Truth Alert: Carbon Dioxide Benefits Phytoplankton

A plethora of media articles this morning claim global warming is killing off phytoplankton, which forms the base of the oceans' food chain. The problem with these articles is they are all based on a single, very shaky study that is contradicted by many more rigorous studies that have reached the opposite conclusion.

To reach the conclusion that global warming is harming phytoplankton, researchers had to rely on indirect indicators of past phytoplankton populations, spotty and geographically incomplete samples for current phytoplankton populations, and speculative theories tying the alleged reduction in phytoplankton populations to global warming.

By contrast, many studies in the peer-reviewed scientific literature have shown that higher temperatures and/or higher amounts of atmospheric carbon dioxide benefit rather than harm phytoplankton. For example:

In 2005, Journal of Geophysical Research published a paper by scientists who examined trends in chlorophyll concentrations, which are the building blocks of ocean life. The French and American scientists reported “an overall increase of the world ocean average chlorophyll concentration by about 22 percent” during the prior two decades of increasing carbon dioxide concentrations.

In 2007, Global Change Biology published a paper by scientists who observed that higher carbon dioxide levels correlate with better growth conditions for oceanic life. The highest carbon dioxide concentrations produced “higher growth rates and biomass yields” than the lower carbon dioxide conditions. Higher carbon dioxide levels may well fuel “subsequent primary production, phytoplankton blooms, and sustaining oceanic food-webs,” the scientists reported.

In 2008, Biogeosciences published a paper by scientists who had subjected marine organisms to varying concentrations of carbon dioxide, including abrupt changes of carbon dioxide concentration. The ecosystems were “surprisingly resilient” to changes in atmospheric carbon dioxide, and “the ecosystem composition, bacterial and phytoplankton abundances and productivity, grazing rates and total grazer abundance and reproduction were not significantly affected by CO2-induced effects.”

For some strange reason, the media largely ignored these peer-reviewed studies showing global warming is benefiting phytoplankton, but are running amuck with articles claiming the sky is falling based on the single, more speculative claims of phytoplankton harm.