In an effort to scale-up climate change mitigation, the largest private sector engagement in the history of the United Nations was drafted to fund clean technology projects in developing countries. Carbon credits were to offset pollution in developed nations and pay for clean energy projects in developing countries. But many developed countries, including the United States, spurned the agreement, preferring to manage greenhouse gas emissions internally and build or retrofit infrastructure in ways that directly benefited their economies. The ambitions of the Kyoto Protocol, which went into effect in 2005, were subsequently stranded and then scrapped.