WEBVTT

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[MUSIC PLAYING]

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LAUR HESSE FISHER:
We know that you

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know that the Earth
is warming, but you

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might have questions like,
how did scientists figure out

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that this warming is happening
and that it's caused by humans?

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How strong is the
evidence, really?

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What risks can we expect?

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And what can we do about them?

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Climate science is
not a new field.

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By the time of the
American Civil War,

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scientists understood that
the Earth is kept warm

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by a handful of gases
that make up less than 1%

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of our atmosphere, but
that these gases keep

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the sun's radiation from being
immediately lost to outer space.

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And they understood
that if humans

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were to change the amount of
these gases in our atmosphere,

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our climate would
be transformed.

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Today, these predictions
are coming to life.

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And as global temperatures rise
and extreme weather intensifies,

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you probably have
more questions.

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The online primer
Climate Science, Risk,

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& Solutions from the
Massachusetts Institute

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of Technology is
our effort to bring

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the story of climate science
to everyone who wants to learn.

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Used in universities and high
schools around the world,

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this primer answers how
scientists know what

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they know about climate change.

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It takes learners through the
history of climate science,

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the risks we face now, and
will face in the future,

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and the options we have to
overcome climate change,

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and secure a safe and
prosperous planet for ourselves

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and for future generations.

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To do this, we worked
with MIT's professor

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Kerry Emanuel, an acclaimed
climate communicator

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who has been studying
the Earth's weather

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system for over 40 years.

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So let's let him share
a peek at what you'll

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learn in Climate Science,
Risk, & Solutions from MIT.

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KERRY EMANUEL:
Human-caused climate change

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began with the
Industrial Revolution,

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when people began burning large
quantities of coal and oil,

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releasing carbon dioxide
into the atmosphere.

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And although
scientists have long

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predicted that
this influx of CO2

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would raise the
Earth's temperature,

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now that we can
see it happening,

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a very reasonable
question people ask

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is, how can we
trace these trends

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all the way back to the
dawn of the fossil fuel age?

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Surely, that's too
long ago for us

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to have accurate records of
world temperatures, let alone

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how much carbon
dioxide was in the air.

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In fact, by the 19th century,
people were using thermometers

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and keeping careful records of
temperature in enough places

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around the globe for us to
reconstruct average world

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temperatures.

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Naturally, most of
these measurements

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were taken at
land-based stations,

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but some came from the
ocean surface, too.

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This is crucial data when
trying to learn the Earth's

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average surface temperature,
since, of course,

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the oceans take up most
of the world's surface.

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It's not enough to simply
average all the temperature

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records we have together.

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One must carefully account
for the uneven distribution

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of temperature measurements
around the world,

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the way growing cities
have become warmer

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than the surrounding
countryside,

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and many other variables.

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But one way to know if
our calculations are good

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is to see if different
groups working independently

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of each other have reached
the same conclusions.

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And indeed, the
five major groups

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tracking global temperatures
have produced very similar

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records, discovering the same
ups and downs from year to year.

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Since the 1960s, we have
been able to add satellite

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measurements of infrared
radiation at the Earth's surface

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to our arsenal of instruments.

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And it is reassuring to see
that these two track closely

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with the thermometer record
from around the world.

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But what about carbon dioxide?

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How can we really know
the temperature rise

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traced by all these
different sources

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is caused by rising CO2 levels?

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Indeed, it was not until the
1950s that scientists began

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measuring the CO2 content
of the atmosphere directly.

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For climate scientists, it's not
enough to know that CO2 levels

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have been rising
since the 1950s.

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We want to return to the
beginning of the Industrial

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Revolution.

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And our greatest asset
here is ice taken

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from Greenland and Antarctica.

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As snow falls in these
frigid parts of the world,

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it traps small samples
of air along with it.

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Because the snow never
melts, over time,

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it becomes compressed
in layers of ice

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with tiny bubbles inside
that preserve ancient air.

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This record of air samples
goes back hundreds of thousands

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of years.

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By drilling into the ice
and collecting cores,

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scientists can create
a year-by-year record

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of our past atmosphere.

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And it is these ice core samples
that show us the history of CO2

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in the atmosphere, which we now
know held steady at around 280

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parts per million for almost all
of recorded human history until

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it began to creep up
in the 19th century,

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and truly take off
in the mid 20th,

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to the point that the CO2
content of the atmosphere is

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fully 50% higher than
it was 150 years ago.

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From these combined
records, we can now

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see plainly what
climate scientists

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have predicted all along.

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CO2 levels have been rising
as we burn fossil fuels,

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and temperatures have
been rising with them.

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LAUR HESSE FISHER: The
pace of climate science

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has never been
faster, which is why

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MIT's Climate Science,
Risk, & Solutions

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has been newly updated
for 2024 with the latest

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data and scientific consensus.

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And with help from
MIT Open Learning,

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all this information has been
paired with fun online learning

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techniques, where you can
watch, listen to, and play

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with the data.

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All of this is connected
to other learning resources

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from MIT that will
help you drill deeper

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into the topics that interest
you the most, whether that's

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the basic science of the
greenhouse effect, the climate

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models that help scientists
peer into our future climate,

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or the solutions at hand, from
renewable energy to carbon

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capture.

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Are you ready to have your
questions answered about climate

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change and climate science?

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Then visit
climateprimer.mit.edu to begin.

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