Swedish climate activist Greta Thunberg took to Twitter on Halloween to mock her detractors by posing as herself – saying she terrifies her critics.

The teenager, who has left school to travel the world preaching her message of climate salvation, said she scared “a bunch of angry climate crisis deniers” without having to dress up.

Posing in a black-and-white photo with her trademark “school strike for climate” placard, she said she did not celebrate Halloween in Sweden but “thought I might give it a try'” if it meant she could affront her critics.

So today is Halloween. I don’t celebrate it back home, but I thought I might give it a try.

And apparently when it comes to scaring a bunch of angry climate crisis deniers – I don’t even have to dress up!! #trickortreat pic.twitter.com/Nt6CHRU3Q8 — Greta Thunberg (@GretaThunberg) November 1, 2019

Thunberg sailed to North America on a carbon fiber racing yacht in August as she refuses to fly on jet planes.

She was due to attend an environmental summit in Chile next month, but the conference has been put on hold amid violent protests in the country.

“I’ve been making my way through the North American continent towards Santiago, but as COP25 will be moved I will now wait until I have more information,” she said.

Thunberg will instead be the main speaker at a rally in Los Angeles on Friday, she confirmed on Twitter:

This Friday November 1st I will be joining the climate strike in Los Angeles!

12am at City Hall! #FridaysForFuture #ClimateStrike #schoolstrike4climate pic.twitter.com/ePVxrEkv0v — Greta Thunberg (@GretaThunberg) October 31, 2019

Last week Thunberg took aim at her opponents in a different way, threatening to quit Facebook if the social media platform refuses to silence her critics, as Breitbart News reported.

“I am, like many others, questioning whether I should keep using Facebook or not,” Thunberg wrote in a Facebook post last week.

“Allowing hate speech, the lack of fact-checking and, of course, the issues of interfering with democracy… are among many, many other things that are very upsetting.”

“The constant lies and conspiracy theories about me and countless others, of course, result in hate, death threats and ultimately violence. This could easily be stopped if Facebook wanted to. I find the lack of taking responsibility very disturbing,” she added.

As well as scolding Facebook for having the temerity to host opposing argument, the pig-tailed activist last month warned the United Nations to step up its climate work, telling 60 world leaders to heed her lecture because, “her generation would never forgive them if they failed to combat climate change.”

Greta Thunberg is 16 years old.