Hey @Ninja, that is possible. What you could do is, use the lookup plugin to get the environment variables and assign this output to a variable, So now you can use this variable at other places in your playbook. 
- hosts: all
  vars:
    local_shell:  "{{ lookup('env','SHELL') }}"
  tasks:
    - debug:
        msg: "{{ local_shell }}"
output
------
"msg": "/bin/sh"