Wednesday, November 10th, 2010
There have been several critiques of geoengineering as a climate mitigation tool. Two of the most incisive, in my opinion, come from science and ethics.
The first is a 2007 paper in PNAS by Matthews and Caldeira showing that if we establish aerosol clouds or space reflectors while doing nothing to reduce carbon emissions, we run the risk of catastrophic rates of warming (2-4 degrees C per decade) if these systems were to fail.
The second is a recent piece in Slate by my colleague, Dale Jamieson, who argued that there is no moral and legal authority to know how and when to deploy geoengineering or by how much.
One proposed geoengineering tool is fertilizing the world’s oceans with iron. The premise behind this idea was developed by John Martin in 1990, who is often quoted as saying something like, “Give me a tanker of iron, and I’ll give you an ice age.” Micronutrients like iron and zinc are extremely limiting to phytoplankton growth in the open ocean—orders of magnitude moreso than nutrients we typically think of in common fertilizers, like nitrogen and phosphorus. Dumping iron into the oceans has been shown to stimulate algal blooms, and the creation of this biomass consumes CO2 from the surface waters and atmosphere, thereby helping to mitigate rising CO2 from fossil fuels. In theory, some of this biomass should sink to the deep ocean where it is sequestered for centuries, but this has yet to be shown definitively on a wide scale.
In a forthcoming paper in the Proceedings of the National Academy of Sciences, Mary Silver and colleagues show that there is another potential risk of geoengineering resulting from ocean iron fertilization…