Rating aviation and shipping

The rating methodology applied for international aviation and shipping policies is different from the rating system for countries. We rate countries based on both what is needed based on fair shares and what is needed for full decarbonisation at the national level.

To rate international aviation and marine sectors we start out with the observation that to achieve the Paris Agreement’s temperature goal, global CO₂ emissions need to reach net-zero around mid-century (IPCC, 2018). If international aviation and shipping decarbonise later than mid-century, other sectors would need to reach net-zero carbon emissions sooner, and/ or deployment of corresponding negative emission technologies will be needed. To reflect that different sectors should share the decarbonisation burden, we applied the principle that aviation and shipping should decarbonise at the same average rate as emissions from energy and industrial processes, thereby taking a comparable share of emissions efforts. This implies that international aviation and shipping (together with all emissions from energy and industrial processes) should reach zero CO₂ emissions by around 2060.

For this assessment, we have taken the global CO₂ emission pathways for energy and industrial processes that are provided for by Integrated Assessment Models (IAMs) and assessed in the IPCCSR1.5. We filtered these pathways to exclude those that exceed sustainability limits for Bioenergy with Carbon Capture and Storage (BECCS) and Agriculture, Forestry and Other Land Use (AFOLU), as defined in the IPCC SR1.5. This gave us 19 scenarios that are consistent with the Paris Agreement and that we define as “CAT Filtered Pathways” (Yanguas Parra et al., 2019). This is the same filtering approach that we used to define global pathways for developing the fair share and modelled domestic pathways ratings used in individual country assessments.

We have also extracted pathways that lead to a temperature increase between 1.5˚C-2˚C; between 2˚C-3˚C; between 3˚C-4˚C; and >4˚C from the IPCC IAM Database, so we have five sets of pathways that correspond to one temperature category each.

From each pathway set, we took the median emission levels between 2000 and 2100, with ten-year intervals. Using these median levels, we then calculated the annual growth rate for each temperature pathway and applied the growth rates to latest historical data for international aviation emissions, provided for by the ICAO. The latest available data is for the year 2019. This approach differs slightly to that adopted for international shipping, where the growth rate was applied to the historical average for the period of 2007-2017 and is due to the fact that emissions in that sector have fluctuated greatly, whereas emissions from international aviation have increased steadily since 1990.

This exercise supplied us with five temperature pathways, leading to global temperature increases ranging from 1.5˚C to over 4˚C compared to pre-industrial levels. We have assigned a rating to each of these temperature categories: 1.5˚C Paris Agreement compatible, 2˚C compatible, correspond to those temperatures, while the insufficient, highly insufficient and critically insufficient ratings correspond to between 2˚C-3˚C; between 3˚C-4˚C; and >4˚C, respectively. While we use the same terms as for the individual country assessments, the definition of the ‘insufficient’ rating is different.

The 1.5˚C pathways reflects the maximum level of international aviation and shipping emissions for the sectors to be rated as ‘Paris compatible’.

Please refer to shipping and aviation assessments for more detail.

• IPCC. (2018). Global Warming of 1.5 °C - An IPCC special report on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat. In Global Warming of 1.5 C :An IPCC special report on the impacts of global warming of 1.5 C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change (Vol. 106, Issue 11, pp. 1323–1330). https://www.ipcc.ch/sr15/
• Parra, P. A. Y., Ganti, G., Brecha, R., Hare, B., Schaeffer, M., & Fuentes, U. (2019). Global and regional coal phase-out requirements of the Paris Agreement: Insights from the IPCC Special Report on 1.5°C.