Launching mirrors into space, triggering algal blooms in the oceans and seeding clouds are among experimental “Plan B” schemes world leaders would have to consider if the rise in carbon emissions cannot be curbed within a couple of decades, one of Britain’s most senior scientists said.
Hacking the planet’s climate through geoengineering, though controversial and “an utter political nightmare,” would buy time to develop cleaner sources of energy, Astronomer Royal Martin Rees said in a speech to the annual British Science Festival in Newcastle, England, on Thursday evening.
Rees, who is a former president of the Royal Society and a cosmologist at Cambridge University, closed the festival with a wide-ranging lecture covering everything from astronomy and global health to the place of science in culture.
On climate change, Rees said he was pessimistic that global carbon dioxide emissions can be reduced to safe levels within the next 20 years, which means that concentrations of the gas in the atmosphere will rise above 500 parts per million (ppm) by the end of the century. This level could mean a rise in average temperatures of up to 6?C, major melting of the ice caps and, potentially, the triggering of tipping points in the global environment that would accelerate dangerous climate change. The level of carbon dioxide in the atmosphere passed 400ppm in May.
“If the effect is strong, and the world consequently seems on a rapidly warming trajectory into dangerous territory, there may be a pressure for ‘panic measures,’” he said. “These would have to involve a ‘Plan B’ — being fatalistic about continuing dependence on fossil fuels, but combating its effects by some form of geoengineering.”
Geoengineering involves deliberate planet-scale interventions to counteract global warming. Techniques suggested include placing mirrors in space that reflect sunlight away from the Earth and fertilizing the oceans with iron to encourage the growth of algae that can soak up atmospheric carbon dioxide. Other options include Rees’s preference — to seed clouds in the upper layer of the Earth’s atmosphere to bounce some of the sun’s energy back into space.
The idea of firing particles into the stratosphere to reduce temperature was inspired by natural events. When Mount Pinatubo in the Philippines erupted in 1991, for example, global temperatures dropped 0.5?C the following year due to the dust it released.
However, enacting such plans would not be without social problems.
“Geoengineering would be an utter political nightmare: Not all nations would want to adjust the thermostat the same way,” Rees said. “There could be unintended side-effects. Regional weather patterns may change. Moreover, the warming would return with a vengeance if the countermeasures were ever discontinued; and other consequences of rising carbon dioxide — especially the deleterious effects of ocean acidification — would be unchecked.”
In 2009, the Royal Society published a report into geoengineering in which it called for experiments in the various techniques to ensure that their effects and limitations are better understood and the technologies are available as a safety net in case global talks to combat climate change fail.
Greenpeace UK chief scientist and policy director Doug Parr said Rees was right about the many downsides and unknowns of geo-engineering.