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.
“Yet [he] advances it as a last resort, despite the obvious, much safer things we can do now,” he said. “It shows the recurrent mirage of a silver bullet solution to climate change is often a sign of despair at world leaders’ unwillingness to seriously tackle carbon emissions. Every new technology in this field comes with issues and if they become an excuse for more foot-dragging on slashing carbon pollution, they will be harming the climate before even research is done.”
However, Rees insisted that considering geoengineering would not be a way to avoid the need for reducing carbon emissions. He said the world also needs to make a commitment to developing clean energy — extracting and storing power from wind, tides, biofuels, solar or nuclear — that matches the ambition of NASA’s Apollo moon landings in the 1960s and 1970s.
“It may take 50 years to decarbonize the world’s power generation, but this could be achieved if we start now,” he said.
Looking ahead in his own field of astronomy, Rees said he was excited by the regular discovery of planets orbiting other stars. In the past decade, space telescopes such as NASA’s Kepler have pushed the number of planets scientists know about into the thousands, but they predict there are probably many billions in our galaxy alone, and some of them could be twins of Earth.
With ever-improving instruments, he said scientists who are now at the start of their careers may be able to answer the question of whether there is life beyond Earth.
Back on our own planet, Rees also called for a more brotherly attitude from his fellow scientists to those of faith. Science, he said, is the one culture that is truly global and should transcend all barriers of nationality and religion.
“The scientists who attack mainstream religion, rather than striving for peaceful coexistence with it, damage science, and also weaken the fight against fundamentalism, but that’s a theme for another talk,” he said.