The 15-year-old Swedish climate activist, who went on school strike at the parliament to ask politicians to act against climate change, on Wednesday asked world leaders to step up action to really make a difference.
"You are never too small to make a difference," student Greta Thunberg said at the Global Climate Action event, which is part of the ongoing UN climate negotiations, known as COP24, which saw world leaders and decision-makers getting to work on mitigating climate change in this Polish city.
Earlier, Thunberg in her speech to UN Secretary-General Antonio Guterres said: "For 25 years, countless people have stood in front of the UN climate conferences, asking our nation's leaders to stop the emissions.
"But, clearly, this has not worked since the emissions just continue to rise," she said, "so I will not ask them anything".
"Rich countries like Sweden need to start reducing emissions by at least 15 per cent every year to reach the two-degree warming target," she added.
(With inputs from agencies.)