- [Narrator] Have you ever tried to imagine
what the world was like in the distant past?
Maybe you'd like to explore the age of the dinosaurs
when the earth was much hotter than it was today.
Perhaps you'd prefer
when temperatures dropped too much colder than today.
You could track a mammoth alongside our early ancestors
who evolved around the end of the last ice age.
We know about all of these ancient climate trends
because scientists learned
how to estimate them using evidence from ice cores,
tree rings, and other natural phenomena.
We now know that for most of human history,
people could expect a pattern
that looks something like this graph
from the National Aeronautics and Space Administration
which shows how temperatures changed each year
in comparison to this line,
which represents the average global annual temperature
from 1880 to 1899.
When we look at the time period between 1880 and 1940,
we can see that some years temperatures would be higher
than this average, some years they would be lower,
but they generally swing back
to a pretty comfortable state.
Around the 1950s, though,
the global average temperature began to climb
to unprecedented levels.
Our ancient temperature records never showed
such a sudden increase.
When we look at the time period from 1950 to today,
we can see that while temperatures
still swing back down some years,
these colder years are still much hotter
than the average temperatures in the past.
Researchers noticed a change in the concentration
of greenhouse gases in the Earth's atmosphere.
These greenhouse gases trap heat
from the sun in our atmosphere,
similar to how a greenhouse allows sunlight
to pass through its glass walls
but prevents the heat it creates from leaving.
This greenhouse effect is what keeps our planet warm
and habitable enough for life.
However, the amount of one particular greenhouse gas
was rising, carbon dioxide or CO2.
CO2 is naturally one of the most notable greenhouse gases
besides water vapor,
but we can also release CO2 by burning wood
or fossil fuels like coal and oil.
Over time, humans have increasingly relied on these fuels
to power things like planes, cars, and trains
as well as to generate electricity.
As a result of these human activities,
more CO2 is being released into the atmosphere
than ever before,
much more than is normally released by the Earth
and at a much faster rate.
The increasingly heavy blanket of greenhouse gases
is trapping excess heat in our atmosphere
rather than allowing more of it
to radiate into space as normal.
This is what's causing Earth's average temperature
to rise beyond what scientists would expect
based on historical patterns.
While scientists once referred
to this process as global warming,
most now prefer the more general term, climate change.
A world that's a little bit warmer on average
might not seem like such a big deal,
but we've learned that even a small shift
in the planet's natural processes
can have drastic consequences.
When studying the early signs of climate change,
scientists predicted that as cold places
like North and South Pole got warmer,
the ice would begin to melt.
All of that frozen water suddenly flowing into the oceans
would cause sea levels to rise,
which would affect the planet's weather system.
Have you heard all the news about weird weather
in the past few years?
Snow in places that's usually warm and dry,
or drought in places that are usually cold and rainy,
huge fires during extremely hot summers,
severe storms battering coastlines and flooding cities.
Many of these natural hazards used to be somewhat rare,
but now they're becoming more common,
exactly as climate scientists predicted.
People have relied on relatively consistent weather patterns
for generations,
so they aren't prepared to adapt
to these changes in their local environment.
Communities that are already feeling the effects
of climate change are worried
that they're gonna lose their homes,
their livelihoods, or their sources of food and water.
Scientists are working on technologies
that can help us remove some of the excess CO2
from the atmosphere,
but in the meantime they recommend that we emit less CO2
in the first place.
This would allow us to limit
how much the global average temperature increases,
giving communities time to adapt
to changes in their surroundings.
Of course, it's complicated
to change the way our societies work.
To help reduce CO2 emissions,
you may see some people advocating
for tweaking individual behaviors,
like eating plant-based diets
or using low carbon transportation methods.
You may see others saying that since large organizations
in highly populated countries emit the most CO2,
we need to push them
to make more wide raging institutional changes.
As someone who works in environmental science,
I know that sorting through all of these different facts
and opinions on climate change can be overwhelming.
It's difficult to think about living in a world
that may be very different
from what I've always known in the past.
I've found it helpful
to both adopt simple sustainable habits in my own life,
while also seeking out community groups
that work on bigger initiatives.
It's easier to imagine the future
when you help others to shape it.
Now that we've taken some time to think about Earth's past
and what's happening to it in the present,
try looking towards the future of our planet.
What is your ideal future?
And how can you help to make it happen?