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Brightening Clouds Could Save Coral Reefs

It's a targeted geoengineering technique that new research suggests may buy us 50 years to reduce emissions and protect imperiled reefs.
Photo: Wikipedia

Trying to manipulate the reflectivity of the clouds over large areas to try cooling the climate is not without serious risks. By nearly every single assessment, save those by proponents of this geoengineering technique, it's a venture bearing great possibility of unintended consequences. But what about trying to brighten clouds in much smaller areas, targeted to protect coral reefs from bleaching?

According to new research published in the journal Atmospheric Science Letters, brightening the clouds over coral reefs by seeding them with tiny droplets of seawater could increase the reflectivity and duration of cloud cover, potentially protecting coral reefs from the increases in bleaching incidents resulting from climate change. The so-called Marine Cloud Brightening would potentially buy reefs 50 years of protection from bleaching.

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Coral bleaching is happening more frequently due to rising temperatures in the ocean, as well as ocean acidification—both of which are consequences of increasing greenhouse gas emissions.

Changing the reflectivity of clouds, either with the targeted technique proposed here or something over a wider area (injection of sulfate particles, say) addresses only temperature increases, not ocean acidification.

According to the Intergovernmental Panel on Climate Change, coral bleaching is the greatest threat facing coral reefs over the next few decades. And as Dr. Alan Gadian, a scientist at Leeds University, says:

We estimate that Marine Cloud Brightening would have have an annual cost of $400 million, however, political, social, and ethical costs make a true figure difficult to estimate. Whatever the final figure, it would be less expensive that the damage the destruction of coral would wreck on neighboring countries, the local food chain, and global biodiversity.

Gadian notes, however, that the true long term solution to protecting coral reefs, and the communities that depend upon them, is to reduce carbon emissions. His proposed technique would simply buy us some time to reduce those emissions, which have hit the Coral Triangle of Southeast Asia particularly hard. There, as temperatures continue to rise, there is a real risk that coral in the region could be wiped out in the next 100 years. Though it accounts for just one percent of Earth's surface, this region contains 30 percent of all coral reefs, 76 percent of all reef-building coral, and 35 percent of all coral reef fish species.

Should the coral in this region die off completely, food production here would drop by 80 percent, imperiling the lives of some 100 million people.

To put the theory to the test, Dr Gadian proposes testing Marine Cloud Brightening on a scale of 100 square meters, so as to be able to assess the technique's true potential while minimizing the risk of unintended side effects to the climate more broadly.