Fourth IMO GHG Study 2020
Faber, J., Hanayama, S., Zhang, S., Pereda, P. Comer, B., Hauerhof, E., Schim van der Loeff, W., Smith, T., Zhang, Y., Kosaka, H., Adachi, M., Bonello, J., Galbraith, C., Gong, Z., Hirata, K., Hummels, D., Kleijn, A., Lee, D.S., Liu, Y., Lucchesi, A., Mao, X., Muraoka, E., Osipova, L., Qian, H., Rutherford, D., Suárez de la Fuente, S., Yuan, H., Perico, C.V., Wu, L., Sun, D., Yoo, D., Xing, H. Fourth IMO GHG Study 2020. International Maritime Organization. Available here.
The study documents a 9.6% rise in total shipping greenhouse gas emissions between 2012 and 2018, reaching 1,076 million tonnes CO₂e, with international shipping maintaining a stable share of roughly 2% of global CO₂ emissions throughout. Carbon intensity improved by 21–29% vessel-based over the same decade, but the efficiency gains are being outpaced by growth in trade volumes; a decoupling problem that has not improved since. Under the study’s central scenarios, shipping emissions in 2050 could reach 90–130% of 2008 levels, making the sector’s decarbonisation trajectory one of the more difficult to align with 1.5°C without structural shifts in fuel and propulsion technology.