Costly trade-off

A reduction in the planet's sulphur dioxide emissions could be behind the recent spike in global warming

- ROHINI KRISHNAMURTHY

AN INTERNATIONAL move to curb air pollution is feared to have added to global warming. In January 2020, the International Maritime Organization (IMO) the United Nations agency responsible for prevention of marine and atmospheric pollution by ships enforced reduction of sulphur content in shipping fuels from 3.5 per cent to 0.5 per cent. The resultant decline in sulphur dioxide (SO₂) emissions, scientists say, could have played a role in the 1.32°C rise in global average temperature between November 2022 and October 2023, over the preindustrial era, as well as the record-breaking rise in sea surface temperature in the North Atlantic ocean in June 2023, which likely led to the worst-ever drought in the Amazon this year.

Mark Parrington, senior scientist at the Copernicus Atmosphere Monitoring Service at the European Centre for Medium-Range Weather Forecasts, tells Down To Earth (DTE) that the "sudden increase (in average global temperature) seems to be a bit of a bigger jump than it has been in recent years." Anoop S Mahajan, senior scientist at the Indian Institute of Tropical Meteorology, Delhi, agrees and says, "There is a pretty good reason to believe that the sudden rise is because of the new regulations in the shipping industry. It might take us closer to a world, where global temperatures reach 1.5°C from the current 1.1°C (above preindustrial era)."

SO2 causes respiratory, cardiovascular and lung diseases, and can induce acid rain, which is a threat to crops, forests and aquatic species. Thirteen per cent of the world's SO₂ emissions come from shipping, states a 2022 paper in peer reviewed journal PNAS. IMO's move has reduced about 70 per cent of SO2 emissions from global shipping, which transports about 90 per cent of world trade, says the multilateral organisation.