Washington: Rapid increase of coal use infast-growing Asian countries such as India and China may weaken monsoon systems and reduce the amount of rainfall in future, a new MIT study has found.
Coal burning, despite recent signs of having peaked in China and pledges made at the Paris Climate talks in December last year, remains the primary source of electric power in Asia. In both China and India, it is responsible for the lion’s
share of human-made sulphur dioxide (SO2) emissions, which drive up concentrations of sulfate aerosols in the atmosphere.
These aerosols not only endanger public health in the region but also contribute to local and global climate change. How much climate change will depend on Asia’s energy choices in the years and decades to come, researchers said.
At one extreme, economic growth and energy demand in China, India and other fast-growing Asian nations would lead to rapid increases in coal use, resulting in more significant climate impacts; at the other, Asia would gradually lessen these impacts by shifting from coal to cleaner burning fuels such as natural gas, and low-carbon energy technologies such as wind turbines and photovoltaics.
The new study assessed the climate’s likely response to aerosol emissions at both extremes, resulting in likely lower and upper bounds for the impact of Asian aerosols on regional surface temperature and rainfall. According to the study, a high coal-use future would entail significant local and global climate impacts.
The increased aerosol levels would have a large cooling effect throughout the Northern Hemisphere, partially offsetting warming from greenhouse gas emissions (including increased carbon dioxide emissions associated with coal
burning, which the study did not model).
Significant cooling would also be felt especially in South and East Asia, researchers said. “Much of these results are related to the impact of sulfates on clouds, which lowers surface temperatures indirectly by increasing the clouds’ reflectivity,” said Chien Wang, from MIT.
These aerosols may also lower surface temperatures by reflecting sunlight skyward. However, as they help offset warming, the aerosols would also weaken several major monsoon systems, suppressing precipitation over vast land masses. “For the high-emissions scenario, we found reductions in rainfall across much of Asia, especially East Asia (including China) and South Asia (including India), and a remote effect leading to a possible increase in rainfall in Australia as
well as a suppression of rainfall in the Sahel region of Africa,” said Benjamin Grandey from MIT.
“We see more reductions in rainfall than increases, especially in regions already struggling with water resources,” said Grandey.