From Red Sea to Hormuz: What Rerouted Shipping Means for Emissions

While the Strait of Hormuz crisis rages on, concerns have expectedly focused on the implications for energy security. While it might be some time before the full effects of the disruptions are felt, a forthcoming article by Ruikai Sun, Wessam Abouarghoub, Emrah Demir, and Andrew Potter in the journal Transportation Research Part A: Policy and Practice provides timely lessons for the ongoing crisis.

The study looks at the Red Sea disruption of 2024 and shows what happens when ships can no longer use their usual routes. Many vessels were diverted around the Cape of Good Hope instead of passing through the Suez Canal. This added several weeks to journeys and increased greenhouse gas emissions by at least 46%, with some routes seeing emissions more than double. To keep deliveries on schedule, companies often increased sailing speeds, which further raised fuel use and emissions. Even when operators tried to optimise routes and speeds, emissions and costs remained higher than before.

How Shipping Companies Respond to Disruptions

In light of the ongoing disruptions in the Strait of Hormuz, a similar pattern is already emerging. Major shipping lines have suspended or rerouted services, in some cases diverting vessels around the Cape of Good Hope and adding additional transit time and cost to global supply chains. When a key maritime chokepoint becomes unstable, companies tend to prioritise reliability by taking longer routes, deploying additional vessels, or increasing sailing speeds—each of which raises fuel use and emissions. These effects extend beyond shipping itself: for many manufacturers and retailers, maritime transport forms a significant share of Scope 3 emissions, meaning longer routes can increase reported supply chain emissions even if their own operations remain unchanged.

Implications for Shipping Sector Climate Goals

This sits alongside the shipping sector’s longer-term climate goals. The International Maritime Organization (IMO) has committed to reaching net-zero greenhouse gas emissions from international shipping “by or around 2050,” with interim targets for 2030 and 2040. While the Red Sea and Strait of Hormuz crises differ in scale and structure, the Red Sea case helps illustrate how disruptions can lead to longer journeys and higher emissions. In the case of Hormuz, where alternative routes are more limited, the outcomes may differ, but the underlying lesson remains relevant. Rather than pointing to a single conclusion, these developments show how geopolitical events can shape emissions, connecting trade disruptions to climate outcomes.