In 1998, Spence left New Zealand to travel, and after spending time in New York visiting friends and searching for work, his focus shifted to international diplomacy, particularly the United Nations negotiations on climate change and other environmental law issues. He worked as a consultant and advisor for a range of international organizations, including the International Institute for Sustainable Development (IISD) and United Nations Development Program (UNDP). Then in 2006, he took on the position of Special Advisor for The World Conservation Union (IUCN). Spence led the Earth Negotiations Bulletin team to United Nations climate change negotiations from 1999–2002, and again in 2005 (Montreal, Canada), 2006 (Nairobi, Kenya), 2007 (Bali, Indonesia) and 2008 (Poznań, Poland).