The navigability of Arctic maritime passages has improved with the rapid retreat of sea ice in recent decades, and it is projected that the Northern Sea Route (NSR) will support further increases in shipping in the future. However, the opening of the NSR may bring potential environmental and climate risks to the Arctic and the rest of the world. This investigation assessed shipping emissions along the NSR and the climate impacts under global warming of 2 degrees C and 3 degrees C to support coordinated international decision-making. The results show that the magnitude of annual energy consumption of ships along the NSR is 109 kWh under global warming of 2 degrees C and 3 degrees C. The environmental impacts of the shipping decrease with fuel transition to clean, carbon-neutral fuel sources. Specifically, the maximum emission is CO2 (106 t), followed by NOX (104-5 t), CO (103-4 t), SOX (103 t), CH4 (102-3 t), organic carbon (102-3 t), N2O (101-2 t), and black carbon (BC, 101-2 t), in which CO2 and BC have great difference under high and low loads. Total emission exacerbates Arctic and global warming, and it is more significant in the Arctic in the next twenty years and across the rest of the world in the next one hundred years. The greatest climate impact factor is CO2, followed by NOX and BC which are more important in global and Arctic warming, respectively.

Arctic navigability is crucial to the global economy and landscape, while there is an omission in understanding how Arctic navigability changes as a function of 1.5 degrees C of the Paris Agreement. This study investigated the impact of 1.5 degrees C global warming above the preindustrial level on sea ice conditions and accessibility of the Northern Sea Route (NSR) and Northwest Passage (NWP) with the Polar Operational Limit Assessment Risk Indexing System and new risk demarcation criteria. The Arctic is colder on the Canadian side than on the European side under 1.5 degrees C warming. Sea ice is mostly less than three years old, and the younger, thinner and less concentrated ice is mainly in the seas along the NSR. Ships above Polar Class (PC) 6 might be unimpeded along two passages all the year. Besides, the NSR and NWP have great potential for PC6 ships in October-December, while it is only the NSR for PC7 ships. Caution is still required when navigating the western East Siberian Sea, its surrounding straits, and the Parry Channel. These changes in hydrological conditions are important for global shipping, and this work is helpful for supporting coordinated international decision-making.