Evaluation 1950 control and historical simulations

[tsemmler05]

The 1950 control and historical simulations are driven by constant 1950 aerosols and transient aerosol concentrations starting from 1950, respectively. The 1950 spinup simulation that has been run for 100 years before branching off 1950 control and historical simulations had constant 2005 aerosols - not ideal but had to be done due to the lack of the necessary subroutine to read in the changing aerosol concentrations. The change in aerosols from 2005 to 1950 conditions (especially over North America) exhibits a PDO pattern both in 1950 control and historical simulations. This is consistent with recent literature:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021EF002249

Aerosol scaling factor 1950 versus 2005:

2 m temperature difference 1950 control (first ten years) minus 1950 spin-up (years 99-107):

2 m temperature difference historical (1950-1959) minus 1950 spin-up (years 99-107):

Interesting side effect: Weddell Sea becomes colder.

[tsemmler05]

Performance index of the first 10 years of the 1950-control simulation:

Performance index of historical simulation, years 1950-1959:

For comparison, also the one of years 99 to 107 of spin-up simulation (slightly worse in Southern hemisphere sea ice):

[tsemmler05]

Another interesting paper looking at the regional imprint of aerosol changes in the US (higher aerosol concentrations over the East Coast leading to lower temperatures): https://iopscience.iop.org/article/10.1088/1748-9326/abbe45

[tsemmler05]

This paper shows the opposite signal for a sudden 10-fold increase of black carbon (BC) - note that we are decreasing aerosols over South East Asia from 2005 to 1950 while increasing them over the East Coast of US: https://journals.ametsoc.org/view/journals/clim/34/5/JCLI-D-20-0423.1.xml All these studies can't be directly compared to our simulations (model set-ups too different) but are a hint that the regional distributions of aerosols do matter (even for a case that the globally averaged aerosol concentration may be not too different between 1950 and 2005).