Climate Change and Shipping: The Ocean's Dual Crisis from Global Warming and Marine Emissions

There is no doubt that Earth’s climate has changed throughout history and that cyclical changes transpired long before humans dominated the planet. Global climate changes have been responsible for mass extinctions in the past and, as it continues to vary, will likely result in future extinction events. During the Quaternary Period, sea levels deviated by as much as 85 metres, which inhibited the evolution of established marine communities in coastal and shelf environments. Unquestionably, humans have affected global temperatures, and since the 1980s, there has been considerable debate on differentiating the natural and anthropogenic contributions to climate change. Recent evidence, however, concludes that climate change since the 1900s is human-induced.

Human activities that influence change include the release of carbon dioxide (CO₂) through the burning of fossil fuels and large-scale deforestation, which decreases the removal of CO₂ from the atmosphere. Changes in ocean temperatures affect marine biological communities in various ways, including changes in geographical distribution, behavior, and life history (e.g., reproduction, growth, and dispersal). Coral reefs, for example, are particularly vulnerable to ocean warming, and even minor temperature increases may cause many coral species to lose their algal symbiotic zooxanthellae (termed “bleaching”) that provide energy through photosynthesis. There is also evidence that the ranges of some species have shifted toward the North and South Poles as temperatures increase in equatorial and temperate waters.

Although shipping is an efficient means of moving goods over short and long distances, the burning of fossil fuels for propulsion emits sulfur dioxide (SO₂), nitrogen oxides (NOx), volatile organic compounds (VOCs), particulate matter (PM), carbon dioxide (CO₂), and other greenhouse gases into the atmosphere. Passenger and cruise ships must also produce power when in ports, which results in increases in air pollution adjacent to the port.

The global shipping industry emits significant amounts of greenhouse gases. The International Maritime Organization (IMO) estimates that shipping was responsible for 796 million tons of CO₂ emissions, or about 2.2 percent of global emissions, in 2012 (IMO 2015). If the global shipping industry were a country, it would be the sixth largest emitter of CO₂ after the United States, China, Russia, India, and Japan. Shipping moves approximately 70 percent of global freight while producing around 15 percent of global CO₂ emissions. Without additional regulations on CO₂ emissions or the adoption of more efficient shipping technologies, shipping emissions are forecasted to increase by a factor of two to three by 2050. On the other hand, if technical and operational improvements are implemented, they could reduce CO₂ emissions by 25 percent to 75 percent below current levels.

In 2011, the IMO’s mandated energy efficiency measures were applied to the global shipping industry and entered into force in 2013. Energy efficiency targets for new ships are at a 10 percent improvement for ships built between 2015 and 2019, 15 percent or 20 percent for 2020 and 2024 (depending on the type of ship), and 30 percent for ships delivered after 2024. In addition, a Ship Energy Efficiency Management Plan is required for all new and existing ships, establishing best practices for fuel efficiency and voluntary guidelines for measuring CO₂ emissions.

Although the IMO has considered a number of market-based incentives for reducing ship emissions, no such market mechanisms are yet in place. However, market mechanisms will likely be incorporated into international shipping in the future, and if the IMO is unable to broker a global consensus, the European Union is likely to bring into force an emissions trading program for shipping.