New research discredits a $100 billion geoengineering fix to global warming
Michael Lutz, University of Miami
November 29, 2007




Scientists have revealed an important discovery that raises doubts concerning the viability of plans to fertilize the ocean to solve global warming, a projected $100 billion venture.

Research performed at Stanford and Oregon State Universities, published in this month's Journal of Geophysical Research, 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 photosynthesize.


This SeaWiFS image shows average chlorophyll a concentration from October 1997 to April 2002. Image courtesy of the SeaWiFS Image Gallery

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However, this process, which is analogous to adding manure 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 as they algae eventually die. 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 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", 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".



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Wind-blown iron contributes significantly to the biological productivity of the Southern Ocean near Antarctica, researchers report in this week's issue of the journal Science.

This study closely follows a September Ocean Iron Fertilization symposium at the Woods Hole Oceanographic Institution (WHOI) attended by leading scientists and concerned representatives from governmental, business, 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 deep ocean carbon sequestration occurs. Scientists suggested that verification may require more massive and more permanent experiments.

During the Ocean Iron Fertilization meeting Dr. Hauke Kite-Powell, of the Marine Policy Center at WHOI, estimated the future value of ocean fertilization at $100 billion of the emerging international carbon trading market, which has the goal of mitigating global warming. Scientists cautiously 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.

However, the global study of Dr. Lutz and colleagues suggests that greatly enhanced carbon sequestration should not be expected no matter the location or duration of proposed large-scale ocean fertilization experiments.

Dr Lutz said "The limited duration of previous ocean fertilization experiments may not be why carbon sequestration wasn't found during those artificial blooms. This apparent puzzle could actually reflect how marine ecosystems naturally handle blooms and agrees with our findings. A bloom is like ringing the marine ecosystem dinner bell. The microbial and food web dinner guests appear and consume most of the fresh algal food."

"Our study highlights the need to understand natural ecosystem processes, especially in a world where change is occurring so rapidly," concluded Dr. Lutz.

The findings of Dr. Lutz and colleagues coincide with and affirm this month's decision of the London Convention (the International Maritime Organization body that oversees the dumping of wastes at sea) to regulate controversial commercial ocean fertilization schemes. This gathering of international maritime parties advised that such schemes are currently not scientifically justified.

Strategies to sequester atmospheric carbon dioxide, such as ocean fertilization, will be considered by international governmental representatives during the thirteenth United Nations Framework Convention on Climate Change conference in Bali next month.

More information

CITATION: Michael Lutz, Ken Caldeira, Robert Dunbar, and Michael Behrenfeld, Seasonal rhythms of net primary production and particulate organic carbon flux describe biological pump efficiency in the global ocean. Journal of Geophysical Research, Vol. 112, C10011, doi:10.1029/2006JC003706 (2007)





CITATION:
Michael Lutz, University of Miami (November 29, 2007).

New research discredits a $100 billion geoengineering fix to global warming.

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