Climate change and spatio-temporal trend analysis of climate extremes in the homogeneous climatic zones of Pakistan during 1962-2019

coldest day increased during 1980–2016 over Pakistan [72,73]. Archer [74] investigated that with the rise of 1˚C in average temperature can cause an increase of 16–17% in river flow in the upper Indus Basin. Few previous studies compared temperature and precipitation trends on local scale glaciers in the Karakoram and Himalayas in the UIB [75,76]. These findings suggest that slight temper- ature and precipitation supported the marginal retreating trends. The glaciers changes in cor- relation with the local climate improves the assessment of contemporary and future glaciers behavior under the changing climate. Our long-term climate assessment would improve the cryosphere changes in the glacier’s rich mountainous region in the context of the Karakoram Anomaly. There are seven meteorological stations with long-term observations in this region as shown in Table 1. The long-term meteorological changes were investigated by using observed data at each station. The significance of difference (average changes) between the two periods (1962–1990 and 1991–2019) was tested by utilizing a t-test to see whether it is significantly changing or not for each station separately on a seasonal basis. This can help to see the signifi- cance of the changes in average temperature and precipitation on a seasonal basis in different parts of the Karakoram region. In addition, the mMK test was used to identify a monotonic trend in temperature and precipitation. Finally, climate extremes were calculated for each sta-

tion to see whether it is behaving differently than the zone wise climate extremes. This special part may disclose the latest status of climate change in different parts of the Karakoram and may update the present status of Karakoram anomaly which was first investigated by [43]. The details of meteorological station in Northern Pakistan are given in Table 1, with four stations are in the Karakoram and the remaining in the Himalaya and Hindukush region. The step-by- step methodology of this study is presented in Fig 2. 4. Results Before the start of formal analysis, the data was investigated carefully for missing values and inhomogeneity. After filling the missing values using imputation, the results of SNHT test show that the data is homogeneous in time. Therefore, there was no need of any adjustment. The climate change extreme results of this study are discussed zone-wise and thereafter the new findings about the Karakoram anomaly. Considering the importance of the Karakoram region, climate extremes analysis is also presented for each station separately in this region. 4.1. Estimation Zone 1. The difference between the two-time slices (1991–2019 and 1962–1990) was tested for possible significance in temperature and precipitation on a seasonal basis. A signifi- cant increase in temperature during DJF and MAM and a significant decrease during JJA and Table 1. Brief information about meteorological stations situated in Northern Pakistan and used for Karakoram Anomalies investigation. S. No Station Latitude Longitude Mountain range Altitude

1 Astore 35 20 74 54 Himalaya 2,168.0 meters 2 Bunji 35.75 74.75 Karakoram 1,372.0 meters 3 Chilas 35.75 74.00 Hindukush 1,250.0 meters 4 Darosh 35.50 71.75 Hindukush 1,464.0 meters 5 Gilgit 36.00 74.50 Karakoram 1,460.0 meters 6 Gupis 36.25 73.50 Karakoram 2,156.0 meters 7 Skardu 35.25 75.75 Karakoram 2,317.0 meters https://doi.org/10.1371/journal.pone.0271626.t001 PLOS ONE Climate change and extremes analysis using observed data (1962-2019) over Pakistan PLOS ONE | https://doi.org/10.1371/journal.pone.0271626 July 27, 2022 7 / 27