Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, building systems resilient to its effects, and possible future climate engineering. Most countries are parties to the United Nations Framework Convention on Climate Change (UNFCCC),[19] whose ultimate objective is to prevent dangerous anthropogenic climate change.[20] The UNFCCC have adopted a range of policies designed to reduce greenhouse gas emissions[21][22][23][24] and to assist in adaptation to global warming.[21][24][25][26] Parties to the UNFCCC have agreed that deep cuts in emissions are required,[27] and that future global warming should be limited to below 2.0 °C (3.6 °F) relative to the pre-industrial level.