Gran Tierra Energy Inc. declared the results of a qualified independent reserve evaluation of the company's reserves by GLJ Petroleum Consultants Ltd. (GLJ) effective December 31, 2012.

Year-end 2012 Highlights, calculated in accordance with United States Securities and Exchange Commission ("SEC") rules (comparisons are to 2011 year-end amounts):

• Total Proved ("1P") reserves net after royalty ("NAR") increased 20% to approximately 40.6 million barrels of oil equivalent ("MMBOE") (approximately 95% light and medium oil and liquids; an increase compared to 91% at year-end 2011); • Total Proved plus Probable ("2P") reserves NAR increased 15% to approximately 56.2 MMBOE (approximately 95% light and medium oil and liquids; an increase compared to 85% at year-end 2011); • Total Proved plus Probable plus Possible ("3P") reserves NAR increased 1% to approximately 86.3 MMBOE (approximately 87% light and medium oil and liquids; an increase compared to 69% at year-end 2011); • Reservoir performance expectations were exceeded at the Costayaco field in Colombia. Costayaco 1P reserves increased to 19.7 million barrels of oil ("MMBO") NAR at year-end 2012 from 16.4 MMBO NAR at year-end 2011 despite total production of 3.8 MMBO NAR before inventory adjustments in 2012; • Appraisal drilling in the Moqueta field in Colombia resulted in 1P reserves increasing 45% to approximately 8.7 MMBO, 2P reserves increasing 54% to 14.9 MMBO and 3P reserves increasing 108% to 26.9 MMBO on a company interest basis, and 1P reserves increasing to approximately 6.8 MMBO, 2P reserves increasing to 11.2 MMBO and 3P reserves increasing to 19.4 MMBO on a NAR basis. The limits of the field have not yet been defined; • Gran Tierra Energy produced approximately 8.4 MMBO of working interest oil before royalties and inventory adjustments or 6.4 MMBO NAR before inventory adjustments and 1.7 billion cubic feet ("Bcf") of company interest gas before royalties or 1.5 Bcf NAR in 2012;

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