Swedish teenager Greta Thunberg has urged politicians to listen to the voices of young people during the second week of international climate negotiations.

The Swedish teenage activist was speaking as thousands of youth activists gathered in central Madrid on Friday to voice their anger about the slow pace of progress so far. The protest, organised by the climate strike movement Fridays for Future, was also attended by many students, families and professionals.

Just a few miles away, in the stuffy surroundings of Madrid’s largest conference centre, negotiators from across the world continued to try to hammer out the final details of the 2015 Paris Agreement.

Ms Thunberg made a surprise appearance at the conference on Friday to meet other young activists before being whisked away by security. She had hitch-hiked her way across the world after the talks were moved from Chile due to civil unrest.

Ms Thunberg later told reporters that the voices of climate strikers were being heard but not enough “concrete action” was taking place. "Of course there is no victory, because the only thing we want to see is real action,” she said. “So we have achieved a lot, but if you look at it from a certain point of view we have achieved nothing."

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Hers was not the only young presence trying to push for more ambitious outcomes in Madrid. Speaking at a panel run by the Association of Small Island States, Samoan student Brianna Fruean from 350 Samoa and the Pacific Climate Warriors, said it was critical to remember that some nations represented at the talks were fighting for sheer survival. “World leaders need to know that people like me are watching them.”

The key sticking points of the talks, which began on Monday, are how to establish new international rules for carbon markets and how to help poorer countries pay for losses and damage caused by climate change.

A decision on carbon market rules is proving tricky because of disagreements about what to do with the surplus credits from earlier emission trading schemes and how to avoid ‘double counting’ emission cuts that are traded overseas.

Progress on loss and damage is also a long way off. Many vulnerable nations are pressing for a new financial mechanism to pay for major, one-off disasters such as hurricanes and typhoons, as well as longer term problems exacerbated by climate change.

But influential developed countries, particularly Australia, Japan and Switzerland (as well as the US, which is withdrawing from the Paris Agreement), do not want finance on the table at all because they think it will open the floodgates for future compensation claims.

Another sensitive subject under discussion is how to ensure human rights are respected in climate action. Russia in particular is resistant to the discussion of human rights in any context.

An underlying concern at the talks is the extent to which countries will be expected to be more ambitious when they revise their national carbon-cutting commitments next year.

A recent report by UN Environment Programme warned that there was a huge gap between what countries had committed to so far and the goal of keeping global warming to a reasonably safe level. It found global fossil fuel production needs to be more than halved by 2030 to stay within a 1.5c temperature rise, with coal the biggest offender.