## 4 Discussion  
The mid-troposphere temperature (TMT, 3-7 km altitude) trend can be practically considered the lower troposphere temperature (TLT, 0-3 km altitude) trend over the high-altitude HKH region, where the average elevation is \(\sim\)5 km. The TMT trend over the dust source, dust sink, and surrounding snow-covered and glacial regions (Himalayas and Tibetan Plateau) shows a statistically significant mean warming trend. The observed warming trends align with the overall warming of the tropical troposphere observed globally during the same period [69,86]. The HKH region is reported to show a warming of almost 1.8 \({}^{\circ}\)K by the end of the century [87]. The high-altitude glacial regions exhibit enhanced warming compared to other low-lying regions (Figure 7). The Tibetan region shows the highest warming trend, followed by the eastern Himalayas and the western Himalayas, respectively. Figure 6: The variation in (**a**) the monthly lower troposphere temperature (TLT) trend (\({}^{\circ}\)K/year) and (**b**) the monthly average of TLT “anomaly data (\({}^{\circ}\)K) from the Microwave Sounding Unit/Advanced Microwave Sounding Unit (MSU/AMSU) data (1978–2022). The monthly breakup of warming trends (Table 5) exhibits that the high-altitude glacial regions clearly show enhanced warming during winter and pre-monsoon months (November to May) and a decline during the other half of the year with a relatively neutral or slightly positive trend. In general, an inequality of warming trend can be observed between the western and eastern Himalayas, where the western Himalayas show a relatively higher warming trend in pre-monsoon months (peak in May, 0.019 \(\pm\) 0.005 \({}^{\circ}\)K/year) compared to other months, while the eastern Himalayas show much higher warming trends in winter months (peak in May, 0.019 \(\pm\) 0.005 \({}^{\circ}\)K/year  
December through February, average of 0.041 \(\pm\) 0.012 \({}^{\circ}\)K/year) compared to pre-monsoon months. Previous studies had reported the unequal distribution of TMT warming with enhanced warming of the western sides of the Himalayas and IG plains compared to the eastern sides in the pre-monsoon months [13; 30]. Significant dust storms originating from arid and desert areas in Africa, Arabia, and western India, including the Thar Desert, occur during the pre-monsoon season (April-June) in the Indian Gangetic (IG) plains [71; 88]. These dust storms, along with locally produced anthropogenic pollutants, affect the entire IG plains during the pre-monsoon. The frequency and impact of these dust storms are higher in the western region and relatively lower in the eastern part of the IG plains. These dust-laden air masses form a layer of aerosols along the foothills of the Indian Himalayas, contributing to the \"elevated heat pump\" (EHP) mechanism [15; 89]. This mechanism enhances convection, causing the vertical advection of dust aerosols to higher altitudes, increasing the seasonal heating during pre-monsoon (MAM) months, and resulting in a decreasing gradient of aerosol optical depth (AOD) towards the east [90; 91]. Though the seasonal anomalous heating of the western Himalayas and IG west during MAM months was distinctly identified by the study, the disappearance of the decreasing TMT gradient from west to east and the strong jump in TMT trends in the eastern Himalayas and IG plains are conspicuous. The annual TMT trends derived in the present study for the IG west and IG east exhibit similar degrees of warming trends (Table 3), in contrast to the earlier works on the TMT trends derived for the IG plains. The annual TMT trends of the Himalayas also show a similar pattern, with not much contrast between the western and eastern Himalayas (Table 3).