The Supreme Court, by agreeing to hear a case on whether the Environmental Protection Agency (EPA) must take steps to reduce carbon dioxide emissions, will finally judge on the alleged threat of global warming. The stakes are huge. Should the Court find in favor of the plaintiffs, it would put the EPA in control of the U.S. economy for the foreseeable future.

The modern global economy is powered by hydrocarbons — oil, natural gas and coal. Burning these fuels releases the energy we need to light our homes, heat and cool our offices, and get us from place to place. But the process also releases a byproduct called carbon dioxide (CO2). We have known for well over a century that, all other things being equal, more carbon dioxide in the atmosphere will warm the atmosphere as it absorbs energy up to a certain point. In recent years, with the atmosphere warming since the 1970s, scientists have connected the warming trend to the amount of carbon dioxide in the atmosphere. This is the phenomenon of global warming.

The case arose when a group of activist state attorneys general (AGs) petitioned the Environmental Protection Agency to make rules to control emissions of carbon dioxide. When the agency determined that it had no power to do so, the AGs and several environmental pressure groups sued, claiming, “The Clean Air Act requires the EPA to take certain actions when it determines that a pollutant may ’cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare.'”

Their petition was turned down on a 2-1 verdict by the D.C. Circuit Court in July 2005. However, the verdict was a curious one, with the majority issuing two separate opinions that dwelt mostly on the merits of global warming science while ignoring the central question of the case — whether or not the EPA has the power to regulate carbon dioxide as a pollutant. (By contrast, the dissenting judge wrote a strong opinion that signified a serious disagreement over the scientific case and also addressed the central issue.)

The Supreme Court’s agreeing to hear the case underscores its importance to the American economy. Regulation would directly affect 70 percent of the electricity sector and 98 percent of the transportation sector — with repercussions throughout the entire economy as those sectors are forced to raise costs to comply with new regulations. Had the Court not agreed to hear the case, the plaintiffs would surely seek out other judicial avenues to force the EPA to regulate. By agreeing to hear the case, the Supreme Court has at least signaled that there will be an end to the uncertainty soon. Businesses around the U.S. will be grateful for that.

It is hard to overstate the effect on the U.S. economy if the Court were to find in the petitioners’ favor. The EPA would be forced to set acceptable carbon dioxide levels nationwide along the lines of the National Ambient Air Quality Standards program, which currently sets such standards at the state level. By enforcing compliance nationwide, the EPA would have to set controls on all those activities that produce carbon dioxide, most notably electricity generation and transportation.

In effect, the Supreme Court would be enacting the Kyoto Protocol, which limits greenhouse gas emissions, and has never been ratified by the Senate. Yet the EPA could well find itself compelled to impose stricter limits than Kyoto. Even the Protocol’s supporters admit it will do little to reduce global warming (averting at most 0.7 degrees Celsius of warming by 2050). Yet the cost of Kyoto alone to the economy could be around $150 billion annually. Stricter emissions controls designed to avert more warming would cost far more.

There is another problem. Carbon dioxide is “well mixed” in the atmosphere, meaning that other countries’ emissions affect the atmosphere over the United States. If other countries, such as fast-growing China and India, continue to emit large amounts of CO2, the entire U.S. could be in violation of the new standards even if emissions were reduced to zero.

Ironically, Congress has repeatedly considered and rejected controls on greenhouse gas emissions. For the Supreme Court to rule that Congress intended to control such emissions when it passed the Clean Air Act would require judicial activism of the highest order. For the sake of the economy and out of respect for the Legislative Branch, the Court should reject this petition.