Guest post by David Middleton
Featured image borrowed from here.
Nearly every catastrophic global warming doomsday scenario, particularity those involving icecap failures and Noah-size sea level rises are based on the “RCP 8.5” scenario.
Representative Concentration (or Carbon)Pathway 8.5 assumes a “rising radiative forcing pathway leading to 8.5 W/m² in 2100.” It is generally assumed, with little dissent, that each doubling of the atmospheric CO2 concentration will add 3.7 W/m² to the net infrared radiative flux.
A doubling of the supposedly stable pre-industrial CO2 level (280 ppmv to 560 ppmv) should yield 3.7 W/m² of additional forcing to the net infrared radiative flux. In order to get 8.5 W/m², the atmospheric CO2 concentration would have to rise to 1,370 ppm…
Note: Yes. The above is from SkepSci. I checked the math. It’s close enough.
Does any sane person really believe that the atmospheric CO2 concentration could rise from the current 400 ppm to 1,370 ppm over the next 85 years? (*)
Using BP’s Statistical Review of World Energy 2015, I built a “model.”
Figure 1. Cross-plots of (top) cumulative fossil fuel consumption (MTOE) vs. atmospheric CO2 (ppm) as measured by the Mauna Loa Observatory (MLO) and (bottom) annual fossil fuel consumption (MTOE) vs time.
This “model” derives two equations:
- CO2 (ppm) = 0.0002*(MTOE) + 320.87 (R² = 0.9986)
- MTOE = 142.16*(Year) – 275,639 (R² = 0.9698)
Note: MTOE = Millions of Tonnes of Oil Equivalent.
Note to nitpickers: Yes, I know the top and bottom charts and equations 1 and 2 should have been listed in the opposite order.
These two equations enable me to project fossil fuel use and atmospheric CO2 into the distant future (beyond my retirement date… which with oil at $30/bbl is either very far off in the future or sooner than I would prefer). Using the assumption that the mix of crude oil, natural gas and coal would remain at a constant ratio (that of the period 2005-2014), I come up with an atmospheric CO2 concentration of 683 ppm in 2100, about half of RCP 8.5 (Venus) and comparable to RCP 4.5 (non-catastrophic).
Figure 2. GIGO is as GIGO does.
The Peak Oilers in the WUWT community will quickly notice that crude oil production in 2100 would have to be about four times that of 2015 for this model to work… In other words, Peak Oil would be delayed again. My “back of the envelope” calculation says that we would have to find and produce about 4 trillion barrels of crude oil between now and 2100 to comply with this model… Since that is about twice the sum of global proved crude oil reserves and the current estimate of technically recoverable resource potential, I better get back to work finding more oil… :)
I didn’t do the calculations for natural gas and coal… because I had to get back to work. My best guess is that there is more than enough coal and natural gas in the ground to make it to 2100 without us having to freeze in the dark.
Disclaimer: These models are based on a whole lot of assumptions… But probably not nearly as many assumptions as RCP 8.5.
(*) Addendum
It has been brought to my attention that RCP 8.5 references “CO2-equivalent,” not pure CO2 and that the CO2-only concentration in 2100 is posited to *only* be 930 ppm, not 1130. 930 is still a lot (36%) higher than 683… And 683 was based on the assumption that the ratio of crude oil, natural gas and coal remains constant. Since natural gas will very likely continue to displace coal and eventually crude oil, 683 is probably unrealistically high as well.
So I will revise and extend my question:
Does any sane person really believe that the atmospheric CO2 concentration could rise from the current 400 ppm to 930 ppm over the next 85 years? Does any sane person really believe that the atmospheric CO2-equivalent concentration could rise from the current 478 ppm to 1,370 ppm over the next 85 years? Why would the non-CO2 GHG’s rise at a 25% faster rate than the already improbable RCP 8.5 rate for CO2?