I’ve been banging on about DTR in Australia for a while, showing that as an indicator of greenhouse warming, decreasing DTR trend has been lacking from Australian records for some time, such that the trend is flat since 1947.
Update:
DTR is Diurnal Temperature Range, the difference between Minimum and Maximum temperature daily. Several previous posts discuss this. Greenhouse gases slow back radiation, and thus night time temperatures are expected to be warmer than normal, and minima are expected to increase faster than maxima, so DTR should decrease.
Fig.1: Australian DTR anomalies, 1947 – 2013
I’ll now show what is happening on a regional basis. This map shows the main meteorological regions of Australia.
Fig. 2: The regions.
The main difference is between Northern Australia and Southern Australia.
Fig.3: Northern Australian DTR anomalies, 1971 – 2013
43 years of flat trend in DTR!
Fig.4: Southern Australian DTR anomalies, 1938 – 2013
76 years!
Fig. 5: South-Western Australian DTR anomalies, 1941 – 2013
73 years. But the real eye opener is South Eastern Australia:
Fig. 6: South-Eastern Australian DTR anomalies, 1934 – 2013
That’s right, in South-East Australia, the DTR trend has been flat for 80 years!
Decreasing DTR as a “fingerprint” of greenhouse warming was championed by the 2004 paper by Dr Karl Braganza et.al,
“Diurnal temperature range as an index of global climate change during the twentieth century” Karl Braganza, 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
Braganza et. al. analysed global DTR from 1951 to 2000, finding a significant decline of ~0.4 degrees C. If we compare Australian data for the same period we find this is corroborated.
Fig. 7: Australian DTR anomalies 1951 – 2000
The observed decrease over this period is ~0.35 – 0.4 C.
With the benefit of an extra 13 years of data, we can check whether this continues to be the case.
Fig. 8: Australian DTR anomalies 1951 – 2013
What a difference a few years make.
Tags: Diurnal Temperature Range, DTR, greenhouse warming, Karl Braganza, temperature
January 13, 2014 at 3:57 am
What is DTR?
Regards
Viv
Viv Forbes
Chairman
Carbon Sense Coalition
http://www.carbon-sense.com
January 13, 2014 at 7:05 am
Good morning Viv
My fault- DTR is Diurnal Temperature Range, the difference between Minimum and Maximum temperature during the day. Several previous posts discuss this. Greenhouse gases slow back radiation, and thus night time temperatures are expected to be warmer than normal, and minima are expected to increase faster than maxima, so DTR should decrease. I will update.
Ken
January 24, 2014 at 6:05 am
Ken
It appears ACORN data for 2013 has just been posted. Haven’t checked all sites to see if all updated. Has this been announced?
January 24, 2014 at 12:15 pm
Hi Ian
Yes I’m using their 2013 data. Data at CDO still not Quality Assured!!
January 26, 2014 at 12:34 pm
Here’s list of papers on diurnal trends globally and regional.
http://agwobserver.wordpress.com/2010/11/24/papers-on-diurnal-temperature-range/
Simple summary – global diurnal trend is negative (nights warming faster than days) since mid-20th century, with regional differences including sign, and flattish for the last 30 years or so, with regional differences including sign (positive/negative).
January 26, 2014 at 1:33 pm
Barry, thank you for the list of papers, which I will read when I get a round too-it. I note the most recent paper in the list is from 2010. I note that the abstracts for a couple of papers mention links between DTR and cloudiness, suggesting that decreasing DTR is due to intensified hydrological cycle, which appears to be what we see in Australia, with very low DTR associated with wet periods, but the long slow decrease in DTR with a rapid increase in the past 15 years or so in Australia complicates this somewhat. I also note a paper suggesting a link with local land use changes. I am also pleased to see papers analysing DTR trends on a regional basis, so I will continue to analyse Australian data as before.
I will try to find what happened to the other comment you mentioned. This has happened to a couple of other comments as well.
January 26, 2014 at 12:36 pm
I also posted in an older thread…
https://kenskingdom.wordpress.com/2014/01/07/the-hottest-year-but-not-due-to-greenhouse-warming/
My comments there are in the moderation cue for some reason.