Limits on upscaling for enhanced weathering

[tabeado]

Purpose of this PR

This PR adds two constraints for the upscaling of enhanced weathering:

(1) Short term limit for rock spreading:
Spreading of rock for EW is set to 0 until 2025, and the 2030 time step was left largely unconstrained. Now, q33_EW_ShortTermBound limits the maximum amount of rock spread per year in 2030 (aggregate across climate and transport grades).
cm_33_EW_shortTermLimit defines the share of the total rock-on-field capacity of each region that is assumed possible to be used already in 2030. In default, cm_33_EW_shortTermLimit is set to 0.005, i.e. in 2030 it is assumed that
rocks are spread on maximum 0.5% of fields.

(2) explicit maximum upscaling rate for rock spreading:
The current parametrization assumes the use of existing infrastructure. Thus, the CAPEX for mining, grinding, and
spreading are so low that the adjustment cost do not constrain upscaling. This leads to very high upscaling rates
of >50% per year in some regions. At the scales reached, the use of existing infrastructure is not realistic in many regions.
We want to update the parametrization of cost (see issue 329). However, there is no easily accessible data such that a cost-based adjustment cannot be made short term.
In the meantime, we thus implement q33_EW_upscaling_rate that limits the upscaling of total annual rock spreading (v33_EW_onfield) based on ah explicitly set maximum upscaling rate.
The maximum annual rate can be changed through cm_33_EW_upScalingRateLimit. The default is 20%

Through these two changes, enhanced weathering in PB650 runs scales up later and slower, but to approximately the same level.

Type of change

• Bug fix
• New feature
• Minor change (default scenarios show only small differences)
• This change requires a documentation update

Checklist:

• My code follows the coding etiquette
• I performed a self-review of my own code
• I explained my changes within the PR, particularly in hard-to-understand areas
• I checked that the in-code documentation is up-to-date
• I adjusted the reporting in remind2 where it was needed
• All automated model tests pass (FAIL 0 in the output of make test)
• The changelog CHANGELOG.md has been updated correctly

Further information (optional):

• Test runs are here: /p/tmp/tabeado/EW_upscalingLimit/remind
• Comparison of results (what changes by this PR?): /p/tmp/tabeado/EW_upscalingLimit/remind/compScen-PB650main-2024-10-15_11.06.42-CDR.pdf

[laurinks]

Thanks a lot, @tabeado ! Very clear and well commented.
Adding a figure from your compScen here for future reference.