Climate change is a grave and urgent threat to human and other life, Earth's ecosystem, and global security and economic well-being. The global community increasingly understands that business as usual is no longer an option. Debate about states' legal obligations to reduce their greenhouse gas emissions is still in its infancy. This seriously hinders progress through the political process or the courts. A group of legal experts has sought to fill this gap by drafting the Oslo Principles on Global Climate Change Obligations. The Principles identify states' reduction obligations and articulate a series of related obligations aimed at prevention. An extensive commentary further explains the Principles and their legal underpinning. The members of the expert group are: Antonio Benjamin, Michael Gerrard, Toon Huydecoper, Michael Kirby, M.C. Mehta, Thomas Pogge, Qin Tianbao, Dinah Shelton, James Silk, Jessica Simor, Jaap Spier (rapporteur), Elisabeth Steiner and Philip Sutherland.