Can we dim the sun to fight climate change? We may have to try

It would take a maniac or a genius to look at the 1991 eruption of Mount Pinatubo in the Philippines, which belched rapid avalanches of hot ash across hundreds of kilometres, and see the solution to climate change.

After an earthquake shook the ground near Pinatubo, the volcano rumbled for months before releasing an ash cloud that rose 35 kilometres in the air and darkened the countryside. The ash was sucked into a nearby typhoon and spread across the Indian Ocean, with its remnants travelling several times around the globe. Thanks to a warning from U.S. scientists who were monitoring the volcano, the area was evacuated and thousands of lives were saved.

And like any large volcanic eruption, the sky blackened, causing about half a degree Celsius of global cooling.

This demonstration of nature’s power could be a solution to the most vexing problem facing mankind. Or it could be the seeds of another man-made catastrophe.

With global emissions still remaining stubbornly high, some scientists and philanthropists, like Bill Gates, have turned their hopes to a technological solution to cool the earth. The plan, which has existed in different forms since the middle of the 20th century, is simply to dim the sun.

The scheme is breathtakingly simple. Rather than shooting ash into the atmosphere, scientists have proposed spraying tiny sulfur-containing particles that would reflect some of the sun’s radiation before it gets trapped by greenhouse gases.

Some environmentalists worry these geoengineering schemes will only discourage people from cutting carbon emissions, relying on evermore sulfate particles in the air. It’s a fair concern that even the most ardent boosters of solar geoengineering take seriously.

The plan requires constant upkeep and new emissions will require more sun-dimming particles in the atmosphere than older ones. The cooling effects last only a year or two and, if for some reason the effort was halted, the atmosphere would spring back to natural levels of warming in less than a decade, causing enormous levels of rapid warming.

Most proponents of solar geoengineering are banking on big improvements in carbon capture technology to one day suck these emissions out of the atmosphere and slowly scale down the sun-dimming effort. Some scientists point out that there’s no guarantee that this technology will exist and so it would be reckless to rely on it.

Although these fears are real, many environmentalists, scientists, and philanthropists think it’s smart to hedge against humanity failing in its quest to lower emissions.

Whatever the number of Canadians who think fighting climate change is important, they don’t seem keen to sacrifice much to do it. Fossil fuels continue to make up 84 percent of all energy consumed on earth, down only two percentage points from 20 years ago. Any effort to lower emissions and meet the goals of the Paris climate deal would necessarily have to be a global effort, which is not necessarily the case for a sun-dimming program.

This is where geoengineering is both attractive and worrying to people who have studied it.

The plan is straightforward and relatively cheap. It would involve spraying some substance, likely tons of sulfate particles, into the earth’s atmosphere from about ten large aircraft. It would cost about a billion dollars to execute and it is technically possible for a single country to do it alone.

One proponent of the idea boasted that it’s possible to create an ice age at a cost of 0.001 percent of U.S. GDP.

The question of whether a single country should do it alone, whether it’s a moral question or one of political and diplomatic backlash, is much more complicated.

“One of the exciting, one of the horrifying things about geoengineering is that it could in theory, at least, be done by a small group of nations, just a small group of assertive countries. It wouldn’t have to have buy-in from everybody. But it would affect everybody,” said Elizabeth Kolbert, the author of Under a White Sky: The Nature of the Future on the Ezra Klein Show. “And I think in general, if you were looking at good governance, you would say, well, every country would have to have a seat at the table.”

The title of Kolbert’s book refers to the eerie potential of a geoengineered future: an atmosphere full of sun-dimming particles may change the appearance of the sky to a sickly white colour, among an abundance of other strange, possible side effects.

These unintended consequences could be incredibly hard to predict. The eruption of Mount Pinatubo, for example, weakened the usual Indian monsoon, which wreaked havoc with the country’s agriculture. A previous, larger eruption in the 19th century brought summer snow and massively cooled the earth.

“Now, one of the other messages of the book is, even when we think we’re acting responsibly, often we’re intervening in systems that are so complicated that we think we’re doing the right thing, as you suggested before, and things get horribly out of control. And that has happened again and again,” said Kolbert.

“So I do think that stressing humility would probably be a good first step, but it doesn’t prescribe a course of action.”