Climate change is intensifying in recent decades. Scientific study showed that global surface temperature is likely to rise a further 0.3 to 1.7 °C during the 21^st century. The case is especially bad in arid and semi-arid regions where ecological environment is rather vulnerable, such as the Central Asia. 

But how bad is the case?  

A study by scientists from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences may prove that the trend of air temperature rise was overestimated, especially in the summer. 

“That may be attributed to the oasis effect, which has an important influence on the temperature background level and the temperature changing trend in arid areas,” said HAO Xingming, corresponding author of the study, and a researcher at XIEG. 

HAO and his colleagues chose Tarim Basin as their study area and assessed the oasis effect and its potential influence through ArcGIS spatial analysis and statistical methods based on the MODIS LST and meteorological data. 

Most of the weather stations in arid regions were built in oasis due to the limitation of the environmental condition and the working condition. Take the Tarim Basin as an example, among the total of 43 weather stations, only one station is located in the desert and four stations in the mountainous area (altitude higher than 1500 m). The other 39 stations are distributed in oases, which account for only 11.5% of the plains area.  

In Tarim Basin, oases had significant cold island effect, especially in summer. “The observed temperature not only can’t represent the temperature background of whole region, but also can’t eliminate the disturbance of oasis Cold Island on temperature,” said HAO. 

Researchers reconstructed the time series data in Tarim Basin from 1961 to 2000, on the basis of a systematic analysis of the oasis Cold Island effect.  

Their study showed that previous data and study underestimated the air temperature background, and overestimated the trend of air temperature rise, especially in the summer, due to the limitations in the spatial distribution of weather stations and the disturbance of oasis effect. 

“The impacts of oasis effect on temperature should be a universal phenomenon in entire warm season of arid region (April to October in every year) based on our previous research,” said HAO. 

The study was published on Scientific Reports, entitled “The oasis effect and summer temperature rise in arid regions - case study in Tarim Basin”.