Global warming tactic cools climate but won’t help corals, say researchers

Christine Blackman in Physorg: “Geoengineering” experiments proposed to reduce global warming by blocking sunlight with atmosphere-injected particles may cool the world but still leave carbon dioxide levels dangerously high, Stanford scientists say.

Sunlight-blocking particles would fail to solve the problems of ocean acidification and dying corals, two significant repercussions of climate change, according to a study by Ken Caldeira of Stanford University and the Carnegie Institution, Damon Matthews of Concordia University, and Long Cao of the Carnegie Institution. Atmospheric carbon dioxide dissolves in ocean water, making it more acidic and difficult for animals to build their shells or skeletons, especially corals.

Proponents of geoengineering have called for injecting small, reflective particles into the atmosphere to partially block sunlight and cool the earth, just as ash from an erupting volcano does. The resulting carbon-dioxide-rich climate would cause land plants to grow more vigorously, hold onto more carbon and release less to the ocean. But the difference would not be enough to fundamentally alter the plight of coral reefs, Caldeira said.

The researchers used computer models of the Earth’s climate system and biosphere to simulate the effect of sunlight-reflecting particles on climate and ocean chemistry. Such geoengineering methods “might be able to address some of the climate effects of carbon dioxide but they don’t fundamentally address the chemical effects posed by carbon dioxide,” Caldeira said.

“Instead of taking till 2050 until there’s no place left in the ocean where corals can survive, it might be 2053. The carbon cycle effects of the geoengineering might delay that outcome in the ocean by a few years but wouldn’t prevent those outcomes from occurring,” he said….

Ancient coral reefs by Heinrich Harder, around 1920