Extremely hot temperatures around the world are 40% more common today than 60 years ago according to new research from the ARC Centre of Excellence for Climate System Science.
In a world first, researchers at the Centre investigated six decades of global observational data with regards to frequencies of certain temperature occurrences. Previously such work had only been done on regional scales.
The results revealed a worldwide shift to warmer temperatures and a dramatic increase in extreme heat conditions.
“The particularly striking aspect of this research is that over this period the increase in the number of extremely hot temperatures has gone up faster than the rise in average temperatures would suggest, in particular for night time temperatures,” said Dr Markus Donat
“Even though the average temperature has only shifted upwards in a range of 0.6-0.8°C over 60 years, the number of extreme heat records have increased by 40% over the same period.”
Extremely hot days are defined as those that fit within the hottest 5% of all temperatures anomalies recorded.
To get their results the researchers divided the collected temperature data from 1951-2010 into two sets, 1951-1980 and 1981-2010. The data across both these times spans were then compared.
Interestingly, the average difference in daily minimum temperatures (up 0.8°C) was greater than the average temperature increase in daily maximum temperatures (up 0.6°C).
But it was at the extreme ends of the temperature spectrum where the most marked differences have occurred.
“The observations show a clear warming shift in temperatures and a marked increase in extreme hot weather events,” said Dr Lisa Alexander.
“Our results showed that the statistical character of the distribution of temperatures in more recent decades has become more skewed towards hotter values for both night-time and daytime temperatures.”
The researchers found that the top 5% of night-time temperatures in the 1981-2010 period were on average 1.1°C hotter than those from the 1951-1980 period.
There was also a marked difference for the coldest 5%, which were 1.2°C warmer during 1981-2010 than the 1951-1980 period.
The paper has been selected as a research spotlight article in Geophysical Research Letters.
- The shifting probability distribution of global daytime and night-time temperatures (Geophysical Research Letters)