The winds of the world were given to Odysseus in a small bag fastened with a silver ribbon. Zeus had forged this package and it was to be given to the traveller to provide a safe breeze to sail him home. But, driven by greed and jealousy, Odysseus’s shipmates ripped the bag open with reckless folly. Violent winds burst forth, creating a storm that swept the crew out to sea.

In myth, controlling the weather is best left to the gods. But today, like Odysseus’s crew, a group of scientists aren’t taking heed. They argue that reckless folly has already tainted our climate, and want to begin controversial experiments in order to restore it.

Rather than employing bags of wind, scientists are hoping to cool our warming world by reflecting sunlight away from our planet. They want to brighten clouds using seawater, and spray aerosols into the atmosphere to mimic the cooling effect of volcanic ash. Their schemes are part of the highly controversial field of geoengineering, which describes an array of techniques aiming to control the climate to mitigate the effects of global warming. Last November, David Keith, a professor at Harvard University, published a detailed road map with his colleagues in the Royal Society’s Philosophical Transactions A, outlining the steps needed to deploy such radical intervention. Given $10 million, the experiments could begin in two years.

Historically, geoengineering schemes have not been taken seriously by politicians or major scientific bodies. Uncertainties surrounding their effectiveness and concerns that tampering with the climate may cause more harm than good have always stood in their way. But as governments delay action on carbon emission reductions, these controversial plans are gaining traction within some scientific circles.

The most recent report by the Intergovernmental Panel on Climate Change named geoengineering, along with adaptation, as our final game plan when ice sheets destabilise, climate thresholds are triggered and irreversible change is upon us. “Given current trends, we are not likely to adequately deal with the climate problem that we are creating,” says Jim Falk, a professor at the University of Melbourne. “So no wonder some hope that we might find a way to put climate change in reverse.”

The idea of tinkering with the climate was born five decades ago, out of chutzpah rather than environmental concerns. In the 1960s, researchers from the former Soviet Union, Nikolai Petrovich Rusin and Liia Abramovna Flit, published an essay they titled “Man versus Climate”. In it, the authors lament the “great disadvantage” of the inhospitable Arctic and propose various harebrained schemes to make the icy terrain “more suitable for life”. Elsewhere they consider the creation of a “Siberian Sea” with water hauled thousands of kilometres from the Caspian and Aral seas. Recalling the text a few years ago, the late climatologist Stephen Schneider, of Stanford University, described it as an “upbeat little pamphlet, written at the height of human technological hubris”.

Fifty years later, however, similar plans are being cited as our last resort. The most ambitious and controversial scheme in Keith’s road map involves sending a balloon into the lower atmosphere where it would spit out sulfate particles into our skies. These aerosols, it is expected, would reflect sunlight away from Earth, hence cooling our climate. The best evidence that such a plan could work comes from observations of volcanic eruptions. For example, the 1991 eruption of Mount Pinatubo in the Philippines belched 17 million tonnes of sulfate particles into the skies, the largest injection of aerosols into the stratosphere since Krakatoa erupted in 1883. The massive explosion created an umbrella of sulfur that cooled large patches of Earth by about 0.5 degrees Celsius. “Our best models show that this could be very effective at mitigating global warming,” says Keith. But there are risks.

Sulfate aerosols release free radicals that can erode the ozone layer, the protection of which has been a success story in global environmental co-operation. Keith’s team argues that it’s unclear how much ozone would be depleted from a planned aerosol introduction. It’s possible that the benefits to our climate would outweigh any damage and, without conducting experiments in the skies, there is no way to accurately know, says Keith’s Harvard colleague John Dykema. “That’s why we need to go up there.”

Groups have tried to predict the risks associated with sulfate aerosol injections using lab chambers and computer models, but there are too many uncertainties. “We don’t fully understand the mixture of chemicals in the atmosphere, or how they react,” says Dykema.

Hence Keith and his colleagues want to start small studies, releasing one kilogram of sulfur into the atmosphere and measuring how the particles interact. According to the group, these experiments would cause less chemical change to the atmosphere than one minute of a commercial air flight. “No one rational is concerned about the risk of these experiments; they’re concerned about the message that it sends,” says Keith.

The potentially worrying message is that if we start investing in geoengineering research, and expecting the results to solve climate change, society will not be as driven to reduce its reliance on fossil fuels. Keith pays short shrift to this argument. “People have to grow up,” he says, likening the avoidance of research into geoengineering to refusing cancer patients promising drugs because they might discourage sufferers from quitting smoking.

There are other reasons to be cautious of atmospheric aerosol injections. We might not know the global and long-term effects of the solution until we are too far down the rabbit hole. According to Will Howard at the Australian National University, it’s “not straightforward to predict” the effects of the small-scale experiments proposed by Keith’s team. For example, some models predict that in the long term, the introduction of sulfate particles could unpredictably change rainfall patterns, possibly leading to droughts and floods. Sulfate injections are also not expected to cool the planet uniformly, meaning that some territories might benefit while others suffered under the blanket of sulfur.

“It’s not easy to carry out an experiment on the long-term effects of sulfate injections without full-fledged deployment,” says Howard. And large-scale deployment brings its own problems, possibly leading to what has been compared to a Kafka-like world. According to Howard, sulfate aerosols are relatively quickly removed from the atmosphere by natural chemical processes. So if governments start to depend on sulfate injections to mitigate global warming, scientists will have to continuously spray sulfur into the skies to sustain the cooling effect.

Meanwhile, the source of the global warming, mainly carbon dioxide, would not be removed from the atmosphere. “If you stopped injections, the planet may undergo a surge of heating,” says Falk, “which could be quite catastrophic.”

Steve Gardiner, a professor of philosophy at the University of Washington, is also concerned that major geopolitical powers – those with the capability and willpower – might seek to limit sulfate injections to attempt to protect their own territories solely, with little concern for other nations. Sulfate injections, he says, are far down the list of options that we should be discussing to mitigate climate change.

There are many other schemes on the table. Another experiment proposed by Keith involves spraying seawater through small orifices in clouds in order to brighten them, which would reflect more solar energy out to space. Teams are also investigating plans to sprinkle iron into the sea, to trigger the growth of phytoplankton, tiny marine creatures that naturally capture carbon from the atmosphere. Once the critters die, so the plan goes, they would fall to the ocean floor and lock the greenhouse gas into the nether regions of the seabed.

Other researchers hope to capture greenhouse gases from the skies and inject them back into the rocks from whence they came. Australia has a testing site for storing carbon dioxide in Nirranda South, three hours south-west of Melbourne, which is partly funded by the federal government.

Each plan has its hazards. Dumping iron into the ocean could trigger toxic phytoplankton blooms. Carbon dioxide injected into rocks may eventually bubble up into the atmosphere.

But these scientists tell us that doing nothing is also a hazard.

“You can’t compare the risks of geoengineering to the magical pre-industrial world,” says Keith. “Nobody knows what nature will do once we start these experiments, but we also don’t know what will happen with an atmosphere filled with carbon dioxide.”

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