Kind: captions
Language: en
[Applause]
let's talk about the science of climate
change
don't you mean global warming how'd you
get in here
I'm the Internet I never left now why
did you change the name global warming
wasn't happening so you have to call it
climate change well the overall average
temperature of the planet is increasing
so global warming is technically correct
but that doesn't mean it's going to be
warmer everywhere all the time and that
leads to some confusion like on a cold
winter's day you might say so much for
global warming exactly so the term
climate change indicates that the
problem is more intense storms droughts
and floods ocean acidification not just
that the globe is warming but it's not
what the globe's not warming since when
1995 that's not how you draw a trendline
through data if the slope is nil the
climates chill you know 13 of the 14
years occurred this century and the
graph you're using is old it doesn't
include satellite data if you take that
into account the trend is obviously
continuing upwards oh so now you say
it's warming in the past scientists told
us it was cooling why can't they just
admit that they have no idea what's
going on it's true in the 1970s there
were some papers published predicting
cooling but over that same time period
there were six times as many papers
predicting warming so scientists really
haven't changed their tune well just
judging by temperatures I say they're
wrong the earth is cooling but you don't
just have to go by the temperatures
there are plenty of other signs that the
globe is warming like sea levels are
rising three millimeters a year that's
an indication that the oceans are
getting warmer and so expanding ice on
Antarctica and Greenland is melting at
unprecedented rates and Arctic sea ice
continues to decline
nah-uh Arctic sea ice increased 40% in
the last two years that last little
uptick that's what you focus on what
about the general downward trend that
could mean anything
you know if the earth is warming the
most likely source of the problem is the
Sun the Sun is getting brighter did you
ever think of that
the Sun was getting brighter in the
1930s and it probably contributed to
some warming then but
since the 50s the Sun has been getting
dimmer and temperatures continue to rise
Oh see you automatically assume it's
man-made co2 you know humans only emit a
tiny fraction of the co2 released into
the atmosphere every year that's true
people emit about 30 Giga tons compared
with 780 Giga tons from natural land and
ocean processes so you admit it
humans aren't the problem no before us
the system was in balance with the land
and oceans absorbing that same amount
780 Giga tons a year this balance kept
carbon dioxide levels in the atmosphere
between 180 and 280 parts per million
for 800,000 years now it's at 400 parts
per million and still rising
but our small contribution couldn't have
caused that well the amount of co2 in
the atmosphere is increasing by about 15
Giga tons or 2 parts per million every
year but how do you know that's man-made
co2 because the isotope carbon 13 is
less common in fossil fuels than it is
naturally in the atmosphere and over
time we're seeing the concentrations of
carbon 13 are decreasing but volcanoes
emit way more co2 than humans no they
don't
they emit about 0.25 Giga tons annually
that's less than 1% as much as human ok
well even if we are responsible for the
rise in co2 it doesn't matter because
water is by far the most potent
greenhouse gas yes it is I win no you
don't water in the atmosphere is
increasing as well but that can't be due
to human activity the only way for the
atmosphere to hold more water vapor is
if it gets warmer so hang on
you're not saying yes it all comes back
to co2 a doubling of co2 on its own
would increase the temperature of the
globe by about 1 degree Celsius but that
warming means there'll be more water
vapor in the atmosphere and ice will
melt reducing the reflectivity of
Earth's surface so it's a positive
feedback loop which a bunch of different
sources of evidence all indicate will
lead to about a 3 degrees Celsius rise
in temperature but if this is true why
have all the predictions failed in
actuality most of the predictions show
remarkable agreement with observations
but you're probably thinking of the
model from 19
88 back when we thought climate
sensitivity was higher if you rerun that
model with three degrees of warming for
every doubling of co2 the predictions
match exactly the warming that we've
observed but the earth has warmed and
cooled in the past so who is releasing
co2 back then aliens
we understand that past changes in the
climate were triggered at regular
intervals by Milankovitch cycles that is
the periodic oscillation of the earth's
tilt precession of the tilt and
stretching and squashing of Earth's
elliptical orbit during every warming
cycle co2 and temperature rise together
ah but if you look closely at that graph
you'll see that co2 lags behind the
temperature rise so it can't be causing
the warming the co2 doesn't cause the
first warming the Milankovitch cycles
changed the way the sunlight hits the
earth and that causes a little bit of
warming decreasing the solubility of co2
in the oceans so some of that co2 is
released and that is a positive feedback
loop which amplifies the warming in fact
over 90% of the temperature increase
happens after the co2 starts to rise
let's say you're right and the co2 we're
releasing is warming the planet what's
so bad about that planet gets a little
warmer big deal I'm not claiming it's
gonna be some sort of crazy catastrophe
but we are gonna get more intense storms
more droughts and floods the oceans will
become more acidic sea levels will rise
and my point is it would be better for
all species on this planet and probably
cheaper for us if we just started
reducing emissions now than if we wait
and pay the consequences later no thanks
why are you wearing sunglasses
[Music]
global warming this episode of
veritasium was supported by audible.com
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and periodicals this week I wanted to
recommend the book merchants of doubt'
which is about scientists who have
spread misinformation about certain
topics like how cigarettes cause lung
cancer or how CFCs caused the ozone hole
or now how co2 is causing the planet to
warm so if you want to find out more
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