Greta Thunberg hits back at Trump taunt

Swedish climate activist Greta Thunberg has quietly shot back at U.S. President Donald Trump.

The 16-year-old slammed world leaders at the UN General Assembly this week...

(SOUNDBITE) (English) SWEDISH CLIMATE ACTIVIST, GRETA THUNBERG, SAYING:

"I shouldn't be up here. I should be back in school on the other side of the ocean. Yet you all come to us young people for hope. How dare you?

Afterward, Trump appeared to mock her on Twitter, saying quote: "She seems like a very happy young girl, looking forward to a bright and wonderful future."

By Tuesday, Thunberg had changed her Twitter biography to quote Trump's calling herself "A very happy young girl."

A Reuters video of Thunberg glaring daggers at Trump as he entered the UN went viral this week.

Trump has questioned climate science and has challenged every major U.S. regulation aimed at combating climate change.

Thunberg's climate activism has inspired millions of children and inspired a global climate strike movement.

On Tuesday the hashtags #GretaThunbergOutdidTrump and #BeBest were trending in the U.S.

'Be Best' is Melania Trump's campaign against cyber bullying.