The clouds are known as Atmospheric Brown Clouds, and are mostly caused by the burning of wood and plant matter for cooking in India and other south Asian countries. They may have enhanced heating of the atmosphere by around 50% and contributed to about half of the temperature increases blamed in recent decades for the glacial retreat, according to the study, published in Nature.
"All we are saying is that there is one other thing contributing to atmospheric warming and that is the brown cloud," said Veerabhadran Ramanathan, chief scientist at the Scripps Institution of Oceanography in California, and lead author of the report.
"If the pollution increases, the glacier retreat will be much worse than projected," said Ramanathan. "It now depends on what energy path that Indian, China and Asia will take."