The world has been looking for ways to stop increasingly large amounts of carbon dioxide entering the atmosphere. Iron fertilization has been studied for over 20 years and is now ready to go to work for us.
Adding small amounts of iron to the ocean in order to increase the amount of phytoplankton is called iron fertilization. Phytoplankton are microscopic organisms that absorb carbon. So increasing the amount of iron increases the absorption of carbon. This much is accepted science.
Only a small amount of iron is needed to make vast increases in the absorption of carbon. One ton of iron can remove 83,000 tons of carbon from the atmosphere. Once the phytoplankton have absorbed the iron, they are consumed by other organisms. Some of the carbon will sink to the ocean floor, where it will remain untouched for thousands of years.
It may be possible to absorb a large percentage of the carbon dioxide generated by human activities. We do not know precisely how much because it has only been tried in small experiments. Estimates are as high as 25%, however. This reduction in greenhouse gases, together with the reduction of these gases that can be achieved through conservation and government regulation, could reduce the rate of global warming.
This change in temperature has happened before. About 49 million years ago, when temperatures on earth were much higher than they are today, carbon dioxide was trapped by a fast-growing fern called azolla. Azolla is able to absorb 6 tons of carbon per acre per year. At that time, conditions were right for the growth of large quantities of Azolla and also the burial of the resultant plants at the bottom of the ocean. The growth and burial of azolla may have been largely responsible for the decline in temperature--and carbon dioxide in the atmosphere--that led to the emergence of mammals and ultimately human civilization.
There are risks associated with iron fertilization, primarily because it has never been tried on a large scale. Because of the capability of this process to slow or even to reverse global warming in a short period of time, more experiments on a larger scale will be undertaken soon. If these are successful, we may see the introduction of large-scale iron-fertilization projects within the next 20 years.