Top Oceans Court Says Nations Must Reduce Greenhouse Gas Emissions

The world’s highest court dealing with the oceans said on Tuesday that excessive greenhouse gases were pollutants that can cause irreversible harm to the marine environment. The groundbreaking advisory opinion was unanimous, and experts say it could lead to more wide-ranging claims for damages against polluting nations.

The opinion by the court, the International Tribunal for the Law of the Sea, is not binding, but it said that legally, nations must take all necessary measures to reduce, control and prevent marine pollution caused by human-made greenhouse gas emissions.

Given the expertise of the court, sometimes called the Oceans court, the opinion is likely to affect how other international and national courts address the growing dangers posed by greenhouse gases that cause the heating and acidification of the oceans.

As the world warms, the oceans are absorbing a significant amount of the excess heat, which has the potential to alter ocean currents and the marine ecosystem and contribute to coral bleaching, among other dangers. Acidification, which is also harmful to sea life and can alter marine food webs, happens as ocean waters absorb carbon dioxide, the main greenhouse gas warming the world.

The request for an advisory opinion was made by a group of small island nations that are already affected by rising sea levels. The court’s opinion applies to the more than 165 countries that ratified the United Nations Convention on the Law of the Sea, which includes large polluters such as China, Russia and India, but not the United States.

The opinion issued by the 21 judges on Tuesday effectively expanded the definition of marine pollution to include greenhouse gases. The convention, which was negotiated in the 1970s, does not mention these emissions and their adverse effects on the world’s oceans, which are based on more recent science.