Roger’s calcs suggest a 15% reduction of CO2 emissions by 2020 will result in 1.13 Gt less CO2 emitted. That 1.13 Gt equates to 0.14 ppm CO2 that has not been added to atmosphere in year 2020. If the climate has a 1.5 degree C sensitivity to a doubling of CO2 from a 380ppm base, the overall impact of a 15% reduction appears to be 0.00055 degree C.

Are my climate temperature impact calculations totally off the wall, or does everyone here just happen to know the impact is ludicrously low and basically unmeasurable? I gotta believe I made a major mistake in my arithmetic because I can’t imagine anyone would propose a 15% reduction resulting in such a tiny temperature “benefit” that I’m calculating.

(Note: if anyone can put together here a lucid explanation of the arithmetic regarding the global temperature impact of a 15% U.S. reduction of CO2 emissions by 2020, I’d be glad to post their explanation on my beginner’s site also, of course with full credit to author.) Thanks to any takers.

The AEO forecast quads are all for primary energy — this is the raw energy in the fuel itself. (1 kg of solid coal has a certain amount of “primary energy”.) Given a OECD average coal power plant efficiency of 37%, the 22.75 quads of coal burned in 2007 generated only 8.4 quads of electricity. (This is before transmission line losses, etc, but those are the same for all technologies, except efficiency.) Natural gas plants are a bit more efficient, at 45%. The transportation sector uses primary energy directly (liquid fuel into your car), so that part is “100% efficient” compared with electricity. (The inefficiency is counted in a different place.) Since not all petroleum is used in cars, let’s assume it’s 95% efficient when counting “usable energy”. AEO Renewables are calculated directly from the energy in the lines, not from “primary energy” of sunlight falling on a given square meter, so they are effectively 100% efficient for this comparison. Nuclear is counted the same way (I think). The upshot of this is that instead of working with 102 quads of primary energy, we ought to be thinking about 72.6 quads of “used” energy in 2007. The most recent AEO numbers (downloaded from http://www.eia.doe.gov/oiaf/forecasting.html and then adjusted in Excel)) show this “used” number growing to 75.2 quads in 2020.

I’m a big efficiency fan, but let’s assume that number is un-changeable. Can we shuffle the proportion around between sources to add up to 75.2, while still cutting greenhouse gas emissions by 14% before 2007? Of course. Start by cutting coal in half. If the average coal plant has a lifetime of 30 years, this should be happening anyway over the next 15 or so years, as long as we don’t build new plants. 4.5 quads of used coal electricity comes from 12.2 quads of primary coal energy. Expand natural gas a bit: 13.1 quads of used natural gas power comes from 29.1 quads of primary energy (AEO forecasts 24 quads of NG). Leave petroleum where the AEO says, at 39 quads of primary energy. The AEO forecasts renewables growing from 6.3 to 9.4 quads. If this is accelerated to 11.5 quads, and nuclear stays where it is, we have 75.2 quads of “usable” energy on the grids/roads, using only 100.7 quads of primary energy, and emitting 86.3% of the carbon emitted in 2007.

Electric efficiency enters the computation the same way renewables do (and in fact better because it avoids the few% transmission line losses). So, if you don’t think we can grow renewables at a big boost over the AEO rate, just think about how to save 2.1 quads of end-user energy (per year) without hurting quality of life. Given that this is just 3% or so of total use, it’s not hard to imagine. (Refrigerators, for example, can easily be 20% more efficient today — look at all the Energy Star models available –and that’s not built into the AEO model.)

What happens if we set the “used” energy in 2020 equal to the “used” energy in 2007? If we just need a “useable” energy of 72.6 quads, we can even leave renewables where the AEO predicts them to be in 2020, and just do a straight swap of coal for natural gas and efficiency. Accelerated renewable R&D beyond the AEO forecast can push the natural gas number down, too.

It’s fun to play with numbers, but this post creates a false problem by ignoring the fact that the AEO numbers quoted are in _primary energy_ terms. I haven’t addressed any policy question here of how one would do this, but any option which results in enough increased renewables, efficiency, and natural gas at the expense of coal (relative to the AEO baseline) ought to work.

From the EIA site linked in the post:

Hydro 2.5
Geot 0.35
Solar 0.08
Wind 0.32
Bio 3.6

Bio is 9 x (solar + wind), yet some states don’t even talk about bio in their renewable portfolio (or so I am told). What am I missing? Are we there already, so bio doesn’t need the attention/subsidies of solar and wind?

New Jersey was subsidizing solar cell installation for a few years. I estimated (their calculator)the cost of replacing 0.75 of my average kilowatt usage. The cost over $40K and even with NJ putting up $27K it didn’t pay out for 10years.
Mike McHenry, NJ

Regarding your previous response to a commenter:

“1 ppmv of CO2= 2.13 Gt of carbon”
http://cdiac.ornl.gov/pns/faq.html

*to convert to CO2 . . . 2.13 * 3.664 = 7.8 Gt CO2

*so for 2020, under the EIA assumptions (in GtCO2):

6.225 – 5.095 = 1.13 GtCO2

1.13/7.8 = 0.14 ppm in 2020

The bottom line here is a reduction of atmospheric CO2 of 14/100’s, correct?

Based on current climate model sensitivity, what would be the temperature reduction of this outcome by 2020? Is there a way to estimate the dollar cost of this project(s) to achieve this?

Reality maybe that 14% is not attainable, but if it is not what is a reasonable number? It is unfortunate that in public policy situations we too often have a ‘single number’ goal, and if we can’t reach it then we revert to the ‘why try’ mentality. So might the better exercise be to determine what values are easily, reasonably, and challenging to obtain and try to work from that perspective?

Roger, I am curious if you have a number you think might be reasonable? I know with an initial post it is sometimes best to leave such thoughts off the table, but now that there is some response I would be curious what your take is.

Certainly any solution is going to involve a mix of processes to achieve the goal, just like when a company sets profit objectives for the year and works towards that objective from all cost and revenue aspects of the business. I personally feel that consumption changes could play a larger role. Having lived outside the US for a significant number of years, I wonder if shifting away from a 24 hour (always open) mentality might not have a meaningful impact on consumption levels? I think there is a fair amount of unneeded consumption that keeps everything going full steam around the clock.