Is the weather actually becoming more extreme? - R. Saravanan
From 2016 to 2019,
meteorologists saw record-breaking
heat waves around the globe,
rampant wildfires
in California and Australia,
and the longest run
of category 5 tropical cyclones on record.
The number of extreme weather events
has been increasing for the last 40 years,
and current predictions suggest
that trend will continue.
But are these natural disasters
simply bad weather?
Or are they due to our changing climate?
To answer this question
we need to understand the differences
between weather and climate—
what they are, how we predict them,
and what those predictions can tell us.
Meteorologists define weather
as the conditions of the atmosphere
at a particular time and place.
Currently, researchers can predict
a region’s weather for the next week
with roughly 80% accuracy.
Climate describes a region’s
average atmospheric conditions
over periods of a month or more.
Climate predictions can forecast
average temperatures for decades to come,
but they can’t tell us what specific
weather events to expect.
These two types of predictions
give us such different information
because they’re based on different data.
To forecast weather,
meteorologists need to measure
the atmosphere’s initial conditions.
These are the current levels
of precipitation, air pressure, humidity,
wind speed and wind direction
that determine a region’s weather.
Twice every day, meteorologists
from over 800 stations around the globe
release balloons into the atmosphere.
These balloons carry instruments
called radiosondes,
which measure initial conditions
and transmit their findings
to international weather centers.
Meteorologists then run the data
through predictive physics models
that generate the final weather forecast.
Unfortunately, there’s something stopping
this global web of data
from producing a perfect prediction:
weather is a fundamentally
chaotic system.
This means it’s incredibly sensitive
and impossible to perfectly forecast
without absolute knowledge
of all the system’s elements.
In a period of just ten days,
even incredibly small disturbances can
massively impact atmospheric conditions—
making it impossible to reliably
predict weather beyond two weeks.
Climate prediction, on the other hand,
is far less turbulent.
This is partly because a region’s climate
is, by definition,
the average of all its weather data.
But also because climate forecasts ignore
what’s currently happening
in the atmosphere,
and focus on the range
of what could happen.
These parameters are known
as boundary conditions,
and as their name suggests, they act
as constraints on climate and weather.
One example of a boundary condition
is solar radiation.
By analyzing the precise distance
and angle between a location and the sun,
we can determine the amount of heat
that area will receive.
And since we know how the sun
behaves throughout the year,
we can accurately predict
its effects on temperature.
Averaged across years of data,
this reveals periodic patterns,
including seasons.
Most boundary conditions have well-defined
values that change slowly, if at all.
This allows researchers to reliably
predict climate years into the future.
But here’s where it gets tricky.
Even the slightest change
in these boundary conditions
represents a much larger shift
for the chaotic weather system.
For example, Earth’s surface temperature
has warmed by almost 1 degree Celsius
over the last 150 years.
This might seem like a minor shift,
but this 1-degree change
has added the energy equivalent
of roughly one million
nuclear warheads into the atmosphere.
This massive surge of energy
has already led to a dramatic increase
in the number of heatwaves,
droughts, and storm surges.
So, is the increase in extreme weather
due to random chance, or changing climate?
The answer is that—
while weather will always
be a chaotic system—
shifts in our climate do increase
the likelihood of extreme weather events.
Scientists are in near universal agreement
that our climate is changing
and that human activity
is accelerating those changes.
But fortunately,
we can identify what human behaviors
are impacting the climate most
by tracking which boundary conditions
are shifting.
So even though next month’s weather
might always be a mystery,
we can work together to protect
the climate for centuries to come.
