At the Toronto Conference on the Changing Atmosphere: Implications for Global Security, hosted by Canada in Toronto, Ontario, starting on 27 to 30 June 1988,[1] the 300 participants—including policy makers, international scientists, non-governmental and governmental organizations, and United Nations organizations—issued a warning at the conclusion of the conference that humans had unintentionally triggered uncontrolled changes to the atmosphere that if left unchecked could ultimately lead to "consequences could be second only to a global nuclear war.
"[4] The Conference "launched" discussions of potential international action and public policy responses to climate change[2][5] which included early targets for CO2 emission reductions.
[8][3][Notes 3] The 1988 Toronto Conference took place in the same week that James E. Hansen director of NASA's Manhattan-based Goddard Institute for Space Studies cautioned in his 23 June 1988 testimony before the United States Senate Committee on Energy and Natural Resources that it was 99% certain that the global "warming trend was not a natural variation but was caused by a buildup of carbon dioxide and other artificial gases in the atmosphere.
They concluded that the changes in the atmosphere due to human pollution "represent a major threat to international security and are already having harmful consequences over many parts of the globe," and declared that by 2005 the world would be well-advised to push its emissions some 20% below the 1988 level.
[6] The 1988 Toronto Conference was the inspiration for the 1989 Canadian Broadcasting Corporation radio series, It's a Matter of Survival,[14][15] and Anita Gordon and David Suzuki's 1990 non-fiction book by the same name[11] describing the next half century in terms of the environment.