A new study has concluded that geoengineering measures designed to reduce global warming will do little to reduce CO2 levels and, subsequently, ocean acidification. CO2 that dissolves in salt water produces carbonic acid that undermines shell formation in crustations and coral. The world's oceans absorb a quarter of atmospheric carbon dioxide, according to an international oceanography research network.
"This century will see the end of coral reefs for the next tens of thousands of years," said Ken Caldeira, a professor of environmental science in the Department of Global Ecology at the Carnegie Institution of Washington and a co-author of the paper.
In fact, coral depletion has the potential to be a major economic disaster as well as an ecological catastrophe. An essay in the March/April issue of Foreign Affairs noted that approximately 100 million people living in coastal areas worldwide depend on coral reef ecosystems for their livelihoods. The problem is that attempts to artificially cool the atmosphere, though necessary to avert more polar melting and the release of methane trapped in sub-arctic tundra, won't slow the build-up of greenhouse gases.
Geoengineering solutions have received a surge of attention in recent months, even though ideas for mechanically altering the atmosphere trace back to the presidency of Lyndon B. Johnson. Some scientists are experimenting with techniques to fertilize oceans so increased plankton growth will absorb excess CO2. Others have studied methods for reflecting sunlight, like seeding white clouds with sea water, launching solar reflectors or painting roofs white, as Energy Secretary Steven Chu famously suggested earlier this year.
Professor Caldeira dismissed most of these approaches as either financially unattainable or, in the case of Secretary Chu's white roof plan, insufficient. On balance, he said the most technically straightforward and cost-effective approach involves attempts to mimic the effect of large volcanic eruptions, like Mount Pinatubo in 1991.
Sulfur-based gases can be introduced inexpensively into the upper atmosphere, where they form sulfate particles that reflect sunlight away from the earth's surface. As the Foreign Affairs essay notes, the cost would be a fraction of emission reduction efforts that take decades to show results.
| Except that the human costs would be far higher: the lowering of global mean temperature would shorten the growing season and lead to lower food production, which would cause people to die. But who cares about humans? |
"Basically, there was cooling despite an increase in greenhouse gases," he sad. "The earth didn't come to an end." But, Professor Caldeira added, these measures "only make sense in an emergency response context." 
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