The Ship Traffic Emission Assessment Model (STEAM) was refined with a capacity to use the data regarding wind, sea currents, sea waves and sea ice in the modelling. The refined model can estimate the influence of these ambient effects to a vessel’s fuel consumption and emissions. The weather and sea condition data were extracted from the Copernicus climate data store and the Copernicus marine services, respectively. The updated model version was used to estimate the contribution of the ambient conditions to the global emissions of CO2 originating from shipping for the years 2014–2021. In addition, we separately estimated the contribution of each environmental variable to the total emissions. In 2014–2021, the simulation results predicted an average increase of 9.5% in the total emissions of CO2 from shipping due to ambient effects. Sea waves had the most significant contribution to the total effect attributed to ambient conditions. The second largest contribution was caused by wind resistance, and the rest of the ambient effects was due to sea currents and sea ice. The predicted results highlight the spatial and temporal variation in the magnitude of the ambient effects on shipping emissions. It is therefore recommended to take into account these effects, especially when using gridded emission data on a finer spatial and temporal resolution.