How to reduce GHG emissions:  Weather routing – Part1


“Earth’s average global surface temperature in 2019 was the second warmest since modern record- keeping began in 1880” (NASA & NOAA) . International trade-related freight transport currently accounts for more than 7% of global emissions and should rise to 28% in 2050 (ITF-OECD). With the arrival of modern technologies and data processing capabilities in the maritime and logistics, reducing GHG (Greenhouse emissions) is within everyone’s reach. One way to do it:  route optimization. In this Blog series, we first take the point of view of fleet managers and show the importance of weather on the overall GHG emissions.


Maritime industry awareness of global warming


With IMO 2020, a lot of recommendations on actions to be taken to reduce GHG emissions are gaining momentum. The objective: reduce the maximum content of sulfur in fuel oil from 3.5% to 0.5%, outside of SECA areas and reduce total GHG emissions from shipping by at least 50% by 2050 (compared to 2008) to meet Paris Agreement temperature goals.

To meet these new regulations, we hear about scrubbers, fuel switching, among other solutions. Despite the advantages these solutions present, they remain controversial for several reasons. In March 2019, IHS Markit explainedusing a scrubber results in an increased fuel consumption of about 1.5 percent-2 percent. Simply put, there is no free ride to reducing emissions, since reducing sulfur increases the CO2 emitted, both for scrubbers and for MGO.


In an interview with Cyprus Shipping News, Andreas Hadjipetrou, managing director of Columbia Ship management Ltd adds ”The availability and quality of complaint fuel is still unclear and scrubbers are not considered the environmental solution for the future.”


What about route optimization? What does ‘route optimization’ actually mean, and how is it done in practice? In this post, we define route optimization and explain how to do it taking into account weather data. We hope this will help you with implementing a ghg emissions reduction strategy in your company.


What is ship route optimization ?


According to Lin, Yu-Hsien & Fang, Ming-Chung. (2013), “The ship routing optimization is the technology of developing the best route for a ship based on the existing weather forecasts, ship characteristics and particular safety requirements. The objective is to find the best balance to minimize transit time and fuel consumption without placing the vessel at risk to vessel damage or crew injury”.

With new regulations, we could also add another objective: minimize ghg emissions. There are so many ways and criteria to take into account when optimizing routes. Port congestion, accidents, collisions, among others, are also to be taken into account when choosing the best route.

Weather alone can account for more than 20% of the increase in fuel (see example below) compared to fuel consumption in calm water.


Why is weather routing important ?


Many surveys show that weather has an impact on fuel consumption (see for instance Prpić-Oršić, Vettor, Guedes Soares & Faltinsen, 2015) and therefore on Co2 emissions. Some of them (Vlachos, 2004, Rusu and Guedes Soares 2014) emphasize that reliable weather (wind and waves) and the performance simulation of ships help find the best route. Methods for calculating CO2 emissions reductions and results vary from one study to another.

On average, optimized weather routing can help fuel saving up to 10% (IMO 2015) and reduce Co2 emissions  up to 4% (European Commission 2013).

We carried out the exercise in the example below. In particular, we focused on fuel consumption,  which has a direct impact on Co2 emissions.


Real Example of weather impact on Co2 emissions


Example – Journey: Barcelona – New York


The report below takes into account ship sizes and speed. We took 2 dates of departure on 02.12.19 and 06.01.20 on the same voyage. As you see below to give you an idea of the fuel consumption differences depending on weather conditions.  You can also make your own test >>searoutes.com

How to reduce GHG emissions: Weather routing - Part1
Figure 1: Impact of weather on fuel consumption with departure on 02.12.2019


How to reduce GHG emissions: Weather routing - Part1
Figure 2: Impact of weather on fuel consumption with departure on 06.01.2020


If we take a 6.000-8.000 TEU container ship with a departure on 2.12.19 and an average constant speed of 13kn, we consume 13,65% more fuel than in calm water. With a departure on 6.01.20 fuel consumption rises to 16,26%, as weather (waves and wind) is worse. Indeed, to keep a constant speed, the more power the engine has to produce to move the vessel through the water, the more fuel it needs. Therefore, to avoid bad weather the ship can slow down (optimize its speed profile) or change its route. It also can be a combination of the two.

Implementing weather routing helps you better manage your ship journey, save fuel and therefore reduce GHG emissions. See how we can help maritime stakeholders better evaluate weather impact on a given journey and help them in decision making.


>> Get reliable weather data 

#Next post: In this first part, we take the point of view of fleet managers and show the importance of weather on the overall GHG emissions. In part two, we’ll take the point of view of freight forwarders and we’ll show the importance of port choice to reduce GHG emissions.



IHS Markit, The JOC, Gemini Shippers Group, Seabury Maritime – IMO 2020: What Every Shipper Needs To Know – WHITEPAPER, March 2019

Miika-Matti Ahokas (2019). Analysis of voyage optimization benefits for different shipping stakeholders, Master’s Thesis Department of Mechanical Engineering

Lin, Yu-Hsien & Fang, Ming-Chung. (2013). The Ship-Routing Optimization Based on the Three-Dimensional Modified Isochrone Method. Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering – OMAE. 5. 10.1115/OMAE2013-10959.

Prpić-Oršić, R. Vettor & C. Guedes Soares, O.M. Faltinsen. (2015) Influence of ship routes on fuel consumption and CO2 emission, Maritime Technology and Engineering – Guedes Soares & Santos (Eds), pp.857-864

Vettor, R., Guedes Soares, C. (2014). Detection and analysis of the main routes of voluntary observing ships in the North Atlantic, (submitted for publication).

Vlachos, D.S. (2004). Optimal Ship Routing Based on Wind and Wave Forecasts. Applied Numerical Analysis & Computational Mathematics 1(2), pp. 547–551