When considering a country’s fair share, we have to ask how much of the global problem it is responsible for. One key challenge here is choosing the year when national emissions should start counting towards historical responsibility. Should it be 1850, a year that predates most all industrial activity? In 1950, when the great global economic boom began in earnest? In 1990, when our governments were drafting the UN Framework Convention on Climate Change? In our analysis, we use 1950, while acknowledging that this is somewhat generous towards the United States since it discounts all of our emissions before that date.
Ideally, a country’s fair share in the global climate mobilization would be directly proportional to its historical responsibility for the climate emergency. However, there are a number of complexities that make this more difficult than it might seem at first glance. For example, how do we account for the early emissions of former colonies, whose people did not enjoy the benefits of their countries’ own early industrialization? Or the emissions that took place in areas that are now part of countries that did not even exist yet?
Fortunately, national historical responsibility is in many cases highly correlated with national wealth and income, which are key determinants of national capacity. This makes it ethically acceptable for us to be conservative (avoiding the deep past) when choosing a responsibility start date, if we know that we will also be taking capacity into proper account. Thus, we have in this analysis used 1950 as our historical start date. For much more on the ethical and political trade-offs here, see The Climate Equity Reference Project approach to Equity Benchmarking. For the specific details of the equity benchmark used in this report, see The U.S. Fair Share – Backgrounder.