Imagine a storm so big it reaches up into the stratosphere, so wide it could cover all
of North America, and so catastrophic it could wipe out almost all life on Earth.
I’m not talking about Hollywood’s next big disaster blockbuster, although they might
want to take notes here, I’m talking about a hypercane!
One scientist hypothesized that this theoretical, super-buff kind of storm contributed to one
of Earth’s mass extinction events.
But could it have happened, and what would it take for it to happen again?
To understand what a hypercane theoretically is, let’s talk about tropical cyclones, rotating
thunderstorms that form over warm ocean water, with wind speeds of 119 kilometers per hour
or more.
We call them hurricanes, typhoons, and just plain cyclones, depending on where the storm
occurs.
And these storms are already pretty huge: at least 15 kilometers high and around 200
kilometers across.
But a hypothetical hypercane could kick up wind speeds to around 800 kilometers per hour,
extend all the way up into the stratosphere, and span the North American continent.
Which sounds… kind of terrifying. But how would a tropical cyclone theoretically even
get that big?
A normal hurricane needs a region of warm ocean water to form, one that’s 26.6 degrees
Celsius for at least 50 meters below the surface. Plus, lots of wind.
The wind blows over the ocean, water evaporates, rises, cools, and condenses into a clump of
thunderstormy cumulonimbus clouds. Y’know, the water cycle.
All this warm, moist air that’s rising creates a region of lower pressure near the
ocean’s surface, so more surrounding air swirls in.
As this mass of stormclouds grows, the winds get more intense, and it spins faster, counterclockwise
in the Northern hemisphere and clockwise in the Southern hemisphere, because of the way
the Earth rotates on its axis.
Faster wind speeds means more evaporation and rising warm air, which causes even lower
air pressure in the center of the storm. This eventually forms a calm, clear region that
we call the eye of the hurricane.
So, as long as the winds keep blowing and there’s enough warm, evaporating ocean water,
the tropical storm keeps growing and spinning faster.
But since hurricanes get their energy from this difference in temperature between the
ocean and the atmosphere, there’s a limit to how big they can grow, and how strong the
winds can get.
MIT climatologist Kerry Emanuel was looking into this limit when he realized that, hey:
if you bump the ocean temperature, things could probably get intense.
To form a hypercane, we’d need the oceans to reach a temperature of almost 50 degrees
Celsius, around 14 degrees hotter than it’s ever been recorded.
And how could that happen...? Well, he suggests either an asteroid impact or a crazy undersea
volcanic eruption. We’ve already got a hypercane, we’re also adding one of those things to
the mix.
Super-warm water would mean that evaporation kicks up, wind speed increases, pressure in
the hurricane’s eye falls even more, and the storm becomes a monster.
A high-wind monster that would wreak havoc on our world, not only during the storm,
but afterwards.
In fact, this hypercane theory was presented as a possible explanation for mass extinction
events, maybe even the extinction of the non-avian dinosaurs around 66 million years ago.
Emanuel hypothesizes that while a volcanic eruption or an asteroid impact could have
catastrophic effects nearby, they wouldn’t throw enough stuff, high enough into the atmosphere,
for long enough periods of time to change global conditions.
Enter the hypercane: either one huge storm or many smaller storms that could pump water
vapor and volcanic ash into the middle stratosphere.
This might’ve shrouded the planet in darkness to cause a global freeze. Or maybe it could’ve
interfered with the Earth's protective ozone layer,
exposing everything alive on the planet to lots of biologically dangerous UV radiation
from the sun. So hypercanes sound terrifying but let’s
remember that it’s a theoretical model and the study’s author admits that they
haven’t found evidence of one ever occurring.
And the theory still needs more review by other scientists.
Not to mention, if a hypercane were to occur, we would already be in hot water, both literally
and figuratively, and probably have lots of other catastrophic weather problems to worry
about.
So don’t despair! A hypercane is just one, very unlikely, hypothetical disaster, among
all of the much more likely hypothetical disasters.
You'll be fine!
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