Paper Reviewed
You, Q., Min, J., Jiao, Y., Sillanpaa, M. and Kang, S. 2016. Observed trend of diurnal temperature range in the Tibetan Plateau in recent decades. International Journal of Climatology 36: 2633-2643.

Introducing their work, You et al. (2016) describe how they determined -- on the basis of temperature data obtained from 71 different observation stations scattered across the Tibetan Plateau (TP) -- that the regional annual mean diurnal temperature range (DTR) of that region is currently 14.17°C, with a maximum in winter of 16.35°C and a minimum in summer of 12.62°C. In addition, the five researchers report that the DTR has most recently been decreasing at an annual rate of 0.20°C per decade.

As for why this has been the case, the five researchers note that the trend in DTR has primarily been "a consequence of greater warming in minimum temperature than maximum temperature." And on a global scale, they write that "it is reported that there are larger increases in minimum temperature than in maximum temperature, resulting in a narrowing of the DTR," citing Karl et al. (1991, 1993), Easterling et al. (1997), Vose et al. (2005), Jhajharia and Singh (2011), Shahid et al. (2012) and the IPCC (2013).

And it is also worth noting that colder temperatures are much more detrimental to human health -- and life itself -- than are warmer temperatures, which means that the type of warming currently being experienced throughout the world is beneficial to the well-being of humanity.

References
Easterling, D.R., Horton, B., Jones, P.D., Peterson, T.C., Karl, T.R., Parker, D.E., Salinger, M.J., Razuvayev, V., Plummer, N., Jamason, P. and Folland, C.K. 1997. Maximum and minimum temperature trends for the globe. Science 277: 364-367.

IPCC. 2013. Summary for policymakers. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

Jhajharia, D. and Singh, V.P. 2011. Trends in temperature, diurnal temperature range and sunshine duration in Northeast India. International Journal of Climatology 31: 1353-1367.

Karl, T.R., Jones, P.D., Knight, R.W., Kukla, G., Plummer, N., Razuvayev, V., Gallo, K.P., Lindseay, J., Charlson, P.J. and Peterson, T.D. 1993. Asymmetric trends of daily maximum and minimum temperature. Bulletin of the American Meteorology Society 74: 1007-1023.

Karl, T.R., Kukla, G., Razuvayev, V.N., Changery, M.J., Quayle, R.G., Helm Jr., R.R., Easterling, D.R. and Fu, C.B. 1991. Global warming: evidence for asymmetric diurnal temperature change. Geophysical Research Letters 18: 2253-2256.

Shahid, S., Bin Harun, S. and Katimon, A. 2012. Changes in diurnal temperature range in Bangladesh during the time period 1961-2008. Atmospheric Research 118: 260-270.

Vose, R.S., Easterling, D.R. and Gleason, B. 2005. Maximum and minimum temperature trends for the globe: An update through 2004. Geophysical Research Letters 32: 10.1029/2005GL024379.