The fact that the Nobel peace prize committee gave its annual award to the U.N. Intergovernmental Panel on Climate Change (IPCC) and Al GoreAlbert (Al) Arnold GoreDems face hard choice for State of the Union response Washington governor proposes new carbon tax The Renewable Fuel Standard is broken beyond repair MORE underscores the need for the U.S. government to move quickly to address global warming.

The IPCC's sober appraisal of the threat posed by global warming makes it clear just how serious this issue is. It found the effects of global warming are now evident in higher average global air and ocean temperatures, retreating glaciers, and rising sea levels. The panel also tied global warming to heavier precipitation over most land areas and increasing hurricane intensity in the North Atlantic.

In addition, the panel looked ahead to what we can expect if the world continues on its current course by failing to dramatically reduce heat-trapping emissions. It found that a 3-degree to 7-degree Fahrenheit increase in the average global temperature could result in the loss of 30 percent of the world's species and water shortages in drought-stricken areas that would affect hundreds of millions of people. The IPCC expects heat waves, droughts, wildfires, floods and severe rain to cause serious economic damage and substantial social and cultural disruption.

IPCC reports showed that higher temperatures bring increasing levels of risk. To prevent some of the most damaging and irreversible climate change effects, industrialized and developing countries must avoid a 2-degree Fahrenheit increase beyond today's temperatures. The panel found that limiting the average global temperature increase to 2 degrees would require cutting worldwide emissions 50 to 85 percent below 2000 levels by 2050. A Union of Concerned Scientists (UCS) study, which assumed both developing and industrialized countries would cut their emissions, found that the United States, to do its share, should reduce its emissions by at least 80 percent below 2000 levels by mid-century.

Congress could take the first step in combating climate change by enacting proposed energy legislation, various aspects of which have been passed by the House and Senate. The final measure should include a provision passed by the Senate that would substantially increase vehicle fuel economy by setting a 35-mpg fleet-wide average by 2020. According to a UCS study, this would cut 206 million metric tons of global warming pollution in 2020, the equivalent of taking 30 million of today's average cars and trucks off the road. Overall, the bill would cut U.S. dependence on oil by 1.2 million barrels a day by 2020, save drivers $25 billion above and beyond the cost of the technology (at the 2006 average gas price of $2.55, in 2005 dollars), and create more than 170,000 domestic jobs, including 22,300 in the auto industry.

The energy legislation also should include the national renewable electricity standard featured in the House version of the bill. The measure would require utilities to generate at least 15 percent of their power from a combination of energy efficiency and renewable sources such as wind, solar and biomass by 2020. Such a standard would cut pollution, save consumers money on their energy bills and deliver other economic benefits. (UCS conducted an analysis of an earlier renewable electricity standard proposal and will complete one based on the standard in the House version of the energy bill soon.)

With these provisions, the energy bill would serve as a down payment in the effort to prevent the worst consequences of global warming. But Congress needs to do more. Lawmakers also should establish a cap-and-trade program.

Under a cap-and-trade program, the federal government would establish an economy-wide cap on emissions, measured in metric tons of carbon dioxide equivalent, and tighten it over time. The program would require electric utilities, refineries and other sources of global warming pollution to have an allowance for each ton of their emissions.

Polluters would acquire allowances during the initial distribution or by trading for them in an "allowance market." This market would enable polluters that are able to reduce their emissions relatively cheaply to sell allowances to those that are unable to do so, thereby establishing a market price for carbon. The program would create an incentive for polluting facilities to implement the most cost-effective emissions reduction options and, by putting a price on global warming pollution, encourage investments in new low-carbon technologies.

The IPCC recognizes the value of tradable permits. It noted that the volume of allowed emissions would determine the program's environmental effectiveness, while the distribution of allowances would determine its competitiveness. For a cap-and-trade system to be effective, all, or a substantial majority of the allowances should be auctioned. Giving away too many allowances would distort the market and could result in windfall profits for polluters.

In addition to a long-term pollution cutting target of at least 80 percent, Congress also should set strong short-term goals to put the country on the right track. For instance, if we waited until 2020 to start emission reductions, we would have to cut twice as fast as if we start in 2010 to meet the same target.