WASHINGTON — An unprecedentedly radical government grab for control of the American economy will be debated this week when the Senate considers saving the planet by means of a cap-and-trade system to ration carbon emissions. The plan is co-authored (with John Warner) by Joe Lieberman, an ardent supporter of John McCain, who supports Lieberman’s legislation and recently spoke about “the central facts of rising temperatures, rising waters and all the endless troubles that global warming will bring.”

Speaking of endless troubles, “cap-and-trade” comes cloaked in reassuring rhetoric about the government merely creating a market, but government actually would create a scarcity so government could sell what it has made scarce. The Wall Street Journal underestimates cap-and-trade’s perniciousness when it says the scheme would create a new right (“allowances”) to produce carbon dioxide and would put a price on the right. Actually, because freedom is the silence of the law, that right has always existed in the absence of prohibitions. With cap-and-trade, government would create a right for itself — an extraordinarily lucrative right to ration Americans’ exercise of their traditional rights.

Businesses with unused emission allowances could sell their surpluses to businesses that exceed their allowances. The more expensive and constraining the allowances, the more money government would gain.

If carbon emissions are the planetary menace that the political class suddenly says they are, why not a straightforward tax on fossil fuels based on each fuel’s carbon content? This would have none of the enormous administrative costs of the baroque cap-and-trade regime. And a carbon tax would avoid the uncertainties inseparable from cap-and-trade’s government allocation of emission permits sector by sector, industry by industry. So a carbon tax would be a clear and candid incentive to adopt energy-saving and carbon-minimizing technologies. That is the problem.

A carbon tax would be too clear and candid for political comfort. It would clearly be what cap-and-trade deviously is, a tax, but one with a known cost. Therefore, taxpayers would demand a commensurate reduction of other taxes. Cap-and-trade — government auctioning permits for businesses to continue to do business — is a huge tax hidden in a bureaucratic labyrinth of opaque permit transactions.

The proper price of permits for carbon emissions should reflect the future warming costs of current emissions. That is bound to be a guess based on computer models built on guesses. Lieberman guesses that the market value of all permits would be “about $7 trillion by 2050.” Will that staggering sum pay for a $7 trillion reduction of other taxes? Not exactly.

It would go to a Climate Change Credit Corp., which Lieberman calls “a private-public entity” that, operating outside the budget process, would invest “in many things.” This would be industrial policy, aka socialism, on a grand scale — government picking winners and losers, all of whom will have powerful incentives to invest in lobbyists to influence government’s thousands of new wealth-allocating decisions.

Lieberman’s legislation also would create a Carbon Market Efficiency Board empowered to “provide allowances and alter demands” in response to “an impact that is much more onerous” than expected. And Lieberman says that if a foreign company selling a product in America “enjoys a price advantage over an American competitor” because the American firm has had to comply with the cap-and-trade regime, “we will impose a fee” on the foreign company “to equalize the price.” Protectionism-masquerading-as-environmentalism will thicken the unsavory entanglement of commercial life and political life.

McCain, who supports Lieberman’s unprecedented expansion of government’s regulatory reach, is the scourge of all lobbyists (other than those employed by his campaign). But cap-and-trade would be a bonanza for K Street, the lobbyists’ habitat, because it would vastly deepen and broaden the upside benefits and downside risks that the government’s choices mean for businesses.

McCain, the political hygienist, is eager to reduce the amount of money in politics. But cap-and-trade, by hugely increasing the amount of politics in the allocation of money, would guarantee a surge of money into politics.

Regarding McCain’s “central facts,” the U.N.’s World Meteorological Organization, which helped establish the Intergovernmental Panel on Climate Change — co-winner, with Al Gore, of the Nobel Prize — says global temperatures have not risen in a decade. So Congress might be arriving late at the save-the-planet party. Better late than never? No. When government, ever eager to expand its grip on the governed and their wealth, manufactures hysteria as an excuse for doing so, then: better never.

George Will is a Washington Post columnist. His e-mail address is georgewill@washpost.com.