We are frequently told that the current CO2 emission is in line with the RCP 8.5 scenario and that this is the future business-as-usual scenario. How do recently published emissions by PBL compare with the old SRES scenario’s?
It is clear that current emissions are inbetween the SRES A1B and SRES A1T emission scenarios. How will future temperature evolve when recent transient sensitivity by Lewis and Curry is applied?
diffusion fluid flow model (Peter Dietze, 2001) is applied that honours the observed CO2 airborne fraction. This follows Fick’s first law of diffusion Darcy’s law of hydraulic flow.
This leads to the following calculated CO2 concentrations. Note that, as the emissions for the A1T scenario near the end of the century are smaller than the sink, the co2 level is decreasing.
Following Lewis & Curry 2018 (LC2018), the CO2-forcing is multiplied by a factor 1.4 to allow for other man-made forcings. Applying a LC2018 transient sensitivity of 1.33 per doubling on this forcing data, the following temperature is calculated.
It is shown that for the A1B business-as-usual scenario the temperature rise relative to pre-industrial temperature in 2100 is just over two degrees, and for the A1T scenario the temperature is 1.5 degrees and decreasing.
So the current emission scenario is right on track to meet the Paris agreement!
* IPCC, Third Assessment Report, SRES CO2 emissions (Link broken, Archived link)
* New link to TAR appendix: IPCC, Third Assessment Report, Appendices (for SRES CO2 emissions see page 801)
* RCP scenario data, PIK Potsdam
* G. Marland, T.A. Boden, and R.J. Andres, Global CO2 emission data
* PBL, Trends in global CO2 emissions
* Peter Dietze, 2001, Carbon model calculations @John Daly
Fick’s First Law of Diffusion (Wikipedia)
* Darcy’s law of fluid flow (Wikipedia)
* Lewis and Curry, The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity 
* Ferdinand Engelbeen, About spurious correlations and causation of the CO2 increase 
Used conversion factors:
1 GtC = 3.67 GtCO2
1 ppm CO2 = 2.13 GtC
Annual diffusion equation:
Sink(y) = 2.13 * k * ([CO2](y-1)-[CO2]eq) (
Fick’s firstDarcy’s law)
Temperature sensitive equilibrium CO2-level:
8 16*T + 280 ppm
T is temperature relative to pre-industrial (=HadCrut4 annual+0.4)
8 16 ppm per degree
FCO2 = 5.35 * ln ([CO2]/280)
Total antropogenic forcing, using an emperical multiplier to allow for other synchronous antropogenic forcings:
Ftot = 1.4 * FCO2
Temperature transient sensitivity is 1.33 °C per CO2 doubling:
T = Ftot * 1.33/3.7
NOTE added 27 december
Thanks to Dirk Visser a small correction was needed, the temperature effect of equilibrium is 16 ppm per degree and not 8. This increases the transfer constant fron 0.01898 to 0.021. Fick’s first law must be Darcy’s law.
But wait.. there is more!
The International Energy Agency, Shell and BP frequently publish energy outlooks. Below is a comparison with the SRES and RCP8.5 scenarios. RCP 8.5 doesn’t even come close. High time to immediately abandon the useless “business-as-usual scenario” RCP8.5.
Lewis and Curry forcings: