THE LOW EXPECTATIONS of progress in advance of the U.N.'s climate change conference in Copenhagen were ratified by the results. Despite boasts by President Barack Obama and some other world leaders of a breakthrough on reducing carbon dioxide emissions, little of real substance was achieved.

There was a pledge by leading industrial powers to give $30 billion in emergency aid to unspecified underdeveloped nations over the next three years and to increase it to $100 billion a year by 2020.

The United States, China, India, Brazil and South Africa decided on a method for verifying reductions in heat-trapping gases, something China had previously opposed. Also, the agreement requires industrial countries to list their individual targets for reducing greenhouse gases.

Most significantly, there were no legally binding commitments, nor was there any agreement on how much and how fast carbon dioxide emissions should be reduced.

The reason Copenhagen fell short was not from a lack of effort, but because the task of cutting back carbon dioxide emissions enough to make a difference in global climate is indeed daunting.

Just to stop increasing the amount of carbon dioxide in the atmosphere, global emissions would have to be cut back by 45 percent.

The only way to achieve such a goal would be for industrialized nations to severely reduce their use of fossil fuels. This is especially difficult for

Cutting carbon dioxide emissions by more than 45 percent would require extreme conservation efforts and the rapid development of alternative, cost-effective fuels, both of which are unlikely.

The massive negative economic impact of quickly transitioning away from fossil fuels, which provide 85 percent of the world's energy, places the goal of cutting carbon dioxide production nearly in half well beyond the political will of most, if not all, nations.

Adding to the difficulty of devising a binding carbon-reduction pact is the significant skepticism, and even denial, that global warming is a major threat. Doubts about the science of climate change have grown with the release of e-mails from the University of East Anglia's Climate Research Unit, indicating a lack of scientific objectivity and transparency, if not outright misuse of climate data.

Even if there were an agreement on how much and how fast to reduce carbon dioxide emissions, it would be nearly impossible to distribute the economic burden, particularly among rapidly industrializing countries like China and India, whose economies depend on even greater use of fossil fuels.

The failure of a binding agreement at Copenhagen does not mean we should do nothing, even if there were no threats of global warming.

Eventually, the world will run out of fossil fuels, and they will become far more costly well before they are consumed. Conservation can begin to make a significant dent in the growth of carbon dioxide emissions. Also, natural gas, which is being discovered in huge quantities, could replace coal and oil, both of which emit far more carbon dioxide. Solar and wind power can help cut emissions, but are far from able to make a major difference anytime soon.

A renewed commitment to building nuclear power plants, as France and Japan have done, also could reduce greenhouse gases.

Longer term, replacing motor vehicle fuels with ethanol from biomass or hydrogen produced by non-fossil fuels, along with accelerated research on developing fusion energy could eventually replace fossil fuels. But it will take considerable time and investment to wean us from fossil fuels.

Perhaps it would be wise to also consider efforts to counter the impact of carbon dioxide emissions or devise ways to deal with the effects of climate change as well as moving ahead with ways to reduce the use of fossil fuels.

Most significantly, transitioning to non-carbon-based fuels must be economically viable. It is unrealistic to believe that any nation, regardless of climate threats, is going to destroy its economy to meet drastic greenhouse gas reduction goals mandated at a global climate conference like the one in Copenhagen.