Yvo de Boer, the head of the United Nations Climate Change Secretariat, has formally announced he’ll be leaving the post this July. The decision is widely thought to come from de Boer’s deep disappointment with the results of the Copenhagen climate talks, and the nonbinding Accord forged there. An energetic and often “sharp-tongued” man, many fear that whomever is selected as his replacement will lack his audacity and enthusiasm. Here’s his statement on why he’s leaving: