evidence: Carbon dioxide emissions are the primary driver of global climate change. It's widely recognized that to avoid the worst impacts of climate change, the world needs to urgently reduce emissions. But, how this responsibility is shared between regions, countries, and individuals has been an endless point of contention in international discussions. [...] Since there is such a strong relationship between income and per capita CO2 emissions, we’d expect this to be the case: countries with high standards of living would have a high carbon footprint. But what becomes clear is that there can be large differences in per capita emissions, even between countries with similar standards of living. Many countries across Europe, for example, have much lower emissions than the US, Canada, or Australia. [...] Since 1751 the world has emitted over 1.5 trillion tonnes of CO2.2 To reach our climate goal of limiting average temperature rise to 2°C, the world needs to urgently reduce emissions. One common argument is that those countries that have added most to the CO2 in our atmosphere – contributing most to the problem today – should take on the greatest responsibility in tackling it.