The U.N. climate chief urged a radical clean-up of the coal industry on Monday to help limit global warming, at an industry meeting in Warsaw condemned by environmentalists as a distraction from the nearby U.N. climate change conference.

Christiana Figueres, head of the U.N.'s Climate Change Secretariat, told the coal summit that the industry had to change "rapidly and dramatically" to limit high pollution and carbon emissions, including in heavily coal-dependent Poland.

She urged the industry to "leave most existing reserves in the ground", to shut inefficient plants and to capture and bury all emissions of carbon dioxide from coal-fired plants, a technology that has proved too costly so far for wide use.

As she did so, Greenpeace activists scaled the Polish Economy Ministry, hosting the coal summit, and unfurled a 15-meter (50 foot) banner asking: "Who rules the world? Fossil industry or the people?"

An international panel of climate scientists says fossil fuel use is extremely likely to be the main cause of a sharp rise in global temperatures since the Industrial Revolution that is now changing the climate.

A group of 27 leading climate scientists working with the panel's data said in Warsaw that there were 3.8 trillion tons of carbon dioxide trapped in the world's fossil reserves, about 60% of it in coal.

They said 1 trillion tons would suffice to push the post-industrial temperature rise past 2 degrees Celsius (3.6 Fahrenheit), set by governments as a ceiling to avoid rising sea levels as well as worsening heatwaves, droughts and floods.

'Move Beyond The Rhetoric'

The World Coal Association (WCA), co-hosting the conference with the Polish government, says the world cannot abandon coal, which generates about 41% of world electricity and is likely to overtake oil as the main source of energy by 2020.

"We want to move beyond the emotional rhetoric, and focus on what we can all do in practical terms," said Milton Catelin, chief executive of the WCA. He said the industry meeting was a "constructive contribution" to the U.N. climate talks.

Environmentalists condemned the summit as a deliberate distraction from the talks involving almost 200 nations at a soccer stadium nearby, which is working on the outlines of a deal meant to be agreed in 2015 to slow climate change.

Poland produces about 90% of its electricity from coal and is among the European Union nations most reluctant to implement deeper cuts in greenhouse gas emissions beyond 2020.

"The summit can develop clear signals that coal is an important component of climate policy," Polish deputy Prime Minister Janusz Piechociski told the start of the two-day coal meeting.

Worldwide, there are plans for almost 1,200 coal-fired power plants to be built, according to the World Resources Institute think-tank.

Developing World Need

Godfrey Gomwe, chief executive of Anglo American Thermal Coal, said coal was vital to help 1.3 billion people with no access to electricity in developing nations to escape poverty.

"A life without access to modern energy is a life lived in poverty," he told the coal summit.

U.S. climate envoy Todd Stern said broad coal use was "not going to change overnight", adding: "The most important technology which can provide a longer-range future for coal in a low-carbon world is CCS (carbon capture and storage)."

The 27 climate scientists said CCS was the only way for the world to limit a rise in temperatures to 2 degrees Celsius while still using coal.

They said that renewable energies such as wind and solar power, usually more expensive than coal, were far more competitive if governments factored in the damage to health and to the environment caused by fumes from coal-fired plants.

The World Bank and European Investment Bank have both decided to curb lending to most coal-fired power projects, and the European Bank for Reconstruction and Development is expected to drastically reduce its involvement.

Some institutional investors are also acting. The Church of Sweden, for instance, will not invest in firms that get more than 5% of their turnover from prospecting for or developing coal.