Looking at our three Goldilocks planets; Venus, Earth, and Mars.
Venus suffered a runaway greenhouse effect, you already know.
And so, the water in the oceans boiled, goes into the upper atmosphere
where the ultra-violet light breaks it apart.
You lose the hydrogen into space, water's gone, that's it forever.
Well, now the nail in the coffin is,
if you have no water, you can't have any weathering.
And so, you have broken the thermostat.
All of the carbon gets cooked and put into the atmosphere.
That's why the atmosphere of Venus has 70 bars of CO2.
That's why all of Venus's carbon is in the atmosphere,
rather than on earth where almost all of our carbon is in
calcium carbonate or other sedimentary rocks.
On Earth, the thermostat will eventually clean up the fossil fuel CO2, but it
takes a very long time. The other thing you should know is
that there are ways in which the geometry of the geology
can alter the set point of the thermostat.
The thermostat regulates the temperature the way a thermostat of house
can regulate the furnace and the house temperature.
Slowly change the dial on the thermostat by changing the geometry of where
the land and oceans are, mountain building,
and how fast the CO2 is coming out of the Earth by de-gassing and things like that.
Earth has tended to drift back and forth between hothouse climates,
where there's basically no ice on earth at all,
and then climates like today, we call this an ice age climate, even though
it's not as big an ice age as it was,
twenty thousand years ago, the last glacial maximum.
But there still are major ice sheets on earth in Antarctica and in Greenland.
And so geologists would say that we are still in an ice age.
If you go to a natural history museum and
go see the dinosaur dioramas, they always looks very tropical.
That was the dinosaurs existed during a
Hot House period of Earth's climate.
This going back and forth between these two major kinds of climate.
Is, is driven by setting the thermostat, by changing the way that the CO2
is degassing from the earth, or the
way that it's weathering.
Mars is a smaller planet than Venus or Earth
which meant that it cooled down more quickly.
Actually the biggest volcano in the solar system
is on mars, Olympus Mons, it's called. But it's tectonically dead;
the interior of Mars has cooled down enough that it doesn't do this trick
of of metamorphosis, cooking the calcium carbonate,
to push the CO2 out to the atmosphere.
The thermostat is broken on Mars, because it's tectonically dead.
It's broken on Venus because
weathering can't happen.
But on Earth, it's still functioning in a very beautiful way.