I'm Rory Stewart and I grew up wanting to be a hero and I'm still fascinated by the ideas of heroism.

In my new series, I'm taking in the long sweep of history from Achilles to Zelensky and asking, what is a hero?

Simply doing your job, being a decent human being.

A true hero is someone who just kind of shines by

their own light and that light is to be recognised by others. The long history of heroism

with me, Rory Stewart. Listen on BBC Sounds. We're currently headed for a catastrophic

global temperature rise of three degrees this century. We're nowhere near

meeting the emissions reductions that would limit us to the internationally agreed safe aim

of one and a half degrees. Already the planet is 1.2 degrees hotter than the pre-industrial average, and rising.

Fires blaze from the Amazon to the Arctic.

Extreme heat kills people and crops as far north as Canada,

while devastating floods and sea level rise drowned cities from India to Europe.

We need to stop adding greenhouse gases to the atmosphere by decarbonising our energy systems much faster. However, even with the

best efforts, it will be decades before we see any change in global temperatures through our mitigation efforts.

Given the pace of global heating and the time lag before our emissions reductions have any impact,

scientists are exploring additional ways of reducing global temperature.

I'm Guy Vince and in this series of Discovery,

I'll be looking at ways of actively removing carbon from the atmosphere

and at ways of reducing the amount of sunlight that heats the Earth.

These are often called geoengineering technologies or climate repair, and they're still in their

experimental infancy. Scaling them up is controversial and may not even be possible. But let's look

at what's involved.

...