LONDON Feb 18 (bdnews24.com/Reuters) - The U.N. climate chief Yvo de Boer has resigned to join a consultancy group as an adviser, the U.N. climate secretariat said on Thursday, two months after a disappointing Copenhagen summit. De Boer will step down on July 1 to join KPMG, the U.N. framework convention on climate change (UNFCCC) said in a statement. He has led the agency since 2006. "It was a difficult decision to make, but I believe the time is ripe for me to take on a new challenge, working on climate and sustainability with the private sector and academia," de Boer said in the statement. "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. This calls for new partnerships with the business sector and I now have the chance to help make this happen," he added.