This story reminds us how uncertain is the science around global warming’s causes and possible fixes.
From: University of Miami Rosenstiel School of Marine & Atmospheric Science
Published January 11, 2008 09:11 AM
Ocean Fertilization 'Fix' For Global Warming Discredited By New Research
Research performed at Stanford and Oregon State Universities suggests that ocean fertilization may not be an effective method of reducing carbon dioxide in the atmosphere, a major contributor to global warming. Ocean fertilization, the process of adding iron or other nutrients to the ocean to cause large algal blooms, has been proposed as a possible solution to global warming because the growing algae absorb carbon dioxide as they grow.
However, this process, which is analogous to adding fertilizer to a lawn to help the grass grow, only reduces carbon dioxide in the atmosphere if the carbon incorporated into the algae sinks to deeper waters. This process, which scientists call the "Biological Pump", has been thought to be dependent on the abundance of algae in the top layers of the ocean. The more algae in a bloom, the more carbon is transported, or "pumped", from the atmosphere to the deep ocean.
To test this theory, researchers compared the abundance of algae in the surface waters of the world's oceans with the amount of carbon actually sinking to deep water. They found clear seasonal patterns in both algal abundance and carbon sinking rates. However, the relationship between the two was surprising: less carbon was transported to deep water during a summertime bloom than during the rest of the year. This analysis has never been done before and required designing specialized mathematical algorithms.
"By jumping a mathematical hurdle we found a new globally synchronous signal," said Dr. Lutz.
"This discovery is very surprising", said lead author Dr. Michael Lutz, now at the University of Miami's Rosenstiel School of Marine and Atmospheric Science. "If, during natural plankton blooms, less carbon actually sinks to deep water than during the rest of the year, then it suggests that the Biological Pump leaks.
More material is recycled in shallow water and less sinks to depth, which makes sense if you consider how this ecosystem has evolved in a way to minimize loss", said Lutz. "Ocean fertilization schemes, which resemble an artificial summer, may not remove as much carbon dioxide from the atmosphere as has been suggested because they ignore the natural processes revealed by this research."
This study closely follows a September Ocean Iron Fertilization symposium at the Woods Hole Oceanographic Institution (WHOI) attended by leading scientists, international lawyers, policy makers, and concerned representatives from government, business, academia and environmental organizations.
Topics discussed included potential environmental dangers, economic implications, and the uncertain effectiveness of ocean fertilization. To date none of the major ocean fertilization experiments have verified that a significant amount of deep ocean carbon sequestration occurs. Some scientists have suggested that verification may require more massive and more permanent experiments. Together with commercial operators they plan to go ahead with large-scale and more permanent ocean fertilization experiments and note that potential negative environmental consequences must be balanced against the harm expected due to ignoring climate change.