Related results were published in Earth-Science Reviews. 

The study was based on literature reviews as well as the latest data and modelling, focusing on the changes and current status of temperature, precipitation, glaciers and glacial lakes, water quality of rivers and lakes, atmospheric environment and vegetation phenology. 

According to historical temperature records reconstructed from ice cores and tree rings, the researchers found significant climate warming in the Mt Everest region during the 20th century. "The Mt. Everest region has experienced significant warming since 1960, about 0.33 °C/decade, based on the meteorological observations from 1961 to 2018, but the precipitation was relatively stable," said Prof. KANG Shichang, leader of the study.  

The researchers projected that the Mt. Everest region usually shows a warming trend in the future (during 2006-2099), and the warming rate in winter is greater than that in summer under different scenarios of Representative Concentration Pathway 4.5 and 8.5. 

They further reported that the current glacier areas in Mt. Everest region is about 3,266 km², which shows a significant shrinkage from the 1970s to 2010. Glacier retreat has led to significant increasing of river runoff.  

Meanwhile, the area of glacial lakes increased from 106.11 km² in 1990 to 133.36 km² in 2018, and the number of glacial lakes increased by 16.9% from 1,275 in 1990 to 1,490 in 2018.  

The team also found that, at present, there were about 95 glacial lakes in the region with potential risks, including 17 lakes with high risks and 59 lakes with medium risks in Mt. Everest region. 

"All these findings indicate that the Mt. Everest region shows its hydrological response to global warming. And it may be intensified in the next few decades, potentially threatening the security of water resources in the downstream region," said Prof. KANG. 

Besides, due to the remote location of Mt. Everest and sparse human activity, the current atmospheric environment is relatively clean. However, the researchers have revealed that long-distance transport of air pollutants from South Asia, West Asia, and Central Asia has exerted impacts on this pristine region, resulting in increasing concentration of pollutants (such as black carbon) since the Industrial Revolution. 

The researchers also investigated the Normalized Difference Vegetation Index (NDVI) in the Mt. Everest region. They revealed that NDVI showed an increasing trend from May to September, but the change of primary production was not obvious from 1982 to 2015.  

The start time of vegetation growth season was delayed by 1.85 days and the end time was advanced by 0.54 days. The end time on the south slope changed slightly, and the start time did not change significantly. 

Furthermore, they pointed out that there was still a lack of first-hand monitoring data, especially for the extremely high-altitude areas, which limited our understanding of the processes and mechanism of multi-sphere interaction in the Mt. Everest region. 

"The establishment of a long-term and sustainable monitoring system for climate, environment and ecology in Mt. Everest is urgent. It will help us to comprehensively evaluate climate warming and its impact on ecosystem, hydrology and water resources in the region," said Prof. KANG. 

Contact:

ZHANG Yulan

E-mail: yulan.zhang@lzb.ac.cn

State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Lanzhou, China.