• Following the IPCC's fourth assessment report, the countries met in Copenhagen in 2009 to set a goal of limiting average global temperature rises to +2°C, which involves halving global emissions by 2050. In 2007, the IPCC estimated that this goal would require reductions of 80-95% by 2050 in developed countries. • now aims to limit global warming "well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C", and to achieve a global balance between greenhouse gas emissions and absorption - "carbon neutrality" - in the second half of the 21st century; • Recognizes the principles of "equity and common but differentiated responsibilities and respective capabilities in the light of different national circumstances." This requires the countries that have contributed the most to climate change (due to their past and current greenhouse gas emissions) and that are in a position to do so (capacity and potential to reduce emissions) to play a more active role in global climate action.