## 2.13.1. Summary of CLM5.0 updates relative to CLM4.5[¶](#summary-of-clm5-0-updates-relative-to-clm4-5 "Permalink to this headline")
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Compared with CLM4.5 ([Oleson et al. 2013](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#olesonetal2013)), CLM5.0 contains substantial improvements in its capabilities for land-ice science. This section summarizes these improvements, and the following sections provide more details.

*   All runs include multiple glacier elevation classes over Greenland and Antarctica and compute ice sheet surface mass balance in those regions.
    
*   A number of namelist parameters offer fine-grained control over glacier behavior in different regions of the world (section [2.13.3](#glacier-regions)). (The options used outside of Greenland and Antarctica reproduce the standard CLM4.5 glacier behavior.)
    
*   CLM can now keep its glacier areas and elevations in sync with CISM when running with an evolving ice sheet. (However, in typical configurations, the ice sheet geometry still remains fixed throughout the run.)
    
*   The downscaling to elevation classes now includes downwelling longwave radiation and partitioning of precipitation into rain vs. snow (section [2.13.4](#multiple-elevation-class-scheme)).
    
*   Other land units within the CISM domain undergo the same downscaling as the glacier land unit, and surface mass balance is computed for the natural vegetated land unit. This allows CLM to produce glacial inception when running with an evolving ice sheet model.
    
*   There have also been substantial improvements to CLM’s snow physics, as described in other chapters of this document.
    

