The effect of updated pledges and business-as-usual projections, and new agreed rules on expected global greenhouse gas emissions in 2020

Abstract

Abstract The Copenhagen Accord of 2009 refers to a 2 °C target and encouraged countries to submit emission reduction proposals and actions (pledges) for the year 2020, which many did. Several studies determined the effect of these pledges on the global emission level in 2020, and analysed the gap between this emission level and the level consistent with least-cost emission pathways for achieving the 2 °C target. These studies were summarised in the UNEP emission gap reports. Since the UNFCCC climate negotiations in Cancun, 2010, business-as-usual emission projections have been updated and some countries submitted new pledges or clarified existing pledges. Furthermore, new accounting rules for land use and the use of surplus units were agreed in Durban (2011) and Doha (2012). This paper shows that together, these developments have led to an increase in the emission level resulting from the pledges of about 4 GtCO2equiv. compared to our assessment before Cancun, mainly due to increased business-as-usual projections. According to our projections, the pledges lead to an emission level of 52.7–56.5 GtCO2equiv. by 2020, which implies an emission gap of 8.7–12.6 GtCO2equiv. for a likely chance (greater than 66% likelihood) and from 6.7 to 10.6 GtCO2equiv. for a medium chance (50–66% likelihood) of achieving 2 °C. This does not imply that achieving 2 °C is out of reach with the current pledges, but it will require higher reduction rates beyond 2020 and will depend more heavily on future technological developments.