This blog is informed by my conversation with Annie Petsonk, International Counsel for the Environmental Defense Fund and expert on aviation and international climate policy. She further introduced me to her colleague Aoife O’Leary’s work on the environmental impacts of international shipping and aviation. 

In November 2016, the International Civil Aviation Organization (ICAO) adopted the first global market-based mechanism to apply to a sector. The Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) aims to limit net CO2 emissions of international flights to 2020 levels with its goal of “carbon neutral growth from 2020 — now 2019 levels because of the COVID-19 interruptions to aviation trends. This scheme is a critical step forward for climate action and could prevent nearly 2.5 billion tonnes of CO2 from entering the atmosphere over the next 15 years. CORSIA also offers a framework for which we can evaluate and apply to another sector: shipping. 

Ships transport roughly 90% of world trade and accounts for 3% of global greenhouse gas emissions, which is more CO2 than all but five countries. Aviation and shipping are two major economic sectors with growing emissions outside the purview of most countries’ NDCs, so adopting an offset program for the International Maritime Organization (IMO) would have great potential for reducing sectoral emissions and consequently, future warming. In fact, one study showed that stringent mitigation measures could avoid over 85% of projected future warming from the shipping sector’s CO2 emissions if the IMO reaches its target of a 50% reduction in CO2 emissions below 2008 levels by 2050, with full decarbonization of the industry by 2100. 

This strict mitigation effort would require the IMO to not only apply ICAO’s current framework for Sustainable Aviation Fuels (SAF) to its own low and zero-emission fuels, but actually exceed the ambition of CORSIA targets. When considering sustainable fuel options, the IMO should include non-CO2 greenhouse gases, take a full lifecycle perspective of emissions, develop guidelines for alternative fuels, and ensure robust, transparent accounting rules to fully achieve climate benefits. That means adopting measures to prevent double counting, regulating zero-emission status of biofuels, and accurately calculating both direct and indirect impacts for the whole supply chain. 

O’Leary also co-authored a paper exploring the legal pathway for enacting a CORSIA-like measure and found that there is already clear legal authority to implement and enforce global climate policy. And unlike the aviation industry, which took a huge hit due to the pandemic, the rate of cargo shipping has actually increased this year. Given its growth and commitment to adopt a climate strategy, IMO should allocate resources and draw lessons from CORSIA as a blueprint to lower its own sectoral emissions.