Trends and uncertainties in surface air temperature over the Tibetan Plateau, 1951–2013

Trends and uncertainties of surface air temperature over the Tibetan Plateau (TP) are evaluated by using observations at 100 meteorological stations during the period 1951–2013. The sampling error variances of gridded monthly data are estimated for every month and every grid box of data. The gridded data and their sampling error variances are used to calculate TP averages, their trends, and associated uncertainties. It is shown that large sampling error variances dominate northern and western TP, while small variances appear over southern and eastern TP. Every month from January to December has a positive linear trend during the study period. February has the largest trend of 0.34 ± 0.18°C (10 yr)–1, and April the smallest at 0.15 ± 0.11°C (10 yr)–1. The uncertainties decrease steadily with time, implying that they are not large enough to alter the TP warming trend.