“School strike week 70. Stockholm!,” wrote Thunberg.
In the photo, Thunberg is dressed in a traditional yellow raincoat, while standing with other protestors.
The climate action, launched in August 2018, has catapulted the 16-year-old into the limelight — she was recently named Person of the Year by Time magazine and awarded this year's Right Livelihood Award, also known as the so-called alternative Nobel Prize for human rights.
On 13 December, Thunberg announced that she wanted to take a break from her activities, and that she would spend Christmas at home and then go on vacation.
Earlier, Thunberg criticised world leaders at a conference in Madrid, saying they were holding talks that were not followed by real actions to combat climate change.