Bonn: A pivotal question has split world powers along unfamiliar lines as they haggle over how to avert catastrophic global warming: Should they set a goal of entirely eliminating carbon-belching industries?
Tensions over the concept, called "decarbonisation", illustrate how wide the divides remain less than six weeks before a 195-nation UN forum gathers in Paris to try to tame climate-altering forces.
Their overarching goal is to limit global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels so as to avoid dangerous consequences such as rising sea levels, increasingly violent storms, large-scale droughts and spreading disease.
Two decades of negotiations over how to rein in global warming have been fraught with disagreements.
But few are so basic as the dispute over how far to go in eliminating emissions of carbon dioxide (CO2) and other so-called greenhouse gases blamed for trapping the Earth's heat.
Just weeks ahead of the November 30-December 11 meeting in Paris, nations cannot even agree on the meaning of decarbonisation -- does it denote a desired outcome, or an open-ended odyssey? Does it apply only to CO2 or other greenhouse gases too?
The term has flashed in and out of various versions of a draft agreement to be presented to ministers and heads of state in the French capital.
Green groups pushing for a 100 per cent renewable economy by 2050 hailed the word's reappearance -- following a minor rebellion by developing nations -- in a revised text unveiled in Bonn Tuesday.
"It tells us the direction of travel, and where we want to be by 2050, by the end of the century, and how we are going to get there," said climate activist Mohamed Adow of Christian Aid, a group fighting for the rights of poor countries.
Unlike many issues bedevilling the talks, the tussle over decarbonisation does not respect the traditional split between rich and developing nations.
It was the United States that insisted on putting the term back on the table after it had been excised by the two presiding diplomats in a radical pruning during the Bonn talks.
The European Union -- aligned with Washington on most climate matters -- resists using the word.
This is despite French President Francois Hollande and German Chancellor Angela Merkel successfully lobbying other members of the Group of Seven (G7) rich nations to enshrine decarbonisation in a joint statement in June.