WASHINGTON -- With the cap-and-trade bill passing the House of Representatives last week by seven votes, the eight Republicans who supported it were bound to feel some rapid, political warming. Conservative Internet and radio accused them of single-handedly passing President Obama's "cap-and-tax" legislation, which is a myth; Speaker Nancy Pelosi likely would have forced the requisite number of Democratic votes in the absence of Republican backing. But these eight Republicans were still termed "traitorous."

It is typical that we praise independent judgment and political nerve in our elected officials -- until they actually show those qualities.

Admittedly, this was not the best time to display conspicuous Republican environmental conscience. Obama's ideological overreach on issues from the fiscal stimulus to health care nationalization has put conservatives in a scrappy mood. The recession has brought the public's economic anxiety into sharp focus, while moving environmental concerns -- droughts in the Sahel or floods in Bangladesh -- into the hazy distance. And the House cap-and-trade bill itself was a riot of loopholes, concessions and offsets -- legislative sausage-making with an excess of offal.

But none of these political considerations change an underlying reality. A serious concern about global climate disruption remains the broad (not unanimous but predominant) view of the scientific community, including the National Academy of Sciences. Global warming since the 19th century is undeniable -- a trend not disproved by year-to-year variations. These changes are closely correlated with increases in the atmospheric concentration of carbon dioxide since the Industrial Revolution. Climate disruption has become so rapid in some places that it is overwhelming the natural process of adjustment, reducing crop yields and leading to the extinction of species. Meanwhile, global carbon emissions are increasing faster than expected. Some scientists warn of possible "tipping points" -- the rapid disintegration of the ice sheets, the sudden release of methane from warming northern soils -- that could turn a challenge into a catastrophe of lethal heat waves and rising sea levels.

Is this scientific viewpoint certain or guaranteed? Not when the scientific models concern a system as complex as the Earth's climate. Neither is it guaranteed that an Iranian nuclear weapon would be used against that country's enemies. But the realistic possibility of disaster, in both cases, would recommend a serious response.

The range of serious responses is limited. The federal government might spend directly on new technologies that produce energy without emitting carbon. But government's record in picking technological winners and losers is poor.

Others propose a carbon tax -- a cost per ton emitted, with no special exemptions. This system would be simple to implement and difficult to game. But it would also disproportionately punish some energy-intensive American industries -- cement, glass, steel and paper -- that face intense international competition. Continued...