- There was a devastating famine in Africa in the 1980s that killed up to a million people.

Back then, it seemed the drought that helped cause this catastrophic event was simply due to climate variability.

But now more and more research suggests that it was caused, at least in part, by something the US and Europe did to cool the North Atlantic Ocean.

And maybe even more importantly, we're considering doing something very similar again, but this time on purpose in a last ditch effort to help stop the worst effects of climate change, we're talking about solar geoengineering, which involves releasing aerosols into the atmosphere to reflect sunlight.

In the past, it was soot from the burning of dirty fossil fuels like coal.

Version 2.0 would be less toxic, but could have similar unintended consequences.

At this point, we really don't know, but what we do know is that releasing certain kinds of particulate matter into the atmosphere can reduce global temperatures extremely quickly.

And that hundreds of scientists have come together to urge against using this technology.

Even still, one startup called Make Sunsets has already started doing it, and not everyone is happy with them.

- Your corporation Make Sunsets has been chosen to be made inoperable.

You're poisoning us for profit.

God sees you, we see you and we're coming for your infrastructure can be eliminated.

(dramatic music) - So we'll get to the famine we mentioned and why that last guy was so hostile.

But first, a little context.

This summer was off the charts high, reaching an all time record of 1.8 degrees Celsius above pre-industrial levels in September, leaving climate scientists grappling for the words to describe the severity.

We knew the combination of global warming and El Nino would likely lead to record temperatures.

But research published this summer on aerosols or soot brought a whole new twist.

- In the post World War II period, there was a rapid industrialization of both Europe and North America.

And there was a lot of soot going into the atmosphere as a consequence of coal burning.

And in the 1970s, we got smart about the fact that that soot was having really negative consequences for humans and ecosystems.

And so there was a Clean Air Act in the US and in Europe, and you know, we really lowered the emissions of soot associated with coal burning.

But as a consequence of that, that meant that this offsetting cooling effect of the soot was no longer there.

And now we're starting to really see the ramping up of the greenhouse gas signal.

And you know, you can't say for sure how much warming in any region is caused by CO2, but what you can say is that the influence of the CO2 that's already been put in the atmosphere has been somewhat masked.

And now we're starting to see the real carbon dioxide driven signals of warming globally.

- These aerosols cool the earth in two ways.

First, the particles act like a bunch of tiny mirrors bouncing some of the sun's light back into space.

And second, they give water vapor something to stick to, making clouds whiter, fluffier and brighter, which also results in more sunlight being reflected back out in the space.

Another dramatic illustration of aerosols cooling power came in 1991 when Mount Pinatubo erupted.

It spewed around 20 million tons of sulfur dioxide into the stratosphere, forming a layer of aerosols across the globe.

Remarkably, global temperatures dropped by nearly one degree Fahrenheit counteracting decades of human induced warming.

But this effect was short-lived as aerosol levels and temperatures soon returned to their earlier trend.

So maybe it shouldn't come as a surprise that a growing number of voices have been calling for geoengineering by intentionally injecting aerosols into the atmosphere.

Now, I know this topic is incredibly controversial, even just to discuss, but the fact is the cat's already out of the bag.

So I believe we have to talk about it.

Luke Iseman founded Make Sunsets.

Now, this is a small startup that deploys reflective clouds into the atmosphere by releasing biodegradable balloons filled with sulfur dioxide.

- I get the balloon, I buy a tank of helium and I light some sulfur on fire.

Sulfur burnt in the presence of air equals sulfur dioxide.

So I get a tiny, tiny amount of sulfur dioxide into the balloon, and then I add a bunch of helium and zip tie the balloon shut and let it go.

Yeah, we're not crazy early tech startup style growth yet, but we're selling a material amount and we're deploying.

- So the idea of solar geoengineering as a future solution to the climate crisis is gaining traction.

And it's largely focusing on something that we all agree on, which is that we need to urgently address the climate crisis.

- But that's about where the agreement ends.

- It's absolutely dangerous to contemplate solar geoengineering now, even as a future option.

- It's important just to halt the promise of this technology because I don't think it can end well, right?

Like it's gonna, it's dangerous in and of itself.

- It's an experiment, life experiment with 8 billion people.

And I believe that we should not go down this road.

- Yeah.

Yep, yep.

Those are some pretty strong words there.

So what's got all these scientists so concerned?

- We don't wanna make an already very, very complex challenge of climate change even worse by having a sort of multi-generational intervention into the earth system in this manner, injecting sulfate aerosols into the stratosphere where we don't know what the impacts will be.

We know there'll be planetary scale impacts, there might be impacts on global temperatures, but that's not the only aspect of climate change, right?

There'll be all kinds of unknowable distributional impacts on precipitation, patterns, et cetera.

- And we actually have a direct example of this, and it's a really big deal.

Remember that devastating drought in the eighties we mentioned in the beginning?

- The Sahel, the entire region south of the Sahara Desert from Senegal to Ethiopia was experiencing drought at the same time.

It was really a huge scale of humanitarian suffering.

And in the decades since, we have really understood that a lot of it came from the fact that the ocean temperature was colder in the north compared to the south.

And that moves the rain band that is usually close to the equator, that rain band gets shifted toward the south.

And so that causes drought.

And there's very strong evidence that some of it was due to the fact that pollution in America, pollution in Europe caused, you know, a lot of reflective aerosols, haze basically, to linger over the North Atlantic, creating this gradient in surface temperature.

- Now, to me, the lesson is not that releasing aerosols into the atmosphere could cause the exact same drought all over again, is that we just don't know what will happen.

- There's a lot that we don't understand, and it's very possible that putting sulfate in the stratosphere would change the patterns of rain fall in way that we cannot anticipate.

- And I think uncertainty is one of the biggest takeaways here.

Not only are there profound uncertainties around how geoengineering might adversely affect weather patterns, like in the 1980s, this technology also poses a political risk.

- Rainfall variability is very strong in the tropics.

So if somebody were to start this experiment, so it could very well be that, you know, there's a drought following the injection of particles in the stratosphere, and it would be interpreted as a consequence of that intervention.

- And if one country is seen as causing a drought that destabilizes or even causes famine in another, tensions could certainly spin out of control.

So on one hand, we have all of the possible repercussions from geoengineering, war, impacts on human health, adverse effects on our climate system, which could result in humanitarian crises and some even say a get out of jail free card for the fossil fuel industry.

On the other hand, an argument that this technology might be our salvation in a world where past climate forecasts have actually underestimated the impacts.

So what do you think?

Are you for it?

Are you against it or to you, is it not that black and white?

Let us know in the comments below.

(soft music)