Indian scientists’ ‘sulphur’ breakthrough on cloud formation in future

New Delhi: Weather scientists from India and Europe on Monday reported a likely rise of a major sulphur bearing compound in the atmosphere in the coming decades, despite a projected decline of the source material generated in the ocean.

A combined climatic push given by a rise in the sea-surface temperature and increase in the speed of surface wind will lead to transport of a larger volume of the chemical – known as DMS or Dimethyl Sulphide – to the atmosphere in future, contributing to more aerosol and cloud formations, the scientists say.

In the atmosphere, the chemical undergoes transformation contributing to the formation of aerosol as well as cloud, which determines how much of the solar radiation will go back to space keeping the earth cool.

“DMS is the largest natural source of atmospheric sulphur, injecting 40% of sulphur into the atmosphere. Our study shows that while oceanic concentration of the chemical will drop, its level in the atmosphere will grow, eventually leading to greater cloud formation,” Anoop Mahajan, a senior scientist at Indian Institute of Tropical Meteorology, Pune, who led the team told DH.

“Greater cloud formation may offset some of the consequences of the warming effect,” he added. However, the impacts of global warming will not be negated completely.

With nations bringing in new air quality policies to reduce the anthropogenic emissions of polluting gases like oxides of carbon, sulphur and nitrogen, scientists have been researching natural sources of sulphur like DMS to figure out how it will impact the weather in future.

“But none of the existing climatic models agree on mimicking the DMS behaviour. Some say its concentration will go up, others say the level will go down. That’s why we decided to look at it comprehensively to get an accurate picture,” Mahajan.

The IITM researchers teamed up with scientists from Europe and pulled together all observation data on DMS. They used machine learning tools trained on global observations of biological processes to model emissions of DMS, which is produced by phytoplankton.

The models simulated seawater DMS concentrations from 1850 to 2100 using predictor variables from eight climate models.

They found that DMS concentrations in the ocean are predicted to decrease under future warming scenarios, but at the same time, its emissions into the atmosphere are set to rise due to increasing surface wind speeds and sea-surface temperatures.

The latter finding contradicts current climate assessments that project a decrease in atmospheric DMS due to global warming.

“The results show that seawater DMS will decrease in the future, but the sea-air emissions will increase. This suggests that DMS will play an increasingly important role as a sulphur source as further air quality measures reduce anthropogenic emissions of sulphur compounds,” the scientists reported.

The study has been published in the Proceedings of the National Academy of Sciences.