Den stora tråden om global uppvärmning/växthuseffekten

Suppose each country implements something called the T3 tax, whose U.S. dollar rate is set equal to 20 times the three-year moving average of the RSS and UAH estimates of the mean tropical tropospheric temperature anomaly, assessed per tonne of carbon dioxide, updated annually. Based on current data, the tax would be US$4.70 per ton, which is about the median mainstream carbon-dioxide-damage estimate from a major survey published in 2005 by economist Richard Tol.

This tax rate is low, and would yield very little emissions abatement. Global-warming skeptics and opponents of greenhouse-abatement policy will like that. But would global-warming activists? They should -- because according to them, the tax will climb rapidly in the years ahead.

The IPCC predicts a warming rate in the tropical troposphere of about double that at the surface, implying about 0.2C to 1.2C per decade in the tropical troposphere under greenhouse-forcing scenarios. That implies the tax will climb by $4 to $24 per tonne per decade, a much more aggressive schedule of emission fee increases than most current proposals. At the upper end of warming forecasts, the tax could reach $200 per tonne of CO2 by 2100, forcing major carbon-emission reductions and a global shift to non-carbon energy sources.

Global-warming activists would like this. But so would skeptics, because they believe the models are exaggerating the warming forecasts. After all, the averaged UAH/ RSS tropical troposphere series went up only about 0.08C over the past decade, and has been going down since 2002. Some solar scientists even expect pronounced cooling to begin in a decade. If they are right, the T3 tax will fall below zero within two decades, turning into a subsidy for carbon emissions.

At this point the global-warming alarmists would leap up to slam the proposal. But not so fast, Mr. Gore: The tax would only become a carbon subsidy if all the climate models are wrong, if greenhouse gases are not warming the atmosphere, and if the sun actually controls the climate. Alarmists sneeringly denounce such claims as "denialism," so they can hardly reject the policy on the belief that they are true.

Under the T3 tax, the regulator gets to call everyone's bluff at once, without gambling in advance on who is right. If the tax goes up, it ought to have. If it doesn't go up, it shouldn't have. Either way we get a sensible outcome.