Facts4Paris: World emission shares are roughly: one quarter: G7, one quarter: China, one quarter: rest of the G20, one quarter: rest of the world.
Although all countries have to varying degrees contributed to the causes of climate change and all countries are impacted by climate change, some countries can have more of a role in emissions reduction than others. This relates very simply to countries' absolute share of global emissions.
While we strive for a global deal in Paris this year, it is worth recognising that a regime focussing on certain countries or certain groupings of countries might also provide a path forward.
In 2014, the rich industrialised countries of the Group of 7 were responsible for one quarter of global emissions. China was responsible for another quarter. The remainder of the G20 countries (Argentina, Australia, Brazil, India, Indonesia, South Korea, Mexico, Russia, Saudi Arabia, South Africa, and Turkey) were together responsible for another quarter. That leaves the entire rest of the world responsible for the final quarter.