Yvo de Boer, the United Nations' (UN) top climate official, unexpectedly announced today he will resign in July - after December's failed summit in Copenhagen dealt a blow to his climate change ambitions, according to dpa. Boer, executive secretary of the United Nations Framework Convention on Climate Change (UNFCC) is to join consultancy group KPMG, as well as working with a number of universities, according to his office in Bonn. The news came two months after the disappointing UN Climate Change conference in Copenhagen, where there was no agreement on the binding targets Boer had campaigned for, and a row between China and the US took centre-stage. Boer's four-year tenure was due to end this September, when it was likely he would be offered a renewed term in office. No possible successors have yet been named. "It was a difficult decision to make, but I believe the time is ripe for me to take on a new challenge," Boer said in a statement. His early resignation came as a blow to the ongoing climate negotiations under the auspices of the UN, ahead of an upcoming climate change conference taking place in Mexico in November. "With Boer, the great steersman of the climate proceedings is abandoning ship," said Greenpeace's Head of Climate Change Policy, Martin Kaiser. The Green Party in the European Parliament also expressed regret at Boer's departure. "His forthright style may have earned him criticism time and again, but his openness invigorated the negotiation procedure," said Green MEP Rebecca Harms, adding that it was crucial now to find the right successor. The Dutchman was appointed to the position in 2006, making him the UN's chief negotiator ahead of the Copenhagen summit which was widely criticized as a failure. "Copenhagen did not provide us with a clear agreement in legal terms, but the political commitment and sense of direction toward a low-emissions world are overwhelming," said Boer, ever the optimist. Boer had campaigned tirelessly for the UN's 192 member states to agree to ambitious targets, hosting a series of discussions ahead of the Copenhagen talks, in a bid to limit global warming to within 2 degrees centigrade of pre-industrial levels. The EU's climate commissioner Connie Hedegaard praised Boer's work, in an interview with Danish news agency Ritzau. "As the head of the UN climate secretariat he campaigned admirably and tirelessly for climate issues," Hedegaard said, adding that his "huge knowledge and broad overview" had helped Denmark chair the Copenhagen summit. The 55-year-old Dutchman is to become KPMG's Global Advisor on Climate and Sustainability, a role in which he is to help the private sector address climate change. "I have always maintained that while governments provide the necessary policy framework, the real solutions must come from business," Boer said. Boer is to remain in his current role until the end of June. During this time he will prepare a spring summit in Bonn and work towards the November conference in Cancun, where there are renewed hopes for a climate agreement to replace the Kyoto Protocol. Boer, the multilingual son of a diplomat, was involved on behalf of the European Union in drafting the Kyoto Protocol, which expires in 2012. Overall, Boer has taken part in 15 years' worth of UN conferences, as well being an advisor to the Chinese government and the World Bank. He formerly held a senior role at the Dutch environment ministry.