Will the Paris Climate Talks be too little and too late?

It's Paris or bust. Climate diplomats are preparing for a United Nations climate conference in the French capital in December that scientists say is probably the last realistic chance for the world to prevent global warming going beyond 2 degrees Celsius. Some kind of a deal will probably be done. But will it be one more diplomatic fudge or a real triumph for the climate?

In the run-up to Paris, governments have been asked to deliver pledges to cut emissions of the greenhouse gases known to cause climate change. The pledges, covering the period between 2020, when the agreement should enter into force, and 2030, are known as Intended Nationally Determined Contributions, or INDCs in the U.N. jargon.

Major nations including the United States, China, the European Union, and Russia have submitted their INDCs. But unlike the Kyoto Protocol in 1997, which only set targets for industrialized nations, all countries are expected to make pledges before Paris.

Many of the pledges sound ambitious, but analysis suggest they fall far short of what is likely to be needed to prevent warming beyond 2 degrees C (3.6 F) later this century - a goal set by nations at the Copenhagen climate negotiations in 2009. "It is clear that if the Paris meeting locks in present climate commitments for 2030, holding warming below 2 degrees could essentially become infeasible," Bill Hare of Climate Analytics, a think tank, said during preliminary negotiations held in Bonn, Germany, this month.

'The proof is in the pudding, and the pudding is going to come out of the oven in Paris,' says a U.N. official. In fact, he said, they leave the world on course for at least 3 degrees C of warming.

But there is some good news out in the real world. The decade-long boom in coal burning across the world appears to be ending, and radically lower costs for renewables, especially solar power, make them increasingly attractive. One economic study published this summer concluded that green energy was usually "nationally beneficial," regardless of the climate benefits. Indeed, there is a growing realization in many countries that cutting emissions is not just cheap, but could actually aid economic development.

Still, progress to a final agreement in Paris is proving painstakingly slow. Delegates left Bonn expressing frustration that too little had so far been settled. Fears were expressed of a repeat of Copenhagen six years ago, when similar talks collapsed in chaos, despite frantic efforts by a galaxy of world leaders, headed by Barack Obama, who flew in to do a deal.

But most delegates believe that this time, with the two biggest players, the U.S. and China, for the first time in broad agreement, there is a much greater chance of a deal. "The proof is in the pudding, and the pudding is going to come out of the oven in Paris," the U.N.'s chief climate negotiator, Christiana Figueres, insisted in Bonn.

Many key commitments are in place. So far, 60 countries have made formal emissions pledges. They cover more than 65 percent of current global emissions. The pledges vary. Some are absolute targets expressed as tons of carbon dioxide per year in 2030; others are targets measured against business as usual, or promises to reduce emissions for every dollar of economic activity.

Following a historic deal in Washington last fall between Obama and Chinese President Xi Jinping, China has pledged that its emissions, which have been growing very rapidly for several decades, will peak by 2030. It has also promised to decrease burning of fossil fuels, to increase forest cover to absorb carbon dioxide, and to reduce emissions per unit of GDP by 60 to 65 percent by the same date. The U.S., the world's second-biggest emitter after China, has pledged to cut its emissions by up to 28 percent between 2005 and 2025. That's not as hard as it sounds, because after peaking emissions a decade ago, the U.S. is already halfway there.

In July, Obama upped the U.S. commitment by announcing a plan to achieve 32-percent cuts in emissions from its power stations by 2030. China, meanwhile, revealed that its coal burning fell in 2014 and may already be in long-term decline. At the same time, the world's third-largest emitter, the European Union, which has already cut its emissions substantially since 1990, has pledged to reach 40 percent below 1990 levels by 2030.

A number of major emitters have yet to submit INDCs. They include India, currently the world's fastest-growing economy, Saudi Arabia, and Indonesia. Brazil has also yet to make its formal pledge. But during a visit to Washington in June, its president, Dilma Rousseff, promised to end net deforestation, which is still the main source of Brazil's emissions. She also boasted that by reducing deforestation in the past decade, Brazil has already cuts its emissions by 40 percent – a greater reduction that any other large country.