Kate Marvel

But there's something even more basic than that, I think, which is that rainfall is very sensitive to the energy balance at the surface.

So rainfall is something that is going to be very, very sensitive to the difference between

Heating up the planet by trapping outgoing heat and trying to cool down the planet by blocking sunlight.

We have reason to expect that that will have consequences for rainfall that are not just an exact cancellation out of the consequences of greenhouse gases.

But the thing for me that is the scariest, the thing that is really hard for me to wrap my mind around and makes me extremely reluctant to advocate geoengineering as a climate solution is the social implications of it.

Right now, I don't see that we have a world government that is capable of making a decision on behalf of everybody who lives on the planet.

And I don't see that as something that is coming down the pike anytime soon.

Oh, you might regret having asked this because I love volcanoes.

I will talk about volcanoes forever.

I'm sure I won't regret it.

So volcanoes are a really interesting test case for geoengineering because they naturally spray a bunch of aerosols in the stratosphere.

And you can see very, very clearly in the global temperature record that there are little spikes, little downward spikes in the global average temperature immediately after certain kinds of volcanoes go off.

What we don't really have a good handle on is the hydrological consequences of what happens when volcanoes go off.

How do they affect regional precipitation patterns?

How do they affect things like drought risk?

And all of these things are really complex and all of these things are really unknown.

When you look at volcanoes throughout history, that's when you kind of smack into the biggest unknowns.

And this is why I am completely obsessed with volcanoes.

Because if you look through human history, there seems to be one constant, which is whenever a massive volcanic eruption happens, stuff gets real weird.

So in 1789, there was a massive volcano in Iceland that went off called Laki.