The publication of the second report by the Intergovernmental Panel on Climate Change (IPCC) led to negotiations resulting in the signing in 1997 of the Kyoto Protocol, which has been ratified by 190 countries. This agreement required developed countries to commit to a 5.2% reduction in greenhouse gas emissions from 1990 levels by 2012. However, the United States, the world's largest emitter of green-house gases, signed the protocol but did not ratify it, and the protocol stipulates no obligations for emerging countries. With the Kyoto Protocol expiring in 2012, the 2009 Copenhagen summit was intended as the platform for negotiating post-Kyoto arrangements. However, this summit foundered on the divergent interests of the developed and the emerging nations, and the negotiations ended in an agreement without any binding targets. It took the Durban conference in late 2011 to reach an agreement on the pursuit of the Kyoto Protocol as from 1 January 2013.