By DON McINTOSH, Associate Editor

Global warming isn’t coming. It’s already here.

From floods to forest fires, droughts to melting permafrost, rising global average temperature is having an impact. The scientific consensus is that human activity is contributing by increasing the amounts of so-called “greenhouse gases” in the atmosphere. Greenhouse gases exist in small concentrations in the atmosphere but have big impacts on temperature. Carbon dioxide (CO2) is the best-known greenhouse gas, but there are others, including methane and nitrous oxide.

The Intergovernmental Panel on Climate Change, a scientific body, was formed by the United Nations in 1988 to study the risk of human-caused climate change. Its latest report, in 2007, notes the observed increase in global temperatures in the last half century, parallelling the increase in greenhouse gas concentrations in the atmosphere. Temperatures have risen about 1 degree Fahrenheit since the mid-20th century, while CO2 concentrations have risen to 380 parts per million (ppm) from 315 ppm in 1960.

There’s a special urgency to reduce the amount of greenhouse gases being added to the atmosphere because of concern about a possible tipping point, where increased temperatures themselves lead to additional releases of greenhouse gases. For instance, hotter, drier forests would be more likely to burn, releasing even more CO2 and reducing the forests’ ability to convert atmospheric CO2 into oxygen. Higher temperatures could also speed up the already melting Alaskan permafrost and the vast Siberian peat bogs, which could result in further release of CO2 and methane, a more potent greenhouse gas.

There’s a lot of scientific uncertainty about when a tipping point would be reached, but the international community is hoping that by limiting CO2 concentration to below 500 ppm (and temperature increase to 3.6 degrees Fahrenheit over current levels), it can be averted.

The reason you’re reading about this in a labor union newspaper is that there are a lot of measures societies can take to achieve the targeted reductions in greenhouse gas emissions, and which ones, and how, will have major impacts on workers throughout the economy. Some industries will be endangered, some will be transformed, and some will see tremendous growth.

The United States is the world’s largest emitter of greenhouse gases, adding an estimated 7.2 billion tons of CO2 equivalent to the atmosphere in 2005 — about 22 percent of the world’s total. Part of it is driving: The average American uses 500 gallons of gas a year to drive 12,000 miles, producing five tons of carbon dioxide. But electricity generation, industry, farming, and residential use of fossil fuels also contribute. U.S. greenhouse gas emissions are on track to increase one-third by 2030, but that trend will have to turn around if the world is to limit CO2 to 500 ppm.

Government can limit greenhouse gas emissions by regulation, or discourage emissions indirectly by taxing them (the so-called “carbon tax” proposal). But a third approach is the one that is gaining the most political support. It’s known as “cap and trade.”

Under a cap-and-trade system, the government sets a limit or “cap” on the volume of greenhouse gases that certain sectors of the economy would be allowed to emit, and issues a permit for each unit of those emissions. Each year, the number of permits — and thus allowable greenhouse gas emissions — would be ratcheted down. The government would give or auction off the permits to emitters, and emitters could trade the permits to each other in a regulated marketplace. Companies that can make reductions cheaply would sell their unused permits to companies that had a tougher time cutting emissions. Thus, the market in permits would allow the necessary reductions to be made as cheaply as possible.

Both presidential hopefuls Barack Obama and John McCain support the cap-and-trade idea; Obama would auction the permits, while McCain proposes giving them away. Giving them away limits industries’ economic pain. Auctioning generates resources that can be used to speed the transition and cushion the hardships.

So far, the cap-and-trade proposal that came closest to passing as the Climate Security Act of 2008, a bill introduced by Senators Joseph Lieberman (I-Conn.), John Warner (R-Va.) and Barbara Boxer (D-Calif.). The Lieberman-Warner bill would start by giving three-quarters of the permits away and auctioning the remainder, but the percentage auctioned would go up each year. The Senate debated the bill in June, but failed to get enough votes to shut off debate and move to a vote. No one expected the bill to become law, because it didn’t have enough support to overcome a filibuster, much less override a threatened presidential veto. The debate was seen as an airing of the issues likely to come up when the proposal comes back next year.

Organized labor was involved in the behind-the-scenes debate over the bill, and was able to get the bill’s sponsors to incorporate a number of union proposals, including a major expansion of the Davis-Bacon prevailing wage requirement to non-federal alternative energy projects. The AFL-CIO’s Building and Construction Trades Department, and the Laborers and Operating Engineers unions support the bill.

Labor unions wanted assurance that increasing costs for U.S. manufacturers won’t drive production to countries that don’t have the climate controls. So the Lieberman-Warner bill included steps the United States could take if countries like China don’t also adopt restrictions on greenhouse gas emissions. Any country that had not capped emissions after the United States begins the program would need to buy allowances in order to sell energy-intensive goods in the U.S. market.

And answering concerns labor leaders raised about potential for speculative abuse in the market for permits, Lieberman-Warner would set up a working group to propose regulations to protect the market from fraud and manipulation.

Above all, union leaders approach cap-and-trade as a way to revitalize America’s manufacturing and support good-paying jobs in the shift to a low-carbon economy.

“Solving the climate change crisis is an opportunity to address the manufacturing crisis,” said AFL-CIO Energy Task Force co-chair Bob Baugh at a House Energy subcommittee in June.

In a statement released in March, the AFL-CIO Executive Council outlined some potentially bountiful sources of green-collar jobs: modernization of high-voltage transmission lines to increase energy efficiency; expansion of mass transit and passenger rail; energy efficiency retrofits of public, industrial and commercial buildings; weatherization of homes; and development of new automotive technologies, not to mention wind, solar and geothermal.

The Lieberman-Warner cap-and-trade program would cover almost nine-tenths of the sources of U.S. greenhouse gas emissions and would be projected to reduce total U.S. greenhouse-gas emissions to roughly 5.8 billion tons a year by 2020 and 2.7 billion tons by 2050.

“Our nation can lead a new technological revolution in the way energy is generated and used,” Baugh told the House subcommittee. “That can be of benefit to the world as a whole, and serve as a foundation for the revival of the middle class in the United States.”