Elite tennis players feel the heat at Australian Open as summers intensify

The average afternoon temperature in January has risen by 0.8 degrees Celsius per decade since 1987. But in the two weeks of the Australian Open -- usually held in mid-late January -- temperatures have increased by 1.25 degrees per decade.

Ben Hague, a third-year Atmosphere and Ocean Sciences student at the University of Melbourne, said extreme summer temperatures have also become more prevalent, like those experienced during the 2014 Australian Open.

Players, officials and spectators were forced to endure four straight days of temperatures over 41 degrees that year.

It is what motivated Mr Hague to analyse HtempMelbourne's weather data in detail.

"This was a particularly extreme event," Mr Hague said. "But the point of this study was to measure whether these events are happening more often."

"And the results suggest that they are."

Mr Hague found both hot days and measures of heat stress increased significantly over the whole summer, but mainly in January -- and particularly, mid-late January.

The number of half-hourly observations where a temperature of 35 degrees or more was recorded in January has more than doubled. The data also suggests high summer temperatures are starting earlier.

The study focuses on temperature and humidity trends since 1987, which was when the Australian Open became a mid-to-late January event.

Mr Hague used temperature data from the Bureau of Meteorology, but also "wet bulb globe temperature" (WBGT) figures which take humidity, wind and sunlight into consideration.

The data suggests a decrease in relative humidity since 1987, but Mr Hague said it wasn't enough to counter an overall climb in the WBGT.

While the study doesn't make any future weather projections, the figures don't bode well for Australian Open organisers, who've previously come under fire over heatwave conditions in Melbourne.

The city is set to play host to the event until at least 2036. Other research has consistently pointed towards ever-climbing summer temperatures.

While the main focus of the study was on the 27 years since the Australian Open moved to mid-late January, Mr Hague also investigated more than 100 years of Melbourne summers.

The results reflect an overall increase of both maximum and minimum temperatures during the season.

He found that since 1911, average daily maximum temperatures throughout all of summer increased by two degrees -- with 1.8 degrees of this warming having occurred since 1990.

Hotter days are also getting hotter, with the data showing a five degree increase in the average temperature of Melbourne's hottest December day since 1989.

Mr Hague's paper has been published in the latest edition of the Bulletin of the Australian Meteorological & Oceanographic Society. The journal can be found here: http://www.amos.org.au/publications

Key findings:

• Average afternoon temperature during January has increased 1.25 degrees per decade since 1987
• Average daily temperature during January has increased 0.8 degrees per decade since 1987
• There has been a doubling of the amount of time that the temperature has reached 35 degrees or more in January from 1987 to 2014
• Melbourne's highest January temperature was on average 3.25 degrees higher between 1990 and 2014
• Melbourne's highest December temperature was on average 4.88 degrees higher in the same period