This graph shows how earlier action to reduce U.S. emissions would be less difficult than delayed action. Two pathways show how a cumulative carbon emissions budget of 265 gigatons of CO2 could be maintained by 2050. By initiating reduced emissions efforts in 2010 (blue line), a 4% per year reduction would have been required; waiting until 2020 to reduce emissions (red line) doubles the rate at which emissions must be reduced. (Figure source: Luers et al. 200724)