"The initial strategy envisages for the first time a reduction in total GHG (Greenhouse Gas) emissions by at least 50 percent by 2050 compared to 2008," the IMO said in a statement.
Major shipping nations such as Saudi Arabia and the United States had objected to earlier drafts in two weeks of discussion at the 173-member organization based in London.
Some countries such as the Marshall Islands, which are at risk of rising seas but are also a major flag state, had wanted a stronger commitment and the EU wanted a 70- to 100-percent cut.
But the agreement was widely hailed by stakeholders.
"This is a ground-breaking agreement — a Paris agreement for shipping — that sets a very high level of ambition for the future reduction of carbon dioxide emissions," the International Chamber for Shipping's secretary general Peter Hinchliffe said.
