Climate engineering may save coral reefs, research shows

May 25, 2015, University of Exeter
Current coral bleaching in Fiji. Credit: Professor Peter J Mumby, University of Queensland

Geoengineering of the climate may be the only way to save coral reefs from mass bleaching, according to new research.

Coral reefs are considered one of the most vulnerable ecosystems to future due to rising and ocean acidification, which is caused by higher atmospheric levels of carbon dioxide.

Mass , which can lead to coral mortality, is predicted to occur far more frequently over the coming decades, due to the stress exerted by higher seawater temperatures.

Scientists believe that, even under the most ambitious future CO2 reduction scenarios, widespread and severe coral bleaching and degradation will occur by the middle of this century.

The collaborative new research, which includes authors from the Carnegie Institution for Science, the University of Exeter, the Met Office Hadley Centre and the University of Queensland, suggest that a geoengineering technique called Solar Radiation Management (SRM) reduces the risk of global severe bleaching.

The SRM method involves injecting gas into the stratosphere, forming microscopic particles which reflect some of the sun's energy and so help limit rising sea surface temperatures.

The study compared a hypothetical SRM geoengineering scenario to the most aggressive future CO2 reduction strategy considered by the Intergovernmental Panel on Climate Change (IPCC), and found that fared much better under geoengineering despite increasing ocean acidification.

The pioneering international study is published in leading scientific journal, Nature Climate Change.

Lead author Dr Lester Kwiatkowski of the Carnegie Institution for Science said "Our work highlights the sort of scenarios that now need to be considered if the protection of coral reefs is a priority".

Dr Paul Halloran, from the Geography department of the University of Exeter added: "The study shows that the benefit of SRM over a conventional CO2 reduction scenario is dependent on the sensitivity of future thermal bleaching thresholds to changes in seawater acidity.

This emphasises the need to better characterise how warming and may interact to influence coral bleaching over the 21st century."

Professor Peter Cox, co-author of the research and from the University of Exeter said: "Coral reefs face a dire situation regardless of how intensively society decarbonises the economy. In reality there is no direct choice between conventional mitigation and climate engineering but this study shows that we need to either accept that the loss of a large percentage of the world's reefs is inevitable or start thinking beyond conventional mitigation of CO2 emissions."

This work shows the very different impacts on coral bleaching of different measures to tackle climate change. These different techniques will also have different effects on other impacts such as regional crop growth or water availability.

Explore further: New climate projections paint bleak future for tropical coral reefs

More information: Coral bleaching under novel scenarios of climate warming and ocean acidification, DOI: 10.1038/nclimate2655

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3 / 5 (6) May 25, 2015
We are dealing with complex interactions of highly-complex systems. When we perturb one part, there will be unanticipated responses in many other interrelated systems, of which we have no advance knowledge.

I recommend extreme caution.
5 / 5 (3) May 25, 2015
so once we pump this "gas" into the atmosphere, what is the shelf life of the particles? Will they persist even after we hit a target protection level? What if we experience too much cooling and have to pump a different gas just to balance this? It feels like we are playing mad scientist enough and i know a lot of people would consider this just as dangerous as the amount of CO2 we are emitting. If much more research is focused on the spiraling effects of this strategy maybe it could ease these feelings, but i have to side with GKam a bit here. caution
5 / 5 (1) May 25, 2015
Actually, the "linger time" for CO2 in the atmosphere is close to 1500 years. So what people don't realize is that the more we pump into the atmosphere, the more it builds up. This one reason why the CO2 levels are climbing exponentially (in addition to mankind's growth and consumption rates). So it's about 1500 years that it will float in the atmosphere, but a lot of CO2 is absorbed in the oceans, some small amount in plants, another fraction is soil. It's called the "Cabon Cycle" and wikipedia has one of the better layman descriptions of it.

The thing I fears, is just like ~500 people that have died in the 117 degree heat wave in India yesterday, some event will afflict the coral reefs and the damage will be done, permanently. With the reefs (in places) never returning. For the worst, we have changed the planet and it might take desperate measures to save small parts of it's past.
5 / 5 (3) May 25, 2015
@howtohot2 While you're completely right about this, it doesn't hurt to point out that our general incompetence and inability to grasp the system-wide impacts of our actions is the reason we're in this mess in the first place. I'm afraid I wouldn't trust humanity with geoengineering. In Australia, we couldn't even get rid of the cane beetle without causing an environmental disaster (cane toads).

1 / 5 (1) May 25, 2015
This scheme is perhaps the biggest foolish idea yet and why the entire idea of "geoengineering" has such a bad reputation. The killer is that "hacking the planet" is the only thing that's going to pull our fat out of the fire, if anything can. But, not this scheme: Too blunt force and uncontrollable.

Besides, this action is already being done: Aerosolized albedo-raising is already happening via Chinese air pollution, as it travels across the Pacific, providing the same type of nuclei for water droplets that become clouds. If Asian pollution was cleaned up and no longer bouncing extra heat back into space, the impact of climate overheating would be double what it is. Talk about a conundrum for the Greenies! See: Global Dimming, 9/11 and "pan evaporation rates."

Our only practical option is global scale, cost-effective carbon capture and sequestration. This is roughly how to do it: http://williamcal...mits.pdf
not rated yet May 26, 2015
How do we know that geoengineering isn't causing severe weather imbalances already? All for the sake of the coral reefs? I smell a red herring.

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