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From 2016 to 2019,

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meteorologists saw record-breaking
heat waves around the globe,

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rampant wildfires 
in California and Australia,

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and the longest run 
of category 5 tropical cyclones on record.

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The number of extreme weather events
has been increasing for the last 40 years,

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and current predictions suggest 
that trend will continue.

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But are these natural disasters 
simply bad weather?

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Or are they due to our changing climate?

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To answer this question

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we need to understand the differences
between weather and climate—

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what they are, how we predict them,
and what those predictions can tell us.

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Meteorologists define weather 
as the conditions of the atmosphere

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at a particular time and place.

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Currently, researchers can predict 
a region’s weather for the next week

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with roughly 80% accuracy.

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Climate describes a region’s 
average atmospheric conditions

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over periods of a month or more.

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Climate predictions can forecast 
average temperatures for decades to come,

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but they can’t tell us what specific
weather events to expect.

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These two types of predictions 
give us such different information

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because they’re based on different data.

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To forecast weather,

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meteorologists need to measure 
the atmosphere’s initial conditions.

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These are the current levels 
of precipitation, air pressure, humidity,

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wind speed and wind direction 
that determine a region’s weather.

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Twice every day, meteorologists 
from over 800 stations around the globe

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release balloons into the atmosphere.

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These balloons carry instruments 
called radiosondes,

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which measure initial conditions

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and transmit their findings 
to international weather centers.

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Meteorologists then run the data 
through predictive physics models

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that generate the final weather forecast.

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Unfortunately, there’s something stopping
this global web of data

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from producing a perfect prediction:

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weather is a fundamentally 
chaotic system.

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This means it’s incredibly sensitive 
and impossible to perfectly forecast

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without absolute knowledge 
of all the system’s elements.

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In a period of just ten days,

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even incredibly small disturbances can
massively impact atmospheric conditions—

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making it impossible to reliably 
predict weather beyond two weeks.

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Climate prediction, on the other hand,
is far less turbulent.

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This is partly because a region’s climate 
is, by definition,

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the average of all its weather data.

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But also because climate forecasts ignore

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what’s currently happening 
in the atmosphere,

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and focus on the range 
of what could happen.

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These parameters are known 
as boundary conditions,

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and as their name suggests, they act
as constraints on climate and weather.

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One example of a boundary condition
is solar radiation.

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By analyzing the precise distance 
and angle between a location and the sun,

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we can determine the amount of heat
that area will receive.

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And since we know how the sun 
behaves throughout the year,

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we can accurately predict 
its effects on temperature.

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Averaged across years of data,

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this reveals periodic patterns,
including seasons.

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Most boundary conditions have well-defined
values that change slowly, if at all.

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This allows researchers to reliably 
predict climate years into the future.

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But here’s where it gets tricky.

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Even the slightest change 
in these boundary conditions

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represents a much larger shift 
for the chaotic weather system.

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For example, Earth’s surface temperature
has warmed by almost 1 degree Celsius

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over the last 150 years.

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This might seem like a minor shift,

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but this 1-degree change 
has added the energy equivalent

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of roughly one million 
nuclear warheads into the atmosphere.

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This massive surge of energy 
has already led to a dramatic increase

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in the number of heatwaves, 
droughts, and storm surges.

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So, is the increase in extreme weather
due to random chance, or changing climate?

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The answer is that—

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while weather will always 
be a chaotic system—

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shifts in our climate do increase 
the likelihood of extreme weather events.

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Scientists are in near universal agreement
that our climate is changing

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and that human activity 
is accelerating those changes.

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But fortunately,

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we can identify what human behaviors
are impacting the climate most

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by tracking which boundary conditions 
are shifting.

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So even though next month’s weather 
might always be a mystery,

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we can work together to protect
the climate for centuries to come.