A research group led by Prof. ZHANG Weijun from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences found that strong aerosol absorption may be a key factor causing warming on the Qinghai-Tibet Plateau (QTP).

The findings were published in Geophysical Research Letters.

The warming rate of the QTP is twice the global average value over the past 50 years, but it varies widely in different areas, adding the complexity to the understanding of the factors influencing TP warming. The optical properties of aerosols, especially single scattering albedo (SSA), are necessary parameters for the calculation of aerosol radiative forcing. However, observations of SSA over the TP have been limited due to technical challenges and the harsh environment.

In this study, using the Cavity-Enhanced Albedometer developed by the researchers over the Lhasa site, the researchers performed in situ measurement of aerosol extinction, scattering and absorption coefficients, as well as SSA simultaneously. Strong aerosol absorption was observed.

"Black carbon was found to be the largest contributor to aerosol absorption, followed by primary and secondary brown carbon," said Prof. ZHANG.

The strong absorption exerts positive direct aerosol radiative forcing at the top of the atmosphere during the day, reaching 2.83 W/m² - exceeding the global mean radiative forcing of CO₂ (2.16 W/m²).

The sites with strong aerosol absorption are all located in the regions with significant warming, suggesting that aerosol may play a significant role in accelerating QTP warming.

"This study shows the relationship between strong aerosol absorption and QTP warming," said WANG Shuo, first author of the study. "Reducing the fraction of absorbing aerosols could be an efficient way to mitigate QTP warming."

Average DARF^TOA (a), DARF^BOT (b) and DARF^ATM (c) based on aerosol optical properties from 11:00 to 19:00 (base case), and their sensitivities to SSA (grey background) and AOD (green background) with -20%, -10%, 10% and 20% variations. (Image by WANG Shuo)