When Doug Gronau looks out the window of his Iowa farmhouse, he sees a profitable investment in the effort to stop global warming.
Most people see cornfields.
His cropland, which he is prohibited from tilling, is a greenhouse gas credit, packaged and sold on the Chicago Climate Exchange. An anonymous trader snapped up the field's ability to absorb carbon dioxide to offset - on paper - a tiny portion of the carbon dioxide emitted by some distant factory.
Gronau, 57, expects a check for $2,800.
"That may not sound like a lot," he said, "but farming is hard, and it adds to your margin."
The Chicago Climate Exchange is the first and only legally binding carbon emissions market in North America. In the absence of federal controls on greenhouse gas emissions, it applies an axiom of economic theory to the problem of global warming: People in search of profit can be expected to do just about anything for a buck - even save the planet.
That concept of the market forms the cornerstone of regulatory efforts to fight global warming.
Interest in carbon trading as an arcane but powerful tool to fight global warming has intensified after the release last week of a United Nations report that found rising temperatures will continue to climb even if greenhouse gas emissions can be held to current levels.
The theory of the market is straightforward: For the right price, a farmer like Gronau will agree to cultivate his fields without plowing, so the soil retains carbon dioxide that would otherwise seep into the air. That "carbon credit" can then be purchased by exchange members and applied against their own emissions. Should the price of carbon credits climb high enough, the theory goes, company executives one day will find it cheaper to reduce their own industrial emissions.
It's a new form of environmental bookkeeping that theoretically reduces emissions of carbon dioxide and the other trace gases responsible for gradually rising global temperatures.
Since the exchange opened in 2003, almost two hundred companies - including the Ford Motor Co., Du Pont, IBM Corp., Amtrak and American Electric Power Co. - have volunteered to buy and sell the right to emit tons of carbon dioxide and five other key greenhouse gases.
Critics, however, question whether new carbon emissions markets have done anything more than generate profits for market traders, while delaying genuine industrial changes that could forestall global warming.
In Europe, where mandatory greenhouse gas controls were recently imposed, the carbon emissions trading system has been marred by foot-dragging, chicanery and profiteering - even as its sales reached $22 billion.
All that buying and selling did almost nothing to reduce the risk of global warming, records show. Indeed, global levels of carbon dioxide in 2005 were the highest ever registered.
"Have they achieved any real reductions in greenhouse gases?" asked Veronique Bugnion, U.S. research director at Point Carbon, a European firm that analyzes carbon trading markets. "There is not much evidence of a reduction."
Carbon dioxide, the invisible, odorless gas that infuses every living breath, seems an unlikely investment. It seeps out anywhere there is a working smokestack or running motor.
As a signatory to the Kyoto Protocol, the European Union has taken the lead in imposing caps on levels of carbon dioxide and other greenhouse gases. Many climate experts expect the United States, which accounts for about a quarter of all greenhouse gas emissions, will have to follow suit.
In the cost-accounting of global warming, the undisturbed soil between Gronau's cornrows retains enough carbon to offset a few of the 2 billion tons spewing from U.S. smokestacks and exhaust pipes every year.
All told, Gronau set aside 1,600 acres of the 2,100 acres he usually farms near Denison as a no-till carbon sink through the climate exchange. That works out to half a ton of carbon per acre kept out of the atmosphere every year. He could have upped his credit to three-quarters of a ton of CO2 per acre by planting grass on his fallow fields.
"When I was taught economics, I was taught that air and water were free goods," said Richard Sandor, the founder of the Chicago Climate Exchange.
But he added: "It was intuitively obvious to me that on a planet of 6 billion or 7 billion people, that was no longer the case."
The companies that have volunteered for his exchange want to learn how to exploit the system in case mandatory controls are enacted by the U.S. government.
Once members promise to reduce emissions, however, the commitment is a legally binding contract. "The binding nature of the constraints is what makes the [Chicago] market work," said carbon finance analyst Karan Capoor at the World Bank. "It provides the integrity. It is not, 'Just do what you want.'"
Even as a voluntary exercise, the exchange has traded 13.6 million tons of carbon dioxide emissions with 200 companies, cities and foundations at prices ranging from $4 to $8 a ton.
As chairman and chief executive of the climate exchange, Sandor could easily become the first magnate of global warming.
Through a European subsidiary, his exchange already handles a lion's share of the annual carbon emissions trade with the 25 countries in the European Emissions Trading System.
Robert Lee Hotz writes for the Los Angeles Times.