Exhibit 23.3

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the Carbon Natural Gas Company’s Registration Statement on Form S-8 (File No. 333-179184) of our report dated March 31, 2018 relating to the audit of Carbon Appalachian Company, LLC’s consolidated financial statements, which appears in this Annual Report on Form 10-K.

/s/ EKS&H LLLP

EKS&H LLLP

Denver, Colorado

March 31, 2018