Mark Maslin

And it's also really science at its naissance.

We really don't know whether we can do it at scale.

We don't know what the consequences are of perhaps chucking all these chemicals into the atmosphere to reflect the sunlight.

And we don't know how long we'd have to do it for because...

The problem with this technology is if you start doing it and you start dimming the sun, you have to keep doing it.

And if you stop, that dimming goes away.

It's like having a parasol up against the sun.

If you close the parasol and you stop chucking chemicals into the atmosphere, the sun comes back and we get heating.

So the key thing is that it's about geoengineering.

And geoengineering covers this multitude of sins.

And there are two things that I think are important.

The first is that we can remove carbon dioxide.

So we can either remove it from power plants, from coal manufacturing, from steel manufacturing, stopping it going into the atmosphere.

Or what is more likely and what we need to do in the future is suck CO2 out of the atmosphere and put it into deep geological reservoirs to trap it.

And we're going to need to do that if we're going to try to keep the world to 1.5.

We can also reforest vast areas of the world to suck CO2 out of the atmosphere.

We can rewild.

And then, and you heard my skepticism, then there's the whole, perhaps we can do the sunshade approach.

And yes, you're absolutely right.

When incredibly large volcanoes go off, they do this and put huge amounts of sulfur dioxide and dust into the atmosphere that reflects the sunlight.