Geoengineering of the climate may be the only way to save coral reefs from mass bleaching which can lead to their mortality, according to new research.
Coral reefs are considered one of the most vulnerable ecosystems to future climate change due to rising sea surface temperatures and ocean acidification, which is caused by higher atmospheric levels of carbon dioxide.
Mass coral bleaching, 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, researchers said.
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 suggests 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 coral reefs fared much better under geoengineering despite increasing ocean acidification.
"Our work highlights the sort of climate scenarios that now need to be considered if the protection of coral reefs is a priority," said lead author Dr Lester Kwiatkowski of the Carnegie Institution for Science.
"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," said Dr Paul Halloran, from the Geography department of the University of Exeter.
"This emphasises the need to better characterise how warming and ocean acidification may interact to influence coral bleaching over the 21st century," Halloran added.
The study was published in the journal Nature Climate Change.
