The American Power Act just introduced in the Senate by John Kerry (D-MA) and Joe Lieberman (I-CT) would require reduction of U.S. carbon dioxide emissions to 17% below 2005 emission levels by 2020, 42% below by 2030, and 83% below by 2050. Achieving that will cost trillions of dollars and millions of jobs.

What will it buy in the way of global average temperature reduction?

Meteorologist Chip Knappenberger ran the calculations and concluded:

The global temperature “savings” of the Kerry-Lieberman bill is astoundingly small—0.043°C (0.077°F) by 2050 and 0.111°C (0.200°F) by 2100. In other words, by century’s end, reducing U.S. greenhouse gas emissions by 83% will only result in global temperatures being one-fifth of one degree Fahrenheit less than they would otherwise be. That is a scientifically meaningless reduction.

The “scoring” of Kerry-Lieberman isn’t done yet, so we can’t be very sure, but it’s reasonable to think its costs will be quite similar to those of the House version of cap-and-trade passed last July, since the CO2 reduction targets are quite similar. That bill would have cost about $9.5 trillion between now and 2035 (with costs continuing afterward but not estimated). The same cost for this bill would mean we pay $4.75 trillion for every (statistically insignificant and ecologically inconsequential) 0.1 degree F of global average temperature by 2100.

Knappenberger’s calculation, however, assumes “climate sensitivity” (temperature increase from doubled effective atmospheric CO2 concentration, after feedbacks) of 3 degrees C (5.4 F). But that’s probably about six times the real rate, as shown by studies by MIT climatologist Richard S. Lindzen, University of Alabama climatologist Roy W. Spencer, Brookhaven National Laboratory atmospheric scientist Stephen Schwartz, and others. If they’re right, then actual temperature reduction by 2050 would be about 0.033 degree F, and the cost per tenth of a degree F would be about $28.5 trillion.

Is either price a good deal?