming the ocean by absorbing more radiation,” says Frouin.

However, the authors say that their study is not conclusive, given that some planktonic species absorb more radiation than others, and a few reflect the sun’s radiation rather than absorb it. There may also be complex biological feedback consequences that lead to less phytoplankton in certain areas of the ocean.

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