The Swedish climate activist Greta Thunberg has condemned the "empty words" of world leaders in a video message released ahead of the fifth anniversary of the Paris climate accord on Saturday.

Since world leaders pledged to limit global temperature rises to 2 degrees Celsius in 2015, "a lot has happened, but the action needed is still nowhere in sight," the 17-year-old said in a video posted to social media.

Thunberg warned "we are still speeding in the wrong direction," and she accused global decision-makers of wasting time "creating new loopholes with empty words and creative accounting."

Although the accord signed in the French capital five years ago committed governments to capping global warming at 2 degrees -- and if possible 1.5 degrees -- compared to the pre-industrial era, the UN warned on Wednesday that the world is currently on course for a temperature rise of 3 degrees, despite the fall in emissions caused by the pandemic.

In its annual assessment of emissions levels, the UN's Environment Programme found that 2020's 7-percent fall in carbon pollution would have "negligible impact" on warming without a broad and rapid shift away from fossil fuels.

On Friday the 27 member states of the EU agreed to raise their greenhouse gas reduction target for 2030 to at least 55 percent of 1990 levels, against the current 40 percent.

Thunberg, the figurehead of the Fridays for Future climate protest movement, regularly calls on governments to set annual emissions targets for now, and not the 2030 or 2050 horizons which are used in most international greenhouse gas agreements.

However, in her latest three-minute video Thunberg said that "the hope comes from the people" and she called on people to act, ahead of a day of 2,500 planned demonstrations worldwide, many online, by her movement to mark the anniversary of the Paris accord. 

The movement claims the objective of 1.5 degrees is now "non negotiable" and the only hope of safeguarding the planet for future generations.