"This Agreement . . . aims to strengthen the global response to the threat of climate change . . . by: (a) Holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above preindustrial levels, recognizing that this would significantly reduce the risks and impacts of climate change" (2).
Canada. Paris Agreement under the United Nations Framework Convention on Climate Change. Department of Foreign Affairs, Trade and Development, 2016.
"The 'guardrail' concept, in which up to 2 °C of warming is considered safe, is inadequate and would therefore be better seen as an upper limit, a defence line that needs to be stringently defended, while less warming would be preferable" (18).
"[I]n some regions and vulnerable ecosystems, high risks are projected even for warming above 1.5 °C. We are therefore of the view that Parties would profit from restating the long-term global goal as a 'defence line' or 'buffer zone', instead of a 'guardrail' up to which all would be safe" (33).
Report on the Structured Expert Dialogue on the 2013–2015 Review. United Nations Framework Convention of Climate Change, 2015.
"Human-induced warming has already reached about 1°C above pre-industrial levels . . . . By the decade 2006–2015, human activity had warmed the world by 0.87°C (±0.12°C) compared to pre-industrial times (1850–1900). If the current warming rate continues, the world would reach human-induced global warming of 1.5°C around 2040" (81).
Global Warming of 1.5°C. Intergovernmental Panel on Climate Change, 2018.