Geo-engineering against climate change

December 19, 2012

Numerous geo-engineering schemes have been suggested as possible ways to reduce levels of the greenhouse gas carbon dioxide in the atmosphere and so reduce the risk of global warming and climate change. One such technology involves dispersing large quantities of iron salts in the oceans to fertilize otherwise barren parts of the sea and trigger the growth of algal blooms and other photosynthesizing marine life. Photosynthesis requires carbon dioxide as its feedstock and when the algae die they will sink to the bottom of the sea taking the locked in carbon with them.

Unfortunately, present plans for seeding the oceans with iron fail to take into account several factors that could scupper those plans, according to Daniel Harrison of the University of Sydney Institute of Marine Science, NSW. Writing in the International Journal of Global Warming, Harrison has calculated the impact of iron seeding schemes in terms of the efficiency of spreading the iron, the impact it will most likely have on algal growth the tonnage of carbon dioxide per square kilometer of ocean surface that will be actually absorbed compared to the hypothetical figures suggested by advocates of the approach.

"If society wishes to limit the contribution of anthropogenic carbon dioxide to global warming then the need to find economical methods of carbon dioxide sequestration is now urgent," Harrison's new calculations take into account not only the carbon dioxide that will be certainly be sequestered permanently to the deep ocean but also subtracts the many losses due to ventilation, nutrient stealing, greenhouse gas production and the carbon dioxide emitted by the burning of fossil fuels to produce the iron salts and to power their transportation and distribution at sea.

His calculations suggest that on average, a single ocean iron fertilization will result in a net sequestration of just 10 tonnes of carbon per square kilometer sequestered for a century or more at a cost of almost US$500 per tonne of carbon dioxide. "Previous estimates of cost fail to recognize the economic challenge of distributing low concentrations of iron over large areas of the ocean surface and the subsequent loss processes that result in only a small net storage of carbon per square kilometer fertilized," says Harrison.

Others have addressed the maximum possible contribution by modeling and the generally accepted figure is around 1 billion tonnes of carbon, but those calculations do not take into account the losses discussed by Harrison. The real limit would be when the macro-nutrients are exhausted, what then is the flux of macro-nutrients into the iron limited regions per year? "Under ideal conditions the cost could be lowered and the efficiency increased but the availability of ideal conditions will be small," says Harrison.
"A method for estimating the cost to sequester carbon dioxide by delivering iron to the ocean" in Int. J. of Global Warming, 2013, in press

Inderscience Publishers

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to