Summary: Diurnal temperature range as an index of global climate change during
the twentieth century
School of Mathematical Sciences, Monash University, Clayton, Victoria, Australia
David J. Karoly
School of Meteorology, University of Oklahoma, Norman, Oklahoma, USA
J. M. Arblaster
National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA
Received 15 March 2004; revised 12 May 2004; accepted 7 June 2004; published 13 July 2004.
 The usefulness of global-average diurnal temperature
range (DTR) as an index of climate change and variability is
evaluated using observations and climate model simulations
representing unforced climate variability and anthropogenic
climate change. On decadal timescales, modelled and
observed intrinsic variability of DTR compare well and
are independent of variations in global mean temperature.
Observed reductions in DTR over the last century are large
and unlikely to be due to natural variability alone.
Comparison of observed and anthropogenic-forced model
changes in DTR over the last 50 years show much less