Thousands of demonstrators converged on Bonn Saturday ahead of UN climate negotiations demanding that governments step up action to halt global warming, starting with a rapid phase-out of coal-burning power plants.

Decked out in red to signify their "Stop Coal" campaign, the protesters chanted slogans and beat drums as they snaked through the former West Germany capital toward the UN centre that will host the 12-day, 196-nation talks, tasked with implementing the landmark Paris Agreement.

Police did not estimate crowd size, but noted that organizers put the figure at more than 20,000.

Inked outside the French capital in 2015, the world's only climate treaty calls for capping global warming at "well under" two degrees Celsius (3.6 degrees Fahrenheit), and 1.5 C (2.7 F) if possible.

Earth has already warmed by 1 C compared to pre-industrial levels.

"The lives and livelihoods of millions of people are under threat, entire island states are in danger of disappearing from rising sea-levels," a coalition of more than 100 civil society groups said in a statement ahead of the march.

"Tackling climate change means a rapid phaseout of fossil fuels, including the burning of coal."

Coal accounts for roughly a third of global energy consumption, and powers 40 percent of all electricity -- twice as much as the next energy source, natural gas.

Compared to gas and oil, coal produces more carbon pollution per unit of energy, making it the "dirtiest" of the fossil fuels.

Coal demand has slowed, especially in the United States where the natural gas fracking boom has undercut its market share.

But globally, demand is projected to expand until at least 2030, according to the International Energy Agency (IEA).

That growth seriously threatens the Paris Agreement's temperature goals, UN and energy experts say.

- 'We have to try' -

If the world's nearly 7,000 coal-fired power plants -- with a combined capacity of nearly 2,000 Gigawatts -- operate to the end of their lifetimes, it will add the equivalent of five years' of global CO2 emissions to the atmosphere, the UN's environment agency noted in a report last week.

Another 850 GW of coal capacity is either under construction or in the pipeline, mostly in India, China, Turkey, Indonesia, Vietnam and other Asian countries.

Under pressure, the coal industry is banking on so-called clean coal technologies, especially one known as "carbon capture and storage," or CCS, that isolates CO2 as energy is being produced and socks it away underground.

So far, despite decades of development, CCS has failed to materialise at scale. But proponents are hopeful that US President Donald Trump -- a "clean coal" booster -- will speed its deployment.

"It is very encouraging to hear a president talk positively about the role of cleaner coal technology," Benjamin Sporton, CEO of the World Coal Association, based in London, told AFP earlier this year.

Solar and wind energy -- while growing rapidly -- still only account for a tiny sliver of global energy production.

According to a study published last week in Environmental Research Letters, holding sea level rise to 50 centimetres (20 inches) by 2100 would become nearly impossible if coal-fired energy is not phased out by mid-century.

"If emissions continue unchecked, oceans could rise by around 130 cm in 2100" -- nearly double the maximum forecast in the UN climate science panel's benchmark report, co-author Carl-Friedrich Schleussner, a scientist at the Potsdam Institute for Climate Impact Research in Germany, told AFP.

For small island nations, and those with densely populated low-lying deltas such as Bangladesh, sea level rise on that scale would be catastrophic, experts say.

That is the hard-to-ignore message that Fiji, presiding this year over the annual climate summit, intends to drive home at every opportunity.

"We can count on Fiji to apply pressure on the major emitting countries in a way they will feel it," Laurence Tubiana, director of the European Climate Foundation and one of the main architects of the Paris Agreement as France's Climate Ambassador, told AFP.

"It is the only thing we can do," said Sabine from nearby Cologne, when asked why she and her two daughters, 16 and 8, had joined the protest.

"I don't know if it will change anything, but we have to try."

Source: AFP