Greta Thunberg at UN climate talks one year apart

At last year's United Nations climate change talks in Poland, not many people knew who Greta Thunberg was.

But in the last 12 months, her school strikes have inspired millions to do the same and to call for more action on climate change.

Now the teenager is back for this year's Conference of the Parties (COP) in Madrid, and was mobbed by crowds from the moment she arrived.