Two sets of reality are clashing as climate talks go into overtime: Diplomatic real politics and hard science.

Top experts say that while a goal of limiting warming in a new draft climate agreement is laudable, the rest of the proposed pact doesn't provide the tools to achieve it — and in some ways, it even goes backward.

"There's an absolutely huge disconnect between the negotiations and the political rhetoric, and what's very clearly coming out of the science," Kevin Anderson, deputy director of the Tyndall Centre for Climate Research in Britain, said Friday as the high-stakes climate talks dragged into an extra day.

The latest draft of a proposed international climate agreement lists a goal of "holding the increase in the global average temperature to well below 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels" and urges efforts to limit it even further, to 1.5 degrees Celsius.

This even as Earth has already warmed nearly 1 degree Celsius (1.8 degrees Fahrenheit) since the mid-18th century.

Dana Fisher, director of the Program for Society and the Environment at the University of Maryland, said she sees "a couple of dueling realities," including one she calls a "kumbaya moment" where everybody talks about the importance of a 1.5-degree cap on global temperature increase but no one does anything to implement it.

And because the Paris draft removes discussion of carbon dioxide emissions from shipping and air travel, Anderson said he considers the Paris proposal even weaker than the one that came out of Copenhagen in 2009.

"It is not consistent with science, which the Copenhagen accord had directly written into it," Anderson told The Associated Press.

And the current language for poor people in developing nations like Africa and Asia, "is somewhere between dangerous and deadly," Anderson added.

The negotiations also don't take into account what emissions cuts are needed to limit warming to 1.5 or 2 degrees Celsius, said Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Research in Germany. "The politics simply leave it out of the equation."

Andrew Jones, co-director of Climate Interactive who runs computer simulations of what individual nations' emissions promises mean in terms of temperature, said current pledges will amount to another couple degrees Celsius warming from now, blowing right past the goal of keeping warming to less than 2 degrees above pre-industrial levels.

And making the goal a more stringent 1.5 instead of 2 degrees without reducing emissions just doesn't cut it, he said.

"It's kind of like this: My friends and I have committed to losing 300 pounds but are failing so far," Jones said. "Instead of eating less and exercising more, I propose that we lose 350."

At a news conference, Anderson and colleagues went through the draft agreement — which still is being modified and negotiated — and said it isn't near to getting close to the goal. They especially criticized vague language that talks of "greenhouse gas emissions neutrality" without really defining it.

"We really need to be keeping around 90 percent of all current reserves (of fossil fuels) in the ground," Anderson said. Burning coal, oil and gas emit heat-trapping gases that cause global warming.

"You have to go to zero carbon dioxide emissions by 2050 in order to have a fair chance" of reaching the 1.5-degree goal, Schellnhuber said.

Joeri Rogelj, of the International Institute for Applied Systems Analysis in Austria, went further: "Without zero emissions, 2 degrees is impossible. Without zero emissions, temperature stabilization is impossible."

But John Reilly, co-director of MIT's Joint Program on the Science and Policy of Global Change, said "that's way out there" and doesn't take into account politics, including U.S. conservative opposition, and the needs of African nations to develop.

"They can say whatever they want in Paris," said Fisher, but Republicans in the U.S. Congress "are screaming no way and we have this huge fossil fuel industry and infrastructure in place."

Still, Fisher and Reilly said the goal of keeping warming to 1.5 degrees is important.

It's especially crucial for small islands, said Reilly, adding: "It's hard to accept a target where some of the negotiating states won't exist, and that's what 2 degrees is."

In the end, some experts were downright gloomy.

"If you ask me if I think we'll succeed," said Anderson. "No, I think we'll fail."