Geoengineering: an ABC Science update

Australia’s ABC recently asked climate scientists for their thoughts on some of the current geoengineering proposals.

Dr Will Howard, a climate researcher from the Antarctic Climate and Ecosystems Cooperative Research Centre, offered these observations on the iron-fertilization concept:

If human societies can’t stop emitting greenhouse gasses, then perhaps we can raise the world’s capacity for taking those gases back out of the atmosphere, some geoengineering advocates suggest.

Among the best-studied options in this category is using iron to stimulate the growth of carbon-capturing plankton in the ocean.

Over the past 15 years or so, several international research teams have completed trials showing that under the right conditions this approach is scientifically feasible.

“The idea is that in some parts of the ocean, the algae that would pick up carbon and store carbon in the deep ocean are limited by iron supply,” explains Howard.

Experiments have shown when you add extra iron into these areas, you stimulate algal productivity.

But the same experiments have also shown that the carbon fixed by this process doesn’t sink very deep into the ocean.

Howard says the key question is whether you can change that: “Can you get that carbon out of the surface ocean and into the thousands-of-metres-deep parts of the ocean where it will stay out of contact with the atmosphere for a long time?”

There are other potential problems with this approach, he warns.

“A possible consequence of fertilization of the ocean is the fact that once this carbon does sink into sub-surface waters… you’ll increase that tendency toward low oxygen.”

“We know there are basins in the water that have dead zones today — where the water is anoxic and nothing that requires oxygen can live. The research would need to very carefully consider those sorts of risks before you went ahead with that kind of manipulation.”

If we discover unexpected adverse effects from a geoengineering technique, how do we recover from our mistake? Earlier in the interview Dr. Howard noted that some of the geoengineering concepts can be quickly reversed – such as sulfate aerosols. How rapidly could we unwind the effects of iron-fertilization?
For more background on geoengineering I recommend the 2.5 hour audio of the AEI seminar on “Governing Geoengineering“. We found this discussion to be one of the more informed and objective reviews of the whole range of policy options relating to climate change.