Other things have changed too - we’ve chopped
down tropical forests,
caused the ozone hole, and
filled the air with soot, smog and
other kinds of air pollution.
And this is on top of natural variations
caused by the dynamics of the oceans, or volcanoes,
or variations in the Sun’s activity.
And so we can ask whether
it’s human activities warming our planet.
At NASA, we have some big and
powerful computers,
able to make 6.8 trillion calculations per second.
We put these huge supercomputers
to work to recreate Earth’s climate.
So, we have thousands of ideas of
what could naturally cause climate change.
We have 4 billion years of history where nearly
anything and everything
you could imagine has impacted Earth's climate!
But each of those events have
their own distinct fingerprint which we can
identify a pattern of behavior with natural variability.
Using supercomputers, we can run simulations of natural climate drivers,
solar energy changes, wobbles in Earth’s orbits, ocean turnover,
volcanic eruptions....
And we can run simulations of human effects.
And what we've seen is...
It's us. There's no way around it.
Looking at the evidence, we're the force that's enacting these changes.
I am so proud of our ability to understand
the climate, but I'm terrified of what we found.