The Earth just keeps getting hotter and so far humanity just isn't doing enough to stop
it.
But a new plan may provide us an answer, if we can’t stop releasing chemicals that make
the Earth warmer, why don’t we just release chemicals to make it colder?
As a scientist, I can tell you, when we get bored, we usually just sit around and think
up really cool things we could do.
So this plan shouldn't be the least bit surprising.
Atmospheric scientists, you know, the ones that study the atmosphere, have come up with
a plan to cool the Earth.
And the plan wouldn't just be doable, it’s also surprisingly cheap.
The basic concept is to develop jets that could fly high up into the atmosphere, and
start releasing chemicals that scientists think would reflect solar rays, thus cooling
the planet.
This cooling wouldn't reverse climate change.
The greenhouse gases we emit in mass like CO2 would still be in the atmosphere, and
even without the warming, there are still plenty of downsides to having higher concentrations
of greenhouse gasses in the atmosphere (if you want us to make a separate video on that,
let us know in the comment section down below).
This concept is called stratospheric aerosol injection and according to researchers out
of Harvard and Yale, this might be our best hope to mitigate the worst effects of climate
change.
While this idea does sound a bit crazy, we do have historical evidence that it would
work.
During particularly strong volcanic eruptions, metric tons of ash are shot into the stratosphere,
where air currents can keep the smallest particles floating for years.
The most famous example was the 1815 eruption of Mount Tambora on the small Indonesian island
of Sumbawa.
The eruption directly killed tens of thousands on the island and expelled as much as 150
cubic km of ash and rock into the air.
Since you probably have no reference for just how much ash that is, that would be enough
to fill the New York Giants stadium more than 80,000 times.
But even more important than the ash was 60 megatons of sulfur released into the atmosphere.
The following year would be known as the "year without a summer" as global temperatures fell
by 1 °C and nearly 100,000 people died of starvation as crop yields suffered around
the globe.
It was until more than a century later that scientists realized that it was really that
sulfur, rather than all the ash, that had cooled the planet.
It turns out that the sulfur dioxide a volcano shoots high into the air combines with water
vapor to form sulfuric acid, which quickly condenses into tiny droplets that can float
along with the air currents.
And while most volcanic ash falls out of the stratosphere within a few days to weeks, these
drops of sulfuric acid can stay airborne for months to years at a time.
As winds carry these aerosols around the Earth, they absorb solar energy and radiate it back
out towards space, which cools the earth’s surface below.
Those researchers found that humanity could, using a similar method, cut the effect of
human’s annual contributions to the greenhouse effect in half.
Development would cost about $3.5 billion over the course of the next 15 years.
Mostly going to designing planes capable of carrying heavy tanks of aerosol spray into
the stratosphere, about double the cruising altitude of a Boeing 747.
Once the tech is ready, the researchers found the project would cost about $2 billion each
year (assuming the project ran for 15 years).
So that’s a total cost of $37 billion dollars for the entire planet spread over 30 years,
so it really isn’t very much.
Sulfur dioxide is actually really cheap, and there's lots of it available.
Most of these costs would just come from flying the SO2 high enough that it would stick around.
Just as a cost comparison, in the next few years Texas will have spent nearly a billion
dollars replacing a single bridge in Corpus Christi.
New York City’s yearly subway budgets routinely run into the tens of billions of dollars.
And the US Air force buys planes that, individually, cost more than $2 billion each.
By the way, if your wondering why we have to fly it high into the stratosphere and can’t
just pump it out of factories down here that’s because if you deploy it at 35,000 feet [10,700
meters], say, where current 737’s flies, it rains back down in a few days, because
it's just being acted on by gravity.
But if you get it high up into the stratosphere, then it stays abreeze for up to 18 months
as it gets carried by air currents.
Just a quick side note, if your wondering, why can’t we just wait a few years for carbon
dioxide and other greenhouse gases to fall out of the atmosphere, it’s because, unlike
sulfates, they can last for a thousand years in the atmosphere, unlike sulfates.
So, is all this a good idea?
Is this the one stop solution to climate change we’ve been waiting for?
Well, like we said at the start of the video, cooling down the planet isn't the same thing
as reversing climate change.
Carbon emissions do a lot more than just heat the planet.
For starters, they make the oceans more acidic which endangers thousands of species and alters
the global movement of water and air, so farmlands that’ve historically got plenty of rain
could find themselves with frequent droughts.
But there’s still a very real reason to cool the Earth, besides just for human comfort.
And it’s the tipping point, after which this plan would no longer work.
Today, about 40% of the world’s population lives within 100 km [62 miles] of the coast
and more than 300 million people live less than 3 meters [10 feet] above sea level.
It’s estimated that sea levels will rise by nearly a meter by 2100, putting 100’s
of millions of people in jeopardy.
Most of this rise comes from the melting of land based ice, like in glaciers.
I always used to assume that water just kind of frooze into glaciers and when it got hot
some melted.
But glaciers actually form from millions of years of snowfall compacting into ice.
This means, once ice sheets melt, they’d never refreeze on human time scales.
Once too many glaciers melt, cooling the Earth wouldn’t be able to combat sea level rise,
and with glacial melt increasing year after year, we’re running out of time to act.
So is this technology the future?
Well, right now, it looks significantly cheaper than alternative geoengineering technologies
like proposals to suck CO2 out of the atmosphere.
But even if humanity decided to aggressively cut CO2 emissions, which at least for now
it doesn’t look like that’ll be the case, it would still take time to reduce emissions
and so we could end up being stuck with this as one of our only options left.
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As always, have a great day, and remember, there is always more to learn.