It may be a little inconvenient if you’re ever caught out without an umbrella, but the importance
of rain to our planet cannot be overstated. It’s the key water source for life on Earth,
but what would happen if it turned against us? This is Unveiled, and today we’re answering
the extraordinary question; what if rain were dangerous?
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For today’s question, we’re mostly thinking alternate reality and sci-fi dystopia, but
there are already many circumstances where rain really is dangerous. If huge quantities come down
too heavily, we get flash floods, where rivers burst their banks and the surrounding ground can’t
absorb the water fast enough… often leaving people and animals with very little time to escape.
Large enough storms can, then, level whole towns and cities very quickly, destroying buildings
and also creating frightening, potentially fatal mudslides. This recipe for disaster has claimed
thousands of lives across history, and displaced thousands more people from their homes.
We also have acid rain to contend with in the real world, although in more recent times
we’ve better learned how to predict and prevent it. All rainwater is slightly acidic, but to be
“acid” rain it generally has to have a pH value of less than 5.5. Acid rain is created naturally
by large volcanic eruptions that eject sulfur into the atmosphere, contaminating the clouds,
then the rain and, eventually, anything that gets rained on. But we now also know that
humans can inadvertently cause acid rain, too, by burning fossil fuels and driving gas-powered cars.
It’s another unwanted by-product of human-led pollution… although one which
can be limited with the right laws in place. But, thankfully, there’s no rain on Earth that’s
currently dangerous all of the time by its very nature. If this was the case, however,
what exactly would the danger be? Well, studies do suggest that diseases can actually be spread
through rainfall. The troposphere is a specific layer of the atmosphere, and it’s been found to
contain lots of bacteria, some of which really could be harmful to humans. We also know that
bacteria and viruses can be spread through water, through sea spray, for example. The idea is, then,
that were dangerous bacteria to be transported via rain, taken from the atmosphere above our
heads and deposited as droplets onto our heads, then we’d have a major problem to deal with.
The good news is that, in the real world, the bacteria in the troposphere is a natural part
of Earth’s ecosystem. It helps to keep our planet working as it does, and it isn’t something we need
to worry about. But there are also some incredibly dangerous, waterborne diseases we know of
on the ground… including cholera, which has fuelled many of history’s deadliest epidemics,
with the World Health Organisation estimating that it kills up to 143,000 people every year.
In an alternate world where rain could become contaminated, then, perhaps
it would be cholera (or a bacterium like it) that would be spreading through the clouds.
And, because all water sources are connected to each other through the water cycle,
even clean water supplies would soon, inevitably, be contaminated, too. Lace rain with disease,
and that disease could very quickly spread across continents, and all around the world. Were such a
process ever to be weaponized - and there have been military experiments with cloud-seeding in
the past - then whoever wielded that weapon could wage war on a truly massive scale.
On the bright side, we do at least know how to beat cholera and many other waterborne diseases:
mainly by building the right infrastructure to treat and deliver clean water,
and administering medicines - with a vaccine for cholera, in particular. If we had these
preventative measures in place for whatever disease today’s hypothetical rain was carrying,
then it needn’t be a global death sentence… even if protecting ourselves against water from the sky
would be a 24/7 logistical headache. But that’s as far as the bright side
goes. If we were instead facing a deadly or unknown pathogen raining down upon us,
with a high mortality rate, no medicine or treatment, and it was something that could
be spread to humans just through skin contact… it would be an entirely different story. If this
was the case, going outside during a rainstorm – or even going outside, period - would amount to
risking death. Even without rain actually falling there would be a certain degree of danger, seeing
as air generally contains lots of moisture… but whenever the heavens truly opened, the sound of
rain on a roof would feel like the drums of doom. In this world, human cities would need to function
more like space colonies, completely closed off from the outside for our own protection. We’d
need rain shelters built over existing cities and towns, levelling every cityscape under universal,
dome-like structures. New cities would likely be much smaller, or at least a lot shorter,
with multistorey skyscrapers becoming a thing of the past on account of it being two difficult to
cover them up. One plus side is that we do already design and build our homes so that they shut out
the weather and the elements, so nothing would change there… but high-rise penthouse suites
wouldn’t be at all desirable anymore. Instead, they’d probably be replaced with sky-homes hanging
off of the inside of any given city’s protective dome. And whenever any home sprung a leak,
it would be more than just a nuisance. But this wouldn’t just mean changes to
how we built our homes, but also where we built them. Human settlements have historically been
based near important water sources, like lakes and rivers… but if the rain was toxic, then all other
natural bodies of water would naturally be toxic as well. This would mean that it could actually
be better for us to flock to the driest and traditionally most inhospitable parts of Earth,
like deserts, to give ourselves the best chance. One of the driest places on the planet is the
Atacama Desert in Chile, South America, with some parts of it thought not to have seen significant
rainfall for at least four hundred years. So, while moving to an arid place like this may not
completely solve the issue of all water sources being tainted, because there are still rivers and
pools there, it would at least mean that just going outside wouldn’t be such a risk. But,
of course, there are many reasons why people don’t generally live in deserts:
they’re incredibly testing environments. And even if we did all up sticks and move to the sand, we’d
still all be human beings… and we’d still all need water to survive. So, what would our options be?
In terms of an alternative, potentially safer water source, there’s always Antarctica. Yes,
it’s wildly inhospitable and considered by some to be the closest thing on Earth to conditions on the
surface of Mars, but Antarctica’s Dry Valleys are also so arid that they have almost no ice cover.
And, in this world, no fresh ice is no bad thing. Antarctica has other benefits, too; parts of
the continent see almost nothing by way of fresh snow, and the air is so cold that it contains very
little moisture, meaning that it would take a long time for contaminated air and rain to reach it.
All of which means that we could potentially mine and thaw out Antarctic ice from below the surface,
to tap a relatively clean water supply… maybe even one that’s safe to drink without treatment.
It’s also fairly hard to imagine the entire population of Earth just relocating to Antarctica,
though. It’s a mass migration that could probably never happen, so we’d surely favour building our
large, climate-controlled, rain-repelling biomes somewhere else (anywhere else!) less
extreme. The key, then, would lay with how effectively we could collect the toxic rain,
and treat and purify it into something that’s usable. Do that, and humanity might have a
future across much of the world map. Fail to do that, and our days would certainly be numbered.
As such, those on the frontline of water treatment would have an extremely hazardous
but extremely crucial job. As just a single drop of water on anybody’s skin, in their eyes, in
their mouths or up their noses would mean death, working with water in any capacity would require
specialist training and nerves of steel. But, until we learnt how to handle and use the rain
for our advantage, we could never hope to survive… with whole industries like food,
agriculture, healthcare and anything requiring any amount of time outside becoming impossible.
We’d obviously see water shortages, but also crop shortages and, ultimately,
millions (if not billions) of people would die. If something as fundamental to life on Earth like
rain and the water cycle was ever to turn against us, there really would be precious
little we could do to save ourselves... because that’s what would happen if rain were dangerous.
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