Conspiracy theorists point to an assortment of groups they think secretly run the country -- the gun lobby, Big Oil, the New World Order and even Yale's Skull and Bones society have all been fingered as the shadowy Illuminati who rule Washington. Yet the nation's real power brokers are in plain sight, amid amber waves of grain: the farmers. The farm lobby demonstrates its awesome might every few years with the passage of a new farm bill, which invariably shovels billions in corporate welfare to agribusiness while damaging U.S. trade relationships and in many cases raising consumer prices for agricultural goods. But its power goes beyond the farm bill; it's hard to pass any legislation even tangentially related to farming without the support of a bipartisan bloc of lawmakers from Midwestern states. Which is why, when congressional Democrats bring their sweeping 1,200-page bill to fight climate change to the House floor Friday, the farm lobby's loamy thumbprints will be all over it. The American Clean Energy and Security Act of 2009 from Reps. Henry A. Waxman, D-Calif., and Edward J. Markey, D-Mass., is an ambitious effort to cut U.S. greenhouse gas emissions 17 percent below 2005 levels by 2020. It would do this by capping emissions and allowing polluters to trade carbon credits; regulating cleaner fuels; investing in clean energy development; and boosting energy efficiency and renewable power. What does that have to do with farming? Not a lot. Although agriculture plays a key role in global warming -- clearing forest land for farms eliminates trees that absorb carbon, and livestock generate hefty emissions of climate-altering methane -- the bill largely ignores such issues. That didn't stop Rep. Collin C. Peterson, D-Minn., chairman of the House Agriculture Committee, from holding up the bill to wrest seed money for his constituents under the theory that heading off global catastrophe is only worthwhile if agribusiness can profit from it. Peterson got what he wanted. Under the bill, polluters can buy 'offsets,' meaning they can invest in carbon-reduction programs on farms or forests rather than cutting their own emissions. Originally, the Environmental Protection Agency was to be in charge of regulating these offsets, because it's the agency with the scientific expertise to do the job. Instead, Peterson ensured that offsets will be governed by the industry-focused Department of Agriculture, with the EPA playing a secondary role; this will help bring rich payouts to farmers while probably reducing the offsets' effectiveness. Also gutted was a provision requiring the EPA to consider the indirect climate impacts of biofuels. This would have imposed penalties on fuels, such as ethanol produced from corn, that encourage landowners to clear forests in order to grow the feedstock. That posed a threat to corn growers and ethanol refiners, whose inefficient and food-price-distorting fuel would most likely have been phased out. Now, the government will merely be required to study the links between such land-use change and carbon emissions. Farmers aren't the only ones who have weakened the Waxman-Markey bill. To win votes from coal-producing and Southern states, its authors agreed to water down the renewable energy standard. The nation will still be required to get 20 percent of its electricity from renewable sources by 2020, but 'renewable' has been redefined to include electricity derived by burning trash or landfill gas, which are highly polluting fuels. What's more, states can reduce their renewable power requirement by improving energy efficiency; as a result, the bill probably won't spur any more renewable power development than would have occurred without it. If the bill is far from perfect, that doesn't mean it isn't good. It's the first significant attempt by the United States to join other responsible nations that are trying to wean themselves off fossil fuels and build a better future for their children. Its provisions are weak and will be almost unnoticeable at first, but they will strengthen over time, and the framework it creates can be improved on later if it's not producing the intended cuts. Opponents complain that the bill would be too costly, raising the prices of energy, fuel and consumer goods. That's based on the mindless notion that doing nothing to fight climate change would have zero economic cost. Yet if the globe warms as much as climatologists predict, the cost of adapting would dwarf the cost of prevention. A report released last week by the U.S. Global Change Research Program found that, without efforts to stem the problem, average temperatures in the U.S. could rise by 7 to 11 degrees Fahrenheit by 2100. The result: large-scale flooding and destruction along the Gulf and Atlantic coasts, ruined crops in the Midwest, rampant fires in California, worsening incidence of insect-borne and plant diseases, skyrocketing heat deaths and a host of other woes. The bill's costs are also being grossly exaggerated. House Minority Leader John Boehner, R-Ohio, claims it would raise annual energy costs by $3,128 per household by 2015, an imaginary figure that he apparently derived from an estimate drawn up by MIT professor John M. Reilly -- who sent Boehner a letter saying the congressman was inflating the cost tenfold. The Congressional Budget Office released its estimate last week, saying the legislation would cost the average household $175 a year by 2020. Even that is probably an exaggeration, because it doesn't take into account improvements in energy efficiency. Though electricity would undoubtedly be more expensive if the bill passes, consumers and businesses would use less of it, meaning they could actually end up saving money. That's what happened after California started imposing energy-efficiency programs in the 1970s. The House should pass the Waxman-Markey bill, and the Senate should speedily follow suit. Even congressional Republicans can't generate as much hot air as the billions of metric tons of carbon dioxide it would eliminate. 