Symposium to discuss geoengineering to fight climate change at the ESA Annual Meeting
"The bigger the scale of the approach, the riskier it is for the environment," says session organizer Robert Jackson , director of Duke University's Center on Global Change. Global alterations of Earth's natural cycles have too many uncertainties to be viable with our current level of understanding, he says.
One global-scale geoengineering method, termed atmospheric seeding, would cool the climate by releasing light-colored sulfur particles or other aerosols into the atmosphere to reflect the sun's rays back into space. This approach mimics what happens naturally when volcanoes erupt; in 1991, for instance, an eruption of Mount Pinatubo in the Philippines cooled the Earth by 0.9 degrees Fahrenheit.
"An increase in ozone depletion over the Arctic could lead to dangerous levels of ultraviolet light hitting the Earth's surface," she says. "In this case, the recovery of the ozone hole over the Antarctic could be delayed by decades."
Another large-scale geoengineering scheme is fertilizing the oceans with iron to increase carbon uptake from the atmosphere. Charles Miller of Oregon State University says that ocean fertilization could create a rise in iron-limited phytoplankton populations, which by dying and sinking would use enough oxygen to create extensive dead zones in the oceans. In addition, he says, the maximum possible rate of ocean iron fertilization could only offset a small fraction of the current rate of carbon burning by humans.
Ocean fertilization also does not alleviate the increasing problem of ocean acidification, caused by carbon dioxide from the increasingly carbon-rich atmosphere dissolving into seawater. In fact, Miller says, ocean fertilization schemes will likely exacerbate this problem.
Despite its apparent hazards at the global scale, Jackson thinks that research should continue on safer ways to use geoengineering at a smaller scale. Geologic sequestration, sometimes known as CO2 capture and storage, takes CO2 out of the atmosphere and stores it in underground reservoirs. Jackson says that this solution has the potential to store more than a century's worth of electric power emissions at a relatively low cost. He notes, however, that some potential risks of geologic sequestration include carbon leakage and the potential for interactions with groundwater.
But on the planetary scale, most ecologists are skeptical of climate engineering.
"Playing with the Earth's climate is a dangerous game with unclear rules," says Jackson. "We need more direct ways to tackle global warming, including energy efficiency, reduced consumption, and investment in renewable energy sources."